ANALYSIS of ALTERNATIVES Public Version

ANALYSIS OF ALTERNATIVES Public Version

Legal name of applicant(s): Società Chimica Bussi S.p.A. (SCB)

Submitted by: Società Chimica Bussi S.p.A.

Substance: Sodium Dichromate

Use title: Use of sodium dichromate as an additive for suppressing parasitic reactions and oxygen evolution, pH buffering and cathode corrosion protection in the electrolytic manufacture of sodium chlorite

Use number: 1 Disclaimer

This report has been prepared by Risk & Policy Analysts Ltd, with reasonable skill, care and diligence under a contract to the client and in accordance with the terms and provisions of the contract. Risk & Policy Analysts Ltd will accept no responsibility towards the client and third parties in respect of any matters outside the scope of the contract. This report has been prepared for the client and we accept no liability for any loss or damage arising out of the provision of the report to third parties. Any such party relies on the report at their own risk.

Note

This complete version of the Analysis of Alternatives includes some text and figures that are highlighted in grey. These parts of text have been blanked out in the public version of this document. Justification for confidentiality claims is provided in the Annex (Section 7) of the present document. Table of contents

1 Summary ...... 1 1.1 Use applied for ...... 1 1.2 Potential alternatives for sodium dichromate ...... 2 1.3 Suitability of the three identified alternatives to sodium dichromate ...... 5 1.4 Feasibility and availability of potential alternatives for sodium dichromate ...... 6 1.5 Actions needed to improve the suitability and availability of potential alternatives ...... 8

2 Analysis of substance function ...... 13 2.1 Introduction ...... 13 2.2 The chlorate production process ...... 13 2.3 Production of sodium chlorite ...... 20 2.4 Conditions of use and technical feasibility criteria ...... 21 2.5 Summary of functionality of sodium dichromate in the “Applied for Use” ...... 27

3 Annual tonnage ...... 31 3.1 Tonnage band ...... 31 3.2 Trends in the consumption of sodium dichromate ...... 31 3.3 Form and usage of sodium dichromate ...... 31

4 Identification of possible alternatives...... 33 4.1 List of possible alternatives ...... 33 4.2 Description of efforts made to identify possible alternatives ...... 33 4.3 Screening of identified alternatives ...... 66

5 Suitability and availability of possible alternatives ...... 87 5.1 Introduction and scope of analysis ...... 87 5.2 Sodium molybdate (two available forms) ...... 87 5.3 Molybdenum-based coatings ...... 96 5.4 Two-compartment electrolytic systems ...... 102

6 Overall conclusions on suitability and availability of possible alternatives ...... 109 6.1 Technical feasibility of shortlisted alternatives ...... 109 6.2 Economic feasibility of shortlisted alternatives ...... 111 6.3 Reduction of risks from the use of shortlisted alternatives ...... 112 6.4 Availability of shortlisted alternatives ...... 113 6.5 Overall conclusion ...... 114 7 Annex – Justifications for confidentiality claims ...... 115

8 Appendix 1 – Information sources ...... 121

1 Summary

1.1 Use applied for

This Analysis of Alternatives (AoA) is part of an Application for the Authorisation (AfA) for the continued use of sodium dichromate (CAS No. 7789-12-0 & 10588-01-9; EINECS No. 234-190-3, hereafter referred to as “SD”) by the applicant, Società Chimica Bussi SpA (hereafter referred to as SCB), in the sodium chlorate (NaClO3) manufacturing process, where it acts as a crucial additive to the process. The sodium chlorate is an intermediate in the production of sodium chlorite.

As is explained in the SEA (page 9), SCB is to build a new plant to produce Sodium Chlorite for use in the water treatment sector.

SCB, the applicant, is part of an industrial holding (Gestioni Industriali Srl) controlled by the same shareholder which owns also Caffaro Brescia Srl (hereafter Caffaro). The new SCB plant will be run on almost the same basic technology as that of the Caffaro plant in Brescia, updated in line with modern techniques resulting in further minimisation of worker exposure and environmental impact.

Caffaro currently holds an authorisation for the use of sodium dichromate in the production of sodium chlorite and is the main EU manufacturer of sodium chlorite for use in the water treatment sector. Caffaro previously applied for the Authorisation of the same use of SD as part of a group of 7 companies that represented 9 applicant companies; that group was known as Sodium Dichromate Authorisation Consortium (hereafter “SDAC”).

As is demonstrated in the Caffaro Analysis of Alternatives1 , there is no other feasible technology available globally which enables the production of sodium chlorate, and this AoA demonstrates that this continues to be the case. The SCB plant has obtained the requisite building permits and financing and construction has begun and the plant is expected to be ready for operation towards the end of 2019. However, production cannot begin until this AfA has been evaluated.

Caffaro holds the Brescia plant under rent and is not the owner of the land. The Brescia site is declared a Site of National Interest by the Italian authorities and a characterisation and reclamation intervention is planned. For this reason, it may be required relatively early, dependent on the needs and time schedule of public authorities, to surrender the facility available for these activities. The Bussi factory is also declared as part of a National Interest Site, but in this case the land is owned by SCB itself, the characterisation has been carried out, the Prevention Measures have been implemented, but no reclamation activities are planned.

Caffaro has a significant commercial / application know-how that the common shareholder intends to continue to enhance. Moreover, if the Bussi site is not ready to replace Caffaro production when it will cease operation, a shortage of chlorite product on the market will occur. So, it must be completely operational in the case of formal request to stop the operation of the Caffaro plant by the public authorities.

Note that the AoA undertaken for Caffaro has been used as the basis for this SCB AoA. Unless otherwise noted, the various relevant analyses and considerations of the first AoA still apply. Also,

1 https://echa.europa.eu/documents/10162/5e4bf84e-5725-4633-bb47-da66770a5b96

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 1 due to the Caffaro AoA being the basis for this AoA, please also note the SCB plant it is frequently referred to in this document in the present tense i.e. as if it is already operational which it is not (construction has just begun).

Generation of sodium chlorate is based on the electrolysis of sodium chloride (NaCl), at a controlled pH range, where the sodium chloride is converted into sodium chlorate while hydrogen evolves as a co-product. SD acts to increase the current efficiency of the conversion process by suppressing unwanted (parasitic cathodic) reactions and thus reducing the use of electrical energy, and acts as a pH buffer to ensure optimal process conditions are maintained. It also has a crucial role in limiting the amount of oxygen generated during the process, as the presence of oxygen poses a serious hazard because it forms explosive atmospheres in the presence of hydrogen.

SCB will use ''#C#'''''''''''' of SD per year in the form of a 67% solution. SD is registered in the 100-1000 tonnes band.

SCB uses SD in the manufacture of sodium chlorate, which is used as an intermediate in the manufacture of sodium chlorite. Sodium chlorite will be sold to customers in a variety of water treatment industry sectors, but primarily in potable, industrial and waste water treatment.

This AoA has been prepared by an independent third party working on behalf of SCB and is based on that of Caffaro, with updates and customisation where relevant. 1.2 Potential alternatives for sodium dichromate

This AoA provides details of an extensive search of literature carried out by the independent third party for the Caffaro AfA, and which has been updated in 2019 for the SCB AfA. In addition, consultation with all seven SDAC members regarding their extensive R&D efforts has been used in conjunction with the publicly available information to ensure all relevant alternatives have been considered. In total, ten alternative substances and technologies were identified and evaluated, and these are summarised in Table 1-1.

Table 1-1: Master list of identified potential alternatives for SD in sodium chlorate manufacture # Potential alternative substances

1 Chromium (III) chloride 2 Sodium molybdate 3 Rare Earth Metal (III) salts # Potential alternative cathode coatings 4 Molybdenum-based cathode coatings 5 Ruthenium-based cathode coatings 6 Zirconium- based cathode coatings # Potential alternative cathode materials 7 Ruthenium alloy cathodes # Potential alternative electrolytic processes 8 Two-compartment electrolytic systems 9 Two-compartment electrolytic cells with oxygen-consuming gas diffusion electrodes 10 Polymeric cathode film coatings

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 2 The screening of the identified alternatives included the following steps:

 Commercialisation status: this step looked into whether each of the alternatives is commercially available. If yes, the question was how quickly could it be implemented on an industrial scale by the applicant; if no, the analysis looked into how quickly it might become available on an industrial scale. This step eliminated Alternatives 9 and 10 as they are currently very far away from any foreseeable commercialisation scenario;

 Suitability for SD replacement: this step looked into the fundamental criterion of whether each identified alternative is able to eliminate the handling of and exposure of workers to SD. Under the current state of knowledge, some of the identified alternatives (Alternatives 2, 5 and 7) cannot perform to an acceptable level unless SD is present in the electrolyte (in the sodium chlorate cell), as is described in detail in Section 4.3.3. Additionally, it should be noted that the use of Alternative 1 results in the formation of SD in the electrolyte (although, compared to the use of SD, it eliminates worker exposure arising from the handling of SD during the dosing task, the first step in the use of SD to produce sodium chromate);

 Technical feasibility criteria comparison: this step utilised a list of seven criteria to compare the technical feasibility of the identified alternatives. The criteria are:

 Formation of protective film permeable to H2 but impermeable to hypochlorite;  Control of oxygen formation;  Cathode protection;  pH buffering;  Current efficiency and overall energy consumption;  Solubility in the electrolyte (for alternative substances only)  Lack of impurities in the sodium chlorate product.

This screening identified specific technical shortcomings for some of the potential alternatives, e.g. poor energy efficiency (Alternative 2), generation of excessive amounts of O2 (Alternative 2), very low solubility (Alternative 3), poor pH buffering (Alternatives 2, 4, 5, 7) and poor reaction selectivity (Alternative 7); and

 Engineering and economic feasibility: this step looked at the practical (incl. engineering) steps required for each of the identified alternatives and the key complexities of these practical steps. A series of alternatives were found to be practically impossible to implement due to inherent and, to the applicant’s best knowledge, insurmountable problems, e.g. poor solubility (Alternative 3), unavailability of suitable cathodes (Alternatives 5 and 6), and lack of industrial scale proof of concept and experience (Alternatives 3, 5, 6 and 7).

An overview of results is given in Table 1-2. The table identifies the three shortlisted potential alternatives which form the core of the assessment in Section 5 of this AoA:

 Alternative 2 (substance): Sodium molybdate  Alternative 4 (technology): Molybdenum-based cathode coatings  Alternative 8 (technology): Two-compartment electrolytic systems.

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 3 Table 1-2: Summary of the screening of identified potential alternatives for SD in the manufacture of sodium chlorate Suitability as SD Compared to SD in Commercialisation Engineering and Alternative replacement terms of technical Shortlisted for further status economic feasibility (exposure) feasibility criteria analysis? # Potential alternative substances 1 Chromium (III) compounds Not immediately Unsuitable as it only Uncertain due to lack Uncertain feasibility and No available leads to a very of knowledge cost while 3rd party limited reduction to patent application worker exposure pending 2 Sodium molybdate Unproven on the Low SD levels may Worse Not available on industrial Yes industrial scale; be required scale uncertain future 3 Rare Earth Metal (III) salts Impossible to use Acceptable Worse Impossible No # Potential alternative cathodic coatings 4 Molybdenum-based Unproven on the SD addition may be Probably worse; Infeasible and unavailable Yes cathode coatings industrial scale; required better claimed energy on industrial scale uncertain future efficiency 5 Ruthenium-based cathode Unproven on the SD addition required Worse Impossible No coatings industrial scale; uncertain future 6 Zirconium- based cathode Unproven on the SD addition may be Too uncertain Impossible No coatings industrial scale; required uncertain future # Potential alternative cathode materials 7 Ruthenium alloy cathodes Unproven on the SD addition required Worse Impossible No industrial scale; uncertain future # Potential alternative electrolytic processes 8 Two-compartment Not used for chlorate Acceptable Uncertain, likely to be Feasible but very costly Yes electrolytic systems production worse than SD

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 4 1.3 Suitability of the three identified alternatives to sodium dichromate

1.3.1 Risks to human health and the environment from direct substitution

For the Caffaro AoA, a detailed comparative risk assessment for environmental and human health effects was undertaken to assess the suitability of sodium molybdate, which could in theory act as ‘drop-in’ replacements for SD. This assessment, included in the Caffaro AoA as Appendix 2 (Section 8), also looked into the risks to human health and the environment from sodium phosphates. These would need to be added to the electrolyte in the absence of SD if sodium molybdate (or molybdenum- coated cathodes) is used to act as pH buffers.

For the comparative assessment of human health and environmental risks of SD and the potential alternative substances, the following approach was used:

 Available reference values (DNELs, PNECs) were analysed;  Where no reference values were available, which were derived by similar methodologies to allow for a comparison, tentative reference values were derived;  An exposure scenario was established similar to the actual exposure scenario for SD;  Exposure modelling input data were compiled for all alternative substances and SD;  Exposure levels and risk characterisation ratios for the environment were calculated using ECETOC TRA;  Exposure levels for workers were modelled using ART (Advanced REACH Tool).

Comparison of hazard data (classifications) revealed that none of the alternatives investigated are Carcinogenic, Mutagenic and Reprotoxic (CMR) substances and that none of the alternatives have been classified for environmental hazards. Moreover, the tentative risk characterisation shows that the alternative substances (sodium molybdate and sodium phosphates) have lower RCRs for both human health endpoints (workers) and the environment; therefore, the alternative substances assessed in detail are beneficial with regard to human health considerations and fulfil the REACH Authorisation requirement of leading to a reduction in overall risks to human health and the environment compared to the Annex XIV substance SD.

For the two alternative technologies, molybdenum-coated cathodes and two-compartment electrolytic cells, a direct comparison of risks against SD is not possible. In the case of molybdenum- coated cathodes, it is assumed that no additives would be required apart from a sodium phosphate buffer. For two-compartment electrolytic cells, no additives are assumed to be added. It is therefore assumed that the risks from the use of SD would be eliminated and new hazards would not be introduced to the operation of the cells (although, the extent to which molybdenum-coated cathodes would control the evolution of oxygen is uncertain), hence, both alternative technologies are assumed to reduce the overall risk to human health and the environment.

1.3.2 Environmental externalities from changes in energy consumption

The Caffaro AoA include a detailed calculation of environmental externalities from the increase in energy consumption that would arise from the implementation of the shortlisted alternatives and the reader is referred to that document. For the present AoA of SCB, as the plant is not currently operational, reliable estimates of energy consumption cannot be provided; however, the principles of that analysis would apply here too.

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 5 1.4 Feasibility and availability of potential alternatives for sodium dichromate

1.4.1 Assessment of technical feasibility

The potentially feasible alternatives have all been proposed in academic literature and in patents as potential alternatives to the use of SD as an additive or, in the case of molybdenum-based coatings and two-compartment cells, as an alternative way of producing sodium chlorate. Neither the applicant nor Caffaro have experience of the technical feasibility of these potential alternatives and this AoA relies substantially on the descriptions and claims made in the relevant published research, some of which has been performed by direct competitors. The conclusions of the assessment of technical feasibility are summarised in Table 1-4.

Table 1-4: Overview of technical feasibility of shortlisted alternatives for Caffaro Conclusion on Alternative Technical advantages Technical disadvantages technical feasibility Sodium - Sufficiently soluble - Unstable protective film on the Infeasible molybdate - Relatively simple, cathode ‘drop-in- substitute - Poor pH buffer requiring the addition of phosphates which interfere with and adversely affect the stability and longevity of the anode and may increase oxygen evolution - High evolution of oxygen gas potentially leading to explosive mixtures with hydrogen - Worse current efficiency and electricity consumption than SD - Presence of transition metal ions may affect the subsequent chlorite reaction - Unproven on an industrial scale Molybdenum- - Patent literature - Poor pH buffer requiring the Infeasible based coatings claims a lower addition of phosphates which electricity interfere with and adversely affect consumption than SD the stability and longevity of the anode and may increase oxygen evolution - Potential issues with high evolution of oxygen gas - Presence of transition metal ions may affect the subsequent chlorite reaction - Would still require Cr(VI) - Unproven on an industrial scale, hence great uncertainty over control of parasitic reactions and cathode lifetime - Necessary cathodes not presently available

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 6 Table 1-4: Overview of technical feasibility of shortlisted alternatives for Caffaro Conclusion on Alternative Technical advantages Technical disadvantages technical feasibility Two- - Solubility, cathodic - Worse current efficiency and Infeasible compartment film formation and electricity consumption than SD electrolytic oxygen evolution - Unproven on an industrial scale systems issues inherently specifically for chlorate manufacture resolved - Would require complete plant - pH control required rebuild but can be addressed without the use of added buffers

1.4.2 Assessment of economic feasibility

From the assessment of technical feasibility, it is clear that the alternatives are not technically feasible. It is therefore concluded that the economic feasibility considerations are not relevant. However, the reader is reminded that a comparison of economic feasibility of the alternatives in the context of an already established plant (that of Caffaro in Brescia) was provided in Section 10 of the Caffaro AoA.

1.4.3 Assessment of availability

Table 1-5 summarises the findings of this AoA with regard to the availability of the shortlisted alternatives for SD. None of the shortlisted alternatives are currently available, either because they have not been proven on the industrial scale, and/or because access to the (pending) patents is not available and these therefore cannot be assessed.

Table 1-5: Overview of availability of shortlisted alternatives Access to required Conclusion on Alternative Quantity availability Quality availability technology (rights) availability Sodium - Sodium - No issue - Existing (known) Unavailable molybdate molybdate is identified but patent rights REACH technology is held by third registered unproven on the parties - Quantity needed industrial scale is less than 10 t/y Molybdenum- - Raw materials - Unknown at - Existing (known) Unavailable based coatings available on the present, as patent rights market technology is not held by third - Required proven on the parties cathodes not industrial scale - '''''''''''''' '''''''''''''' currently ''''''''''''''''' '''' available ''''''''''''''' '''''''' ''''''''''''''''''''''' ''' ''''''' ''#I#'''''''''''''''' ''''''''''''''''' ''I''''''''''' ''''''''''''''''' ''''''' ''''''' '''''''''''''''

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 7 Table 1-5: Overview of availability of shortlisted alternatives Access to required Conclusion on Alternative Quantity availability Quality availability technology (rights) availability Two- - Chlor-alkali - Unknown at - Technology is Unavailable compartment technology present, as not proven for electrolytic widely available technology is not chlorate/chlorite systems on market proven for manufacture on chlorate/chlorite the industrial manufacture scale

1.4.4 Summary of feasibility and availability of shortlisted alternatives

The findings of the analysis on the technical and economic feasibility and availability of alternatives are briefly summarised in Table 1-6 below.

Table 1-6: Overall conclusions on suitability and availability of shortlisted alternatives Economic Technical Feasibility Reduction Alternative Availability Conclusion Feasibility based on in risk Caffaro AoA) Not a CMR therefore  suitable, increased (unproven, pH  environmental Sodium buffering, HH:  (high energy  molybdate energy ENV:  externalities. cost) consumption, Technically and O2 evolution) economically infeasible and unavailable  (unproven, pH  buffering, (high plant Not a CMR therefore Molybdenum- uncertain conversion HH:  suitable, technically and based  energy cost, ENV: ? economically infeasible coatings consumption, uncertain and unavailable possible O2 profitability) issues) Not a CMR therefore suitable, increased Two-   environmental compartment (unproven, (high energy HH:   electrolytic high energy costs, poor ENV:  externalities. systems use) profitability) Technically and economically infeasible and unavailable : better than SD; : worse than SD; ?: uncertain

1.5 Actions needed to improve the suitability and availability of potential alternatives

The actions and timescale that would theoretically be required before the shortlisted available became feasible and suitable are presented in Table 1-7.

The alternatives that have been identified have already been the subject of significant R&D efforts by members of the SDAC and by other entities. Despite this, the identified shortcomings are yet to be

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 8 overcome. Their transition from the laboratory to the industrial scale has not been possible nor can the timeframe for such a transition be predicted with any degree of accuracy.

The use of two-compartment electrolytic systems would currently result in unacceptable increases in electrical consumption and the technology has not been proven for chlorate production. Given the likelihood of increases in the cost of electricity in the EU (S&P 2018), energy prices would need to decrease significantly for investment in such large-scale projects to become attractive. Even if this were to happen, increases in CO2 production can be expected to play a significant negative role in decision-making.

The most promising technology might be implied to be molybdenum-based coatings, as these have been suggested to result in significantly reduced energy consumption. However, current indications suggest that this technology may still result in increased oxygen levels and compromise process safety unless small amounts of SD are used2. In addition, the expected lifetime of these coated cathodes has not been evaluated. In particular, the scientific community needs to undertake further R&D on this technology and then demonstrate it on a commercially relevant scale in a pilot plant facility before any suggestion of economic feasibility can be confirmed. The technology that has been described in the known patents is protected until 2028, and it is unlikely that further R&D will yield results before then.

2 Note: the 2019 literature review (see section 4.2.3.2) indicates there has been no change in this conclusion.

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 9 Table 1-7: Actions and timescale required for improving the suitability and availability of shortlisted alternatives Potential timeframe for the Actions for improving of Actions for improving of Actions for improving of Alternative alternative becoming feasible feasibility suitability availability and suitable Already suitable for CMR effects; Further R&D is required before Technology needs to be technical improvements required Sodium molybdate energy use, pH buffering and O2 developed further to become Uncertain, but long for control of energy issues are addressed commercially viable consumption increases Further R&D is required before Technology needs to be pH buffering and possible O2 Already suitable for CMR effects; developed further and reach Molybdenum-based issues are addressed and reduction in energy consumption commercialisation. Uncertain, but long coatings reduction of energy consumption not certain, needs to be verified Mo-coated cathodes need to is proven under industrial scale become available on the market operating conditions Technology already available, but Chlor-alkali technology is known for use in chlorate manufacture it Already suitable for CMR effects; Uncertain, but long Two-compartment but needs to be proven on an is unlikely to improve due to very increased environmental (will probably never become an electrolytic systems industrial scale for chlorate high initial costs and increasingly externalities are difficult to avoid attractive solution) manufacture unappealing electricity costs in the EU

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 10 In conclusion, this Application for Authorisation is being made so that SCB can produce sodium chlorite until a technically and economically feasible alternative to the use of SD is developed. The benefits from the use of SD under closely controlled conditions and with minimisation of worker exposure significantly outweigh the risks to human health posed by the use of SD in the applicant’s new plant, as shown in the accompanying Socio-Economic Analysis (SEA) document. It is not realistic for SCB to aim towards the adoption of any one of the known, published technologies as their feasibility is uncertain and the time required for their industrial scale-up is unclear.

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 11 Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 12 2 Analysis of Substance Function

2.1 Introduction

This application for authorisation concerns the use of SD as an additive in the manufacture of sodium chlorate which is used as an intermediate in the manufacture of sodium chlorite. As is explained in Section 1, Caffaro currently holds an authorisation for the use of SD in this process, and the sodium chlorite produced is sold predominantly to the water treatment sector. A new plant is being built by SCB in Bussi, Italy, which is part of the same holding company as Caffaro. The new plant needs to be operational before Caffaro is required to close down its plant, so as to ensure continuity of supply to Caffaro’s customers. The new plant will use almost the same technology as the Caffaro plant, modernised to today’s standards and therefore with worker exposure to Cr(VI) further minimised.

From the perspective of the applicant, sodium chlorate is an intermediate to their final product sodium chlorite, which will be sold to downstream customers. SD is employed in the manufacture of sodium chlorate in aqueous solution that is subsequently present in the first step (ClO2 generation) required to convert sodium chlorate to chlorite. Therefore, this AoA will describe the chlorate process and only provide an overview of the subsequent sodium chlorite manufacturing process. Note that the sodium chlorite product placed on the market does not contain SD. It is also relevant to know that two significant differences in the potential worker exposure to Cr(VI) at the SCB and Caffaro plants are documented in the CSR:

 Whilst the Caffaro CSR considered two sampling and two laboratory testing tasks (sodium chlorate production (low% SD in the brine) and the sodium chlorite production (high% SD in the brine due to concentration in the chlorine dioxide generator)), due to technological improvements this concentration of SD does not occur in the SCB plant i.e. there is only one task for sampling (T2) and one task for production lab (T3); and

 Unlike Caffaro, SCB will not use a filter press, i.e. Task 5 in the Caffaro CSR has been deleted. The technology used instead only requires infrequent maintenance, therefore this is not calculated as a regular operational task. 2.2 The chlorate production process

2.2.1 Description and electrochemical reactions

The “Applied for Use” is the use of SD as an additive in the manufacture of sodium chlorate from sodium chloride by electrolysis, with no SD presence in the sodium chlorite product. In short, chlorate is produced in undivided cells with oxidation of chloride to chlorine on the anodes, and hydrogen evolution on the cathodes made of steel or titanium (Cornell, 2002)(Cornell, 2002). The manufacture of sodium chlorate in the EU is the same as anywhere else in the world and involves the following steps (note that the chlorate process is detailed in the IPPC BREF - Best Available Techniques for the Manufacture of Large Volume Inorganic Chemicals; photographs showing some tasks involved are available in the Chemical Safety Report):

 Brine preparation: saturated sodium chloride brine needs to be used and the electrolytic process requires high purity brine. Therefore, after the preparation of the brine by dissolving 2+ 2+ 2- the solid sodium chloride salt in hot water, impurities in the salt (e.g. Ca , Mg , SO4 ) are removed through precipitation (using NaOH, Na2CO3 and CaCl2) and filtration (IPPC, 2007)(IPPC, 2007). This brine preparation is needed only for the first charge of the chlorate plant and for some refilling: normally, the actual raw material is hydrogen chloride solution;

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 13  Electrolysis: the brine is transferred to an electrolysis cell along with SD as an additive (and potentially hydrochloric acid or chlorine for pH adjustment). As will be discussed in more detail below, SD is used to ensure suitable conditions for promoting sodium chlorate formation and avoiding side reactions during electrolysis.

The electrolysis of sodium chloride into sodium chlorate takes place in a controlled range of temperatures, 60-90 °C, and a pH of 6.0-6.5 (IPPC, 2007)(IPPC, 2007). The anodes are typically made of titanium covered with a noble metal coating and cathodes are generally made of steel (IPPC, 2007)(IPPC, 2007). Cathode materials in the first years of chlorate manufacture were copper, nickel and platinum. Today, apart from steel, some plants use titanium or a Ti-0.2% Pd alloy (Cornell, 2002)(Cornell, 2002).

The production of chlorate relies on the electrolysis of chloride (eqs. 1-4), also producing hydrogen as a co-product (eq. 5) (Mendiratta & Duncan, 2003)(Mendiratta & Duncan, 2003). Chlorine, due to the pH conditions, remains in solution forming hypochlorous acid and hypochlorite ions. The liquor (the solution from cells) is continuously circulated between the cells and the reaction tanks (IPPC, 2007)(IPPC, 2007). The overall reaction can be summarised by equation 6:

- - 2Cl ⇄ Cl2 + 2e (1)

Cl2 +H2O ⇄ HOCl + HCl (2) - - - + 2HOCl + ClO ⇄ ClO3 + 2Cl + 2H (3) - - - + - 6ClO + 3H2O ⇄ 2ClO3 + 4Cl + 1.5 O2 + 6H + 6e (4) + - - - 2H + 2e ⇄ H2 (this equation is often presented as 2H2O + 2e ⇄ H2 + 2OH ) (5)

NaCl + 3H2O ⇄ NaClO3 + 3H2 (6)

The production of protons (equations. 3 and 4) and their conversion into hydrogen (equation 5) indicate that the control of electrolyte pH is a key variable in the process. A further issue is the evolution of oxygen during the process by another competing electrochemical reaction (eq. 7).

+ - 2H2O ⇄ O2 + 4H + 4e (7)

Inhibition of this side-reaction is an important part of the process, both for current efficiency and safety reasons due to the explosive atmospheres potentially formed in the presence of hydrogen. The anodic selectivity can be disturbed by certain compounds in the electrolyte, thus further increasing oxygen formation (Kus, 2000)(Kus, 2000); and

 Crystallisation and drying: sodium chlorate is generally recovered from the liquors in a crystallisation unit by first concentrating the liquor using vacuum followed by cooling to precipitate the crystals of sodium chlorate. These are then separated from the liquor by centrifugal filtration. The crystals are dried, commonly using fluidised bed dryers using heated air (IPPC, 2007)(IPPC, 2007). The applicant is a producer of sodium chlorite and as such does not have a need to crystallise the sodium chlorate. Instead, the electrolytic solution of sodium chlorate produced in the sodium chlorate plant is passed directly to the sodium chlorite unit for processing.

This process is illustrated in Figure 2-1.

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 14 Figure 2-1: The Sodium Chlorate Process Showing Outputs and Emissions for the SCB plant

Two key characteristics of the process must be noted:

 Use of closed loop systems and recycling of liquors: a predominantly closed system is used. Where this is not possible, a high degree of recycling of chlorate and liquors (containing SD) is maintained to minimise the output of Cr(VI) in the chlorate and the release of Cr(VI) to the aquatic environment. In SCB, a closed system allows the circulation of the solution rich in sodium chlorate from the sodium chlorate plant to the sodium chlorite plant and, inversely, of the solution poor in sodium chlorate from the sodium chlorite plant to the sodium chlorate plant where, by electrolysis, the solution is newly enriched in sodium chlorate. Therefore, SD passes from one process to the other and vice versa and this allows a low loss of SD from the processes; and

 High hydrogen utilisation to improve the economics of the process: besides the main product, a co-product of approximately 57 kg of hydrogen3 is produced per tonne of chlorate as indicated in the relevant BREF document (IPPC, 2007)(IPPC, 2007). '''' '''''''#A# '''''''' '''' ''''''' ''''''' ''''''''''' ''''''''''''''''' ''''''''''''''' ''''''''' '''''''''''''' ''''''''''' ''''''''''''' '''' ''' ''''''''''''''''''''' ''''''''' '''' ''''' '''' '''' '''''''''''''''''' ''''''' '''''''''''' ''''' ''''''''''''''''. This by-product is also collected and, for overall energy and economic efficiency, it is important to utilise this hydrogen to a high degree. This depends on local conditions and the possibility of finding an outlet for using the hydrogen, either as a source of energy or as a raw material for chemical reactions. The possibility of utilising hydrogen outside of the sodium chlorate plant substantially reduces the amount of the fossil fuels required either for the production of the equivalent amount of energy or hydrogen used in chemical synthesis or both. This improves the overall economics of the chlorate production plant. In the SCB plant hydrogen is mainly used to produce HCl, which is the raw material of the plant.

Typical conditions for the process are shown in Table 2-1, as described in literature. The values shown are approximate and other concentrations of sodium chloride and final chlorate can be used. The example uses a platinum-iridium anode but other electrode materials may also be used. Typically, these are ruthenium oxide, platinum-iridium coated titanium-based anodes (Tilak & Chen, 1999)(Tilak & Chen, 1999).

3 Theoretical production 56.9 kg of hydrogen per 1000 kg of sodium chlorate according to: NaCl + 3H2O  NaClO3 + 3H2.

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 15 Table 2-1: Example operating conditions for a chlorate cell (steel cathode and Pt/Ir anode) Parameter Valuea Valueb Unit Current density 2-3 1-3 kA/m2 Current efficiency 94 - % Average cell voltage 3-3.5 2.6-3.5 V Electrical energy requirement 5,700 5,000-6,000 kWh/t Process temperature 80 - °C Electrolyte Composition Valuea Unit NaCl 150 g/L Na2Cr2O7 2-5 g/L NaOCl 3-5 g/L NaClO3 500-600* g/L Source: a Mendiratta & Duncan (2003)(2003); b IPPC (2007)(2007) * based on Cornell (2002)(2002)

With particular regard to energy requirements, electricity consumption is typically in the range of 5000 – 6000 kWh/t, depending on the current density (IPPC, 2007)(IPPC, 2007).

2.2.2 The role of sodium dichromate

Overview

SD plays four interlinked roles in the sodium chlorate production process:

1. It acts as a pH buffer

2. It suppresses the production of oxygen, thus preventing the creation of explosive mixtures with hydrogen

3. It passivates the steel cathodes, thus protecting them from corrosion

4. It increases energy efficiency and the overall efficiency of the chlorate process by suppressing certain parasitic reactions at the cathode.

The suppression of cathode reactions appears to be by far the most critical task for SD and is explained under Point 4 below.

Function 1: pH buffering

SD acts as a buffer, i.e. a weak acid or base which maintains the acidity of a solution at a chosen value that resists changes to the pH from the addition of another acid or base. The dichromate anion has the ability to react with both hydrogen cations and hydroxide anions in accordance to eqs. 8 and 9.

2- + Cr2O7 + 2H ⇄ H2Cr2O7 ⇄ H2CrO4 + CrO3 (8) 2- - - Cr2O7 + 2OH ⇄ 2CrO4 + H2O (9)

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 16 Speciation of SD varies with pH in a water solution, as shown in the above equations and in Figure 2-2. The species will be the same in the chlorate electrolyte but the pH scale might differ slightly. As can be seen, in the pH range relevant to chlorate production (pH 6.0-6.5, as explained in Section 2.4.4), all three species - -2 -2 -2 (HCrO4 , Cr2O7 and CrO4 ) will be present. At alkaline conditions the chromate ion CrO4 with sodium as counter ion (Na2CrO4) will dominate, whereas in the acidic pH range the sodium dichromate (SD) Na2Cr2O7 and or NaHCrO4 will dominate. Therefore, when reference is made in this AoA to the “presence of SD in the electrolyte”, it is meant that Cr(VI) may be found in a variety of forms which, in co-existence, deliver the required functionality at an concentration equivalent to 3 g SD per litre of electrolyte.

Figure 2-2: The distribution of Cr(VI) species in aqueous solution as a function of pH. The lines represent -2 - -2 H2CrO4 (…), Cr2O7 (- - -), HCrO4 (_.._), and CrO4 (̶ ̶ ̶). A Cr(VI) concentration of 0.05 M applies Source: Ramsay et al (2001)(2001)

According to Tilak & Chen (1999)(1999), to maximise the electrolytic cell efficiency and ensure the safety of the plant, the pH must be controlled within a narrow range, 6.0-6.5, as shown in the BREF Document referred to above. Controlling the pH can be beneficial because at low pH the evolution of oxygen decreases (eq. 7) but that of Cl2 increases (eq. 1); at high pH, the opposite occurs. Moreover, maintaining the pH of the cell solution at the given range helps in avoiding the corrosion of the anode due to oxygen evolution.

Function 2: Suppression of oxygen production

As shown above, at low pH the evolution of oxygen decreases. In chlorate producing cells, because there is no separating membrane to confine the anodic and cathodic products, the oxygen becomes mixed with the hydrogen evolved at the cathode and, therefore, there is a danger of forming an explosive mixture. Similarly, the evolution of too much chlorine could make the cell combustible or explosive (Tilak & Chen, 1999)(Tilak & Chen, 1999). It is not desirable to operate chlorate production cells with greater than 2.5% oxygen in the evolved hydrogen. Thus, the amount of oxygen evolved from an anode used for the electrolysis of halide solutions is important for both safety reasons and current efficiency (Alford & Warren, 1994)(Alford & Warren, 1994).

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 17 Function 3: Passivation of steel cathodes

Cr(VI) is known to passivate steel, as its reduction forms a Cr(III) oxide/hydroxide film (eq. 10) (Brasher & Mercer, 1965)(Brasher & Mercer, 1965) on the cathode in chlorate cells (Tilak & Chen, 1999)(Tilak & Chen, 1999). This helps slow the corrosion of the electrodes down, thus resulting in savings and reduced contamination of the sodium chlorate product by iron compounds.

2- + - 3+ Cr2O7 + 14H + 6e ⇄ 2Cr + 7H2O (10)

The purity of the sodium chlorate product is important when it is used to generate ClO2 from sodium chlorate for bleaching. The higher purity sodium chlorate that is obtained when SD is used in the electrolyte has superior performance and is thus preferable for consequent internal use of sodium chlorate.

Iron oxides may also cause short-circuits and poor electrolyte circulation due to obstruction in the narrow (2-4 mm) electrode gaps. However, a benefit of this corrosion phenomenon is that the surface is continuously renewed, thereby removing deposits consisting of mainly calcium and magnesium compounds (Cornell, 2002)(Cornell, 2002)4.

Function 4: Increase of the overall efficiency and energy efficiency of the chlorate process

Suppression of parasitic reactions at the cathode

The main reaction on the cathode is hydrogen evolution from water, eq. 11. Two important side reactions are the reduction of hypochlorite and of chlorate, eqs. 12 and 13. These compete with the chemical (eqs. 2 and 3) and electrochemical reactions of hypochlorite and chlorate (eq. 4) (Cornell, 2002)(Cornell, 2002).

- - 2H2O + 2e  H2 + 2OH (11) - - - - ClO + H2O + 2e ⇄ Cl + 2OH (12) - - - - ClO3 + 3H2O + 6e ⇄ Cl + 6OH (13)

The reduction of hypochlorite and chlorate ions on the cathode by parasitic reactions may cause a lowered current efficiency, thus leading to increased energy consumption.

Additions of SD to the electrolyte have long been known to suppress reactions (12) and (13). A thin film, less than 10 nm thick, of chromium hydroxide, Cr(OH)3·xH2O is formed by reduction of Cr(VI) during cathodic polarisation (see eq. 8). Cornell (2002)(2002) has documented that the film electrochemically hinders the reduction of hypochlorite and chlorate; on the other hand, the hydrogen evolution reaction can still take place on the cathode after SD addition. During cathodic polarisation, the film grows at a rate that decreases with time until a final film thickness is reached. Thus, the film

4 Typically, salt contains sulphate and it accumulates in the cell solution. When the sulphate level becomes high enough, a part of the cell solution is taken out of the process circuit and sulphate is precipitated by 2+ 2- calcium salts (batch process): Ca + SO4  CaSO4(s). The precipitate is settled and filtered out. This calcium sulphate “cake” may contain small amounts of SD. The second step of the process is to remove excess Ca by 2+ 2- precipitating it out by sodium carbonate. Ca + CO3  CaCO3(s). This precipitate is also filtered out of system. The amount of calcium sulphate (and calcium carbonate) formed depends on salt quality. In the case of SCB, however, no salt is fed to the cell, as the raw material is HCl obtained by synthesis of Cl2 and H2, partly in the existing chloro-alkali plant, partly in the dedicated synthesis using chlorine and hydrogen by- produced by the chlorite plant itself. So, sulphate accumulation cannot occur.

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 18 inhibits not only the reduction of hypochlorite and chlorate but also limits its own growth (Cornell, 2002)(Cornell, 2002).

- The Cr(III) film acts as a temporary diaphragm that is permeable to H2 and OH but prevents access of hypochlorite ions to the cathode. As hypochlorite is less available to the cathode surface, its electrochemical reduction (eq. 12) is hindered. Notably, this diaphragm is present only during production i.e. when the electrolysis current is on. It is oxidised immediately to SD after the electrolysis current is stopped by the active chlorine species present in the electrolyte.

Another important cause of lowered current efficiency is oxygen production, as discussed earlier. Oxygen production normally results in <2.5% oxygen content in hydrogen. By control and optimisation of the process parameters, including the addition of SD as described above, the production of oxygen can be minimised (IPPC, 2007) (IPPC, 2007) resulting in increased current efficiency and reducing safety risks.

Energy consumption at a sodium chlorate plant

Usually, in a production plant, the chlorate cells are operated in the cell voltage range 2.75 – 3.6 V at an average current efficiency of 95% (IPPC, 2007)(IPPC, 2007)5. Energy consumption is directly proportional to the voltage and inversely proportional to the current efficiency (IPPC, 2007)(IPPC, 2007). From a historical perspective, it is possible to say that the energy consumption of chlorate manufacture decreased to one-third during a little more than 100 years. The first sodium chlorate plant started 1886 and the energy consumption was 15,000 kWh/t of crystallised product. In addition to the electrical energy requirement for electrolysis, additional energy is required to drive other plant equipment such as pumps, compressors and centrifuges amongst other operations. This can contribute significantly to the total energy requirement. With modern technology, the total consumption of electrical energy is 5,000 – 6,000 kWh/t of crystal product. Typical ranges of energy consumption for electrolysis and ancillary equipment are shown in Table 2-2.

Table 2-2: Electricity consumption parameters in a chlorate plant (according to BREF) Parameter Typical ranges Electrical energy use for electrolysis 4,700-5,200 kWh/t chlorate Electrical energy use for other electrical equipment (pumps, compressors, 100-500 kWh/t chlorate etc.) Total energy use 5,000-6,000 kWh/t chlorate Source: BREF (IPPC, 2007) (IPPC, 2007)

Finally, energy consumption can also be controlled by controlling the impurities in the salt (NaCl). These impurities can ‘blind’ both the anode and cathode surface and deactivate the anode. Efficient brine purification is, therefore, important even if it generates an increased amount of solid waste (IPPC, 2007)(IPPC, 2007).

Conclusion

Overall, the beneficial action of the SD can be summarised in Table 2-3.

5 The IPPC (2007) quotes a range of 2.75 – 3.6 V and 2.6 – 3.5 V. To ensure consistency in the analysis, this AoA will use the latter range and 3.1 V as a mid-range cell voltage value.

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 19 Table 2-3: Important roles of sodium dichromate in the chlorate process Action Effect Reaction with H+ and OH- (pH Formation of Cr(III) on the buffering) cathode Improvement of current energy Controlling the evolution of O2 Cr(III) film prevents competing efficiency and thus of yield and reduces the consumption of parasitic reactions at the cathode reduction in operating costs energy Improvement of safety of process Controlling the evolution of O2 and Cl2 and explosive mixtures Protection of anode Controlling the evolution of O2 provides corrosion protection Protection of cathode Cr(III) passivates steel and protects it from corrosion Improvement of sodium chlorate Avoidance of corrosion prevents product quality contamination of the chlorate product by iron compounds Improvement of chlorine dioxide Prevention of contamination of product quality chlorate product ensures high quality ClO2 product in downstream use

2.3 Production of sodium chlorite

2.3.1 Description and electrochemical reactions

The section above describes the role of SD in the production of sodium chlorate. SCB’s electrolytic production of sodium chlorate is devoted to the production of sodium chlorite through the generation of chlorine dioxide at the gaseous state. In the sodium chlorate plant, sodium chlorate is produced by electrolysis of NaCl. The solution in exit has a concentration of about 500 g/L. This solution also contains 4 - 5 g SD/L and is sent to the sodium chlorite plant where chlorine dioxide gas is coproduced with chlorine by reaction of sodium chlorate with hydrochloric acid. The gases (chlorine dioxide and chlorine) are separated by exploiting their different solubility in water.

While the separated chlorine is used (without storage) to produce hydrochloric acid solution which is feed to the chlorine dioxide generator together with fresh hydrochloric acid, chlorine dioxide is reduced to sodium chlorite in the presence of hydrogen peroxide and NaOH. The obtained sodium chlorite solution is further diluted to 31 or 25% (w/w) that are the typical concentrations at which the product is sold on the market.

Chromium remains in the solution of chlorate/hydrochloric acid. This solution is fed to the sodium chlorate plant. In this way, the cycle between the two plants is closed.

The equations below describe the conversion of sodium chlorate into chlorine dioxide gas and then sodium chlorite (Hoist, 1950)(Hoist, 1950):

NaClO3 + 2HCl  ClO2 + 0.5Cl2 + H2O + NaCl (14)

2ClO2 + 2NaOH + H2O2  2NaClO2 + 2H2O + O2 (15)

In the above process, the sodium chlorate is converted into gaseous chlorine dioxide and chlorine (equations 14 and 15), leaving all SD in the depleted brine solution. As noted above, the brine is recirculated back into the chlorate process (along with any chromium) while the chlorine dioxide is absorbed into a solution of sodium hydroxide and reduced to sodium chlorite by hydrogen peroxide (equation 15). The chlorine in gaseous phase is used to produce hydrochloric acid solution which is

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 20 feed to the chlorine dioxide generator together with fresh hydrochloric acid. The sodium chlorite is then free of Cr(VI) residues and it is this product that the applicant sells to customers.

2.3.2 The role of sodium dichromate

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''''''' ''' ''' ''' ''''''''''''''''' '''' ''''''''' '''''''''''#A#'''''' '''''''''''''''''' ''''''''''''''' '''' ''''''''''''''''''' ''''''' '''''''''''''''' '''' ''''' '''' ''''''''''' ''''''''''''' '''''' '''''' ''''''''''''''''' ''''' '''''' ''''''''''''' ''''''''''''' '''''''''''''''''' 2.4 Conditions of use and technical feasibility criteria

2.4.1 Approach to information collection and overview of technical feasibility criteria

The development of technical feasibility criteria for SD and its alternatives has been based on a combination of consultation between the independent third party that has authored this AoA and the applicants, and the review of available scientific literature.

Through the use of a detailed written questionnaire (disseminated in December 2012), Caffaro and other applicant companies belonging to the SDAC, were asked to provide details of the (ideally) measurable, quantifiable technical performance criteria which SD (or the SD-based technology) meets and that any alternatives (substances and technologies) would also need to meet before they are seriously considered as replacements. These criteria could relate to issues of molecular structure, solubility, transformation products, product purity, energy consumption, etc. anything that is relevant and important to the process in which SD is used and the roles it plays in that process.

In parallel, scientific literature delving into the parameters of the chlorate process and the assessment of the technical suitability of specific alternative technologies was collected and analysed (with the assistance of the applicants) and has been incorporated into the analysis. The role of SD in meeting the four main tasks in the production of sodium chlorate has been described above in Section 2.2.2.

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 21 The technical feasibility criteria that shall be used in the assessment of the technical feasibility of selected alternatives are as follows.

 Formation of protective film that is permeable to hydrogen and impermeable to hypochlorite  Control of oxygen formation  Cathode protection  pH buffering  Current efficiency and energy consumption  Solubility in electrolyte  Impurities control.

The discussion below explains the relevance and importance of the criteria for the chlorate process and presents in more detail the threshold values (or ranges) that will be used in Section 4 for the comparison of alternatives to SD. These criteria remain relevant for the use of SD by SCB.

2.4.2 Formation of protective film permeable to hydrogen

Importance of the technical criterion

As explained earlier, SD acts to limit side reactions, which themselves limit the achievable process efficiency (both electrical and chemical) and can cause potential safety concerns due to the formation of oxygen. During the chlorate production process, SD, a source of Cr(VI), is reduced to Cr(III) by cathodic polarisation (Cornell, 2002)(Cornell, 2002). The equation for the reduction from Cr(VI) to Cr(III) can be found in section 2.1.2, equation 10. This Cr(III) is present only during production i.e. when the electrolysis current is on as it is oxidised immediately to SD if the electrolysis current is stopped due to the presence of hypochlorite. This less than 10 nm thick Cr(III) hydroxide film on the - cathode acts as a temporary diaphragm that is permeable to H2 and OH , but prevents hypochlorite ions from accessing the cathode (Ahlberg Tidblad & Lindberg, 1991)(Ahlberg Tidblad & Lindberg, 1991). This hinders the electrochemical reduction of hypochlorite and chlorate, yet allows for hydrogen evolution (Lindbergh & Simonsson, 1991)(Lindbergh & Simonsson, 1991) that is an inherent by-product of the process. The hydrogen evolution equation is:

+ - 2H + 2e  H2 (17)

- - - - ClO3 + 3H2O + 6e  Cl +6OH (18)

On the other hand, in relation to hypochlorite, as stated above, the Cr(III) hydroxide film on the cathode effectively hinders the undesired hypochlorite and chlorate reductions, while still allowing for the required hydrogen evolution reaction to occur (Lindbergh & Simonsson, 1991)(Lindbergh & Simonsson, 1991). This is important because it allows for an increase of production and current efficiency, and minimises cathode corrosion. For this effect to take place, as well as the limiting of oxygen production at the anode, the concentration of SD should be a minimum of 3 g/L. Hindering hypochlorite reductions (eq 19) is also important in controlling the rate of oxygen formation reactions (see below, eq 20). (Cornell, 2002)(Cornell, 2002).

- - - - ClO + H2O + 2e  Cl + 2OH (19)

Threshold value

There is no suitable threshold value that can be used in the comparison of alternatives to SD. A thin, permeable, film must be generated by any alternative substance or technology, in a fashion similar to the film generated in the presence of >3 g/L SD in the electrolyte.

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 22 2.4.3 Solubility in electrolyte

Importance of the technical criterion

SD is very soluble, with a water solubility of 2355 g/L at 20 °C (Munn, et al., 2005)(Munn, et al., 2005). SD’s solubility allows it to be present in solution in the electrolyte and thus be reduced to Cr(III) on the cathode. An insoluble substance limits the rate at which it is able to partake in reactions with other species in solution and thus its ability to act as an effective pH buffer is drastically reduced. Furthermore, insoluble particles contribute to sludge and may interfere with the flow of electrolytes and product solutions during the process6.

Threshold value

No specific threshold can be set; in general, the solubility of any alternative substance must be as high as possible.

2.4.4 pH buffering and control of oxygen formation

Importance of the technical criterion

One of SD’s key uses is as a pH buffer and equations 8 and 9, under section 2.1.2, illustrate how SD acts as one. The buffering of the pH allows for many SD benefits as it facilitates corrosion inhibition, oxygen evolution control, and maximisation of current efficiency. Without effective buffering, pH- influenced reaction inefficiencies would increase; a decrease in pH would result in more chlorine being formed, and, an increase would result in more oxygen being formed. Electrochemically produced oxygen in a chlorate cell may be detrimental to the anode, limiting the coating lifetime (Cornell, 2002)(Cornell, 2002). Additionally, chlorine and oxygen gases would contaminate the hydrogen gas co-product and might not only decrease its value (if used as a raw material for later syntheses or sold) but also decrease process safety (as discussed elsewhere). Therefore, it is very important to maintain the optimum pH to maximise the electrolytic cell efficiency and ensure the safety of the plant (Tilak & Chen, 1999)(Tilak & Chen, 1999). Finally, unfavourable pH may also result in undesired precipitation of compounds in the electrolyte (Hedenstedt & Edvinsson-Albers, 2012)(Hedenstedt & Edvinsson- Albers, 2012).

There are several possible side reactions leading to the formation of oxygen, and the selectivity for oxygen formation depends on several factors: the concentration of hypochlorite, the current density, the chloride concentration, the temperature, and on the anode coating (Cornell, 2002) (Cornell, 2002). Hypochlorite is an important source for oxygen in chlorate electrolysis, and can form oxygen via a number of reactions (eq 20 and 21):

- - 2ClO  O2 + 2Cl (20)

- + - - ClO + H2O  2H + Cl + O2 + 2e (21)

Without hypochlorite, and at potentials lower than the reversible potential for chlorine evolution, oxygen evolution from water discharge is the main reaction (eq 7, see Section 2.2.1), and is an electrochemical reaction (Cornell, 2002)(Cornell, 2002). However, it has been pointed out that there are difficulties in separating the different contributions that generate oxygen (Nylén, 2006)(Nylén, 2006).

6 e.g. the reason for the removal of cathode corrosion sludges is in part due to their insolubility.

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 23 These processes occur at the anode and thus the Cr(III) film that is formed at the cathode does not limit these reactions. However, SD is still important in minimising these reactions due to its pH buffering properties and because when the other side-reactions are limited, there is less HClO/ClO- available to decompose into oxygen.

Threshold value

According to the literature, the pH is kept between 6.0 and 6.5 to minimise anodic oxygen formation (Cornell, 2002) (Cornell, 2002). The acidic anode surface not only suppresses oxygen evolution, but also favours chloride oxidation. Having the pH more acidic would suppress oxygen evolution further, but would also decrease the rate of chlorate-producing reactions (Nylén, 2006)(Nylén, 2006). Importantly, a minimum SD concentration of >3 g/L in the solution is required to hold the pH in the range of 6.0 to 6.5 and below this value SD begins to fail as a pH buffer.

According to the relevant BREF Document, under the conditions used in the sodium chlorate industry, a 2-2.5% oxygen content in hydrogen can be achieved. The explosive limits of H2 in O2 are 4.65% the lower and 93.9% the upper (Li, et al., 2007)(Li, et al., 2007). From an applicant-specific perspective, the safety limit for oxygen in hydrogen is 4.0% to avoid explosions. Therefore, while the concentration of O2 should ideally be below 2.5% (to be on par with SD), 4.0% is the safety limit which an alternative must not exceed at the applicant’s plant.

2.4.5 Cathode protection

Importance of the technical criterion

The Cr(III) hydroxide film that forms on the cathode in chlorate cells passivates the steel, and slows the corrosion of the electrodes which occurs at shutdown in the presence of hypochlorite. As has been mentioned before, this effect limits the side reactions that reduce process efficiency but it also has other beneficial effects. It also reduces contamination of the sodium chlorate product and reduces cost by decreasing the time required for maintenance of the equipment. The corrosion of steel cathodes produces sludge (e.g. iron oxides) over time and these must be periodically removed. The greater the rate of corrosion, the more often this process must be carried out. Maintaining an effective concentration of SD in the system helps prolong the time between maintenance; the operating limit for the concentration of SD required for the prevention of corrosion is a minimum of 3 g/L. Below this value, cathodic corrosion in the presence of hypochlorous acid will occur at an increased rate (Speight, 2002)(Speight, 2002).

Threshold value

No threshold for the degree of tolerable corrosion has been set. However, sodium chlorate manufacturers may have a minimum acceptable lifetime of a single cathode that may be company specific. This can be assumed to be 8-16 years based on experience. For the applicant, the lifetime of current cathodes while employing SD is expected to be ''' '''''''''' '''''''''' ' '#A#'' '''' ''''''' '''''''' '''''' ''''''''''''''''. This applicant value can be used to establish technical feasibility at a minimum.

2.4.6 Current efficiency and energy consumption

Importance of the technical criterion

The presence of SD limits electrochemical side reactions that consume electrical energy and, thus, decrease the overall process efficiency. This has been described by the criteria above but the current efficiency and energy consumption of the process are important measures that are critical to both the technical and economic feasibility of the process. As electrical energy represents the largest part of

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 24 the overall cost of sodium chlorate manufacture, maintaining a high current efficiency is of paramount importance. Theoretically, the amount of electrical charge required to produce a tonne of sodium chlorate is 1511 A.h per kg of chlorate7. However, the efficiency of any process is not 100% and thus the actual energy required is greater. Cell current efficiency is a function of the cell operating characteristics and cell design. Cell operating characteristics include flow rate, pH, and temperature, for example. Generally, cell current efficiencies in the range of 93-96% can be achieved using metal electrodes (Tilak & Chen, 1999)(Tilak & Chen, 1999). The overall energy consumption of a chlorate cell is in-turn a function of current efficiency and cell voltage (Tilak & Chen, 1999)(Tilak & Chen, 1999):

P = 1511E / (ԑ/100) (22)

Where P is energy consumption (kWh/tonne), ԑ is the current efficiency (%), and E is cell voltage (volts). As can be seen, the energy consumption is inversely proportional to the current efficiency (IPPC, 2007)(IPPC, 2007).

As stated in Table 2-1, a typical operating voltage for a cell is between 2.6-3.5 V. Assuming a voltage of 3.1 V and a cell efficiency of 90% would predict an energy consumption of 5,204 kWh/tonne of chlorate compared to a 4,930 kWh/tonne if the cell was 95% efficient. This is a potential saving of ca. 274 kWh/tonne if a high efficiency can be achieved with a concomitant reduction in the release of greenhouse gases.

SD must be maintained in the range of 3-6.5 g/L of electrolyte and in this range, the efficiency of the process is acceptable8; above that range, no benefit may be apparent and, in fact, a higher concentration may hinder the electrical efficiency of the anode (Cornell, 2002)(Cornell, 2002). Thus, it is beneficial for the process to keep the SD concentration as low as possible while still enabling the performance of its other tasks (e.g. pH buffering, corrosion inhibition).

In addition to the electrical power consumed by the electrolysis cell, a smaller amount of additional energy is required to run ancillary equipment such as pumps, mixers and centrifuges to prepare and transport electrolyte as well as to recover the chlorate product (IPPC, 2007)(IPPC, 2007). The mid- range value for electricity consumption of other electrical equipment is assumed to be 300 kWh/tonne bringing the total theoretical energy consumption at 95% cell efficiency to 5,230 kWh/tonne chlorate when using SD.

Threshold value

The minimum acceptable current efficiency or power consumption values for the applicant may differ to those of other manufacturers of sodium chlorate depending on the specific production parameters of each plant. Specific information from the applicant is considered confidential. Taking into account what is shown in the relevant BREF Document, the following threshold values will be considered in this analysis.

7 Equation 6 shows the overall reaction for the production of NaClO3. This reaction requires 6 electrons per chlorate atom produced or 6 Faradays (160.8 A.h/mol) per mol of chlorate or 1510.8 A.h/kg.

8 In some references, slightly different SD concentration ranges are quoted. To ensure consistency in the analysis, this range will be used to represent typical chlorate manufacture conditions.

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 25 Table 2-4: Energy efficiency and consumption thresholds for potential alternatives for SD Applicant-specific thresholds Parameter Literature thresholds used in this analysis Minimum energy efficiency Minimum: 90% #A#''''' Ideal: >95% Maximum energy 5,700 kWh/t chlorate (see Table 2-2) ''''''''''' ''#A#'''''''''''' consumption * For Caffaro, the electrolysis process requires ''''''''''' ''''''''''''' ''''''''''''''#A#''' ''''''''''' '''''' '''''''' ''''''' '''''''''''''' '''' '''''''' ''''''''''''' ''''' ''''''''''''''' ''''''''' ''''''''''''''' '''''''''''' ''''''' '''''''''''''''''''''''. It is assumed that the same will apply for SCB.

2.4.7 Control of impurities

Importance of the technical criterion

Because SCB does not sell sodium chlorate on the market and does not crystallise sodium chlorate but rather uses the electrolytic sodium chlorate aqueous solution (as is) as an intermediate for the production of sodium chlorite, the purity of the solid sodium chlorate is not of fundamental importance to the applicant or their clients. On the other hand, the presence of impurities in the aqueous chlorate solution may affect the efficiency of the gaseous ClO2 generation reaction. '''''''''''''''''''' '''' ''''''' ''''''''''''''''''' ''''''' ''''''''''''''''''' '''''''''''''' '''' ''''''''''''''''' ''''' ''''''''''''''''''''' '''''''''''' '''' ''''''''' ''''''''''''' '''''' '''''''''''''''' '''' ''''''''''''''''' '''''''''''''' ''''''''''' ''''' '''#A#'''''''''''''''''''' ''''''''' ''''''''''''''''''''''''''''' ''''''''' ''''''' '''''''''''''' '''''''''''' '''''''''''''''''''''''' ''''''' ''''''''' ''''''''''''''''' '''''' '''''''''''''''''''' '''''''''''''' '''' '''''' ''''''''''''' ''''''''''''''' ''''''''''''''''' ''''''''''''''' '''''''''''''' ''''''' '''' ''''''' '''''''''''''''' '''''''''''''' ''''''''''''''''' ''''''''' '''' ''' ''''''''''''' '''' '''''' ''''''''''''''' '''''''''''''' '''''''''''''''''''' ''''''''''''''''''' ''''' '''''' ''''''''''''''''' '''' ''' '''''''''''' ''''''' ''''''''''''''''' ''''''''''' ''''''''''''''' '''''''' '''' '''''''''''''''''' '''''' '''''''''''''''''' '''' ''''''''''''''''''''' '''' '''''' '''''''''''''' '''''''''''''' '''' ''''''' ''''''' ''' '''''''' '''''''''''''' '''''''''''''''''''''.

Threshold value

Each impurity has to be considered separately. With alternatives to SD, one particularly needs to consider risks for the ClO2 process from the presence of metals even at the ppm level'' '''''' ''''''' '''''''''''''''' '''' '''''''''''''''''' ''''''' ''''''''' '''' ''''''''''''''''' #A#'''''' '''''''''''''''' '''''''''''''''' ''''''''''''''' ''''''''''' ''''''''''''''' ''''''' '''''''''' ''''''''''''''''''' '''''''''''' ''''''' '''''''''''' ''''''''' '''''''' '''' '''''''''''''''''''' ''''''' ''''''''''''''''' '''''''''''' ''''''''' ''''' '''''''''''''''

2.4.8 Summary of technical feasibility criteria

Table 2-5 summarises the analysis presented above on the technical feasibility criteria that will be used for the assessment of the technical feasibility of alternatives to SD. Where SCB-relevant information, which is taken directly from Caffaro data, diverges from the literature values, the former is provided instead, but it is confidential.

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 26 Table 2-5: Summary of technical performance criteria of sodium dichromate Primary relevance SD and Chlorate Relevant threshold Technical criteria replacement process and value or ideal Notes substances quality of range chlorate output Formation of protective  No specific A sufficiently robust film that is permeable threshold can be diaphragm should be to hydrogen and identified deposited to prevent impermeable to parasitic reactions hypochlorite Solubility in electrolyte  Highly soluble – as Solubility of SD: high as possible ca. 2355 g/L pH buffering and   pH: 6.0 to 6.5 This links to the control of oxygen O2: ideally, less presence of a formation than 2.5% by minimum of 3 g/L volume of O2 in H2 Cr(VI) in the electrolyte with a maximum of 4% Cathode protection   Minimum cathode lifetime ' '#A# ''''' Current efficiency and  Energy efficiency: Threshold values may energy consumption '''''#A#''' or more vary by chlorate plant Total energy consumption (electrolysis and auxiliaries): ''#A#' kWh/t chlorate or less Control of impurities in  '''''' '''''''''' '''''''' '''''''' the NaClO3 solution in '''''''' '#A#'''''''''' ''''''' exit from the ''''''''''''''''''''' '''''''''''' electrolytic cell and in ''''''''' ''''''''''''''' entrance into the ClO2 '''''''''''''''' generator

2.5 Summary of functionality of sodium dichromate in the “Applied for Use”

The information in the preceding parts of Section 2 are summarised in the Table 2-6 below.

Table 2-6: Parameters for SD use in sodium chlorate manufacture used as an intermediate for the production of sodium chlorite and assessment of alternatives Functional aspect Explanation - Tasks performed by pH buffer for the electrolyte, to maintain process parameters to ensure rate of ClO3 the substance forming reactions remains feasible Suppression of oxygen evolution to prevent formation of explosive atmospheres Cathode protection to minimise maintenance costs and to maintain product purity Maintain current efficiency to ensure economic feasibility Physical form of the SD is purchased by the applicant in solution form to minimise (to the extent possible) product worker exposure from handling solid SD. SD is added as an aqueous solution (60- w 70% /w)

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 27 Table 2-6: Parameters for SD use in sodium chlorate manufacture used as an intermediate for the production of sodium chlorite and assessment of alternatives Functional aspect Explanation Concentration of the SD is present in the sodium chlorate aqueous solution used as intermediate at a level substance in the of about 4-5 g/L. marketed product Sodium chlorate is subsequently converted to chlorine dioxide and finally to sodium chlorite. '''''''' ''''''#A#'''''''''' '''' '''''' '''''''''' '''''''''''''''' ''''''' ''''''''''''''' '''''''''''''''' ''''''''''''''' ''''''''''''''''. During this step, SD remains in solution while chlorine dioxide is stripped in a gaseous phase as described in Section 2.3.1. In the final product sodium chlorite sold to the market the concentration of total chromium is well within the limits defined for Type 1 in the EN 938 (2009) (Chemicals used for treatment of water intended for human consumption – Sodium Chlorite) Critical properties and Ability to form a protective film, which is permeable to hydrogen and quality criteria the impermeable to hypochlorite – this suppresses the side (parasitic) reactions. If substance must fulfil these side reactions take place, they will limit the evolution of hydrogen, reduce current efficiency and result in increased oxygen concentration which can lead to explosion through mixtures with hydrogen Solubility in electrolyte – must be highly soluble and must not interfere with process and increase need for sludge removal pH buffering and control of oxygen formation- must provide a stable pH which ensures corrosion inhibition, oxygen evolution control, and maximisation of the efficiency of the process Cathode protection (corrosion inhibition) – must limit frequency of maintenance of cathodes and sludge removal Current efficiency and energy consumption – must maintain high current efficiency and low energy consumption, to ensure the economic viability of the process (energy is the largest production cost component) Control of impurities – ''''''''''' '''''' '''''#A#'''''''''' '''''''''''''''''' ''' '''''' ''''''''''''''''' ''''''''''''''' '''''''''''' '''''''' '''''''''''' ''''''' '''''''''''''''' '''' ''''''' ''''''''''''''' '''''''''''''' '''''''''''''''''''' Frequency of SD is added to the process periodically when process monitoring indicates that its substance use and concentration needs to be adjusted. Typically, this occurs a few times a year as usage quantities indicated in the CSR. Small amounts of SD are lost during the process, requiring the addition of ca. '''''''''''' ''''''''#A#''' ''''' '''''''' of sodium chlorate product. The total tonnage of SD used by the applicant is 1-10 tonnes per year based on anhydrous SD (see further detail in Section 3.1) Process and Process pH Typically, between pH 6-6.5. performance and O2 Ideally less than 2.5% O2 in H2 by volume with 4% as a safety limit constraints generation for the applicant concerning the use of Acceptable Minimum ''' '#A#''''' for the applicant the substance cathode lifetime Energy For the applicant, ''''''#A#'''''''''''' chlorate or less with energy consumption efficiency ''#A#'''' and above and efficiency Concentration The concentration of SD in the electrolyte and an ideal range of in electrolyte concentrations has been established, 3-6.5 g/L. Below that range, SD cannot perform its intended tasks (energy consumption increases affecting the economics of the process, pH is not buffered sufficiently this making the process unstable, corrosion phenomena increase). Above the ideal range, no discernible benefit may arise. Impurities Each impurity has to be considered separately due to its variable effect on the reactions the chlorate will participate in' ''''' ''''''''''' ''''''''' '''''''' ''''''''' '''''''''' '''''''''''''''#A#'''''''''''' ''''' '''''''''''''''''''' ''''''' '''''''' '''''''''''' ''''''''''''' '''' ''''''' ''''''''''''' '''''''''''''' '''' ''''''' '''''''''''''''' '''''''' ''''''' '''''''''''''''''''''

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 28 Table 2-6: Parameters for SD use in sodium chlorate manufacture used as an intermediate for the production of sodium chlorite and assessment of alternatives Functional aspect Explanation Current 1-3 kA/m2 density Temperature Process temperatures may vary and are confidential but typically in the region of 60-90 °C Conditions under The use of SD fulfils many roles and if it were to be eliminated, alternative methods which the use of the of controlling pH, corrosion and process efficiency would need to be found in order substance could be to have a feasible process without the use of SD. Without a way of fulfilling these eliminated roles, the use of SD cannot be eliminated, as the chlorate production process would become too inefficient, thus uneconomical Customer Not relevant for the applicant, as the product sold to customers is sodium chlorite. requirements In the final sodium chlorite product sold on the market the concentration of total associated with the chromium is well within the limits defined for Type 1 in the EN 938 (2009) (Chemicals use of the substance used for treatment of water intended for human consumption – Sodium Chlorite) Industry sector and No industry sector or legal requirements that require the use of SD apply legal requirements for technical acceptability that must be met

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 29 Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 30 3 Annual tonnage

3.1 Tonnage band

Confidential annual tonnage (anticipated): ''' ''''##C#C#''''''' of SD anhydrous (maximum).

Annual tonnage band: 0.1 - 2 tonnes of SD per year based on anhydrous SD.

This tonnage is very low compared to the overall tonnage registered: ECHA’s Dissemination Portal9 indicates that the substance registration was updated in December 2018 and it is now registered at the 100-1000 t/y band. The CSR also explains the use of predominantly closed loop systems to reduce releases of and exposure to chromates during the manufacture of sodium chlorate. 3.2 Trends in the consumption of sodium dichromate

Taking into account the aforementioned consumption in recent years, the applicant assumes stable consumption in the future. 3.3 Form and usage of sodium dichromate

During the chlorate production process, SD is dosed when required to keep a constant level in the electrolytic cell. The number of times that SD is added varies by production plant but generally takes place a few times per year and the quantities added are very small as described in the CSR. The addition is done to compensate for small losses deriving from the following processes:

1. Sludge formation from the filtration of the NaClO3 solution in exit from the electrolytic cell and from cleaning waters used during scheduled maintenance: this solid sludge is disposed of according to the Italian law.

2. SD losses during the etching operation in the NaClO3 electrolytic cells.

3. Accidental SD losses in the sewage treatment unit of the chlorite plant: this water treatment consists in closed vessels where water flows and is treated with sodium bisulphite (NaHSO3) and sodium hydroxide (NaOH) / hydrochloric acid (HCl), on the basis of sensors that can detect redox potential and pH values. The Cr(VI) in the resulting water will be below the maximum allowable value of 0.2 mg/L, as it has been reduced to Cr(III). The resulting treated water is then collected with the other waters coming from the whole factory; another pH correction is made before the discharge. The factory is authorised to the discharge into surface water by authorization n° DPC025/301 released on 24/09/2018 by the Regione of Abruzzo (Italian local authority for IPPC authorisation). For the new plant, SCB asked a new authorisation. The Services Conference (mainly participants Regione of Abruzzo and ARTA - Regional Environmental Protection Agency) of 13/11/2018 expressed a favourable opinion on the issue of the Integrated Environmental Authorisation for the sodium chlorite plant and we are waiting the definitive document.

9 Available at: http://echa.europa.eu/information-on-chemicals/registered-substances (accessed on 6 November 2013).

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 31 The limits, according to the Italian laws, to be respected at the dedicated sewage water treatment of the sodium chlorite waters are as follows: Total chromium ≤ 2 mg/L, Hexavalent chromium ≤ 0.2 mg/L.

w The substance is added in the form of solution, the concentration of which is typically 60-70% /w (as Na2Cr2O7·2H2O). The final concentration of SD in the chlorate cell is '''#A#''' g/L. According to the BREF Document for Large Volume Inorganic Chemicals (Solids), the dose rate for SD is 0.01-0.15 kg/tonne of sodium chlorate product (IPPC, 2007)(IPPC, 2007). Information from the applicant suggests that the consumption of SD is within this range at '''''''''''#C# '''' '''''' or less per tonne of sodium chlorate.

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 32 4 Identification of possible alternatives

4.1 List of possible alternatives

This AoA is an updated analysis of that presented in the Caffaro AfA. It evaluates a broad range of alternatives, as the SDAC applicants wished to demonstrate that very thorough research for the identification of suitable alternatives has been undertaken.

This section presents an assessment from a screening of the available information. The alternative substances and technologies presented in Table 4-1 were identified through literature research and industry consultation, and have been screened as, in principle, realistic potential alternatives for the replacement of SD and are further assessed in Section 4 of this AoA. Several other alternatives have been identified (see rest of Section 4) but were subsequently eliminated as infeasible and/or unsuitable.

Table 4-1: Shortlisted potential alternatives for the replacement of sodium dichromate Alternative substances Sodium molybdate Na2MoO4 Cathodic coatings based on metals Cathodes coated using Na2MoO4, FeCl3 (not present Molybdenum-based coatings in the electrolyte) Other technologies Two-compartment electrolytic cell systems

It must be noted that the use of SD in the manufacture of sodium chlorate is the current ‘state-of-the- art’ and is the only technology used for this purpose not only within the EU but also elsewhere in the world. As will be discussed, the above alternatives currently find no commercial use; indeed, EU- based chlorate producers are at the forefront of research for the development of low-Cr(VI) or Cr(VI)- free processes for the manufacture of sodium chlorate. 4.2 Description of efforts made to identify possible alternatives

4.2.1 Overview

This AoA document has been prepared by an independent third party. This section presents both the efforts made by the applicant’s group to research and develop alternatives and those by the independent third party to identify in the literature efforts by various stakeholders towards the development of alternatives.

4.2.2 Research and development by the applicants

Introduction

The process of chlorate manufacture is well understood and has been described extensively in the IPPC BREF - Best Available Techniques for the Manufacture of Large Volume Inorganic Chemicals (2007). The BREF describes the historic improvements that have been made to the chlorate process and highlights the importance of SD as a necessary additive, as well as the steps taken to reduce its use (recirculation and recycling of solutions) and minimise exposure.

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 33 The removal of SD and other Cr(VI) species from processes is and has been of high interest for many decades, but in spite of extensive research, an alternative that fulfils the role of SD in a manufacturing process environment has not been developed at the industrial scale. Instead, the trend has been to minimise the output of and worker exposure to chromium from the process and work towards a predominantly closed loop system.

Some members of the SDAC that Caffaro is a member of, have been actively involved in research and development. Several PhD projects and a number of published papers have been sponsored in part by SDAC companies. In addition to academic research, attempts to apply alternative technologies to the production of sodium chlorate have been made, including pilot production scale trials. Although the removal and reduction of the use of Cr(VI) has been an objective of these trials, they have not succeeded in completely removing its presence.

Past and current R&D activities of the applicant

The plant is not operational yet so past and current R&D activities are taken to be those of Caffaro. Neither SCB nor Caffaro have dedicated R&D staff or a pilot plant that could be used to test alternative substances. Thus, other than literature review, no R&D on alternatives to SD has been carried out exclusively by SCB or Caffaro. Literature data have been always monitored and extensively examined. Technical contacts with Caffaro’s technology and electrodes’ supplier have been continued in order to improve the performance and minimise the environmental impact of the new SCB plant’s processes but there are currently no valid alternatives at industrial level to substitute SD in the manufacture of sodium chlorate. '''''''' ''''' '''''' ''''''''''''''''''''' '''' ''''''' '''''''' '''' '''''' ''''''' ''''''' '''' '''''''' '''' ''''' ''''''''''''' '''''''''''''' '''''''''''''' ''''''' ''''''''''''''''''''''''' '''' '''''''''''' ''''''''''''''' ''''''''''#I# ''' ''''' '''''''' '''''''' ''''''''''''' '''' ''''''' ''''''''' '''''''''''' ''''''''''''''''''' '''''''''''''''''' '''' ''''''''''''''''''''''''' '''''''''''''''''''''' '''''''''''''''' '''' ''''''' ''''''''''''''''''''''''''''''''' '''''''''''''''' ''''''''' ''''''' ''''''' '''''''' ''''''''' '''''''''''''''''

Future R&D activities of the applicant

4.2.3 Literature searches

Introduction

This section of this SCB AoA includes both the literature searches undertaken for Caffaro and an updated literature search undertaken for this SCB AoA. The following paragraphs summarise information that is available in the scientific literature on efforts that have been made towards identifying and developing alternatives to SD and to SD-based chlorate cells. The tables provided below summarise the key findings of the identified literature sources. The updated information is presented in a table in section 4.2.3.2.

4.2.3.1 Original literature research

Alternative substances used as additives to the chlorate process

Alternative 1: In-situ generation of dichromate from trivalent chromium (chromium (III) chloride)

Patent applications have been published describing the use of trivalent chromium (Cr(III)) as a replacement of SD in the chlorate process. Two are the key sources of information:

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 34  A patent by Dobosz (1987), associated with Canadian interests  A patent application by Hedenstedt & Edvinsson-Albers (2012), associated with AkzoNobel (EKA).

A number of key points have been highlighted in this research:

 Engineering requirements: a separate vessel, for example a tank, for the in situ formation of Cr(VI) from a Cr(III) compound might be required

 pH levels: according to Hedenstedt & Edvinsson-Albers, Cr(III) can be oxidised to Cr(VI) by sodium chlorate and hypochlorite under acidic conditions and at elevated temperatures. On the other hand, Dobosz described the process as most effective at pH values between ca. 8 and ca. 10. Generally, its assumed that pH conditions similar to the applicant’s current operating conditions would be sufficient

 Chromate use and presence: Cr(VI) is formed in situ from the addition of a suitable Cr(III) compound. Such a compound is oxidised in a vessel to hexavalent chromium by means of hypochlorite, chlorine, chlorite or chlorate. Suitable Cr(III) substances that could be added include chromic chloride, chromic oxide and chromic hydroxide; CrCI3·6H2O has been suggested as a suitable option. The dosage of the Cr(III) compound could be similar to that of SD in the current conditions of use (2-6 SD equivalents per litre).

Overall, under the processes outlined by these patents and patent applications, Cr(VI) is still present the electrolyte but is not handled by the workers in the make-up and dosing of the electrolyte solution. This would reduce potential exposures of workers to Cr(VI). However, exposure to Cr(VI) would still result from other processes involving the electrolyte such as sampling/testing, cleaning and maintenance and washing of filter cakes. It is estimated that using a Cr(III) compound instead of SD would reduce exposure by approximately 20%.

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 35 Table 4-2: Research into the use of in-situ oxidation of Cr(III) Dobosz, 1987 Parameter Details Year 1987 Source (Dobosz, 1987)(Dobosz, 1987)- Patent Associated company/ Tenneco Canada Inc. research organisation Objective of research or - Developing a method for formation of Cr(VI) useful in the electrolysis of invention chlorides to form chlorates by reaction between a Cr(III) compound and hypochlorite present in an effluent from the chloride electrolysis. In this way, at least part of the hypochlorite ions are converted to harmless chloride ions while providing the needed Cr(VI) from readily-available trivalent chromium compounds. - The process of the invention can be used to effect treatment of the hypochlorous acid-containing condensate, to effect treatment of aqueous chlorate solution to achieve dehypoing (hypochlorite removal), or a combination depending on the hexavalent chromium ion requirement and the amount of oxidising agent available for oxidation. When the condensate is treated with Cr(III), the resulting deactivated condensate containing only chloride ions and chromate ions, then can be used in brine preparation for the cell Relevance to the chlorate High, but priority seems to have been the removal of hypochlorite rather than the process elimination of Cr(VI) for environmental/health reasons Key changes to current - Cr(III) substances that could be added include chromic chloride, chromic oxide chlorate process and and chromic hydroxide notable improvements and - The process may be effected over a wide range of pH but is most effective at pH shortcomings values are from ca. 8 to ca. 10. These pH conditions facilitate dissolution of the Cr(III) and oxidative conversion to Cr(VI). It is preferred to add sodium hydroxide or other suitable alkali to the condensate prior to reaction with the Cr(III) compound - Cr(III) is used to effect dehypoing in the tank to remove hypochlorite and again form Cr(VI) and chloride ions. The Cr(VI) ions so produced are recycled to the brine preparation tank with the mother liquor Presence of Cr(VI) in the Handling of Cr(VI): the invention demonstrates a manner of providing Cr(VI) for use electrolyte in the electrolytic production of chlorates which uses by-product hypochlorite from the chlorate production to oxidise Cr(III) to Cr(VI) Presence of Cr(VI) in electrolyte: Cr(VI) is still present as a result of the oxidation of Cr(III) to Cr(VI)

Table 4-3: : Research into the in-situ oxidation of Cr(III) – Hedenstedt & Edvinsson-Albers, 2012 Parameter Details Year 2012 Source (Hedenstedt & Edvinsson-Albers, 2012)(Hedenstedt & Edvinsson-Albers, 2012) - Patent Associated company/ AkzoNobel (EKA) research organisation Objective of research or - Development of a process of producing alkali metal chlorate in an electrolytic invention cell comprising an anode and a cathode, wherein substantially no hexavalent chromium is added to the process from an external source - Provision of an alternative compound entirely substituting or to a large extent substituting Cr(VI) compounds as raw material, while safeguarding a controlled supply of Cr(VI) in the cell electrolyte which is independent on the amount of for example hypochlorite in condensate streams - Provision of a process which facilitates production of alkali metal chlorate wherein Cr(VI) can be provided at an acidic pH whereby necessary pH adjustment can be reduced or eliminated Relevance to the chlorate Highly relevant process Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 36 Table 4-3: : Research into the in-situ oxidation of Cr(III) – Hedenstedt & Edvinsson-Albers, 2012 Parameter Details Key changes to current - At least one chromium compound having a valence lower than +6 may be added chlorate process and to at least one process stream containing either alkali metal chloride or alkali notable improvements and metal chlorate or to at least one process stream containing both alkali metal shortcomings chlorate and alkali metal chlorate - Formation of Cr(VI) is made by addition of a the chromium compound with a valence lower than +6 to for in a separate vessel, for example a tank, and oxidised in such vessel to hexavalent chromium (in-situ generation thereof), for example by means of hypochlorite, chlorine, chlorite, chlorate, etc. - Example dosage for the chromium compound having a valence lower than +6 is 2 to about 6 g (calculated as SD equivalents)/L electrolyte solution or from ca. 2 to ca. 20 g chromium/t produced chlorate - Chromium compounds having a valence lower than +6 may be for example chromium halides such as chromium(III) chloride, chromium(III)chloride hexahydrate, and several others, or their mixtures - The examples shown in the patent utilise chromium trichloride hexahydrate (CrCl3·6H2O) - The chromium compounds can for example be added as salts, aqueous solutions or as melts if the melting point is sufficiently low, for example chromium trichloride hexahydrate having a melting point of 83 °C - it can be concluded that CrCI3·6H2O crystals can be easily dissolved and that pH is reduced on dissolution of acidic CrCI3·6H2O. Precipitation occurred close to neutral pH and in weakly alkaline solutions, presumably due to formation of Cr(OH)3(s) or CrO2(s). Sodium chlorate was found to oxidize Cr(III) to Cr(VI) under acidic conditions and at elevated temperatures. Sodium hypochlorite can oxidise Cr(III) to Cr(VI) in strongly alkaline solutions and down to to at least pH 5 or below pH 5. Hypochlorite can even dissolve precipitations formed in neutral solutions and oxidise chromium with a valence lower than +6 to hexavalent state - the molar ratio of hexavalent chromium to chromium having a valence lower than +6 ranges from about 0:10000 to about 1:10000 Presence of Cr(VI) in the Handling of Cr(VI): several examples do not involve Cr(VI), some do electrolyte Presence of Cr(VI) in electrolyte: Cr(VI) always present as a result of oxidation

Alternative 2: Sodium molybdate

Sodium molybdate (Na2MoO4 or its dihydrate Na2MoO4·2H2O) or the Mo(VI) oxide have been proposed as an alternative to SD in the chlorate process. Key sources of information in the open literature include:

 A journal article by Li et al (2007), associated with Canadian interests  A patent by Rosvall et al (2010), associated with AkzoNobel (EKA)  A thesis and journal articles by Gustafsson and colleagues in 2012, associated with the Royal Technical Institute (KTH) of Stockholm and AkzoNobel (EKA).

A number of key points have been highlighted in this research:

 Oxygen evolution: sodium molybdate interferes with the anodic reactions and results in the release of significant volumes of oxygen, even when used at low concentrations. In the work of Li et al, the measured off-gas O2 level was observed to be high and the H2 explosive upper limit (4.8%) was nearly reached. In the Rosvall et al patent, additions of MoO3 as low as 1-10 mg/L led to oxygen release in excess of 3.5% and in some cases well above 4% (Li et al used a concentration of Na2MoO4 of 8 g/L). There is a clear need for adding as little Mo(VI) as possible;

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 37  Buffering: according to Li et al, SD has a better buffer “fit” for the chlorate reaction and Gustafsson et al assert that, to fully replace Cr(VI) or significantly lower the Mo(VI) concentration in the electrolyte, a buffer agent such as phosphate will be needed. Investigation of the films formed on the cathode by co-additions of molybdate and phosphate showed that the molybdenum-containing cathode films became thinner if the electrolyte also contained phosphate during the film build-up. With 80 mM molybdate in the electrolyte a cracked film was formed on the cathode surface. The cathode film that was formed in presence of both molybdate and phosphate looked similar but was thinner, yet the activation of hydrogen evolution was still as effective. If the amount of molybdate was low (4 mM) and the electrolyte also contained between 10 and 40 mM phosphate, no molybdenum film was visible with Scanning Electron Microscopy (SEM) or detectable with Energy-dispersive X-ray spectroscopy (EDX) on the cathode surface. This may be due to competitive adsorption of molybdate and phosphate, where the higher molybdate concentration is necessary for the molybdate to be favoured. Addition of molybdate was found to activate the hydrogen evolution reaction even when no film could be detected, suggesting that a catalytic film was formed which then dissolved, detached or was too thin to be detected by EDX (Hummelgard, 2012)(Hummelgard, 2012);

 Current efficiency (CE): efficiencies documented in the literature are not ideal. Li et al referred to a 91% efficiency, while Gustafsson and his colleagues showed that 80 mM Mo(VI), only increased the CE from 80% to about 83% despite being present in a concentration about 30,000 times higher to a comparison cell that contained a small concentration of Cr(VI) (the latter increased current efficiency to 94%). Adding 80 mM Mo(VI) to the Cr(VI)-containing electrolyte did not have a negative effect on the CE, but instead a small positive effect; and

 Chromate use and presence: in the work of Rosvall et al and Gustafsson, small additions of SD (ca. 3 mg/L) were deemed necessary for the efficient operation of the cell. Gustafsson et al also suggest that it will be difficult to replace Cr(VI) in the existing process without replacing the steel cathodes with a more dimensionally stable material.

Overall, the use of Mo(VI) ions shows some promise but also has significant shortcomings with the evolution of oxygen, its poorer buffering, and a current efficiency, which may not be ideal. The elimination of Cr(VI) cannot be guaranteed under the conditions demonstrated in the literature. Evidence of commercial use of this alternative could not be established, and the applicant has no knowledge of any such commercial use.

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 38 Table 4-4: Research into sodium molybdate – Li et al, 2007 Parameter Details Year 2007 Source (Li, et al., 2007)(Li, et al., 2007) – Journal article Associated company/ Aker Kvaerner Chemetics, Canada research organisation Natural Science and Engineering Research Council of Canada (NSERC) for its Industrial R&D Fellowship fund Objective of research or - Identification of a suitable alternative with similar buffering characteristics to invention dichromate and without adverse effect on the electrolytic performance of sodium chlorate production is important to reduce the environmental impact Relevance to the chlorate High; sodium molybdate is examined as a replacement for SD in the chlorate process process

Key changes to current - 8 g/L Na2MoO4 were used chlorate process and - At 22–23 °C, without electrolysis occurring, buffer regions were observed to be notable improvements and pH 5.0–6.0 for molybdate and 5.0-6.5 for dichromate. Dichromate has a better shortcomings buffer “fit” for the chlorate reaction - The current efficiency ranged from 85% to 92% at pH lower than 5.7 and increases to ca. 98% in the pH range 5.75 to 5.95 and drops again above pH 5.95. At lower pH of 5.4, Mo oxides are likely to form at the cathode and adversely affect the current efficiency. At higher pH of 7–10, Mo electrodeposition becomes a main cathodic parasitic reaction with the effect of significantly lowering the current efficiency - The measured off-gas O2 level was observed to fluctuate between 3.7% and 4.8%. At these values, the current efficiency was only about 91% after 55 hours of operation and the H2 explosive upper limit was nearly reached (with 4.8% O2). The high off-gas O2 levels clearly show the adverse influence of molybdate on the DSA® anode, because O2 is only generated from the anodic parasitic reactions - In an effort to minimize and control this adverse anodic effect of molybdate on the anode, silica solution was added to the chlorate cell to form polysilicamolybdate anions; the O2 level in the cell off-gas dropped from 4.8% to 4.3% - Mixed additives based on Mo(VI) and Cr(VI) were also trialled. Although cathode surface potential was lowered substantially at pH 6.7, this pH was outside the buffer region and is not optimum for the chlorate reaction. On the other hand, increased complexity resulting from adding one more compound would counteract the advantage of the reduction of HER overpotential Presence of Cr(VI) in the Handling of Cr(VI): in the absence of SD, molybdenum interferes with the anodic electrolyte reaction and leads to increased evolution of O2 Presence of Cr(VI) in electrolyte: SD not present (but results not favourable)

Table 4-5: Research into sodium molybdate – Rosvall et al, 2010 Parameter Details Year 2010 Source (Rosvall, et al., 2010)(Rosvall, et al., 2010) – Patent Associated company/ AkzoNobel (EKA) research organisation Objective of research or - Developing a process of for activation of a cathode which reduces the cell invention voltage, while using low amounts of chromium and activating metal(s) - A further object of the invention is to provide a process with high cathodic current efficiency, in which the formation of oxygen is decreased whereby energy losses and the risk of explosions in the cell also are decreased Relevance to the chlorate Significant; the key aim was not to eliminate the presence of Cr(VI) in the electrolyte process

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 39 Table 4-5: Research into sodium molybdate – Rosvall et al, 2010 Parameter Details Key changes to current - Titanium cathodes were used in the presence of SD in the electrolyte. The chlorate process and addition of SD was at the level of 9 μM Na2Cr2O7•2H2O (ca. 0.003 g/L) notable improvements and - MoO3 was added at variable (low) concentrations ca. 1-10 mg/L. Despite the shortcomings low Mo addition, significant cathode activation was noted but also significant release of oxygen (oxygen evolution of 3.5-3.8%) - Long term effects were studied with 1 mg/L and 100 mg/L MoO3 added to the electrolyte, this resulted in cathode activation but also release of oxygen which would exceed 3.5% and might even reach >>4% - Experiments made it clear that small amounts of molybdenum species reduces the voltage on the titanium cathode Presence of Cr(VI) in the Handling of Cr(VI): the experiments made did not eliminate the use of SD, but its electrolyte addition was very limited, well below the typical operating conditions of a chlorate cell Presence of Cr(VI) in electrolyte: SD still present but at very low levels

Table 4-6: Research into sodium molybdate – Gustafsson et al, 2012 Parameter Details Year 2012 Source (Gustafsson, 2012)(Gustafsson, 2012) – Thesis (Gustafsson, et al., 2012)(Gustafsson, et al., 2012) – Journal article (Gustafsson, et al., 2012b)(Gustafsson, et al., 2012b) – Journal article (Hummelgard, 2012)(Hummelgard, 2012) – Thesis Associated company/ Royal Technical Institute, Stockholm research organisation AkzoNobel (EKA) Objective of research or - The goal was to better understand how molybdate (and REMs) can be used as invention additives to pH neutral electrolytes to activate the Hydrogen Evolution Reaction (HER) Relevance to the chlorate High; the ability of molybdenum to replace SD was considered process Key changes to current - Additions of 4 mM Mo(VI) were made into the electrolyte chlorate process and - Addition of molybdate to neutral and alkaline electrolytes activates the notable improvements and electrolytic HER (on electrode substrates with poor activity for the HER). The shortcomings added molybdate ions are reduced on the cathode forming for example films of oxides or alloys. These films give different electrode substrates a similar activity for HER - The activation for neutral electrolytes was larger with 4 mM molybdate as electrolyte additive than with 100 mM. Large amounts of molybdate appear to be detrimental to the activation. Molybdate also increased the overpotential on the anode due to either adsorption or precipitation of film. Side reactions to the HER can be inhibited by molybdate additive. The additive is more efficient when added to neutral than to alkaline electrolytes. In alkaline electrolytes, films of molybdenum oxides are not stable and thus less efficient at hindering for example hypochlorite reduction. For inhibiting side reactions, molybdate is far less efficient than dichromate - Increased cathode potential, increased anode potential, and increased oxygen level in the presence of high Mo(VI) concentrations give very strong motivation to use a low level of Mo(VI) in the process. Even if the partial current for the side reaction of Mo(VI) reduction appeared to be quite low even for 100 mM Mo(VI), the current efficiency of the HER would probably be even higher if a low Mo(VI) level was used, thus giving another motivation to use a low Mo(VI) level - Comparisons were made of the changes to current efficiency (CE) with Cr and Mo. The addition of 2.7 μM Cr(VI) increased the CE, as measured after 20 minutes of electrolysis, from about 80% to over 94%. This can be compared to 80 mM Mo(VI), which only increased the CE to about 83% despite being present

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 40 Table 4-6: Research into sodium molybdate – Gustafsson et al, 2012 Parameter Details in a concentration about 30,000 times higher. Adding 80 mM Mo(VI) to the Cr(VI)-containing electrolyte did not have a negative effect on the CE, but instead a small positive effect - A low concentration of Mo(VI) alone will not be sufficient to achieve a high current efficiency in the chlorate process. Some other additive therefore also has to be used, for example low levels of Cr(VI). To fully replace Cr(VI) or significantly lower the concentration, a buffer agent such as phosphate will be needed - It will be difficult to replace Cr(VI) in the existing process without replacing the steel cathodes with a more dimensionally stable material Presence of Cr(VI) in the Handling of Cr(VI): a significant reduction in the use of SD could be achieved, but electrolyte other issues would remain (e.g. need to replace cathodes) Presence of Cr(VI) in electrolyte: SD would still be present in low concentrations

Alternative 3: Rare Earth Metal salts

Rare Earth Metal (REM)10 salts have been investigated as an alternative to SD in the chlorate process. Among rare earth metals, yttrium has been given particular attention in relation to the manufacture of sodium chlorate but also lanthanum and samarium have been discussed. The metals are added in the form of their chlorides.

Key sources of information in the open literature include:

 A thesis and associated journal articles by Nylén and colleagues in 2007-2008, associated with the Royal Technical Institute (KTH) of Stockholm and AkzoNobel (EKA); and  A thesis and associated journal articles by Gustafsson and colleagues in 2010-2012, similarly associated with the Royal Technical Institute (KTH) of Stockholm and AkzoNobel (EKA).

A number of key points have been highlighted in this research:

 Effectiveness of REM salts: the addition of Y(III)/La(III)/Sm(III) ions to a suitable (NaCl) electrolyte results in the formation of a hydroxide film on the cathode during hydrogen evolution. According to Nylén and colleagues, a gel-like Y(OH)3 film formed on the iron surface has been found to inhibit the reduction of protons, nitrate ions and of hypochlorite ions. Under certain conditions the film also catalyses hydrogen evolution from the reduction of water;

 Permanence of the REM hydroxide film: the Y(OH)3 film has been found to be sensitive to certain operating parameters; (a) temperature: at 25 °C, additions of 10 mM YCl3, SmCl3 and LaCl3, the REM hydroxide film could easily be seen by the naked eye on the electrode surface after experiments at this temperature, but not after trials at 70°C. It probably dissolved at the higher temperature as the current was switched off; (b) current density and concentration: a low concentration of Y(III) or a high current density when extensive gas evolution disturbs the film formation, hinders the reduction of ions but the film does not activate water reduction. At higher Y(III) concentration (5 M) and lower current densities, the film formed has inhibiting as well as catalytic properties. In addition, when adding Y(III) to chlorate electrolyte at concentrations higher than those experimented with, yttrium precipitates

10 Rare earth metals as defined by IUPAC are a set of seventeen chemical elements in the periodic table, specifically the fifteen lanthanides plus scandium and yttrium. Scandium and yttrium are considered rare earth elements since they tend to occur in the same ore deposits as the lanthanides and exhibit similar chemical properties.

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 41 immediately, most likely as Y(OH)3. Higher concentrations may also lead to thicker diffusion layers and concomitant precipitation of Y(OH)3 at a distance from the electrode and no film formation on the surface; (c) pH: at the optimal pH for the chlorate process, Y(III), Sm(III) and La(III) will be very close to precipitation. The exact solubility of REM salts was not determined but REMs started to precipitate at pH 4.8 and therefore it was not possible to perform trials at the normal operating condition of pH 6.5 (Gustafsson, et al., 2010)(Gustafsson, et al., 2010); and

 Chromate use and presence: not all of this research has focused specifically on the replacement of chromates from the sodium chlorate process. Nevertheless, the experiments undertaken did not involve the use of SD, hence Cr(VI) would be eliminated from the electrolyte.

Overall, REM salts pose insurmountable problems to their implementation as additives to the chlorate process. At low concentrations, they give a thin cathode film, while at higher concentrations (and lower current densities) the film formed has inhibiting as well as catalytic properties. Given these problems with solubility, temperature and concentration, trivalent metal ions such as REM salts cannot be recommended as an additive to the chlorate process at normal chlorate process conditions.

This alternative is not known to be employed in any commercial application.

Table 4-7: Research into REM salts – Nylén et al, 2007-2008 Parameter Details Year 2007-2008 Source (Nylén, 2008)(Nylén, 2008) – Thesis (Nylén, et al., 2008)(Nylén, et al., 2008) – Journal article (Nylén, et al., 2007)(Nylén, et al., 2007) – Journal article Associated company/ Royal Technical Institute, Stockholm research organisation AkzoNobel (EKA) Objective of research or - The purpose of this work was to identify possible improvements in chlorate invention electrolysis, with the long-term goal of reducing its energy consumption Relevance to the chlorate High, but replacement of Cr(VI) not the main focus of the research process Key changes to current - The addition of Y(III) ions to a 0.5 M NaCl electrolyte resulted in the formation chlorate process and of an yttrium hydroxide film on the cathode during hydrogen evolution. The notable improvements and hydrous, gel-like Y(OH)3 film formed on the iron surface inhibits the reduction of shortcomings protons, nitrate ions and of hypochlorite ions. At certain conditions the film also catalyses hydrogen evolution from the reduction of water. The reactant of the catalysed water reduction is most likely water molecules coordinated to Y(III) within the yttrium hydroxide film - Two forms of film may be distinguished. A film formed at conditions expected to favour a relatively thin film, i.e. a low concentration of Y(III) or a high current density when extensive gas evolution disturbs the film formation, hinders the reduction of ions but the film does not activate water reduction. At higher Y(III) concentrations and lower current densities the film formed has inhibiting as well as catalytic properties. Loss of activation at high current densities may be a problem in electrolysis applications - When adding Y(III) to chlorate electrolyte having a higher ionic strength than the electrolyte in this work, yttrium precipitates immediately, most likely as Y(OH)3 in the bulk. Another problem might be the mass transport in industrial cells, which has to be good enough for developing a thin diffusion layer of OH-. Thicker diffusion layers may lead to precipitation of Y(OH)3 at a distance from the electrode and no film formation on the surface

Presence of Cr(VI) in the Handling of Cr(VI): no SD is used in the experimental systems that used YCl3 electrolyte Presence of Cr(VI) in electrolyte: SD is not present (but the Y(OH)3 film does not survive under the typical operating conditions of a chlorate cell)

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 42 Table 4-8: Research into REM salts – Gustafsson et al, 2010-2012 Parameter Details Year 2010-2012 Source (Gustafsson, 2012)(Gustafsson, 2012) – Thesis (Gustafsson, et al., 2010)(Gustafsson, et al., 2010) – Journal article Associated company/ Royal Technical Institute, Stockholm research organisation AkzoNobel (EKA) Objective of research or - The goal was to better understand how (molybdate and) trivalent cations can be invention used as additives to pH neutral electrolytes to activate the Hydrogen Evolution Reaction (HER) Relevance to the chlorate Highly relevant; successful results could open a pathway to the elimination of SD process Key changes to current - The addition of Y(III) to a pH neutral electrolyte has been found to catalyse the chlorate process and HER. Addition of Y(III) results in the formation of a Y(OH)3 film at the cathode. notable improvements and Experiments suggest that the efficiency for yttrium hydroxide deposition based shortcomings on the transport of yttrium was about 7%, so the film appears to be destroyed by vigorous gas evolution - At 25°C, additions of 10 mM YCl3, SmCl3 and LaCl3, the REM hydroxide film could easily be seen by the naked eye on the electrode surface after experiments at, but not after trials at 70°C. It was probably dissolved at the higher temperature as the current was switched off - The optimal pH of the chlorate process is close to neutral pH. Y(III), Sm(III) and La(III) will be very close to precipitation around neutral pH. Experiment observations showed that Y(III) precipitated already at pH 4.8 in 550 g/L NaClO3 at 70°C, which means that the Y(III) will be in precipitated form at pH 6.5. It is possible that the trivalent cations also form precipitations with anions in the electrolyte. In the chlorate process, the sodium chlorate is separated from the electrolyte with crystallization at alkaline pH. If added to an industrial chlorate electrolysis process, the trivalent cations would precipitate in this step and potentially contaminate the chlorate product - High chloride concentrations form complexes with Y(III) and probably also with other trivalent metal ions and thus decrease the activation of the HER. High temperatures also decrease the degree of activation achieved by addition of trivalent cations - Given these problems with solubility, temperature and chlorides, trivalent metal ions cannot be recommended as an additive to the chlorate process. Trivalent cations can be a promising additive to activate the HER at room temperature and chloride levels below 0.5 M Presence of Cr(VI) in the Handling of Cr(VI): the experiments did not involve SD; however, this is of limited electrolyte relevance given the above shortcomings of REMs Presence of Cr(VI) in electrolyte: in theory, absent, but not relevant due to technical shortcomings

Alternative technologies for the sodium chlorate process

Introduction to alternative electrode materials and coatings

Section 2.2.2 describes It has already been described that SD is added to the electrolyte to form a thin film of chromium hydroxide on the cathode, and the film electrochemically hinders the reduction of the hypochlorite and chlorate and thus improves the current efficiency of the chlorate process. It also affects the rate of the hydrogen evolution reaction (HER). There has been research that has specifically aimed at improving current efficiency and/or control over the hypochlorite reaction by means of developing novel coatings for electrodes or novel electrode materials. Relevant technologies suggested in the literature include:

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 43  Coatings based (primarily) on

 Molybdenum  Ruthenium  Zirconium

 Electrodes based on

 Ruthenium-titanium alloys  Ruthenium-based, titanium-free alloys.

A summary of the available literature information regarding to alternative electrode materials and coatings is presented below.

Alternative 4: Molybdenum-based cathode coatings

The use of molybdenum-based coatings has been investigated as an alternative to SD in the chlorate process, although some of the relevant research was not specifically aimed at eliminating the use of SD. The material deposited on the cathode in one patent was made out of a bath comprising FeCI3, Na2MoO4, NaHCO3 and Na2P2O7 or RuCl3 and MoCl3. Another patent has also been filed on cathodes coated with Ni-Mo but that does not address the use of SD in chlorate cells.

Key sources of information in the open literature include:

 A patent by Krstajic et al in 2007, associated with Industrie De Nora S.p.A., a leading electrode supplier; and  A patent by Rosvall et al in 2009, associated with AkzoNobel (EKA).

A number of key points have been highlighted in this research:

 Current efficiency and oxygen evolution: molybdenum-based coatings show some promise as regards the achieved oxygen evolution, cell voltage and cathodic current efficiency;

 pH buffering: to ensure adequate buffering of pH at the desired level (achieve an initial pH 6.4), sodium acid phosphates (3 g/L) needed to be added to the electrolyte; and

 Chromate use and presence: in the Krstajic et al patent, a low addition of SD (0.1 g/L) was required to ensure acceptable (equivalent) current efficiency. In the Rosvall et al patent, SD was used at typical concentrations (4.4 g/L).

Overall, the use of Mo-based cathode coatings shows some promise but may need to be accompanied by the addition of phosphate to ensure adequate pH buffering which can be problematic, as discussed in Section 5. The elimination of Cr(VI) cannot be guaranteed under the conditions demonstrated in the literature but a (significant) reduction in the concentration of SD to the electrolyte seems plausible. Evidence of commercial use of this alternative could not be established, and the applicant has no knowledge of any such commercial use.

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 44 Table 4-9: Research into molybdenum-based cathode coatings – Krstajic et al, 2007 Parameter Details Year 2007 Source (Krstajic, et al., 2007)(Krstajic, et al., 2007) – Patent Associated company/ Industrie De Nora S.p.A. research organisation Objective of research or - The patent relates to a process for the industrial electrolytic production of invention sodium chlorate, characterised by a high yield and a high electrical efficiency - The patent is aimed at developing a system for sodium chlorate production with low energy consumption making use of a nil or extremely limited amount of chromium compounds Relevance to the chlorate High relevance; elimination of SD was among the objectives of the patent process Key changes to current - Activation of the carbon steel cathodes was achieved through a bath prepared chlorate process and by dissolution of 9 g/L FeCI3, 40 g/L Na2MoO4, 75 g/L NaHCO3 and 45 g/L Na2P2O7 notable improvements and in distilled water, and the deposition was carried out at a constant current shortcomings density of 100 mA/cm2 at a temperature of 60°C, making use of a platinum fine mesh as the counterelectrode, under stirring. The deposition was protracted until obtaining a 20 micrometre thick alloy comprised of 47% by weight molybdenum and 53% by weight iron, as detected by a subsequent X-ray energy dispersion spectroscopy test - The voltage and energy efficiency of the cells with and without Mo-activated electrodes are shown below

Electrolyte Conditions Cell with activated Cell with non- cathodes activated cathodes 300 g/L NaCI pH = 6.41 Voltage: 3.01-3.02 Voltage: 3.14-3.17 3 g/L SD 2.5 kA/m2 Efficiency: 98% Efficiency: 97% 61°C 300 g/L NaCI pH = 6.40 Voltage: 2.86-2.87 Voltage: 3.08-3.12 3 g/L sodium acid 2.5 kA/m2 Efficiency: 97% Efficiency: 91% phosphates (Na2HPO4 and 60-61°C NaH2PO4) 0.1 g/L SD 300 g/L NaCI pH = 6.41 Voltage: 2.50-2.53 Voltage: 3.16-3.17 3 g/L sodium acid 2.5 kA/m2 Efficiency: 94% Efficiency: 72% phosphates (Na2HPO4 and 61°C NaH2PO4) Presence of Cr(VI) in the Handling of Cr(VI): one of the embodiments does not include the use of SD, but electrolyte results in lower current efficiency and lower voltage Presence of Cr(VI) in electrolyte: an option was investigated where SD was not present in the electrolyte Notes: Another patent (Krstajic, et al., 2010)(Krstajic, et al., 2010) has also been filed on cathodes coated with Ni-Mo but that does not address the use of SD in chlorate cells

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 45 Table 4-10: Research into molybdenum-based cathode coatings – Rosvall et al, 2009 Parameter Details Year 2009 Source (Rosvall, et al., 2009)(Rosvall, et al., 2009) Associated company/ AkzoNobel (EKA) research organisation Objective of research or - The patent relates to the process of preparing an electrode for the production invention of alkali metal chlorate and improving the electrolytic process. Emphasis is given on providing a cell in which a bipolar electrode or hybrids of bipolar and monopolar electrodes are mounted and to investigate a cell in which the polarity of the electrodes can be reversed such that the electrodes successively can work as anode and cathode within a given period of time. - A further object of the invention is to provide an electrode improving the cathodic current efficiency when in operation in an electrolytic cell, particularly while reducing the cell voltage - A further object of the invention is to provide electrodes which may lower the metal loading of precious metals on an electrode substrate while substantially maintaining the performance of commercial electrodes Relevance to the chlorate High; but invention not aimed at replacing or reducing the use of SD; SD was used in process the experiments Key changes to current - Experiments were based on an electrolyte containing 120 g/L NaCI, 580 g/L chlorate process and NaCIO3, and 4.4 g/L SD notable improvements and - RuCl3 and MoCl3 were used to deposit a layer on a Ti-based electrode shortcomings - The results of oxygen evolution, cell voltage and cathodic current efficiency are shown below - In this experiment, the current efficiency of the titanium cathodes coated with molybdenum oxide and were superior to the current efficiency of the baseline electrodes (PSC 120). For the molybdenum oxide-coated cathode, a decrease in oxygen formation was also observed

Oxygen (%) CCE (%) Cell voltage (V) Comment 2.3 95 2.87 Baseline 2.3 96 2.85 After stop 2.0 100 3.14 Mo/Ru-oxide on Ti (Grade 1) 2.1 99 3.18 After stop Presence of Cr(VI) in the Handling of Cr(VI): SD was used as normal electrolyte Presence of Cr(VI) in electrolyte: SD was present at typical operating levels

Alternative 5: Ruthenium-based cathode coatings

The use of ruthenium-based coatings has been investigated in the context of the chlorate process, however, the research has so far focused on the development of new cathode coatings that would allow more efficient operation of the cell and reduced energy consumption, rather than the reduction or elimination of the use of SD in industrial chlorate cells. The material deposited on the cathode is RuO2, although a patent has provided a comparison of the RuO2 coatings to Ru/W oxide and Ru/Mo coatings (on Ti3SiC2 ceramic material).

Key sources of information in the open literature include:

 A thesis and journal articles by Cornell and colleagues, associated with the Royal Institute of Technology (KTH) in Stockholm and AkzoNobel (EKA);  The 2009 Rosvall et al patent, associated with AkzoNobel (EKA); and  The aforementioned 2009 Rosvall et al patent associated with AkzoNobel (EKA).

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 46 A number of key points have been highlighted in this research:

 Oxygen evolution: when RuO2 coatings were used in experiments (Ti0.7Ru0.3O2) in the presence of chromates, oxygen evolution somewhat increased (as shown by Rosvall et al). On the other hand, when in the presence of molybdenum or tungsten, such an issue did not arise;  Current efficiency: RuO2 coatings on titanium electrodes have a current efficiency poorer than under typical SD use. However, current efficiency may improve when mixtures of other oxides (TiO2, MoO2, WO2) are used alongside RuO2;

 Stability concerns: thicker RuO2 coatings may be eroded by the vigorous gas evolution and improved stability is necessary before RuO2-based activated cathodes can be used industrially; and

 Chromate use and presence: hypochlorite and chlorate ions are reduced on RuO2 in the absence of the chromium hydroxide film, under typical conditions (70 °C, 3 kA/m2). An addition of SD to the chlorate electrolyte is necessary in order to keep a high current efficiency on the cathode. The level of SD addition would appear to be similar to that of current practices (3-6.5 g/L).

Overall, the conclusion so far has been that the use of SD cannot be eliminated as the RuO2 coatings lead to the reduction of chlorate at fast rates. There is no available evidence that the dosage of SD can be reduced compared to the current state of the art. Evidence of commercial use of this alternative could not be established, and the applicant has no knowledge of any such commercial use.

Table 4-11: Research into ruthenium-based cathode coatings –Cornell et al, 1993-2006 Parameter Details Year 1993, 2002, 2006 Source (Cornell & Simonsson, 1993)(Cornell & Simonsson, 1993) – Journal article (Cornell, 2002)(Cornell, 2002) – Thesis (Nylén & Cornell, 2006)(Nylén & Cornell, 2006) – Journal article Associated company/ AkzoNobel (EKA) research organisation Royal Institute of Technology, Stockholm Objective of research or - Investigation of Ru-based DSA® anodes and how the concentrations of chloride, invention chlorate, chromate, as well as pH, mass-transport and temperature affect the anode potential - Investigation of RuO2 coatings on activated cathodes and their role in reducing energy consumption - Investigation of the role of the Cr(III) hydroxide film around the cathode Relevance to the use and Limited; the research was not focused on the replacement of Cr(Vi) but did replacement of Cr(VI) in investigate its role in the electrolyte and around the anodes the chlorate process Key differences to current - The rate of the hydrogen evolution reaction in the chlorate process strongly chlorate process and depends on the electrode material. Thermally prepared RuO2 coatings are notable improvements and relatively active due to a favourable reaction mechanism in combination with shortcomings large real surface areas. At the current density of 3 kA/m2, typical for industrial electrolysis, the overvoltage for hydrogen evolution is about 300 mV lower on RuO2 than on corroded iron - In chlorate electrolyte, the 100 % RuO2 electrodes are more active than the DSA®s, and the overpotential depends on the coating thickness - In chlorate electrolyte, the effect of the film on hydrogen evolution on an iron or a RuO2 cathode is difficult to estimate, since the current in a chromate-free solution is a sum of currents from hydrogen evolution, chlorate reduction and hypochlorite reduction - The thicker RuO2 coatings prepared in the laboratory were eroded by the vigorous gas evolution and improved stability is necessary before RuO2-based activated cathodes can be used industrially

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 47 Table 4-11: Research into ruthenium-based cathode coatings –Cornell et al, 1993-2006 Parameter Details

- A thin film of Cr(III)hydroxide is formed on the RuO2 cathode in the chlorate process. The film efficiently hinders the reduction of hypochlorite and chlorate - Hypochlorite and chlorate ions are reduced on RuO2 in the absence of the chromium hydroxide film, the chlorate reduction reaction being relatively fast on RuO2 and by far the dominating reaction in chromate-free chlorate electrolyte at 70°C, 3 kA/m2. Chlorate reduction on iron is faster if the electrode is corroded. In the chlorate process, chlorate reduction is activation controlled. Therefore, a mass transport barrier, as an alternative to dichromate addition on the RuO2 cathode, will not efficiently hinder chlorate reduction. An addition of SD to chlorate electrolyte is necessary in order to keep a high current efficiency on the cathode - Catalytic electrode materials, such as RuO2, were deactivated after dichromate addition whereas the film activated inferior electrocatalysts, such as gold - RuO2 showed relatively good resistance to iron poisoning and other electrolyte impurities Presence of Cr(VI) in the Handling of Cr(VI): the addition of Cr(VI) was necessary in order to suppress parasitic electrolyte reactions (an addition of 0.015M of Na2CrO4 is described (ca. 2-3g/L)). Presence of Cr(VI) in electrolyte: Cr(VI) still present, probably at similar concentrations to current practices

Table 4-12: Research into ruthenium-based cathode coatings – Rosvall et al, 2009 Parameter Details Year 2009 Source (Rosvall, et al., 2009)(Rosvall, et al., 2009) – Patent Associated company/ AkzoNobel (EKA) research organisation Objective of research or - Development of an electrode which has improved performance in an electrolytic invention cell, notably improving the cathodic current efficiency when in operation in an electrolytic cell, particularly while reducing the cell voltage, showing reduced thickness resulting in material savings and optimisation enabling an increased number of 5 electrodes arranged in the same cell space whereby production may be increased without up-scaling an existing plant - Development of an electrode that does not corrode whereby sludge which could be deposited on the anodes is not formed - Development of an electrode that is resistant to hydrogen evolving conditions and reducing conditions in alkaline environment and at least shorter exposures in oxidative environment - Development of an electrolytic cell and a process for the production of alkali metal chlorate. It was particularly desired to provide such a cell in which the formation of oxygen and thereby danger of explosions is decreased while the operating conditions are facilitated - Development of an electrolytic cell in which a bipolar electrode or hybrids of bipolar and monopolar electrodes are mounted - Development of an electrolytic cell in which the polarity of the electrodes can be reversed such that the electrodes successively can work as anode and cathode within a given period of time Relevance to the Highly relevant to the chlorate process, but not relevant to the removal of SD from the chlorate process process/electrolyte Key changes to current A series of experiments were conducted under different configurations the results of chlorate process and which are summarised below. notable improvements and shortcomings Ru-based Cathode SD Cathodic Cell Oxygen* cathode coating material current voltage* efficiency* No coating Ti No SD 92% 3.30 V 3.7%

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 48 Table 4-12: Research into ruthenium-based cathode coatings – Rosvall et al, 2009 Parameter Details 96% AS No coating Mild steel No SD 86% 3.01 V 4.2% Failed AS N/A AS No coating Ti3SC2 No SD 100% 3.24 V 3.9% No coating Ti 4.4 g/L 99% 3.37 V 2.3% Failed AS No coating Mild steel 4.4 g/L 97% 3.00 V 2.2% 90% AS 3.01 V AS 2.4% AS No coating Ti3SC2 4.4 g/L 100% 3.28 V 2.3% 3.23 V AS No coating, Ti3SC2 4.4 g/L 100% 3.35 V 1.8% machined 3.33 V AS No coating, Ti3SC2 4.4 g/L 100% 3.29 V 2.1% sandblasted 3.28 V AS No coating, Ti3SC2 4.4 g/L 100% 3.36 V 1.7% polished 3.34 V AS Ti0.7Ru0.3O2 Ti 4.4 g/L 95% 2.87 V 2.3% 96% AS 2.85 V AS Mo/Ru oxide Ti 4.4 g/L 100% 3.14 V 2.0% 99% AS 3.18 V AS 2.1% AS W/Ru oxide Ti 4.4 g/L 99% 3,22 V 2.2% 3.27 V AS st nd rd 1 , 2 , 3 layer Ti3SC2 4.4 g/L 100% 2.85 V 2.1% Ru0.83Mo0.17O2 2.89 V AS st 1 Ru0.3Ti0.7O2; Ti3SC2 4.4 g/L 100% 2.93 V 2.2% 2nd and 3rd layer 2.94 V AS Ru0.83Mo0.17O2 st nd rd 1 2 and 3 Ti3SC2 4.4 g/L 95% 2.80 V 2.8% RuO2 (no result 2.93 V AS AS) * AS = after stop Presence of Cr(VI) in the Handling of Cr(VI): SD needs to be used at concentrations within the typical operating electrolyte range Presence of Cr(VI) in electrolyte: Cr(VI) still present in the electrolyte

Notably, older research focused on the potential benefits of replacing iron cathodes with titanium ones coated in oxides such as RuO2 and the results were encouraging (see the table that follows), but the state of the art described in the relevant patent is outdated compared to current development and the invention based on RuO2 and other metal oxides has not developed into an industrially-proven alternative.

Table 4-13: Research into ruthenium-based cathode coatings – Yoshida et al, 1981 Parameter Details Year 1981 Source (Yoshida, et al., 1981)(Yoshida, et al., 1981) – Patent Associated company/ Hodogaya Chemical Co., Ltd research organisation Objective of research or - Development of an activated cathode which is capable of preventing a cathode invention current loss due to the reducing reaction in the aqueous solution electrolysis, has a low overvoltage, a high corrosion resistance and a high mechanical strength and is easy to handle - Prevention of the contamination of product and effluent by metal salt added to the electrolytic bath in the aqueous solution electrolysis Relevance to the chlorate High relevance; reduction of use of chromate is presented as one of the benefits of process the invention

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 49 Table 4-13: Research into ruthenium-based cathode coatings – Yoshida et al, 1981 Parameter Details Key changes to current The patent refers to an activated cathode which comprises: chlorate process and - A base plate, e.g. titanium notable improvements and - A metal oxide layer formed on the surface of the base plate, e.g. ruthenium, shortcomings rhodium, palladium, osmium, iridium and platinum, the most efficient appearing to be ruthenium - An oxide of one or more metal elements selected from the group consisting of calcium, magnesium, strontium, barium and zinc in the group II and chromium, molybdenum, tungsten, selenium and tellurium in the group VI - Titanium cathodes coated with Ru or Rh were accompanied of considerable cathode current loss in the absence of chromate - Titanium cathodes with Ru+Rh coatings and the addition of metal oxides such as CaO, MgO, BaO, SrO and Cr2O3 showed cathode current loss lower than iron cathodes in the presence of 2 g/L SD Presence of Cr(VI) in the Handling of Cr(VI): the use of 2 g/L SD could be eliminated with the use of a electrolyte combination of metal oxides on a titanium base. However, according to (Lindbergh & Simonsson, 1991)(Lindbergh & Simonsson, 1991), these cathodes only allow the kinetics of the hypochlorite ion reduction reaction to be slowed down but do not allow the reaction to be eliminated (Andolfatto & Delmas, 2002)(Andolfatto & Delmas, 2002) Presence of Cr(VI) in electrolyte: Cr(VI) would still be present in the electrolyte to ensure the efficiency of the process

Alternative 6: Zirconium-based cathode coatings

The use of zirconium-based coatings has been investigated in the context of the chlorate process, however, the relevant research may not have aimed at the reduction or elimination of the use of SD in industrial chlorate cells. The material deposited on the cathode is ZrO2 (the layer can be applied on a zirconium surface by thermal decomposition of a Zr-containing solution), although patents describe external layers of ZrTiO4 accompanied by RuO2 (and optionally by ZrO2 and/or TiO2) and ZrO2 modified with Y2O3 on a zirconium plate.

Key sources of information in the open literature include:

 A journal article by Herlitz et al in 2001, associated with the Royal Institute of Technology in Stockholm;  A patent by Andolfatto & Delmas in 2002, associated with Atofina; and  A patent by Brown et al in 2010, associated with Industrie De Nora, S.p.A.

A number of key points have been highlighted in this research:

 Suppression of parasitic reactions: ZrO2 reduces the rate of hypochlorite reduction, but does not entirely inhibit it. Combinations of Zr with Ti and/or Ru are required for a better suppression;

 Cathodic current efficiency: when ZrO2 modified with Y2O3 was deposited on a zirconium plate, a cathodic efficiency of up to ca. 91% (after 104 days) was recorded. However, this was in a hypochlorite cell without direct linkages to the use of SD for the manufacture of chlorate, therefore, the applicability of the described system to the chlorate cell is unclear; and

 Chromate use and presence: no chromate was used in the experiments described in the patents above.

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 50 Overall, the conclusion so far has been that Zr-based coatings may be used in the absence of chromate, but the achieved cathodic current efficiency may not necessarily be as high as in a typical chlorate cell in the presence of a cathodic chromium hydroxide film. It is understood that efforts have been made to implement a Zr-coated cathode on an industrial scale, but this was unsuccessful and led to the abandonment of the relevant research.

Table 4-14: Research into zirconium-based cathode coatings – Herlitz, 2001 Parameter Details Year 2001 Source (Herlitz, 2001)(Herlitz, 2001) – Patent Associated company/ Royal Institute of Technology, Stockholm research organisation Objective of research or To clarify the effect of oxidised zirconium on parasitic cathodic reactions in the invention chlorate process, electrochemical studies were carried out at laboratory scale. The techniques used were cyclic voltammetry and recording of polarisation curves Relevance to the chlorate Significantly relevant; oxidised zirconium was considered as a means for suppressing process the hypochlorite parasitic reaction, but not as a direct replacement additive for SD Key changes to current - Oxidised zirconium cathodes reduce the rate of hypochlorite reduction, chlorate process and although not entirely inhibiting it, which is mainly related to a lowered active notable improvements and area due to the porous layer of zirconium dioxide. shortcomings - The oxidised samples are partly passivated, giving high over-voltages for the hydrogen evolution reaction. These over-voltages gradually decrease during cathodic polarisation due to the simultaneous reduction of the zirconium oxide - Studies of the selectivity indicate that hypochlorite reduction occurs on the oxidised zirconium cathodes to a high extent, the thermal oxide being somewhat better - It is concluded that zirconium oxide is not a suitable cathode material for the sodium chlorate process Presence of Cr(VI) in the Not relevant, the alternative has not proven technically feasible electrolyte

Table 4-15: Research into zirconium-based cathode coatings – Andolfatto & Delmas, 2002 Parameter Details Year 2002 Source (Andolfatto & Delmas, 2002)(Andolfatto & Delmas, 2002) – Patent Associated company/ Atofina research organisation Objective of research or Development of a cathode which allows the chlorate of an alkali metal to be invention electrolytically synthesised with a high coulombic yield and in the absence of SD Relevance to the chlorate Highly relevant; Zr/Ru coatings were considered in order to eliminate the parasitic process hypochlorite reduction and eliminate the need for SD Key changes to current - This specific cathode comprises a titanium substrate with an external layer of chlorate process and ZrTiO4 accompanied by RuO2 and optionally by ZrO2 and/or TiO2 notable improvements and - Depending on the ration Zr/Ti and Ru/(Zr+Ti+Ru), different suppression of the shortcomings hypochlorite reduction can be achieved in the absence of SD - For a ratio Zr/Ti equal to 1 and Ru/(Zr+Ti+Ru) equal to 0.001, the new electrode would appear to limit the hypochlorite reduction to the same extent as SD on a mild-steel electrode Presence of Cr(VI) in the Handling of Cr(VI): SD was eliminated in the examples shown in the patent; some electrolyte embodiments achieved results similar to those obtained with SD and steel cathodes Presence of Cr(VI) in electrolyte: Cr(VI) would not be present in the electrolyte

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 51 Table 4-16: Research on zirconium-based cathode coatings – Brown et al, 2010 Parameter Details Year 2010 Source (Brown, et al., 2010)(Brown, et al., 2010) – Patent Associated company/ Industrie De Nora, S.p.A. research organisation Objective of research or A cathodic member for electrochemical cells used in hypochlorite production invention comprises a zirconium plate coated with a zirconium oxide layer, which is particularly suitable for minimising the decomposition of the hypochlorite product while ensuring a prolonged lifetime. The coated zirconium plate can be used as the cathodic plate in a monopolar cell, or can be welded to a titanium plate for use in a bipolar configuration Relevance to the chlorate The invention relates to electrochemical cells for the production of hypochlorite process solutions; although reference is made to chlorate cells, the applicability of the invention is uncertain. It is mentioned that the addition of SD in hypochlorite systems for water disinfection is not relevant, as the presence of chromium is not acceptable

Key changes to current - Although ZrO2 is very stable to the caustic environment established on cathode chlorate process and surfaces, the cathodically-evolved hydrogen tends to detach the protective layer notable improvements and from the titanium body in a short time shortcomings - The invention comprises a zirconium oxide coated zirconium plate for use as a cathode member in an electrolytic cell for the production of hypochlorite - While titanium has always been the valve metal of choice for valve metal-based cathode plates of hypochlorite cells due to its lower cost and its superior resistance against corrosion, it has been found that ZrO2 layers grown on zirconium surfaces are much more resistant to detachment induced by cathodically-evolved hydrogen compared to similar layers grown on titanium - In thermal-sprayed layers, ZrO2 can be mixed with other suitable oxides to modify the structure of the layer, for instance to obtain an adequate porosity. Zirconium oxide modified with a small amount of Y2O3, usually less than 10% molar is sometimes used on titanium plates and proves beneficial also on zirconium plates.

The results on current efficiency suing different versions of Zr plates are shown below.

Cathode material Initial CE after Cathode material Initial CE after CE 104 CE 104 days days Zr plate with ZrO2 93.0% 88.4% Ti plate uncoated 78.4% 72.5% deposited with thermal decomposition of Zr acetate Zr plate with 87.2% 91.3% Ti plate with 89.3% Failed plasma-spraying of plasma-spraying after 44 ZrO2 modified with of ZrO2 modified days 8% of Y2O3 with 8% of Y2O3 Zr plate with 93.4% 90.0% Pt plate with 91.8% Failed thermally grown plasma-spraying after 44 ZrO2 layer of ZrO2 modified days with 8% of Y2O3 Bipolar Ti/Zr 88.5-92.7% cathode with 4 coats of Ru/Ir/Ti Presence of Cr(VI) in the Not relevant to SD electrolyte

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 52 Alternative 7: Ruthenium alloy cathodes

The use of ruthenium-titanium-based alloys as cathode materials has been investigated in the past as a means for reducing of energy consumption, rather than with the aim of eliminating SD from the electrolyte.

Key sources of information in the open literature include patents and journal articles associated with Canadian interests, particularly the Canadian Institut de recherche d'Hydro-Québec, as shown in Table 4-17 and Table 4-18.

A number of key points have been highlighted in this research:

 Hydrogen overpotential reduction: Ru-Ti alloy cathodes significantly reduce the hydrogen overpotential by 300 mV more than the steel cathodes;

 Suppression of hypochlorite decomposition and oxygen evolution: the speed of - - hypochlorite decomposition (2 ClO  2 Cl +O2) was found to be low, even lower than the speed measured on the steel electrodes, which meant that there was very little molecular oxygen released; and

 Chromate use and presence: the use of SD is uncertain. The patents and journal article published in the 1990s suggest that SD may not be used but the alloy may comprise up to 50% chromium. On the other hand, the 2006 patent by Schulz et al refers to an aluminium- containing nanocrystalline alloy, which, apparently, might be used in the presence of a cathodic Cr(OH)3 film.

Overall, these ruthenium-titanium alloys show some good performance in terms of current efficiency and suppression of parasitic reactions, however, they seem unable to guarantee the elimination of the use of SD or the presence of chromium in the electrolyte. Evidence of commercial use of this alternative could not be established, and the applicant has no knowledge of any such commercial use.

Table 4-17: Research into ruthenium/titanium alloy cathodes – Van Neste et al, 1996, Boily et al, 1997, Schulz et al, 1997 & 2006 Parameter Details Year 1996, 1997, 2006 Source (Van Neste, et al., 1996)(Van Neste, et al., 1996) –Journal article (Boily, et al., 1997)(Boily, et al., 1997) – Patent (Schulz, et al., 1997)(Schulz, et al., 1997) – Patent (Schulz, et al., 2006)(Schulz, et al., 2006) – Patent Associated company/ Institut de recherche d'Hydro-Québec research organisation EKA Chimie Canada Objective of research or - The present invention relates to new nanocrystalline alloys containing Ti, Ru, Fe invention and O. The invention also relates to a process of preparation of these new alloys - The patent was the result of a research carried out to improve the electric efficiency of the cells used for the electrochemical synthesis of sodium chlorate, whose consumption is very high (about 50 to 100 MW per plant) Relevance to the chlorate High, but no mention to the presence of SD in the electrolyte is made process Key changes to current - According to the 1997 patents, a method of producing sodium chlorate by chlorate process and electrochemical synthesis in an electrolysis cell having cathodes made of a notable improvements and complex alloy according to of the formula: shortcomings Ti30+x Ru15+y Fe25+z O3u+t Mu where M is preferably chromium and x is between -5 and +5 y is between -5 and +5 z is between -5 and +5

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 53 Table 4-17: Research into ruthenium/titanium alloy cathodes – Van Neste et al, 1996, Boily et al, 1997, Schulz et al, 1997 & 2006 Parameter Details t is between -28 and +5 u is between 0 and +10, x + y + z + t + u = 0 - The alloy may comprise up to 50% at chromium. This addition could reduce substantially or even eliminate the use of SD - When measured under a current of density of 250 mA/cm2 at 70 °C in an electrolyte cell, the overpotential of hydrogen was approximately 300 mV lower than the one of the steel cathodes. The latter have an overpotential of hydrogen equal to approximately 900 mV while the cathodes made from the alloys according to the invention have an overpotential of hydrogen equal to about 600 mV. When multiplied by the number of cathodes and the number of cells in a sodium chlorate production plant, this reduction in the overpotential of hydrogen represents a net gain of electric energy of more than 10% - The speed of decomposition of the hypochlorite in contact with the material forming the cathodes was very low, even lower than the speed measured on the steel electrodes, which meant that there was very little molecular oxygen released. This reduced even more the risks of simultaneous release of molecular hydrogen and oxygen with all the inherent risks of explosion that such implies - The cathodes made from the alloy can be welded directly on titanium anodes - The 2006 patent refers to an alloy of the formula Ti2+t(Ru(1-x_Al(1+x))(1-u/2)MuTy, wherein: t is a number preferably between -0.5 and +0.5; x is a number preferably between +0.5 and +0.9; u is a number preferably less than 0.25; y is a number preferably equal to 2; M represents one or more elements selected among Ag, Pd, Rh, Fe, Cr and V, the elements being preferably, Ag, Pd or Rh; and T represents one or more elements selected among O, B, S, C, N, Si, P and H, the elements being preferably oxygen. Said alloy is preferably in nanocrystalline form - This latter patent suggests that suitable alloys should not interfere with the Cr(OH)3 film on the cathode, suggesting that SD may still be used Presence of Cr(VI) in the Handling of Cr(VI): it is implied that SD may not need to be used, but the cathode electrolyte would contain significant levels of chromium in the older Schulz et al patent. For the second patent, Cr may comprise up to 50% of the alloy Presence of Cr(VI) in electrolyte: uncertain

Table 4-18: Research into ruthenium/titanium alloy cathodes – Gebert et al, 2000 Parameter Details Year 2000 Source (Gebert, et al., 2000)(Gebert, et al., 2000) – Journal article Associated company/ École Polytechnique de Montréal research organisation IFW Dresden Institut de recherche d'Hydro-Québec Objective of research or Development of cathodes that wil allow a reduction to energy consumption invention Relevance to the chlorate Uncertain; cathodes for chlorate electrolysis are discussed but it is uncertain if this is process in light of the use of Cr(VI) in the electrolyte Key changes to current - Cathodes for chlorate electrolysis were prepared by mixing nanocrystalline Ti– chlorate process and Ru–Fe–O catalyst powder with small amounts of Teflon and subsequent hot notable improvements and pressing on a carbon–Teflon sub-layer shortcomings - The behaviour of electrodes with catalyst loadings from 300 mg/cm2 reduced to 10 mg/cm2 was investigated in chlorate electrolyte with pH 6.5 and in part, for comparison, in 1 M sodium hydroxide solution at 70 °C

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 54 Table 4-18: Research into ruthenium/titanium alloy cathodes – Gebert et al, 2000 Parameter Details - The as-milled catalyst powder electrodes showed a high activity for the HER in chlorate electrolyte particularly expressed in low overpotentials of about 580 mV at −250 mA/cm2 for catalyst loadings down to 20 mg/cm2 and high double layer capacitances in the freshly prepared state. These electrodes show increased activity at low polarisation. The long-term stability during electrolysis was also analysed Presence of Cr(VI) in the Handling of Cr(VI): uncertain electrolyte Presence of Cr(VI) in electrolyte: uncertain

Later research by scientists at the Canadian Institut de recherche d'Hydro-Québec focused on a new family of electrocatalytic materials consisting of an iron aluminide (Fe3Al) alloy doped with ruthenium and with the potential addition of tantalum. Experiments with these new alloys still require the use of SD, the addition of which is described at 3 g/L.

These alloys have not yet found commercial use. On the Institut de recherche d'Hydro-Québec’s website an invitation for Expressions of Interest was available in early 2014 aimed at the attribution of a worldwide exclusive license for the valorisation of the technology based on the Ru-alloys, a technology entitled “Chlorate Efficient Cathode Technology”. The call for expressions of interest has been issued to selected parties that have interests in sodium chlorate production technologies. The Canadian Institute claims that, “the new cathodes can provide up to approximately 10% of energy savings to the sodium chlorate production process depending on operating conditions. These electrocatalytic electrodes which are highly resistant to corrosion are dimensionally stable and lead to very low levels of iron impurities as a result of their utilization”11.

Overall, these alloys cannot guarantee the elimination of SD use or the presence of chromium in the electrolyte and have not yet found commercial use.

Table 4-19: Research into ruthenium alloy cathodes – Schulz & Savoie, 2009-2013 Parameter Details Year 2009, 2010, 2013 Source (Schulz & Savoie, 2009)(Schulz & Savoie, 2009) – Journal article (Schulz & Savoie, 2010)(Schulz & Savoie, 2010) – Journal article (Schulz & Savoie, 2010b)(Schulz & Savoie, 2010b) – Patent (Schulz & Savoie, 2013)(Schulz & Savoie, 2013) – Patent Associated company/ Institut de recherche d'Hydro-Québec research organisation Objective of research or The journal articles and patents discuss a new family of electrocatalytic materials invention consisting of an iron aluminide (Fe3Al) alloy doped with a catalytic element such as ruthenium. High energy ball milling is used to prepare these new metastable nanocrystalline alloys and their cathodic overvoltages for the hydrogen evolution reaction in a chlorate electrolyte are about 400 mV lower than that of iron cathodes Relevance to the chlorate Substantially relevant, but not aimed at replacing SD process Key changes to current - The catalysed iron aluminide nanocrystalline powders were prepared by high chlorate process and energy ball milling starting from mixtures of Fe3Al and Ru powders notable improvements and - The electrochemical set-up consisted of a two-compartment cell with a shortcomings capacity of about one litre. The counter electrode was a DSA anode. The electrolyte was a synthetic standard chlorate electrolyte containing 550 g/L of

11 Information on the Call for Expressions of Interest is available at http://www.hydroquebec.com/innovation/en/partenariats.html (accessed on 11 April 2014).

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 55 Table 4-19: Research into ruthenium alloy cathodes – Schulz & Savoie, 2009-2013 Parameter Details

NaClO3, 110 g/L of NaCl, 3 g/L of SD and 1 g/L of NaClO. The pH was regularly adjusted at 6.5 using NaOH or HCl. - The electrodes made of compacted ball milled powders have overpotential values for the HER at 250 mA/cm2 in a chlorate electrolyte about 400 mV lower than that of iron cathodes - The 2010 patent does not describe the use of SD, but this is implied as it mentions “One sees on this figure the characteristic peaks of Fe, Al, and Ru but also of Na and Cr coming from the electrolyte”. - The 2013 patent discusses the corrosion resistance of the alloys described earlier. This was found to be good at pH 6.5 but poor in acidic conditions (standard industrial practises use acid wash from time to time to clean electrochemical cells and electrodes). To solve this problem, the inventors discovered that the addition of a small amount of Ta to these materials could make these new alloys not only highly resistant to corrosion in chlorate electrolyte but also in acidic (HCl) solutions without losing performance regarding the electrochemical synthesis of sodium chlorate. The alloys of interest are Fe3-xAl1+xMyTzTat (x is between -1 and +1, y is between 0 and +1, z is a between 0 and +1 and t is between 0 and +1). The electrolyte again contains 3 g/L SD Presence of Cr(VI) in the Handling of Cr(VI): SD is still added to the electrolyte at typical concentrations electrolyte Presence of Cr(VI) in electrolyte: SD is still present in the electrolyte

Other technologies

Alternative 8: Two-compartment electrolytic systems

Other technologies that may be considered alternatives to chromate-based solutions go beyond the electrode level. These could include variations of two-compartment cells (for example, membrane- type ‘chlor-alkali’ cells).

The key sources of information regarding this alternative are a number of patents. These include:

 A patent by Cook in 1975, associated with Hooker Chemicals Plastics Corp;  A patent by Millet in 1990, associated with Atochem (now Arkema); and  A patent by Delmas & Ravier in 1993, associated with ELF Atochem (now Arkema).

The chlor-alkali process is a process related to a chlorate cell but with some important differences. The electrodes in a chlorate cell are in one compartment, allowing the anode and cathode reaction products to mix and to react together. This allows chlorine to react with hydroxide to form hypochlorite and finally sodium chlorate. In a two compartment-cell, such as a chlor-alkali cell, the electrodes are physically separated and thus their products cannot react together. These cells can be operated without SD and can produce sodium chlorate under certain conditions (Millet, 1990)(Millet, 1990) (Delmas & Ravier, 1993) (Delmas & Ravier, 1993). The usual electrolytic reactions operating in chlor-alkali cells are as follows:

- - 6Cl  3Cl2 + 6e (22)

- - 6H2O + 6e  3H2 + 6OH (23)

Overall: 6NaCl + 6H2O  3Cl2 + 3H2 + 6NaOH (24)

If the process is modified so that the chlorine gas is reacted with the hydroxide solution, sodium chlorate can also be generated as shown in eq. 23 below (Tilak & Chen, 1999)(Tilak & Chen, 1999):

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 56 - - - 3Cl2 + 6OH  5Cl +ClO3 + 3H2O (25)

with counter-ions: 3Cl2 + 6NaOH  5NaCl + NaClO3 + 3H2O (26) Combined (24 & 26): 6NaCl + 6H2O + 6NaOH  5NaCl + NaClO3 + 3H2O + 3H2 (27) Eq. 27 simplified: NaCl + 3H2O  NaClO3 + 3H2 (6)

It can be seen that overall, the process is chemically identical to the conventional undivided cell process but in practice quite different. Chlorine is produced in the anode compartment of a membrane chlor-alkali cell is hydrolysed into hypochlorous acid (eq. 2) (Hakansson, et al., 2004)(Hakansson, et al., 2004). The pH and temperature of the solution of hypochlorous acid is then maintained so that the formation of chlorate is maximised (pH 6-6.5 at around 80 °C). At this pH, the correct ratio of hypochlorite and hypochlorous acid is achieved. Equation 29 shows the balanced equation, in this case showing sodium hydroxide acting as a base. The cathode compartment would serve as the source of sodium hydroxide that would be introduced into the chlorate reactor and in limited amounts to a chlorine absorption unit or anode compartment (Delmas & Ravier, 1993)(Delmas & Ravier, 1993). The use of sodium hydroxide for pH control in this manner potentially avoids the need for further buffering agents to be added to the electrolyte.

3Cl2 + 3H2O ⇄ 3HOCl + 3HCl (2) 3HOCl + NaOH ⇄ 2HOCl + NaClO (29)

The current process involving SD uses undivided electrolysis cells while chlor-alkali cells use membrane cells and would also involve separate chlorate reactors and gas processing equipment. A change to this type of cell would require a rebuild of current plant technology as all existing single compartment cells would need to be scrapped.

It is considered that modified chlor-alkali type-cells could be technically feasible for the production of chlorate without the use of SD. For this reason, further consideration to production of chlorate via two-compartment cells and reaction of chlorine with sodium hydroxide will be given.

Table 4-20: Research into two-compartment electrolytic systems – Cook, 1975 Parameter Details Year 1975 Source Cook (1975)(1975) Associated company/ Hooker Chemicals Plastics Corp research organisation Objective of research or - A process for producing alkali metal chlorate using two different cells. The first invention being a two-compartment membrane cell and the second being a conventional single-compartment chlorate cell. - The patent describes a process that produces sodium hydroxide, chlorine, sodium chlorate and hydrogen as outputs of one overall process. Relevance to the chlorate High relevance, but no mention is made of the use of SD in the electrolyte. A process conventional cell is used so use of Cr(VI) can be expected. Key changes to current - The examples describe a process producing 1.7 tons per day of sodium chlorate process and chlorate using the linked cells. The first cell produces a concentration of 100 notable improvements and g/L of sodium chlorate and this is increased to 430 g/L in the second cell. shortcomings - With a current efficiency of 94%, at a cell voltage of 4.2 V and a current density of 4 A/sq. inch (0.62 kA/m2). - Part of the hydrogen generated is burned with part of the chlorine produced to generate hydrogen chloride. This is then used for pH control at some stages. It is not clear how much of the hydrogen produced is diverted in this manner

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 57 Table 4-20: Research into two-compartment electrolytic systems – Cook, 1975 Parameter Details Presence of Cr(VI) in the Handling of Cr(VI): the patent does not mention the use of any electrolyte additives electrolyte nor describe any steps to limit corrosion. As the chlorate is primarily manufactured in a conventional chlorate cell, it is expected that Cr(VI) would be used as normal. Presence of Cr(VI) in electrolyte: Cr(VI) could be expected to be present in the electrolyte

Table 4-21: Research into two-compartment electrolytic systems – Millet, 1990 Parameter Details Year 1990 Source Millet (1990) (1990) Associated company/ Atochem (Arkema) research organisation Objective of research or - Production of alkali metal chlorates or perchlorates using a two-compartment invention membrane cell - Avoiding the use of Cr(VI) was a stated objective of the patent Relevance to the chlorate High relevance to both chlorate process and the elimination of the use of Cr(VI) process Key changes to current - The patent claims processes carried out at pH 6.2-6.6 controlled by introducing chlorate process and sodium hydroxide from the cathode compartment into the anode notable improvements and compartment. shortcomings - The examples employ an electrolyte consisting of 150-160 g/L NaCl and 500 g NaClO3 at a temperature of 63-71 °C and pH 6.3-6.4 - A current of 10 A was applied to a 0.5 dm2 electrode (equivalent to 2 kA/m2) but no mention of cell voltage is made - The yield of sodium chlorate is claimed at 87.3%-93% based on the oxygen present in the chlorine in the absence of SD. - Yield of pure hydrogen is claimed at practically equal to 100%. - No mention of how long the process was operated for nor the scale of the process - Two examples are shown with the following chlorate generation efficiencies based on amount of oxygen formed

Temp Anolyte pH Anolyte Membrane Sodium recycling flow (by Dupont) chlorate rate efficiency 63 °C 6.3-6.4 70 L/h Nafion 117 87.3% 71 °C 6.3-6.4 160 L/h Nafion 902 93% Presence of Cr(VI) in the Handling of Cr(VI): the invention is claimed without the use of chromates. electrolyte Presence of Cr(VI) in electrolyte: No SD present in the electrolyte.

Table 4-22: Research into two-compartment electrolytic systems –Delmas & Ravier, 1993 Parameter Details Year 1993 Source Delmas & Ravier (1993) (1993) Associated company/ ELF Atochem (Arkema) research organisation Objective of research or - Method of manufacturing chlorate alkali metal by electrolysis in a membrane invention cell without adding chromium Relevance to the chlorate High relevance to both chlorate process and the elimination of the use of Cr(VI) process Key changes to current - The invention comprises of two linked chlor-alkali cells and a scrubbing column chlorate process and and does not involve the use of Cr(VI)

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 58 Table 4-22: Research into two-compartment electrolytic systems –Delmas & Ravier, 1993 Parameter Details notable improvements and - The process preferably runs at pH 6.5-7 and temperature of 70-90 °C shortcomings - Chlorate production is carried out by transfer of chlorine gas and the solution of alkali metal hydroxide from a chlor-alkali cell to react in a scrubbing column - pH maintained at 6.5-7 in the scrubbing tower by addition of sodium hydroxide from cathode compartments - Column output is recycled by circulating in a second chlor-alkali cell - The output of the anode compartment of the second cell is diverted to a crystalliser to obtain the chlorate and to recycle mother liquors back to the second chlor-alkali cell - The method is claimed to result in a reduction in water consumption: the usual method of production of sodium chlorate requires the introduction of 1,563 kg of water per tonne of NaClO₃, associated with sodium chloride fed in the form of brine containing 26% by weight of NaCl. In the process disclosed, the second cell is fed by a stream from the reaction between chlorine and the aqueous solution at 33% by weight of soda with the introduction of 719 kg of water per tonne of NaClO₃ product. There is a saving of 844 kg of water that would otherwise need to be evaporated in a sodium chlorate crystallisation facility Presence of Cr(VI) in the Handling of Cr(VI): no use of SD electrolyte Presence of Cr(VI) in electrolyte: no presence of SD in the electrolyte

It is worth noting that the 2019 literature review update undertaken for the SCB AoA12 found two comprehensive review articles that were published in 2017 (Endrődi., 2017)(Endrődi., 2017) and 2018 (Gharbi., 2018)(Gharbi., 2018) summarising all prior research on potential alternatives to sodium dichromate in chlorate electrolysis.

Both articles concluded that there currently are no commercially available alternatives to sodium dichromate for sodium chlorate manufacture. It is therefore concluded for the purposes of this AoA that the two-compartment electrolytic systems potential as an alternative to the use of SD in the production of sodium chlorate is not feasible for SCB.

Alternative 9: Oxygen-consuming gas diffusion electrodes

A recently developed technology for an improved chlor-alkali process replaces the conventional steel or titanium cathodes in chlor-alkali membrane cells with an oxygen-consuming electrode, fundamentally changing the chemistry of the process. This change results in the production of chlorine and sodium hydroxide without the production of hydrogen. The process is claimed to result in up to 30% reductions in electricity requirements in laboratory trials (Chlistunoff, 2004)(Chlistunoff, 2004). However, this is at the cost of a valuable hydrogen co-product and significant technical barriers to limit cathode corrosion are yet to be overcome. This means also there isn't available hydrogen to re- convert to hydrochloric acid the by-produced chlorine; in other words, this technology seems applicable only having the possibility to use chlorine for other productions. The use of oxygen- consuming electrodes in the production of chlorate is currently under patent (Hakansson, et al., 2004)(Hakansson, et al., 2004). Although the patent states that, an embodiment of the patent does not necessitate the use of chromates, the examples in the patent use of SD at a concentration of 3 g/L, as shown in Table 4-23.

The purpose of the project was continuation of the development of new chlor-alkali electrochemical reactors (ECRs) that employ oxygen-depolarised cathodes. Due to their lower operating voltages, the

12 See Section 4.2.3.2

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 59 oxygen-depolarised reactors consume up to 30% less electrical energy per unit weight of the products (chlorine and caustic soda), than the state-of-the-art membrane electrolysers with hydrogen-evolving cathodes.

Evidence of commercial use of this alternative could not be established, and the applicant has no knowledge of any such commercial use. The elimination of the use of SD under this method has not been demonstrated, therefore, this cannot be considered a realistic alternative for the purposes of this AfA.

Table 4-23: Research into oxygen-consuming gas diffusion electrodes – Hakansson et al, 2004 Parameter Details Year 2004 Source (Hakansson, et al., 2004)(Hakansson, et al., 2004) Associated company/ AkzoNobel (EKA) research organisation Objective of research or - A process for producing alkali metal chlorate in an electrolytic cell that is divided invention by a cation selective separator into an anode compartment in which an anode is arranged and a cathode compartment in which a gas diffusion electrode is arranged - The patent is aimed at developing a chlorate cell where the cost and handling of HCl and NaOH are reduced while improving energy efficiency Relevance to the chlorate High relevance, but the embodiments described use SD at typical electrolyte process concentrations Key changes to current - The experiment was run as a batch process with a start volume in the reactor chlorate process and vessel of 2 litres. The start concentration of the electrolyte in the anode notable improvements and compartment was 110 g of NaCl/L, 550 g of NaClO3 and 3 g/L SD. This solution shortcomings was pumped through the anode compartment of an electrolytic cell at a rate of 25 L/h corresponding to an approximate linear velocity across the anode of 2 cm/s - An excess of oxygen gas was fed to the gas compartment. The cell was a laboratory cell containing an anode compartment with a dimensionally stable (DSA) chlorine anode and a cathode compartment with a silver plated nickel wire gas diffusion electrode loaded with uncatalysed carbon (5-6 mg/cm2). The anode and cathode compartments were separated by a cation selective membrane, Nafion 450, and the distance between each electrode and the membrane was 8 mm - Electrolysis was conducted at a temperature of 70 °C in the electrolysis cell, a current density of 0.2-3 kA/m2 and at a pH of 6.2. The current was varied between 0.5- 6.3 A. The electrolysis was run for 30 h - The achieved efficiencies under two examples are shown below. Example – conditions Current Current Current efficiency for efficiency efficiency for electrolysis for chlorate (based on OH-) chlorine 50 g/L NaOH solution was pumped through the cathode 92% 100% 95% compartment at linear velocity across the cathode of 2 cm/s Solid sodium chloride was added to the reactor vessel and fed to 100% 97% the anode compartment at a rate of 0.71 g/Ah

The cell voltage for the overall chemical reaction in the gas diffusion electrode cell is about 2V, which implies that considerable operation costs can be saved by replacing the hydrogen evolving cathode with a gas diffusion electrode acting as cathode Presence of Cr(VI) in the Handling of Cr(VI): the invention is claimed with and without the use of chromates. electrolyte However, example embodiments in the patent use SD at 3 g/L

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 60 Table 4-23: Research into oxygen-consuming gas diffusion electrodes – Hakansson et al, 2004 Parameter Details Presence of Cr(VI) in electrolyte: as per typical operating conditions, where SD is used

Alternative 10: Polymeric cathode film coatings

Finally, the use of polymeric films as cathode coatings has been discussed in the literature in the past. A 1981 patent by Bommaraju et al discussed the elimination of chromates from the electrolyte in favour of a polymeric cathodic film made of chlorinated or fluorinated polymers and copolymers. An example shown based on a proprietary tetrafluoroethylene fluorocarbon showed comparable reductions in current efficiency for chlorate and/or hypochlorite reduction when compared to the use of a conventional steel cathode in a chlorate electrolyte which includes a chromate additive.

Nevertheless, this patent is now more than 30 years old; evidence of commercial use of this alternative could not be established, and the applicant has no knowledge of any such commercial use. This novel method cannot be considered a realistic option for the replacement of SD and will be given no further consideration in favour of other options discussed in this AoA.

Table 4-24: Research into polymer cathode film coatings – Bommaraju et al, 1981 Parameter Details Year 1981 Source (Bommaraju, et al., 1981)(Bommaraju, et al., 1981) Associated company/ Hooker Chemicals & Plastics Corp. research organisation Objective of research or Provision of a viable alternative to the use of chromates in chlorate cells, without invention sacrificing cell performance and efficiency through the use of a protective porous film on the surface of the cathode Relevance to the chlorate High relevance process Key changes to current - A non-conductive material is used to generate a cathode film with an average chlorate process and thickness of from about 10-4 μm to about 103 μm, and has sufficient porosity to notable improvements and permit the transport of hydrogen molecules leaving the cathode shortcomings - Materials that are substantially nonconductive and chemically resistant or inert to the chlorate solution, remaining stable in the solution during conditions of prolonged operation include various halogenated polymers, copolymers and resins, both of the thermosetting and thermoplastic variety, and particularly chlorinated and fluorinated polymers and copolymers, such as polyvinyl chloride, Teflon, Kel-F (proprietary chlorotrifluoroethylene), and Kalgard (proprietary tetrafluoroethylene fluorocarbon). The polymeric material may also be a thermoplastic polymer, such as polysulphone, or an elastomeric material, such as neoprene rubber or a silicone material. Also suitable as film- forming materials are various metallic and non-metallic oxides such as zirconium dioxide, titanium dioxide, tantalum oxide, chromic oxide (Cr2O3), vanadium trioxide, iron oxide, cobalt oxide, aluminium oxide, hafnium dioxide, niobium pentoxide, and silicon dioxide - The film-forming material can be applied to the substrate by plasma or thermal spraying, chemical vapour deposition, emulsion techniques, or other suitable techniques which will form a thin, porous surface on the substrate material - Examples of the invention have been described where the film is formed either with Kalgard or Cr2O3. These examples showed comparable reductions in current efficiency for chlorate and/or hypochlorite reduction when compared to the use of a conventional steel cathode in a chlorate electrolyte which includes a chromate additive Presence of Cr(VI) in the Handling of Cr(VI): SD was eliminated in the examples shown in the patent electrolyte Presence of Cr(VI) in electrolyte: Cr(VI) would not be present in the electrolyte

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 61 4.2.3.2: Updated literature search (2019)

The original AoA submitted by Caffaro detailed an extensive search of literature carried out by the independent third party that authored the AfA. In addition, consultation with all seven SDAC members regarding their extensive R&D efforts was used in conjunction with the publicly available information to ensure all relevant alternatives had been considered. In total, ten alternative substances and technologies were originally identified and evaluated, and as summarised in Table 4-25:

Table 4-25: Master list of identified potential alternatives for SD in sodium chlorate manufacture # Potential alternative substances 1 Chromium (III) chloride 2 Sodium molybdate 3 Rare Earth Metal (III) salts # Potential alternative cathode coatings 4 Molybdenum-based cathode coatings 5 Ruthenium-based cathode coatings 6 Zirconium- based cathode coatings # Potential alternative cathode materials 7 Ruthenium alloy cathodes # Potential alternative electrolytic processes 8 Two-compartment electrolytic systems 9 Two-compartment electrolytic cells with oxygen-consuming gas diffusion electrodes 10 Polymeric cathode film coatings

As part of this AoA update, supporting SCB’s AfA, a thorough review of literature published since 2015 on potential alternatives has been undertaken.

The following terms were searched on Elsevier’s Scopus (‘the largest abstract and citation database of peer-reviewed literature), Google, Google Scholar, Google Patents alongside ‘alternatives’, ‘sodium’ ‘dichromate’, ‘chloride’ ‘cathode coatings’ and ‘chromium IV’:

1. Sodium molybdate 2. Chromium (III) 3. Rare Earth Metal (III) salts 4. Ca(II) salts 5. Mg(II) salts 6. Yttrium 7. Samarium 8. lanthanum 9. Molybdenum 10. Ruthenium 11. Zirconium 12. Ruthenium 13. Electrolytic 14. Two-compartment electrolytic systems cells 15. Oxygen electrolytic 16. Polymeric cathode film coatings

A summary of each peer reviewed article published since 2015 relating to sodium dichromate alternatives in the manufacture of sodium chlorate is given in Table 4-26.

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 62 Of note is that for the production of sodium chlorate, two comprehensive review articles were published in 2017 (Endrődi., 2017)(Endrődi., 2017) and 2018 (Gharbi., 2018)(Gharbi., 2018) summarising all prior research on potential alternatives to the use of sodium dichromate in chlorate electrolysis.

Both articles concluded that there currently are no commercially available alternatives to sodium dichromate for sodium chlorate manufacture. Endrődi (2017) suggested that a combination of modifications may lead to the solution. Despite this, in 2018, Endrődi proposed sodium permanganate as a new alternative to chromate.

Sodium permanganate forms manganese oxide (MnOx)-containing films on cathodes during electrolysis. While these films seem to effectively supress unwanted reduction of hypochlorite and O2, the film growth is not limited (Endrődi. B., 2018)(Endrődi. B., 2018). Unlimited film growth creates larger resistances and higher cell potentials, impacting system efficiency and potentially causing practical problems, such as short-circuiting or cell clogging (Smulders, 2019).

A further search of academic and grey literature using the terms ‘sodium permanganate’, ‘dichromate’, ‘chromium’ and ‘chlorate’ revealed no further research on this potential alternative and it must be concluded that the potential alternative remains at the ‘novel’ stage only.

As such, it can be concluded that, as per the original AoA submitted by Caffaro, none of the shortlisted alternatives are feasible alternatives for SD that would eliminate the exposure of workers to the Cr(VI) species responsible for SD’s SVHC status, and this conclusion supports the SCB’s request for the Authorisation of the continued use of SD in the manufacture of sodium chlorate, as remains standard practice in the chlorate industry across the world.

SCB believes that the practical implementation at the industrial scale of the above or more novel solutions may lie many years into the future.

A long review period for the Authorisation would not only allow time to attempt to overcome the limitations in the currently known technologies, but also to explore potentially better long-term solutions.

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 63 Table 4-26: Literature review of potential alternatives to sodium dichromate for sodium chlorate manufacture between 2015-2019

Reference Alternative Conclusion Outcome Safizadeh Molybdenum-based Fe-Mo-P coatings on mild steel substrates had greater corrosion resistance Increasing knowledge of a potential (2018)(2018) cathode coatings than Fe-Mo coatings. No comparison with sodium dichromate is given alternative, no viability of replacing sodium dichromate given Endrődi (2017)(2017) Review (numerous) No single candidate has been found so far to replace sodium dichromate for No new potential alternative given the electrocatalytic production of sodium chlorate Gajić Krstajić Molybdenum-based A low dichromate content (0.1 g dm–3) is sufficient for complete suppression The application of phosphate and (2016)(2016) cathode coatings of cathodic hypochlorite and chlorate reduction onto Fe-Mo catalyst in dichromate buffering system with Fe–Mo phosphate buffering system, with little change in current efficiency alloy as a cathode might be promising technology for chlorate production Safizadeh Molybdenum-based The electrocatalytic activity of Binary Fe-Mo and ternary Fe-Mo-P coatings Fe-Mo-P could be a candidate in enhancing (2017)(2017) cathode coatings towards hydrogen evolution reaction (HER) was assessed the hydrogen evolution reaction for alkaline media. However, the corrosion performance of this alloy should be considered in the future Hedenstedt (2016) Fe(III) and Cr(III) cathode Investigated the effect of the underlying electrode on Fe(III) and Cr(III) films Increasing knowledge for potential (2016) coatings on hypochlorite reduction. Chromium films completely block the reduction alternative of hypochlorite, while for the iron oxyhydroxides films have the ability to reduce hypochlorite Smulders N/A (basis for research on Provides a mechanism for the deposition and growth termination of Describes the dynamics of formation of a III III (2019)(2019) alternative film behaviour) protective Cr Ox films on silver electrodes. Provides a basis for research on film of Cr Ox from sodium dichromate in alternative film behaviour order to aid the ongoing search for Cr(VI) replacements III Gomes (2018)(2018) Potential alternative Describes the structure of the Cr Ox film on the cathode Describes the properties of the current cathode coatings system used in order to aid research on potential alternatives Gharbi (2018)(2018) Review Review on chromium compound alternatives as a whole. No suitable No new potential alternative given alternatives to sodium dichromate in the manufacture of sodium chlorate are mentioned Kalmár (2018)(2018) None A detailed kinetic study under industrially relevant conditions describing the Describes the properties of the current thermal decomposition of HOCl/OCl- to yield ClO3- and Cl-. Demonstrates system used in order to aid research on how chromium (VI) in the electrolyte catalyses the chlorate formation in the potential alternatives solution

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 64 Table 4-26: Literature review of potential alternatives to sodium dichromate for sodium chlorate manufacture between 2015-2019

Reference Alternative Conclusion Outcome Wanngård None Describes the parallel reactions in chlorate formation and how these are Describes the properties of the current (2017)(2017) catalysed by hexavalent chromium system used in order to aid research on potential alternatives Endrődi (2018)(2018) Sodium permanganate Sodium permanganate is assessed as a possible alternative to chromate. Manganese oxides have potential in MnOx-containing films, which were deposited from permanganate solution, inducing selective hydrogen evolution, and were shown to supress unwanted reduction of hypochlorite and O2. may open new research avenues to the Unfortunately, contrary to chromium, MnOx film growth is not limited, rational design of selective cathodes creating larger resistances and higher cell potentials, alongside practical problems, including short-circuiting or cell clogging (Smulders, 2019)

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 65 4.2.4 Consultation with the supply chain

Given that SD is only used as a process aid and does not play a role in the final product (which, in the case of the applicant, is sodium chlorite into which sodium chlorate is converted), consultation with customers '''' '''''''''''''' '''''''' ''''''''''''''''' '''''' ''''''''''''#D#'''' '''' ''''''''''''' ''''''' '''''''''''''' ''''''''''''''''''' '''''''''' '''''' ''''''''' '''''''''' '''' '''''''''''''''''''' ''''''' '''''' '''''''''''''' ''''''''''' ''''''''''''' was not deemed necessary for the purposes of the AoA and was not undertaken. 4.3 Screening of identified alternatives

4.3.1 Screening of identified alternatives for commercialisation status

As already explained, this application for use of SD in the new SCB plant is based on the AfA of Caffaro. Caffaro was a member of a consortium of sodium chlorate manufacturers (SDAC) who worked together towards the preparation of their individual AfAs. Each individual applicant within this consortium supported the development of the AoA by providing information on the current commercialisation status of the identified alternatives. The aim of this analysis was two-fold:

 Establish which alternatives (if any) were immediately or otherwise readily available for adoption as a replacement for SD  Collect information on the availability of the alternatives that would be shortlisted, to inform the analysis presented in Section 5 of the AoA.

The analysis prepared on the basis of the applicants’ submissions was used in the preparation of Caffaro’s AoA documents. The overall conclusion from Table 4-27 is that none of the identified alternatives was commercially available at the time of the Caffaro application, and none would become available by the sunset date. This continues to apply in 2019, and the situation therefore remains unchanged for the SCB AoA. Several of the identified alternatives are solutions that have only been trialled at the laboratory scale with often unsatisfactory results. As is detailed in section 4.2.3.2, the updated literature review confirms that this is still the case.

Conclusion: Two of the identified alternatives, two-cell systems with oxygen-consuming diffusion electrodes and polymeric film coatings, were eliminated on the basis of commercialisation issues; the former had not been proven beyond the lab scale and only in the presence of SD, while the latter had not found commercial applications for over 30 years, therefore, could be considered a realistic option. The remaining alternatives are screened further in the rest of this section.

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 66 Table 4-27: Commercialisation status of identified alternatives for SD in the sodium chlorate process Commercial availability for the sodium chlorate process Is this a realistic Alternatives If commercially used, timeframe for If not commercially used, timeframe Currently used? alternative option? implementation for becoming available # Potential alternative substances 1 Chromium (III) No Patent (filed by Akzo Nobel) remains Impossible to estimate No chloride under examination 2 Sodium molybdate No - Impossible to estimate; still under Not currently research with significant shortcomings 3 Rare Earth metal No - Impossible to estimate; still under Not currently, (III) salts research with significant shortcomings overcoming the poor solubility is a major challenge # Potential alternative cathodic coatings 4 Molybdenum- No - Uncertain; depends on the rate of Not currently based cathode replacing of cathodes at the affected coatings plant (explained further below) 5 Ruthenium-based There are Ru-coated DSA- Generally, impossible to estimate. Not currently cathode coatings type anodes on the If the technology would be effective in replacing SD (not currently the case), the market; these cannot be first stage of implementation could potentially take less than a year, for used as cathodes since companies with access to Ru-based electrode technology. they are not stable due to Full implementation would depend on the rate of replacing of cathodes at the hydride formation on the affected plant titanium substrate, which ‘peels off’ the coating. The availability of Ru- coated cathodes is limited 6 Zirconium- based No Impossible to estimate, as past trials have been unsuccessful. Not currently cathode coatings If the technology would be effective in replacing SD (not proven to be the case, concerns exist over the coating’s lifetime), the first stage of implementation could potentially take less than a year, for companies with access to the electrode technology. Full implementation would depend on the rate of replacing of cathodes at the affected plant

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 67 Table 4-27: Commercialisation status of identified alternatives for SD in the sodium chlorate process Commercial availability for the sodium chlorate process Is this a realistic Alternatives If commercially used, timeframe for If not commercially used, timeframe Currently used? alternative option? implementation for becoming available # Potential alternative cathode materials 7 Ruthenium alloy Not for cathodes, already Uncertain; depends on the rate of replacing of cathodes at the affected plant; Not currently; may not cathodes in use as anodes uncertain commercial availability of the required alloys eliminate the use of SD # Potential alternative electrolytic processes 8 Two-cell Not for chlorate Uncertain; entire new plant would be Impossible to estimate - Not currently electrolytic production required (note: as this technology has systems not been trialled for chlorate production) 9 Two-compartment No - Impossible to estimate; still under Not foreseeably; will not electrolytic cells research. Lab trials used SD in the be considered further with oxygen- electrolyte given the use of SD consuming gas diffusion electrodes 10 Polymeric cathode No - Impossible to estimate Given the date of the film coatings patent (1981), this cannot be considered realistic and will not be considered further

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 68 4.3.2 Screening of identified alternatives for suitability in eliminating Cr(VI) exposure

An alternative to SD in the applied for use should ideally eliminate the use of SD and any associated worker exposure to the Cr(VI) anion that confers to SD its SVHC properties during the sodium chlorate production process (worker exposure for downstream users as well as consumer exposure are of no relevance to the applied for use, as discussed in the CSR). However, it is not always the case that alternatives may eliminate the use of SD or indeed the exposure to Cr(VI). Some alternatives may limit the handling of SD solution but may still result in the presence of Cr(VI) in the electrolyte; other alternatives may simply need the addition of SD (possibly, at variable concentrations) otherwise they would not be able to ensure the required current and process efficiency of the chlorate process. It is clear that if an alternative requires the addition of a similar dose of SD into the electrolyte, it could not be assumed a suitable option for the replacement of SD.

The following table summarises the available information on the identified alternatives and identifies those that would not eliminate worker exposure to Cr(VI), thus in principle would not make suitable alternatives for SD in the applied for use. The colours signify elimination of exposure (green), reduction of exposure or uncertain change (orange) and no (significant) change on current exposure conditions (red).

Table 4-28: Preliminary screening of the suitability of the identified alternatives in eliminating worker exposure to SD Current situation Alternatives Comparison to SD using SD # Potential alternative substances 1 Chromium (III) In the current No significant improvement: does not eliminate worker chloride situation, 4-5 g of exposure to Cr(VI) 2 Sodium SD is added to the Better but not optimal: to achieve acceptable process molybdate electrolyte efficiency, low presence of Cr(VI) needed 3 Rare Earth metal Better: no Cr(VI) required (III) salts # Potential alternative cathodic coatings 4 Molybdenum- In the current Uncertain: past research has shown that SD is either not based cathode situation, 4-5 g of replaced or may still need to be present at lower coatings SD is added to the concentrations (0.1 g/L) 5 Ruthenium-based electrolyte No improvement: Cr(VI) is required and a SD dosage similar cathode coatings to current would be required. The shortcomings identified in the published research will need to be overcome 6 Zirconium- based Uncertain: could eliminate the use of SD but this is not cathode coatings certain, as some of the past research was not aimed at replacing SD # Potential alternative cathode materials 7 Ruthenium alloy In the current No improvement: some alloys used in lab tests may contain cathodes situation, 4-5 g of up to 50% Cr which would reduce the consumption of SD but SD is added to the might not eliminate the presence of Cr(VI) in the electrolyte. electrolyte Later research indicates use of 3 g/L SD # Potential alternative electrolytic processes 8 Two-cell In the current Better: would eliminate the use of SD and the presence of electrolytic situation, 4-5 g of Cr(VI) in the electrolyte systems SD is added to the electrolyte

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 69 The table suggests that ruthenium-based cathode coatings and ruthenium alloy cathodes would offer no improvement; therefore, they cannot be considered realistic alternatives for SD. Cr(III) compounds would eliminate only exposure from the handling/dosing of SD solutions which only represents a substantially small proportion of overall worker exposure; Cr(III) is oxidised into Cr(VI) in the electrolyte thus generating a Cr(VI) concentration essentially identical to that obtained from the addition of SD under the Applied for Use. Cr(III) thus cannot be considered a real alternative to the use of SD.

In addition, sodium molybdate may indeed reduce worker exposure to SD but certainly does not eliminate exposure to Cr(VI). Similarly, molybdenum-based cathode coatings and zirconium-based cathode coatings are likely to require addition of SD at typical concentrations of SD in order for performance to be maintained at acceptable standards.

Only REM salts and two-cell electrolytic systems may claim that they require neither the addition nor the presence of SD in the electrolyte (but the former is clearly technically infeasible, as discussed below).

4.3.3 Screening of identified alternatives against the technical feasibility criteria

Comparison of SD to potential alternative substances

A list of technical feasibility criteria were developed and discussed in Section 2 (see Table 2-5). This development originally involved all members of the SDAC, who were asked to:

 Provide quantitative values or qualitative descriptions of how each of the technical feasibility criteria are fulfilled by SD along with a minimum value or threshold that must be achieved by an alternative  Use the technical feasibility criteria and their thresholds or ideal values/ranges to (a) compare each alternative substance to SD, and (b) compare the SD-based state-of-the-art chlorate technology to the alternative technologies identified, in support of the information obtained from the literature review.

Generally, a semi-quantitative approach was taken where each alternative to SD is compared and rated as “Similar”, “Better” or “Worse”.

This systematic comparison of alternatives is shown in Table 4-29. The colouring code of the cells is as follows:

 Green colour indicates an alternative that meets and notably exceeds the value achieved by SD under the criterion (i.e. the substance is “Better” than SD)  White colour indicates an alternative that meets the threshold/range of a criterion (i.e. the substance is “Similar” than SD)  Orange colour indicates an alternative that may or may not meet the threshold/range of a criterion, i.e. there is uncertainty or it may marginally fail the criterion  Red colour indicates an alternative that does not meet the threshold/range of a criterion (i.e. the substance is “Worse” than SD).

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 70 Table 4-29: Comparison of alternative substances to SD against the technical performance criteria Criteria Sodium dichromate Alternative substances Result or numerical Threshold or Chromium (III) chloride Sodium molybdate Rare Earth metal (III) salts value achieved by acceptable range for sodium dichromate replacing sodium dichromate Formation of No suitable  2 % Similar: Cr(III) is oxidised to Uncertain: it creates a Worse: salts are not soluble at protective film numerical value, but Cr(VI) immediately (in the protective film but the process conditions. In trials, permeable to hydrogen efficiency presence of active chlorine) thickness of the film grows too rare earth metals started to hydrogen >98 % and acts as if SD had been thick and energy consumption precipitate at pH 4.8 and trials used as an additive will increase at normal operating pH 6.5 were not even possible to perform. REM hydroxide film is not permanent at typical operating conditions Formation of No numerical value Ideally, similar to SD Similar (assumed) Worse: worse current Worse: salts are not soluble at protective film efficiency implies lower process conditions impermeable to selectivity hypochlorite Control of oxygen SD achieves <2.5% Ideally less than Similar (assumed) Worse: research indicates 3.6- Worse: salts are not soluble at formation (and O2 evolution 2.5% by volume of 4.8% O2 generation, process conditions control of oxygen O2 in H2 with 4% an suggesting Mo(VI) needs to be content in absolute maximum as low as possible hydrogen) Cathode Cannot be At least ''' ##A#''''''''' Similar (assumed) Uncertain Worse: salts are not soluble at protection quantified; minimum cathode lifetime process conditions (corrosion lifetime of cathode is inhibition) assumed to be ''''#A#''''' for the applicant pH buffering 6.0-6.5 6.0-6.5 Similar (assumed) Worse: addition of phosphate Worse: salts are not soluble at buffer is required; this leads to process conditions cracks on the cathodic film and affects the durability of the anodes

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 71 Table 4-29: Comparison of alternative substances to SD against the technical performance criteria Criteria Sodium dichromate Alternative substances Result or numerical Threshold or Chromium (III) chloride Sodium molybdate Rare Earth metal (III) salts value achieved by acceptable range for sodium dichromate replacing sodium dichromate Current efficiency >95%, 5,230 kWh/t Energy efficiency: Similar (assumed) Worse: 80-91% or lower. Worse: salts are not soluble at and energy theoretical ''##A#''''' or more However, similar process process conditions consumption ''''''''' Total energy efficiency can be reached by ''''''''''' #A#'''' '''''' consumption: '''''''''' only partially replacing SD with ''''''' '''''''''''''''''' ''''''''''''##A#'''''''''''' or molybdate less Solubility in Highly soluble (Highly) soluble Similar (assumed) Similar Worse: salts are not soluble at electrolyte Solubility of SD: process conditions ca. 2355 g/L Control of ''''''''''''' '''''''''''''''''''' ''''''''''''' ''''''''''''''''''' ''''' Similar (assumed) ''''''''''''''' '''''''''''''' '''''''''''' ''''' ''''' '''''''''''''''' '''''''''''''' ''''''''''''''''' Impurities in the ''''' '''''''''''''' ''''' ''''''' #A# '''''''''''' '''''''''''''' ''''''''''' '''''''''''''''''' '''''''''' ''''''''''' ''''''' '''' '''''''' '''' ''''''''''''''''' NaClO3 solution in '''''''''''''#A#''' ''''''' '''''''' ''''''''' ''''''''''''' ''''''''' ''''''''' '''' '''''' ''''''''''''''' '''''''' '''''''''''' '''''''''''' '''''''' ''''''''' ''' exit from the '''''''' ''''''''''' '''''''''''''' '''''''''''' '''''''''''''''''''''' '''''''' '''''''''' ''''' ''''''' '''''''''''''' electrolytic cell ''''''''''''''''' #I# '''''' '''''''''''''''' '' ''''' '''''''''''''#I# ''' '' '''''''' ''''''' and in entrance in '''''''''''''''' '''''' ''''' ''''''''''''' '''''''''''' ''''''''''''''''' ''''''''''''''''' ''''''' '''' the ClO2 generator '''''''''''' '''''''''''''''''''''' ''''''' ''''''''''''''' ''''''''''' ''''''''''' '''''''''''''''''' '''''''''' ''''''' ''''''''''''''' ''''''''''''''''''''' ''''''' ''''''''''''''''' ''''' ''''''' ''''''''''''' ''''''''''''''' ''''''''''' '''''' '''''''''''''' '''' ''''''' ''''''''''''''' ''''''''''''''

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 72 The conclusions from this analysis are as follows:

 The only alternative substance that theoretically could be considered to meet the technical feasibility criteria is CrCl3 (more accurately, Cr(III)), as it is assumed to effectively give Cr(VI) in the electrolyte and thus deliver the technical functions of the chromates within the chlorate cell). However, the applicant does not have access to the details of this technology and therefore the exact conditions and parameters under which such performance equivalence can be obtained are not known, nor does this alternative reduce worker exposure to Cr(VI);

 Rare Earth Metal salts are clearly infeasible replacements for SD. Their solubility at process conditions is very poor and prevents them from performing their intended role. No solution has been found so far on making the solubility of these compounds acceptable for the purposes of sodium chlorate production. These substances cannot be considered technically feasible alternatives;

 Sodium molybdate is accompanied by a major hazard concern, the generation of O2 in quantities that may lead to explosive mixtures with H2, which is also released. This inherent hazard does not exist in the current technology that is based on SD. Sodium molybdate is a poorer pH buffer, which requires the addition of phosphates; however, the presence of phosphates has an adverse effect on the stability of the cathodic film and the durability of the anodes. In addition, Mo(VI) is accompanied by poorer current efficiency, which may be around or below 90%, unless some SD is added to the electrolyte; and

   

Comparison of the SD-based chlorate production process to potential alternative technologies

A similar comparison of the SD-based chlorate process was performed for alternative technologies. The overview of comparison against the technical feasibility criteria is shown in Table 4-30. The colour coding is similar to the one in the previous table on alternative substances. The following conclusions may be reached:

 All of the alternative technologies have technical disadvantages, for example, poor pH buffering would require in each and every case the use of phosphate additives which could cause problems at the anode;

 Alternatives other than two-cell electrolytic systems are shrouded by uncertainty as regards their ability to generate a film around the cathode of ‘equivalent’ impermeability to hypochlorite and permeability to hydrogen;

 The control of O2 formation is likely to be worse for Ru-based coatings;

 The use of two-cell electrolytic systems might lead to higher energy consumption;

 Technologies other than two-cell electrolytic systems may not be able to eliminate the use of SD. Notably, relevant past research has not really focused on the elimination of SD and for Ru-based cathode coatings and Ru alloys there are well-founded concerns that Cr(VI) will continue to be present in the electrolyte; and

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 73   

Conversely, from a more positive perspective,

 Mo-based coatings may be accompanied by improvements in current efficiency (this may also be the case for Ru-based coatings and Ti-Ru alloys, but this is uncertain); and

 Two-cell electrolytic systems use separated electrodes, thus eliminate the need for the formation of selective films on the cathode and would prevent the development of explosive atmospheres as the generated gases (H2 and O2) would not be allowed to mix.

Overall, it would seem that two-cell electrolytic systems would have some distinct advantages over other technologies but would not be ‘trouble-free’. Ru-based coatings and Ru alloys would appear to be the least appropriate alternative technologies.

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 74 Table 4-30: Comparison of alternative technologies to SD-based chlorate process against the technical performance criteria Criteria Sodium dichromate Alternative technologies Result or Threshold or Mo-based Ru-based coatings Zr-based coatings Ru alloy cathodes Two- numerical value acceptable range coatings compartment achieved by for replacing electrolytic sodium sodium systems dichromate dichromate Formation of No numerical  2 % Uncertain: Uncertain: different Uncertain: Uncertain: Not relevant to protective film value, but different technology to SD. It different different this technology: permeable to hydrogen technology to SD. may perform well if technology. The technology. The cells/electrodes hydrogen efficiency >98 % The film is not SD is present. RuO2 film is not formed film is not formed are separated formed may reduce cathodic but imposed; its but imposed; its electrolytically but overpotential to effectiveness is effectiveness is imposed as a hydrogen evolution. unclear unclear coating Coating has shown poor stability Formation of No numerical Ideally, similar to Uncertain: Worse: different Worse: different Uncertain: Not relevant to protective film value SD different technology to SD. technology. The different this technology: impermeable to technology to SD. RuO2 coating film is not formed technology. The cells/electrodes hypochlorite The film is not effectiveness in but imposed; ZrO2 film is not formed are separated formed electrolytic preventing parasitic based coatings but imposed; its ally but imposed reactions is poor reduce the rate of effectiveness is as a coating (reduction of hypochlorite unclear. Lab tests hypochlorite and reduction, but do with Ru-Ti alloys chlorate ions) not entirely inhibit would suggest a it (unless perhaps low rate of combined with hypochlorite other oxides) reduction

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 75 Table 4-30: Comparison of alternative technologies to SD-based chlorate process against the technical performance criteria Criteria Sodium dichromate Alternative technologies Result or Threshold or Mo-based Ru-based coatings Zr-based coatings Ru alloy cathodes Two- numerical value acceptable range coatings compartment achieved by for replacing electrolytic sodium sodium systems dichromate dichromate Control of SD achieves Ideally less than Uncertain Marginally worse: Ru Uncertain Similar: Ru-Ti Better: cathode oxygen <2.5% O2 2.5% by volume released from the alloys have shown and anode are formation (and evolution of O2 in H2 with coating can increase low evolution of physically control of 4% an absolute the bulk formation of oxygen, but separated by a oxygen content maximum oxygen generally membrane and in hydrogen) the bulk of anodic produced gases formation of (H2 & O2) do not oxygen is not mix influenced by change of the cathode coating/material Cathode Cannot be At least ''' '''' Uncertain, Uncertain: requires Uncertain Worse: no film or Better: no protection quantified; cathode lifetime possibly similar further study coating at all; particular need for (corrosion minimum presence of iron in this. The special inhibition) lifetime of the alloy may lead materials used are cathode is to corrosion not easily '''''''''' ''' ''''' effects. Ru alloys corroded '''' '''''''''' '''''' '''''' with Fe/Al show '''''''''''''''''' poor stability in acidic pH and require addition of metals such as Ta to improve corrosion resistance

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 76 Table 4-30: Comparison of alternative technologies to SD-based chlorate process against the technical performance criteria Criteria Sodium dichromate Alternative technologies Result or Threshold or Mo-based Ru-based coatings Zr-based coatings Ru alloy cathodes Two- numerical value acceptable range coatings compartment achieved by for replacing electrolytic sodium sodium systems dichromate dichromate pH buffering 6.0-6.5 6.0-6.5 Worse: need for Worse: need for Worse: need for Worse: need for Worse: need for addition of addition of buffering addition of addition of adjustment of pH buffering agent, agent, e.g. sodium buffering agent, buffering agent, (e.g. NaOH/HCl e.g. sodium phosphate. e.g. sodium e.g. sodium feedback loops) phosphate (3 g/L). Phosphates as Cr phosphate, phosphate, Phosphates as Cr replacement may expected expected replacement may cause problems at cause problems at the anode the anode Current >95%, 5,230 Energy efficiency: Better: according Uncertain: past Uncertain: 91% Uncertain, Worse: using efficiency and kWh/t '''''' or more to patents, a lower research would current efficiency probably worse: typical electricity energy theoretical Total energy cell voltage can be suggest it is possibly reported for ZrO2 past research consumption consumption ''''' consumption: achieved using this better (activated modified with Y2O3 would suggest it is figures for a chlor- ''''''''''''''''''' ''''' ''''''''''''' technology, cathodes decrease on a zirconium possibly better by alkali plant, the ''''' '''''' ''''''''''''''''' ''''''''''''''' or less resulting in a lower energy plate in a reducing specific overall energy energy consumption), if hypochlorite cell energy consumption can consumption RuO2 used alongside consumption (Ru be calculated to be other oxides but only alloys lead to a worse than what is in the presence of SD reduction of the achieved with SD hydrogen overpotential). Materials based on Fe3Al alloy doped with Ru and Ta may still require SD (3 g/L)

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 77 Table 4-30: Comparison of alternative technologies to SD-based chlorate process against the technical performance criteria Criteria Sodium dichromate Alternative technologies Result or Threshold or Mo-based Ru-based coatings Zr-based coatings Ru alloy cathodes Two- numerical value acceptable range coatings compartment achieved by for replacing electrolytic sodium sodium systems dichromate dichromate Solubility in Highly soluble (Highly) soluble Not relevant Not relevant Not relevant Not relevant Not relevant electrolyte Solubility of SD: ca. 2355 g/L Control of '''''''''''''' ''''''''' ''''' ''''''''''''' Probably worse Probably worse for Probably worse Probably worse Uncertain Impurities in the ''''''''''' ''''' ''''''''''''''''' ''''' for the stability of the stability of the for the stability of for the stability of NaClO3 solution '''''''''''''''''' ''''''' ''''''''''''' '''' the subsequent subsequent chlorite the subsequent the subsequent in exit from the '''''''' '''''''''''' ''''''''''''''''''' ''''''' chlorite process process chlorite process chlorite process electrolytic cell '''''''''''''' '''''''' ''''''''''' and in entrance ''''''''''''' in the ClO2 generator

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 78 4.3.4 Screening of identified alternatives for practicality and (preliminary) economic feasibility

Members of the SDAC, including Caffaro, were requested to outline the practical (engineering) steps that would be required for the implementation of each alternative. They were also asked to identify the most critical of these steps and highlight any issues that would require substantial expenditure or extended timelines. The results are shown in Table 4-31. The conclusion on the realism of each alternative solution is highlighted in colour:

 Green, for feasible and readily implementable solutions  Orange, for alternative solutions with distinct engineering challenges and/or practicality issues  Red, for alternatives that are infeasible from a practical and engineering perspective.

The results are valid also for the SCB in the case new technology becomes available after the construction of its plant.

We therefore can identify the following ‘groups’ of alternatives that may be feasible alternatives in terms of practicality:

 CrCl3 could theoretically be feasible to implement (in comparison to other alternatives), on the basis of its similarities to SD and the (limited) information that is publicly available. However, as the applicant does not have access to the relevant patent, access rights need to be secured first, after the patent has been granted, before the ease or not of implementation can be confirmed; however, it is very important to note that this alternative does not reduce worker exposure to Cr(VI)  Sodium molybdate, molybdenum-based cathode coatings, ruthenium-based cathode coatings, ruthenium alloy cathodes and two-cell electrolytic systems are technically demanding and not immediately available, but could theoretically be implemented in the longer term. Of these, the use of sodium molybdate as an additive would be the relatively simpler option. On the other hand, the use of new cathode coatings and alloys would require the gradual replacement of existing cathodes; due to the number of cathodes involved, this can only be undertaken over a long period. In addition, the implementation of two-cell systems would practically require a new plant to be set up  Rare Earth Metal salts and zirconium-based cathode coatings are not considered realistic. The former simply cannot work as additives to the electrolyte, and the latter have not been proven as their industrial upscale failed in the past.

4.3.5 Summary of screening process for alternatives

A summary of the entire screening approach presented above is given in Table 4-30. The colour code is as follows:

 Green: acceptable/feasible  Orange: feasible with complications and/or disadvantages in comparison to SD  Red: infeasible/unrealistic.

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 79 Table 4-31: Practical and economic feasibility screening of potential alternatives Alternatives Practical steps required Key complexities of practical steps Conclusion # Potential alternative substances 1 Chromium (III) - The patent is still under examination. The applicant - Need to wait for patent to be granted and become Uncertain feasibility compounds has no access to the details of the technnology available for licensing and cost, while 3rd - Securing access to relevant patent once it is granted - Unclear complexity party patent - R&D to assess feasibility for the SCB plant - The cost of licensing is uncertain; reliance on this application and technology would also mean reliance on a patent held access to patent by a direct competitor pending 2 Sodium - Needs to be scaled up from lab scale - In theory, technically feasible but scaling up fraught From an engineering molybdate - Substitution of overall volume of the electrolyte with uncertainties perspective feasible (solution of chlorate) available in a plant; potentially - Separation of SD from electrolyte and management of but yet unavailable possible to have both substances in the same the waste on an industrial electrolyte, cutting off one and adding the other - Changes to the equipment for handling hydrogen scale - Redesign of safety measures and hazard controls with - Equipment clean-up and preparation of new solution regard to hydrogen handling (vis-à-vis the increased would require downtime generation of O2 gas) 3 Rare Earth - Needs to be scaled up from lab scale - Very difficult to address the issue of poor solubility From an engineering Metal (III) salts - Substitution of overall volume of the electrolyte - Separation of SD from electrolyte and management of perspective (solution of chlorate) available in a plant; unclear if the waste infeasible and possible to have both substances in the same - Changes to the equipment for handling hydrogen unavailable on an electrolyte, cutting off one and adding the other - Equipment clean-up and preparation of new solution industrial scale would require downtime

# Potential alternative cathodic coatings 4 Molybdenum- - Substitution of overall volume of the electrolyte - Separation of SD from electrolyte and management of From an engineering based cathode (solution of chlorate) available in a plant the waste perspective very coatings - Activation of new iron cathodic sheets would be - Existing cathode replacement would be very costly and demanding and necessary* will only be possible to undertake over several years or costly; unavailable - Assembly of new cathodic sheets and replacement of involve a significant plant shutdown on an industrial all cathodes currently in use - Known patents are held by third parties scale; potential - Requires an upgrade of process management software patent issue

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 80 Table 4-31: Practical and economic feasibility screening of potential alternatives Alternatives Practical steps required Key complexities of practical steps Conclusion 5 Ruthenium- - Substitution of overall volume of the electrolyte - Separation of SD from electrolyte and management of From an engineering based cathode (solution of chlorate) available in a plant the waste perspective very coatings - Activation of new Ti sheets would be necessary to give - Existing cathode replacement would be very costly and demanding and them the morphology (physical dimensions) of actual will only be possible to undertake over several years or costly; unavailable cathodes (current Ru-coated electrodes are used as involve a significant plant shutdown on an industrial anodes) - Compared to Mo-based coatings, additional cost for scale - Assembly of new cathodic sheets and replacement of titanium rather than iron electrodes plus activation- all cathodes currently in use related costs for the use of precious metals - Requires an upgrade of process management software 6 Zirconium- - Needs to be scaled up from lab scale - Past attempts at industrial scale-up have failed From an engineering based cathode - Substitution of overall volume of the electrolyte - Separation of SD from electrolyte and management of perspective very coatings (solution of chlorate) available in a plant the waste demanding and - Activation of new iron cathodic sheets would be - Existing cathode replacement would be very costly and costly. Unavailable necessary will only be possible to undertake over several years or on an industrial - Assembly of new cathodic sheets and replacement of involve a significant plant shutdown scale all cathodes currently in use - Requires an upgrade of process management software # Potential alternative cathode materials 7 Ruthenium - Needs to be scaled up from lab scale - Separation of SD from electrolyte and management of From an engineering alloy cathodes - Substitution of overall volume of the electrolyte the waste perspective very (solution of chlorate) available in a plant - Existing cathode replacement would be very costly and demanding and - Activation of new alloy cathodic sheets would be will only be possible to undertake over several years or costly; unavailable necessary involve a significant plant shutdown on an industrial - Assembly of new cathodic sheets and replacement of - Compared to Mo-based coatings, additional cost for scale and issues with all cathodes currently in use titanium rather than iron electrodes plus activation- market availability - Requires an upgrade of process management software related costs for the use of precious metals - Uncertain commercial availability of alloys - May need to obtain access to patents held by 3rd parties

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 81 Table 4-31: Practical and economic feasibility screening of potential alternatives Alternatives Practical steps required Key complexities of practical steps Conclusion # Potential alternative electrolytic processes 8 Two-cell - Substitution of overall volume of the electrolyte - The applicant is not familiar with this technology being From an engineering electrolytic (solution of chlorate) available in a plant used for the manufacture of chlorate perspective feasible systems - Replacement of all the cells would be necessary. The - In theory, technically feasible but scaling up fraught in the medium-long brine treatment would require consequent with uncertainties term; very costly overhauling, the crystallisation section debottlenecked - Replacement of all the electrolysers with new and time-consuming and the electrical power supply increased without electrolysis cell-rooms and long period of shut-down increasing capacity - Several years may be required for design planning and - New retention systems for Cl2 on the production of scaling; even engineering implementation after all chlorate would be required other steps have been taken could require several - Significant number of HAZOP studies and additional years training of personnel due to fundamental changes to - Costs will be several millions of Euros (including costly the chlorate production process membranes) - Requires an upgrade of process management software - Effectively, a new plant would be required * Activation refers to the coating a base metal (Fe, Ti) with an active layer which acts as a catalyst for the generation of hydrogen. This active layer is composed of various metals and requires a treatment process of the surface base and its components. Also, the composition and morphology of the active layer must match very strict ranges of variation, i.e. an anode and a cathode, whether or not coated, are not interchangeable in their functions

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 82 Table 4-32: Summary of the screening of identified potential alternatives for SD in the manufacture of sodium chlorate Suitability as SD Comparison to SD Shortlisted for Commercialisation Engineering and Alternative replacement against technical Overall commentary further status economic feasibility (exposure) feasibility criteria analysis? No Potential alternative substances 1 Chromium (III) Unavailable Not suitable due to Uncertain due to lack Uncertain feasibility With only a minor No; it is not a compounds minimal reduction in of knowledge of and cost while 3rd reduction in worker suitable but not elimination conditions and party patent exposure to Cr(VI), it alternative of worker exposure parameters of use. application pending cannot be considered to Cr(VI) a suitable option 2 Sodium Unavailable; To achieve Poorer current From an engineering Yes molybdate unknown future acceptable process efficiency and release perspective feasible efficiency, low of O2 that may lead to but yet unavailable on A simple alternative; concentrations of explosive an industrial scale however, with worse Cr(VI) in the atmospheres; performance than SD electrolyte may be phosphate presence and not proven on an needed has a serious effect on industrial scale anodes; metal impurities 3 Rare Earth Unavailable; In theory, no Cr(VI) Poorly soluble with From an engineering No; cannot be Not soluble at normal Metal (III) salts unknown future required impurities issues; perspective infeasible used chlorate production technically infeasible and unavailable on an conditions; unusable industrial scale

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 83 Table 4-32: Summary of the screening of identified potential alternatives for SD in the manufacture of sodium chlorate Suitability as SD Comparison to SD Shortlisted for Commercialisation Engineering and Alternative replacement against technical Overall commentary further status economic feasibility (exposure) feasibility criteria analysis? No Potential alternative cathodic coatings 4 Molybdenum- Unavailable; SD is either not Poorer pH buffering; From an engineering Patent literature Yes based cathode unknown future replaced or may still unclear reaction perspective very suggests reduced coatings need to be present at selectivity; better demanding and costly; energy consumption lower concentrations claimed energy unavailable on an and avoidance of SD (0.1 g/L) efficiency; phosphate industrial scale (but uncertain); not presence has a serious proven on an effect on anodes; industrial scale metal impurities 5 Ruthenium- Unavailable; Cr(VI) is required and Poorer pH buffering From an engineering Unproven and No; it is not a based cathode unknown future a dosage similar to and reaction perspective very infeasible; still requires suitable coatings current would be selectivity; demanding and costly; the use of SD; alternative, required impurities issue; metal existing electrodes are unsuitable neither is it impurities used as anodes rather technically than cathodes; feasible unavailable on an industrial scale 6 Zirconium- Unavailable; Could eliminate the Generally uncertain; From an engineering Costly and demanding No; cannot be based cathode unknown future use of SD but this is poorer pH buffering; perspective very alternative; used coatings not certain may still require SD; demanding and costly; unavailable on an impurities issue; metal unavailable on an industrial scale impurities industrial scale

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 84 Table 4-32: Summary of the screening of identified potential alternatives for SD in the manufacture of sodium chlorate Suitability as SD Comparison to SD Shortlisted for Commercialisation Engineering and Alternative replacement against technical Overall commentary further status economic feasibility (exposure) feasibility criteria analysis? No Potential alternative cathode materials 7 Ruthenium alloy Unavailable; Some alloys used in Poorer pH buffering, From an engineering Technically interesting No; it is not a cathodes unknown future lab tests may contain cathode corrosion perspective very due to its potential to suitable up to 50% Cr. More protection and demanding and costly; reduce energy alternative, recent research reaction selectivity; unavailable on an consumption but, neither is it indicates use of 3 g/L impurities issue; metal industrial scale and unproven, costly, technically SD impurities issues with market raises concerns on feasible availability cathode lifetime and alternative buffering agents may also cause unexpected problems (e.g. higher O2 evolution). Would still require SD No Potential alternative electrolytic processes 8 Two-cell Unavailable for chlorate Would eliminate the Better separation of From an engineering Theoretically feasible; Yes electrolytic manufacture; use of SD and the electrodes and gases perspective feasible in however, not without systems unknown future presence of Cr(VI) in and lower product the medium-long disadvantages and the electrolyte impurities but poorer term; very costly and extremely costly current efficiency time-consuming; increased energy consumption can be calculated

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 85 Based on the above findings and using expert judgement, some of the identified alternatives can be excluded from further consideration:

 Cr(III) compounds would confer only minimal improvements to worker exposure to Cr(VI) and thus could only be seen as an additional Risk Management Measure (RMM) when and if the technology becomes available beyond the patent holder;

 Rare Earth Metal salts (due to their poor solubility);

 Ruthenium-based cathode coatings (as they could not reduce or eliminate the use of/exposure to Cr(VI));

 Zirconium-based cathode coatings (as their industrial scale-up has failed in the past and they cannot guarantee the elimination of SD use); and

 Ru-based alloy cathodes (as they are found to be fraught with uncertainty and unable to reduce or eliminate the use of/exposure to Cr(VI)).

In conclusion, the following three alternatives are considered – in principle – realistic and will be assessed further in Section 5 of this AoA:

 Alternative 2 (substance): Sodium molybdate  Alternative 4 (technology): Molybdenum-based cathode coatings, and  Alternative 8 (technology): Two-compartment electrolytic systems.

The analysis in Section 5 is essentially provided for completeness. As it was demonstrated in the Caffaro AoA, these alternatives were not feasible replacements for SD and this remains the case as of 2019.

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 86 5 Suitability and availability of possible alternatives

5.1 Introduction and scope of analysis

The analysis below includes the following elements:

 Analysis which has to a great extent been based on publicly available information; and  Where available and appropriate, applicant-specific information has been included.

For this SCB AoA specifically, there are a number of points which apply to the assessment of the suitability and availability of the three alternatives under consideration. Because this is a new plant, currently under construction, it should be noted that:

 The new plant will be a modern update of the Caffaro plant technology with minimised worker exposure compared to Caffaro;

 Because all three alternatives are technically unfeasible, the economic feasibility is of little relevance. Moreover, the SCB plant is not operational so there are no operational data which could be used for quantifying changes in operating costs. The Caffaro AoA Section 10 details these costs, and these offer an indication of what the costs could be for SCB13;

 If an alternative were to become technically feasible and available, in terms of timing it would be too late to redesign and reconstruct the new SCB plant to implement the new alternative as the plant must be built and become operational before Caffaro stops production so as to ensure continuity of supply to Caffaro’s customers; and

 SCB’s investment in the new plant amounts to over ''''''###B#' '''''''''''' which is an additional amount that would need to be written off if an alternative were to be in the future found to be feasible. 5.2 Sodium molybdate (two available forms)

5.2.1 Substance ID and properties

The two relevant disodium molybdate substance identities are presented in Table 5-1.

13 Caffaro AoA: https://echa.europa.eu/documents/10162/5e4bf84e-5725-4633-bb47-da66770a5b9 6

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 87 Table 5-1: Identity of available forms of disodium molybdate

Properties Disodium molybdate Sodium molybdate di-hydrate

EC Number 231-551-7 CAS Number 7631-95-0 600-158-6 Sodium dioxide(dioxo)molybdenum IUPAC Name: Disodium dioxide-dioxomolybdenum hydrate (2:1:2) Formula MoO4·2Na Na2MoO4·2H2O Molecular weight 205.92 241.92

Structure

Sources: 1: http://esis.jrc.ec.europa.eu/ 2: ECHA dissemination portal: http://apps.echa.europa.eu/registered/data/dossiers/DISS-9eb7d44e-5b59- 695c-e044-00144f67d031/AGGR-d3c96bda-6117-42e7-bf76-918c545cb4f7_DISS-9eb7d44e-5b59-695c- e044-00144f67d031.html#section_1.1 3: https://upload.wikimedia.org/wikipedia/commons/0/08/Natriummolybdaat.png 4: http://pubchem.ncbi.nlm.nih.gov/summary/summary.cgi?cid=16211258

Table 5-2 provides an overview of the physicochemical properties of disodium molybdate.

Table 5-2: Physicochemical properties of disodium molybdate Property Value Note Physical state at 20°C and 101.3 Crystalline solid colourless to at 20 °C and at 1013 hPa kPa white Melting/freezing point No data Decomposes > 100 °C Boiling point - - Density 2.59 at 23.3 °C OECD Guideline 105 (Water Water solubility ca. 654.2 g/L at 20 °C at pH 8.8 Solubility) Auto-flammability Not justified Flammability Not justified Explosiveness Not justified Recommendations on the Transport of Dangerous Goods, Oxidising properties No oxidising properties Manual of Tests and Criteria, Part 34.4.1, Test O.1: Test for oxidizing solids Guideline 67/548(EEC (Council Directive 92/69/EEC) % ile: D10, Mean: 34.5 µm OECD Guideline 110 (Particle Size Granulometry % ile: D50, Mean: 143.1 µm Distribution / Fibre Length and % ile: D90, Mean: 295.9 µm Diameter Distributions) CIPAC MT 187: Particle Size Analysis by Laser Diffraction

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 88 Table 5-2: Physicochemical properties of disodium molybdate Property Value Note ISO13320-1: Particle Size Analysis- Laser Diffraction Methods Sources: 1. ECHA dissemination portal: http://apps.echa.europa.eu/registered/data/dossiers/DISS-9eb7d44e-5b59- 695c-e044-00144f67d031/AGGR-e8329392-562d-40df-96dc-082576cf46a0_DISS-9eb7d44e-5b59-695c- e044-00144f67d031.html#AGGR-e8329392-562d-40df-96dc-082576cf46a

5.2.2 Technical feasibility

Assessment of technical feasibility

The use of sodium molybdate as a potential alternative to the use of SD has been proposed due to a combination of its buffering properties and an ability to form a protective film on the cathode. The available information indicates that the use of sodium molybdate has not yet been demonstrated on a commercial scale and that academic R&D efforts have identified significant limitations.

Important differences to SD have been found to affect the ability of sodium molybdate to meet the technical feasibility criteria, as shown in the available scientific literature. In general, sodium molybdate is lacking in performance, in comparison to SD and this has led some researchers to trial the use of sodium molybdate in parallel with reduced amounts of SD with the aim of achieving the required process parameters. As the aim of the alternative in this case is to eliminate SD, the comparison between sodium molybdate and SD that is shown in Table 5-3 has been carried out assuming no SD is present.

Table 5-3: Comparison of sodium molybdate and sodium dichromate according to technical feasibility criteria Result or value achieved Technical Sodium Criteria pass? feasibility criteria Threshold Sodium molybdate dichromate It creates a Formation of protective film but protective film that published research is permeable to Sufficient Similar to SD suggests it grows  hydrogen and too quickly and is impermeable to potentially hypochlorite unstable pH 5.0-6.0; O2 in H2 pH buffering and pH 6-6.5; <4% O2 in 3.6-4.8% control of oxygen pH 6-6.5; <2.5%  H2 by volume Additional buffer is formation required Cathode protection Unknown Minimum ''''''''''''''' (corrosion Sufficient (laboratory scale ? ''''''''''' ''' '''''''''' inhibition) only) 95%, 5,230 kWh/t Current efficiency theoretical 86% current ''''''''' '''' ''''''''''' '''' and energy '''''''' efficiency; 5,746  ''''''''''''' ''' consumption '''''''''' ''''''''' ''''' kWh/t theoretical '''''' '''''' '''''''''''''''' Solubility in 654.2 g/L Highly soluble Sufficient  electrolyte Sufficient

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 89 Table 5-3: Comparison of sodium molybdate and sodium dichromate according to technical feasibility criteria Result or value achieved Technical Sodium Criteria pass? feasibility criteria Threshold Sodium molybdate dichromate Control of '''''''''''''''''' '''' Impurities in the '''''''''''''' '''''''''''''''''' '''''''''''''' ''''''''''''''''''' '''''''''''''''''' ''''''''''' NaClO3 solution in ''''' ''''''''''''' '''' ''''' '''''''''''''' '''' ''''''''' exit from the '''''''''''''''''' '''''' '''''''''' '''''  '''''''''''''''''' '''''' electrolytic cell and ''''''' ''''''''' '''''''''''' ''''''' ''''''' ''''''''''''' ''' '''''''''''''''''''''''' '''' in entrance in the '''''''''''' '''''''''''' ''''''' ''''''''''''''''''''' ClO2 generator

Overall, the comparison suggests that sodium molybdate meets one criterion, under the current state of knowledge, fails four criteria and for a sixth criterion, no conclusion can be reached on the basis of available information. The following paragraphs explain the shortcomings of this alternative in more detail.

Detailed presentation of technical characteristics of the alternative

Formation of a protective film: the substance is capable of forming a protective film around the cathodes; however, its thickness may grow excessively quickly, thus affecting the efficiency of the electrochemical reactions by increasing energy consumption. In comparison, the dichromate film only grows to a certain extent (it is self-limiting) depending on current density and chromate content. Also, as discussed in Section 4.2.3, the presence of phosphates (the necessity of which is discussed below) interfere with the formation of the molybdate film. At high Mo concentrations, 80 mM molybdate in the electrolyte, a cracked film was formed on the cathode surface. If the amount of molybdate in the lab tests was low (4 mM) and the electrolyte also contained between 10 and 40 mM phosphate no molybdenum film was visible with Scanning Electron Microscopy (SEM) or detectable with Energy- dispersive X-ray spectroscopy (EDX) on the cathode surface. ''''''''''''''''''' '''' '''''''''''''''' ''''''' '''''''''''''''''' '''''''''' '''''''''''''''''''''''' ''' ''' ''''''''''''''' '''' ''''''''''''''' ''' '''''''''''''''''''''''''' ''''''' '''''''''' ''''''' ''''''''''''''' '''''''' ''''''' '''''''''''''' '''''''''' ''''''''''''''''' '''''''''' ''''''''''' ''''' ''''' '''''''''''''''''''''''''''''''''' ''''''''''''''''''' ''''''''''''''' '''''''''' ''''''''''''' ''''''''' '''' ''''' '''''''''''''''' '''''''' ''''''''''''''''''''''''' '''''''''''' ''''''''''''''''' ''''''''''''''''' '''''''''''''''' '''''''' ''''''''''''''''' '''''' '''''''''''''''''' ''''' '''''' ''''''''''''''''' '''''''''''''' '''''''' '''' '''''' '''''''''''''''''''' '''' ''''''''''''''''' ''''''''''''''''' '''''''' ''''''''''''''''''''''''' '''''''''''''''''' '''''''''''''''''''''''''

In addition, as discussed in Section 4.2.3, the presence of phosphates (the necessity of which is discussed below) interfered with the formation of the molybdate film. At high Mo concentrations, 80 mM molybdate in the electrolyte, a cracked film was formed on the cathode surface. If the amount of molybdate in the lab tests was low (4 mM) and the electrolyte also contained between 10 and 40 mM phosphate no molybdenum film was visible with Scanning Electron Microscopy (SEM) or detectable with Energy-dispersive X-ray spectroscopy (EDX) on the cathode surface. pH buffering and oxygen formation: molybdate’s typical buffer region (pH 5-6) is lower and narrower than SD and low level of Mo(VI) in the electrolyte cannot assure a good buffering performance. As the ability of sodium molybdate to function as a pH buffer in the region required for the chlorate reaction (see Section 2.2.1) is limited, it may require the addition of an additional phosphate buffer. However, such an addition would cause very serious technical problems. While typically a maximum of 5 mg PO4/L cell solution can be acceptable, the concentration that might be required if sodium molybdate were to replace SD would be 4.9 g/L, i.e. ca. 1,000% higher than what is currently assumed acceptable. Several problems might arise from the addition of a phosphate buffer at such high levels:

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 90  Side reactions at the anode: phosphates would cause precipitations on the anode surface in the presence of Fe and Si, potentially leading to a failure of the coating of the anodes. The durability of the anodes would be seriously compromised in the presence of 4.9 g/L phosphates under normal conditions of use. This has been documented in the scientific literature; for example, Krstajić et al (1984)(1984) have documented that the standard mixed RuO2·TiO2 coated titanium anodes deteriorates very quickly in the presence of ionic phosphate species (and go on to recommend the development of a different type of anode containing palladium and tin oxides in the coating mixture which are not currently state of the art). Such high concentration may have been suitable for lab experiments such as those described in the patent literature but these are typically very short and not representative of the continuous operation of a chlorate plant;

 Increase in the release of oxygen: literature suggests that deposits on the anode associated with phosphate impurities in the brine cause an increase in production of oxygen at plant scale14 (Kus, 2000)(Kus, 2000);

 Increased maintenance requirements: acid washing of the electrolysers would need to be undertaken more frequently; and

 Higher energy consumption: the above adverse effects would result in an increase to the consumption of electricity during the electrolysis.

Overall, the use of phosphates at the required concentration is technically a “non-starter” under the current technological knowledge and with existing anodes. In this regard, the remainder of the discussion on the technical feasibility of sodium molybdate is largely theoretical and academic.

Meanwhile, molybdate itself also causes higher levels of oxygen production, thus increased concentration of oxygen in the hydrogen gas stream, far higher than what is possible to achieve when using SD. This represents a serious process safety concern related to the risk of explosion. For these reasons the use of both molybdate and phosphate should ideally be as low as possible.

If the oxygen generation increased in comparison to the present SD-based technology to a level that would pose a safety risk (and this would indeed be the case with an oxygen concentration in hydrogen of 3.6-4.8%), action would need to be taken to dilute the generated gas. This could include a nitrogen purge, a fairly well established method of dilution. However, operation of the plant with a continuous purge of nitrogen to decrease oxygen concentration below the explosion limit would pose significant problems:

 Additional instrumentation would need to be introduced;  The amount of nitrogen required would be significant; and  The use of the H2/N2 mixture in reactions where H2 is needed as a raw material, would be impossible, particularly as the flow of variable content H2/N2 mixtures cannot be measured. The presence of nitrogen limits the purity of the hydrogen, and using the hydrogen when it contains high amounts of nitrogen would be technically very challenging.

Cathode protection: the long-term effect over multiple years on cathode protection is not known due to lack of large-scale trials outside of the laboratory.

14 The effects have been found to affect large scale production in very low levels of phosphate (down to 1-5 ppm) but short duration laboratory scale trials had not reproduced the effect (Nylén & Cornell, 2006).

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 91 Current efficiency and energy consumption: Mo(VI) requires higher concentrations and longer polarisation times to show the effect on the current efficiency in comparison to SD. Publicly available information suggests that when sodium molybdate is used, in the absence of any Cr(VI) in the electrolyte, it is unlikely that a current efficiency above 80-91% could be achieved (Li et al. (2007)(2007); Gustafsson (2012)(2012)). If a mid-range value of 86% were to be assumed, the loss of efficiency relative to SD would be significant and technically infeasible as the current efficiency would be below 90%. The total theoretical anticipated energy consumption would be 5,746 kWh/t of chlorate produced15. For the applicant, there is an additional energy requirement associated with the production of sodium chlorite. This energy requirement is independent of the use of an alternative.

Impurities in the chlorate product: '''''' ''''''' '''' ''''''''''''''' '''''''''''''''''''''' '''' ''''''''' '''' '''''''''' '''' ''''''''''' '''' ''''''' '''' '''''' '''''''''''''''''''''' '''''''' '''' ''''''''''''''''' ''' ''''''''''' '''''''''''''''''''' ''' ''''''''''''''''' '''''' ''''''''''''''''''''''''' '''' '''''''''''''''''''' ''''''''''' '''''''''' '''''''' ''''''' ''''''''''''''' '''''''''''''' ''''''' '''' '''''''''''''' '''''''''' '''''''''''' ''''''''''''''''' ''''''''''' ''''''' '''''''''''''' ''''' '''''' '''''''''''''' ''''''''''''''''' '''''''''''''' ''''''''''''''''''' '''' ''''''' '''''''' ''''''''' '''' '''''' '''''''''''''''''''''' '''''''''''''''''

Conclusion and required steps to allow use of sodium molybdate as an alternative to sodium dichromate

As shown above, poor pH buffering, increased oxygen formation, impaired current efficiency and unwanted metal impurities are the key issues faced by sodium molybdate. While the addition of a phosphate buffer would address the issue of pH, it would seriously impact upon anode performance (Kus, 2000)(Kus, 2000) and would further increase in oxygen formation, thus affecting the stability and economics of the electrolysis process. In addition, the removal of SD would result in a loss of inhibition effect on the undesired/parasite reaction in the ClO2 generator of the NaClO2 plant which could impact on the efficiency of the NaClO3 conversion to ClO2 and consequently on the overall management of the plant. The addition of phosphates at the high concentrations described in the patent literature make this alternative entirely infeasible.

Even if the key issue of phosphate presence were to be disregarded, the implementation of sodium molybdate would likely require the introduction of cathodes made of more dimensionally stable material.

The most practical way of addressing these problems may be to introduce SD at a lower level (<3 g/L) in combination with a lower level of molybdate without the presence of phosphate. However, the use of SD would still cause concern over human health and environmental exposure and would require a REACH Authorisation, thus this cannot be a substantial solution to the problems faced by sodium molybdate.

Consequently, for sodium molybdate to be considered a viable replacement for SD, further research will be needed in order to improve its identified shortcomings. Elements of further R&D might include the following:

1. R&D phase in existing electrolyte to verify robustness

2. R&D to optimise the mixture of molybdate and phosphate

15 The following conditions for a chlorate cell employing SD were used to enable a comparison to be made to a theoretical change to sodium molybdate. A cell voltage of 3.1 V (mid-range value from BREF (IPPC, 2007)) and current efficiency of 95% gives a theoretical energy requirement of 4,930 kWh/tonne of chlorate + 300 kWh/tonne (mid-range value for other electrical equipment) = 5,230 kWh/tonne chlorate using SD. Using sodium molybdate, the literature indicates a current efficiency in the range 80-91% efficiency. Using the mid-range value of 86% and the same cell voltage, an electrical consumption of 5,446 kWh/tonne can be calculated + 300 kWh/tonne = 5,746 kWh/tonne of chlorate or a 9.9% increase in electrical consumption.

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 92 3. R&D to scale-up to (a) long-term tests, lab pilot (b) intermediate scale, (c) commercial scale

4. Possible change from steel cathode to alternative dimensionally stable cathode technology

5. Replacement of the existing Cr(VI) containing electrolyte solution with newly developed electrolyte

6. Implementation of additional safety measures to decrease oxygen concentration to an acceptable level (such as a hydrogen DeOxo plant (BASF, 2014)(BASF, 2014) and/or use of inert gas).

7. Implementation of systems for gas treatment to ensure clean-up of hydrogen before further use.

The applicant is aware of R&D on molybdate additives in chlorate production that has already taken place by third parties and that the reduction and removal of Cr(VI) from the chlorate process has been the goal for more than a decade. Only limited progress has been made so far towards the total removal of Cr(VI) from the process but potential reductions in the level of Cr(VI) have been suggested. The applicant assumes that, in order to make significant gains to a commercially feasible alternative using this technology, substantial further R&D will be required. This would then need to be followed by process scale-up trials before commissioning any changes required to existing plant technology.

5.2.3 Economic feasibility

Further to the comments noted in Section 5.1, it is concluded that this alternative has been found to be technically infeasible to implement and therefore it cannot be considered economically feasible for the applicant.

5.2.4 Reduction of overall risk due to transition to the alternative

Overview

This sub-section presents a comparison of risks from the alternative and SD with regard to worker exposure during the manufacture of sodium chlorate and further estimates and monetises the environmental impacts arising from the increase in energy consumption that would arise from the replacement of SD with the alternative. Note that the Caffaro AoA16 Section 9 (Annex 2) provides extensive detail on the hazards and risks of these potential alternatives; a summary of findings is presented here.

Classification and Labelling

Sodium molybdate (anhydrous, CAS No. 7631-95-0) does not have a harmonised classification under CLP (EC No 1272/2008). In the C&L inventory a total of 446 notifications have been identified. Registration dossiers and the majority of notifiers do not classify the substance; however, a notable number of notifications include categories such as Eye Irrit. 2, Skin Irrit. 2, STOT SE 3, Acute Tox 4 and Aquatic Chronic 3.

16 https://echa.europa.eu/documents/10162/5e4bf84e-5725-4633-bb47-da66770a5b96

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 93 Figure 5-1: Hazard classification for sodium molybdate (from ECHA)

Sodium molybdate(VI) dihydrate is a possible alternative to sodium dichromate; similar to above there is no harmonised classification for it and notifications generally do not classify the substance. Data on sodium molybdate(VI) (anhydrous, CAS: 7631-95-0) are reported as toxicity is independent from water of hydration. Where toxicity is related to elemental Mo, no explicit reference is made in every instance to what exactly was the species used in the test.

On the other hand, sodium phosphates have been looked at as required additives alongside the molybdate. Disodium hydrogen orthophosphate (CAS No. 7558-79-4) and sodium dihydrogen orthophosphate (CAS No. 7558-80-7) are both in equilibrium with each other in aqueous solution and the state of equilibrium solely depends on the pH of the solution. Therefore, they have been assessed together.

For sodium phosphates, no Harmonised Classification according to Annex VI of the CLP Regulation is available. In the registration dossiers of both substances, no classification has been recommended.

Comparative risk characterisation

The Caffaro AoA (Section 9, Annex 2), compared the risks of SD and sodium molybdate. That document concluded that the ecotoxicity RCR of sodium molybdate is far lower than the respective RCR for SD. In addition, the human health RCRs for both the molybdate and the phosphates were several orders of magnitude lower than the RCR for SD. Although the risk characterisation was based on assumptions for release and exposure calculations are tentative and were not meant to represent real conditions at Caffaro’s production site, use of sodium molybdate in combination with phosphate buffer would appear to be beneficial with regard to human health considerations. Under the conditions of use assumed here, the comparative environmental risk characterisation leads to the

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 94 conclusion that there is less risk associated with the use of the molybdate compound. Again, it must be noted that the RCRs for SD are also below 1 both for ecotoxicity and human health toxicity.

These conclusions apply for SCB’s use of SD too.

Externalities from energy usage

The Caffaro AoA had estimated that the implementation of this alternative would result in an increase in releases of greenhouse gases by ca. ''''''''''''''''''''' ''''' (range: 1,000-10,000) tonnes of CO2e per year as a result of increased energy consumption compared to SD. As the SCB plant is not yet operational, it is not possible to fully update those calculations to adapt them to SCB’s plant.

Conclusion on suitability

Sodium molybdate when used alongside a phosphate buffer is a more benign substance than SD. The substance is considered to be a suitable alternative for SD in the applied for use. However, its use would require additional energy thus would result in an increase in CO2 emissions.

5.2.5 Availability

Three elements of availability can be considered:

 Availability of the alternative in quantities sufficient for the applicant’s production processes;  Availability of the alternative in the quality required by the applicant’s production processes; and  Access to the technology that allows the implementation of the alternative as a SD replacement.

With regard to the quantity required, Table 5-4 summarises the available information on the status of REACH Registration for disodium molybdate.

Table 5-4: REACH registration status of disodium molybdate Status Tonnage band Date of search Registered 100 – 1,000 tonnes per annum 27 March 2013 Sources: ECHA Dissemination Portal: http://apps.echa.europa.eu/registered/data/dossiers/DISS-9eb7d44e- 5b59-695c-e044-00144f67d031/DISS-9eb7d44e-5b59-695c-e044-00144f67d031_DISS-9eb7d44e-5b59- 695c-e044-00144f67d031.html

The tonnage of sodium molybdate that would be required is very small; in Caffaro’s AoA it had been estimated that the applicant may need ''v'''''' kg of sodium molybdate per tonne of sodium chlorite produced. Therefore, the tonnage of sodium molybdate required would be well below 10 t/y. '''''''' ''' ''''''''''' ''''' ''' ''''''''#B#'''''''''' '''''''''''''''

Issues of quality have not been identified.

Finally, with regard to access to the technology required, as already explained, the required technology that would render this alternative feasible is not currently available.

5.2.6 Conclusion on suitability and availability for sodium molybdate

Sodium molybdate was investigated as an alternative substance that would replace the use of SD in the production of sodium chlorate. The substance (used in combination with a phosphate buffer) is a

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 95 suitable alternative as it has a more benign hazard profile than SD. The comparative risk assessment performed for the purposes of this AoA suggests a lowering of risk from the replacement of SD by the molybdate salt. Nevertheless, environmental impacts from an increased release of CO2 are to be expected as a result of increased electricity consumption.

It was found that sodium molybdate fails the majority of the technical feasibility criteria and its poor pH buffering capabilities necessitate the addition of phosphate buffers at concentrations much higher than the electrolysis cell can tolerate. It is particularly the addition of phosphates that render this alternative unrealistic: their presence in the electrolysis cells is currently kept at a minimum level and if addition of several g/L would be required, the stability and durability of the anodes would be severely impacted.

In addition, sodium molybdate would result in the generation of excessive volumes of oxygen in the hydrogen co-product at levels close to the explosion limit. The presence of phosphates would exacerbate the generation of oxygen. This would raise serious safety risks and would necessitate the introduction of processes that would allow the dilution of the generated gas mixture, typically by means of nitrogen purging.

Issues of economic feasibility are not relevant as the alternative has been concluded to be technically infeasible. However, it is worth noting that the Caffaro AoA concluded:

“the implementation of sodium molybdate would require significant (one-off) investment costs, including the costs of developing or acquiring access to the relevant technology (when and if this materialises in the future), the disposal of the existing electrolyte and the generation of new electrolyte, '''''' '''''''''''''''''' '''''''' '''''''''''''''''''''''''''''' ''''''''''''' ''''''''''' ''''''''''''''''''' the losses of chlorite sales from the stoppage of the production during conversion, and the cost of introducing/expanding oxygen controls. These costs are substantial and unjustifiable, in light of the poor technical feasibility of the alternative”.

“As far as operating (on-going) costs would be concerned, sodium molybdate is accompanied by impaired energy efficiency, which is significantly lower than what is achieved using SD. This fact alone would significantly increase production costs for the chlorite plant and would significantly affect the applicant’s profitability. Notably, the cost of electricity is expected to rise (S&P 2018) and as such, this cost component, which is the single most important cost component, will only increase in importance. Therefore, the use of sodium molybdate cannot be considered economically feasible to the applicant.”

Finally, in terms of availability, the molybdate substance itself is available on the EU market; however, the technology that would allow its implementation under conditions that would guarantee a minimum level of technical feasibility and economic viability is not available.

Overall, sodium molybdate has not been found to be a technically or economically feasible alternative to the use of SD in the applicant’s production of sodium chlorate and sodium chlorite. Even if significant further R&D were to overcome the technical barriers, its economic feasibility would be unlikely to substantially improve. In practice, already extensive R&D presented in the open literature indicates that this is only likely if it is employed alongside a reduced level of Cr(VI). 5.3 Molybdenum-based coatings

5.3.1 Description of alternative technology and properties

This alternative technology involves the use of cathodes that have been coated with molybdenum prior to use in the chlorate process. The aim of the coating is to improve the current efficiency of the

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 96 process by providing a coating to supress parasitic reactions that can occur during the process, as described in Section 2.2.2. The patents describing the use of molybdenum-coated cathodes are summarised in Section 4.2.3. These patents indicate that molybdate salts (such as those shown in Table 5-1 in Section 5.2.1), would be required initially to prepare the coated-cathodes but they would not be added into the process electrolyte afterwards. As a result of this, the buffering effect provided by the presence of sodium molybdate will not be present and will entirely need to be replaced with another agent. The Rosvall et al (2009) patent continues to use SD in the process while the Krstajic et al (2007) patent application replaces the buffering effect of SD using sodium acid phosphates. Therefore, the analysis of the technical feasibility of this alternative assumes that sodium acid phosphates are required if this alternative is being employed without the presence of Cr(VI) in the process.

5.3.2 Technical feasibility

Assessment of technical feasibility

Research into molybdenum-based coatings for chlorate cathodes has focused more on increasing current efficiency than reduction of SD content in the electrolyte. However, some patents nonetheless claim no SD content, and therefore the analysis below has been carried out assuming this can be achieved.

A comparison of technical performance of molybdate-coated cathodes to the identified technical feasibility criteria is shown in Table 5-5.

Table 5-5: Comparison of molybdenum-based coatings and sodium dichromate according to technical feasibility criteria Result or value achieved Technical feasibility Sodium Molybdenum- Criteria pass? * criteria Threshold dichromate based coatings Uncertain: Formation of different protective film that technology to SD. is permeable to The film is not Sufficient Similar to SD () hydrogen and formed impermeable to electrolytically but hypochlorite imposed as a coating Separate phosphate buffer pH buffering and pH 6-6.5; <4% O2 required; control of oxygen pH 6-6.5; <2.5%  in H2 by volume uncertain effect formation on oxygen concentration Uncertain: lab tests are generally Minimum cathode very short and not Cathode protection Sufficient '''''''''''''''''''' ''' representative of ? (corrosion inhibition) ''' '''''''''' continuous operation at the industrial scale

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 97 Table 5-5: Comparison of molybdenum-based coatings and sodium dichromate according to technical feasibility criteria Result or value achieved Technical feasibility Sodium Molybdenum- Criteria pass? * criteria Threshold dichromate based coatings 95%, 5,230 kWh/t '''''''' Current efficiency theoretical ''''''''''''''''''' ''' 94%; 4,342 kWh/t and energy '''''''' () ''''''''''' '''''''''''' theoretical consumption ''''''' ''' '''''''''''' ''''''''''''' '''''' ''''''' '''''''''''''''' Solubility in Not relevant to Highly soluble Sufficient Not relevant electrolyte this technology Control of Impurities '''''''''''''' '''''''''''''''''''' ''''''''''''' ''''''''''''''''' in the NaClO3 ''''''''''''''''''' ''''' '''''' ''''''''''' '''' ''' ''''' solution in exit from '''''''''''' '''' ''''''''''''''''' ''''''' '''''''' ''''' '''''''''''''''''''' () the electrolytic cell '''''''''''''''''''' ''''''''''' '''''''' ''''''''''''' ''''''' ''''''''' '''''''''''' and in entrance in ''''''''' ''''''''''''''' '''''''''''''' ''''''''''''' the ClO2 generator * parentheses indicate uncertainty over the conclusion reached due to lack of data. A tick is given only if the entire criterion is met

Detailed presentation of technical characteristics of the alternative

Formation of protective film: the technology differs in that the film is not formed electrolytically but imposed as a coating on the electrode substrate. The evidence available from past R&D is not sufficient to conclusively confirm the technical equivalence of this technology, but it may be assumed that it could perform to an acceptable level. pH buffering and control of oxygen formation: the relevant embodiment of the patent application avoids the use of SD but requires phosphate as a buffer. As discussed in Section 5.2.2, the presence of phosphate in the electrolyte is of concern because it can result in increased oxygen levels. The patent, however, does not discuss the level of oxygen achieved. Therefore, taking these factors into consideration, this alternative seems unlikely to fulfil this technical feasibility criterion, although further R&D would be required to determine this conclusively.

Cathode protection: cathode durability would be a concern. The patent applications describing the use of this alternative reference tests lasting four (Rosvall, et al., 2009)(Rosvall, et al., 2009) or eight hours (Krstajic, et al., 2007)(Krstajic, et al., 2007), and no long-duration trials are known. Therefore, the effect of this technology on long term corrosion inhibition and cathode lifetime is highly uncertain. Long-duration pilot plant trials would be required to establish the likely rate of corrosion.

Impurities in chlorate product: the effect of transfer to this alternative on the purity of the resulting sodium chlorate is not known due to the lack of pilot scale trials. It seems probable that chlorate purity could be linked, in large part, to any corrosion observed and on the presence of any additive other than chromium that may be used to take over any of the roles of SD in the process. As discussed above, transition metal salts used in the chlorate electrolytic cells could be released into the chlorate solution fed to chlorite plant. These ‘impurities ‘can adversely affect the stability of the gaseous chlorine dioxide generated in the first step of the sodium chlorite process.

On the other hand, the use of this technology could in theory have notable benefits in comparison to the use of SD-based cells, on the basis of published test results.

Current efficiency and energy consumption: according to the patent application by Krstajic et al (2007)(2007), lower cell voltages and hence lower energy consumption can be achieved using

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 98 molybdenum-based cathode coatings. In the patent, a cell voltage of 2.50-2.53 V with a current efficiency of 94% is implied. Yet, the patent application examples are run over a very short period of time, 8 hours. After such short a period of time, corrosion of the electrodes may not be apparent. As noted by Kus (2000), phosphate may cause negative effects at the anode. These may only become apparent after longer periods of operation time as would be expected in a commercial setting. However, if the results indicated by the patent are used for the sake of a conservative estimate, a theoretical energy consumption of 4,042 kWh per tonne of chlorate can be calculated for the electrolysis. This results in a theoretical energy consumption of 4,342 kWh per tonne of chlorate, assuming 300 kWh/t is required for ancillary equipment, representing a considerable decrease in electrical consumption relative to the use of SD17.

The publicly available information does not provide sufficient guarantee that these limited results can translate to energy savings at the industrial scale and, to the best of the applicant’s knowledge, this technology has not come any closer to commercialisation (see Section 4.2.3.2). SCB does not consider molybdenum-based cathode coatings to be a realistic technically feasible alternative to the use of SD.

Conclusion and required steps to allow use of molybdenum coatings as an alternative to sodium dichromate

Overall, while this alternative promises complete removal of Cr(VI) from the system, without Cr(VI) in the electrolyte, additional buffer must be used. The phosphate buffer would have a detrimental effect on the stability and durability of the anodes and could lead to increased oxygen generation; it is not clear whether additional controls on oxygen would be required. A relevant patent application has claimed a reduction in cell voltage and a concomitant reduction in energy consumption. However, this has not been proven at the industrial scale, especially during continuous operation of the electrolysis cells. Overall, this as yet unproven alternative is not considered technically feasible.

Due to the lack of commercial scale applications known to the applicant, significant uncertainties exist regarding the commercialisation of the technology and whether or not it would work in practice. In particular, the cathode lifetime must be long enough to consider the technology technically feasible, but no data on the cathode lifetime has been found. Although this technology is promising, it can be expected that considerable R&D would still be required to demonstrate that this technology is technically feasible for commercial production of sodium chlorate (and thereon, sodium chlorite). The typical steps in undertaking the required R&D and implementation steps may include:

1. R&D phase in existing electrolyte (without SD) to verify robustness

2. R&D phase to optimise buffer system needed, and effects on anodes

3. R&D to scale-up to (a) long-term tests, lab pilot (b) intermediate scale, (c) commercial scale including demonstration of cathode lifetime

4. Replacement of all Cr(VI) containing electrolyte

17 The following conditions for a chlorate cell employing SD were used to enable a comparison to be made to a theoretical change to molybdenum-coated cathodes. A cell voltage of 3.1 V (mid-range value from BREF (IPPC, 2007)) and current efficiency of 95% gives a theoretical energy requirement of 4,930 kWh/tonne of chlorate + 300 kWh/tonne (mid-range value for other electrical equipment) = 5,230 kWh/tonne chlorate using SD. Using molybdenum-coated cathodes, the patent indicates a current efficiency of 94% and a voltage between 2.50-2.53 V. Using these data; a mid-range cell voltage of 2.515 V and 94% efficiency, an electrical consumption of 4,042 kWh/tonne can be calculated + 300 kWh/tonne = 4,342 kWh/tonne of chlorate or a 9.9% increase in electrical consumption.

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 99 5. Replacement of all existing electrolytic cell cathodes

6. Process optimisation

7. Preparation of new buffered electrolyte and its maintenance

8. Investigation of oxygen evolution and potentially implementation of safety measures to reduce the oxygen content of hydrogen stream

9. Potentially, implementation of systems for gas treatment to ensure clean-up of hydrogen before further use.

5.3.3 Economic feasibility

5.3.4 Reduction of overall risk due to transition to the alternative

Overview

Due to the nature of this alternative, a direct comparison of hazards and risks to SD cannot be performed here. However, it is of note that sodium molybdate would be the basis of the coating and the new cathodes would be used alongside a sodium phosphate buffer. Due to the lack of experience with this technology at the industrial scale, it cannot be predicted whether other additives might be needed or what species may be found in the electrolyte during the use of a chlorate cells that uses molybdenum-coated cathodes. We therefore tentatively assume that no further substance would be added to the electrolyte and no releases due to corrosion or other effects might occur. Under this assumption, it can be assumed that this alternative would have a more benign risk profile than SD.

Externalities from energy usage

There is significant uncertainty on how energy consumption might change were molybdenum-coated cathodes to be used in the continuous operation of industrial-scale chlorate plants. Some very tentative assumptions were made above on how energy might theoretically decrease in comparison to SD, but these were only used to illustrate the potential changes to the operating costs of the applicant. In light of such significant uncertainty, a detailed calculation of externalities is not provided as it, in all likelihood, would be of dubious accuracy.

Conclusion on suitability

Molybdenum-coated cathodes could reduce risks to workers during the manufacture of sodium chlorate but environmental impacts are uncertain.

5.3.5 Availability

As noted above, three elements of availability can be considered:

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 100  Access to the technology that allows the implementation of the alternative as a SD replacement.

According to the patent describing the manufacture of molybdenum-based cathodes, they are made using iron(III) chloride and sodium molybdate in a buffer solution. It can safely be assumed that these materials would be available to any company (other than the applicant) that would wish to manufacture coated cathodes. The applicant would not coat the cathodes themselves, as this is not their core business. The applicant has no knowledge of any supplier of suitable cathodes.

With regard to quality, given that the technology is not proven and unavailable on the market, assumptions on quality would be based on speculation.

Most importantly, access to the technology is the key issue. The aforementioned patent application was filed by Industrie De Nora (Krstajic, et al., 2007). The patent was be granted and the technology is yet to be proven outside the laboratory. Indeed, the European Patent Office suggests that the patent is deemed to have been withdrawn in Europe (as of November 2015)18.

Therefore, whilst the technology may not end up being protected by a patent, there are clear indications that it did not progress beyond the application stage and thus its commercialisation in the future is highly uncertain.

5.3.6 Conclusion on suitability and availability for molybdate-based coatings

Molybdate-coated cathodes were investigated as an alternative technology that would replace the use of SD in the production of sodium chlorate. The coated cathodes (used in combination with a phosphate buffer) could be considered to be a suitable alternative, although a direct comparison to the hazard profile of SD cannot be made. Calculations on the environmental externalities that would accompany the implementation of this alternative technology have not been made due to the significant uncertainties over the technical characteristics of molybdate-based coatings in an industrial environment.

It was found that molybdenum-based coatings fail to meet the majority of the technical feasibility criteria and their poor pH buffering capabilities necessitate the addition of phosphate buffers at concentrations much higher than the electrolysis cell can tolerate. It is particularly the addition of phosphates that render this alternative unrealistic: their presence in the electrolysis cells is currently kept at a minimum level and if addition of several g/L were required, the stability and durability of the anodes would be seriously impacted, unless new, more durable types of anodes could be developed.

It is unclear whether molybdenum-based coatings would result in the generation of excessive volumes of oxygen in the hydrogen co-product. Certainly, the presence of phosphates would exacerbate the generation of oxygen to some extent. Whether this would raise safety risks and would necessitate the introduction of processes that would allow the dilution of the generated gas mixture (typically by means of nitrogen purging), it remains to be seen. The presence of metals in the chlorate solution used in the production of sodium chlorite is also a concern, which is not possible to allay or confirm under the current state of knowledge.

Issues of economic feasibility are not relevant as the alternative has been concluded to be technically infeasible. However, it is worth noting that the Caffaro AoA had concluded:

18 See https://register.epo.org/application?number=EP06819847&tab=main and https://patentscope.wipo.int/search/en/detail.jsf?docId=WO2007063081&tab=NATIONALPHASE&maxRec =1000 (accessed on 24 January 2018).

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 101 “In terms of economic feasibility, any possible future implementation of molybdenum-coated cathodes would require significant investment (one-off) costs, including the costs of developing or acquiring access to the relevant technology (when and if this materialises in the future).

As far as operating (on-going) costs are concerned, molybdenum-coated cathodes have been claimed in a relevant patent application to be capable of decreasing cell voltage and thus reduce energy consumption. This has not been possible to demonstrate at the industrial scale and such claims cannot be relied upon, although information from said patent application has been used in the calculation of the potential theoretical energy savings from the use of the molybdenum-coated cathodes. Beyond the issue of energy consumption, adverse effects on the durability of the anodes coupled with uncertainty on the long-term durability of the cathode coating paint a picture of poor long-term economics for the chlorate production process. If nitrogen purging were to be needed, the costs associated with impacts on ancillary operations would be very severe. Therefore, the use of molybdenum-coated cathodes cannot be considered economically feasible”.

Finally, in terms of availability, the substances needed for the generation of the coatings are available on the EU market; however, the technology that would allow their implantation under conditions that would guarantee a minimum level of technical feasibility and economic viability on the commercial scale is not available.

Overall, molybdenum-based coatings have not been found to be a technically or economically feasible alternative to the use of SD in the applicant’s planned production of sodium chlorate. Even if significant further R&D would be able to overcome the technical barriers, their economic feasibility would still remain highly uncertain without first testing the feasibility of implementing this technology at the industrial scale. 5.4 Two-compartment electrolytic systems

5.4.1 Description of alternative technology and properties

Two-compartment electrolytic systems are a different technology to the existing sodium chlorate production method employing SD. As described in Section 4.2.3, there are patents describing the use of modified chlor-alkali type cells to generate sodium chlorate. This process is currently used by some of the manufacturers of sodium chlorate to generate sodium hydroxide, sodium hypochlorite, chlorine and hydrogen. It involves combining the output streams of the process in separate chemical reactors in order to produce hypochlorite and convert it into sodium chlorate. The process is preferably carried out in a separate reactor at a different pH and temperature to an ordinary chlor-alkali cell. Figure 5-2 below shows an example process diagram for a membrane chlor-alkali type cell employed for the production of sodium chlorate. The technology is not limited only to this configuration. Potentially, it could also consist of two or more membrane cells linked in series. The pH ranges shown in the diagram are indicative but the anode compartment pH would be substantially lower than the cathode compartment.

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 102 Figure 5-2: Example chlor-alkali type chlorate production process. Based on (Cook, 1975)(Cook, 1975) (Millet, 1990) (Millet, 1990) (Delmas & Ravier, 1993) (Delmas & Ravier, 1993) (Hakansson, et al., 2004) (Hakansson, et al., 2004)

5.4.2 Technical feasibility

Assessment of technical feasibility

Table 5-6 presents the comparison of the two-cell technology to the technical feasibility criteria for the replacement of SD in the sodium chlorate production process. As this alternative is a different technology, some of the criteria are not relevant to this comparison.

Table 5-6: Comparison of two-compartment electrolytic technology and sodium dichromate according to technical feasibility criteria Result or value achieved Technical Criteria Two-compartment feasibility criteria Sodium dichromate Threshold pass? * systems Formation of protective film that is permeable to Not relevant to Sufficient Similar to SD Not relevant hydrogen and technology impermeable to hypochlorite pH control required; pH buffering and pH 6.0-6.5; <4% O2 in oxygen produced control of oxygen pH 6.0-6.5; <2.5% O2 () H2 by volume separately from formation hydrogen

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 103 Table 5-6: Comparison of two-compartment electrolytic technology and sodium dichromate according to technical feasibility criteria Result or value achieved Technical Criteria Two-compartment feasibility criteria Sodium dichromate Threshold pass? * systems Cathode protection Sufficient Minimum cathode Uncertain: likely to (corrosion () (confidential) lifetime ''' ''''' ' be acceptable inhibition) 95%, 5,230 kWh/t Current efficiency theoretical '''''''' '''' '''''''''''' 5,880 kWh/t and energy '''''''''  '''''''''''''' theoretical consumption '''''''''' ''' ''''''''''''' ''''' ''''''' ''''''''''''''''' Solubility in Not relevant to Highly soluble Sufficient Not relevant electrolyte technology Control of ''''''''''''''' '''' Impurities in the '''''''''''''' ''''''''''''''''''' ''''''''''''' '''''''''''''''''''' '''' '''''''''''''''''' ''''''''''' NaClO3 solution in ''''' ''''''' '''''''''''''' '''''' '''' ''''''' ''''''' exit from the () '''''''''''''''''''' ''''''' '''''''' ''''''''''''''''''' ''''''' ''''''''' '''''''''''''''' ''''''''''''''' electrolytic cell and ''''''''''''' ''''''''''''' '''''''''''' ''''''''''''' ''''''''''''' '''''''''''''''' in entrance in the '''''''''''' ClO2 generator * parentheses indicate uncertainty over the conclusion reached due to lack of data. A tick is given only if the entire criterion is met

Detailed presentation of technical characteristics of the alternative

Formation of protective film & solubility in electrolyte: these criteria are not of relevance to this technology. pH buffering and oxygen formation: ordinarily, chlor-alkali cells do not require pH buffers as they operate at a different pH range to the chlorate reaction. For the chlor-alkali process, the anode compartment is maintained at a low pH specifically to prevent formation of chlorate (IPPC, 2001)(IPPC, 2001), while the cathode compartment is at a high pH due to the formation of sodium hydroxide. In order to effectively produce chlorate; however, the chlorate reactor or anode compartment must be at pH 6-6.5 and thus pH adjustment is needed. Therefore, pH control is required in the modified chlor- alkali technology. This can be, at least in part, achieved by addition of sodium hydroxide and hydrochloric acid produced from the product streams. This would involve careful process optimisation to balance the pH by the use of online monitoring and feedback loops between different process stages. Alternatively, non-Cr(VI) pH buffers could be used but their presence may complicate the electrochemistry in the electrolysis cell in a similar fashion to conventional systems. Both of these approaches – pH balance through process optimisation and the use of non-Cr(VI) buffers – would demand significant R&D for the applicant in order to optimise the conditions required.

With regard to oxygen generation, this is released in a separate compartment to hydrogen, therefore, the hazard of explosive mixtures formation is eliminated.

Cathode protection: the protection of the cathodes is less of a concern with this alternative because chlor-alkali cells are resistant to corrosion due to their requirement to handle chlorine gas. They are constructed from more expensive materials (e.g. titanium) than chlorate cells. The technical criterion for cathode protection is therefore met by this alternative. Membrane chlor-alkali cells require relatively frequent maintenance due to the short (2-5 years, according to literature) lifetime of the selective membrane that divides the cell compartments, but does not introduce additional corrosion

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 104 products that have a potential effect on product quality in the same way as steel cathode corrosion in chlorate cells.

Current efficiency and energy consumption: the theoretical energy consumption of the process can be estimated using typical consumption figures for a chlor-alkali plant BREF (IPPC, 2001)(IPPC, 2001) and assuming the process of converting chlorine to chlorate is 100% efficient, which means the resulting estimate will be highly conservative. A chlor-alkali plant requires 1,750 kg NaCl and 2,790 kWh of electricity to produce one tonne of chlorine gas (Cl2). Ordinarily, this energy would also produce sodium hydroxide (1.128 t/t Cl2) but it is converted into sodium chlorate in this alternative process. As discussed in Section 4.2.3 on “Other technologies”, 3 moles of Cl2 are required to produce 1 mole of NaClO3 or, if converted to tonnes, 2 tonnes of Cl2 is required to produce 1 tonne of sodium chlorate. In electrical consumption alone, a modified chlor-alkali plant would require 2,790 × 2 = 5,580 kWh/t of sodium chlorate produced. In addition to this, further energy would be required to heat solutions and concentrate them for crystallisation. Using the same assumption as for the theoretical calculation of the energy requirement for auxiliary processes used for SD of 300 kWh/t chlorate gives a total energy consumption of 5,880 kWh/t sodium chlorate produced. In addition to this, it is expected that additional water would have to be removed from the caustic by evaporation, which would further increase energy consumption. A more precise estimate of the energy consumption cannot be provided without pilot plant scale trials of this technology but it is clear that this high energy consumption would render the process technically infeasible according to the technical feasibility criteria.

Control of impurities: as far as impurities are concerned, the sodium chlorate product would not contain any Cr, as the use of SD would be eliminated' '''''''''''' '''' ''''''''''''''''''''' ''''''''''' '''''''''' ''''''''''''''''''' '''''''''''''''' ''''''''''''''''''''' '''''''''''''''' '''''' ''''''''' '''''''''''''' ''''''' '''''''''''''''''''' ''''''' ''''''''''''''' ''''''' '''''''' '''''''''' '''' ''''''' ''''''''''''''''' ''''' ''''''' There is no firm data on which a conclusion can be reached as regards the overall level of impurities, but any impurities such as NaCl would not pose problems in the production of sodium chlorite.

Conclusion and required steps to allow use of two-compartment electrolytic systems as an alternative to sodium dichromate

The chlor-alkali technology is widely known in the industry. This technology is optimised for the production of chlorine and sodium (or potassium) hydroxide and not for the production of sodium chlorate. The use of two-compartment electrolysis cells is largely theoretical.

If this technology were to be adapted for the production of sodium chlorate, it can be assumed that further R&D would be required. As identified above, the energy consumption of the process must be improved for this alternative to become technically feasible. This would involve at a minimum:

1. Selection of the most appropriate ion-selective membrane for compatibility with chlorate  Identification of appropriate membrane suppliers.

2. Optimisation of process conditions for any electrolysis cells and chemical reactors:  Temperature, concentration, pH at each stage  Identity and concentration of buffers (if found necessary or beneficial)  Flow rate (or residence times) for solutions at each stage  Combination of the chlor-alkali system with the sodium chlorite reactor' ''' '''''''''' ''''' ''''''''''' '''''''''' ''''''' '''''''''''''' '''' '''''' '''' '''''''' ''''''''''''' '''''''''''''''' ''''''''''''''' '''' ''''' '''''''''''''''''' ''''''' ''''''' '''''''''''''''' ''''''''''''''' ''''''''''''''''''''' '''''''''' '''' ''' ''''''''''''''' '''''''''''''''''' '''' '''''''''' ''''''''''''''''''''' ''''''''''''''' '''''''''' '''' ''''' ''''''''''''''' '''' '''''''''''''' '''''''''''''''''.

3. Evaluation in the lab before scaling up to the pilot scale.

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 105 The above steps would need to be demonstrated on a commercially relevant scale. This is likely to require the construction of a pilot plant. As with all R&D efforts, the outcome of the research is not certain to results in improved technical feasibility. Generally, the technology cannot be considered a technically realistic alternative for large-scale production of sodium chlorate and its onward use in the manufacture of chlorite.

5.4.3 Economic feasibility

5.4.4 Reduction of overall risk due to transition to the alternative

Overview

The comparison of hazards and risks between two different technologies is not as straightforward as in the case of the other alternatives assessed above. The two-compartment system removes the need for SD without introducing any new substances and without generating significant operating hazards. It would appear that the use of the technology could be beneficial in terms of eliminating exposure to and risks from SD.

The following analysis estimates and monetises the increase in environmental damage costs impacts arising from the increase in energy consumption that would arise from the replacement of the SD- based technology with the alternative.

Externalities from energy usage

The Caffaro AoA had estimated that the implementation of this alternative would result in an increase in releases of greenhouse gases by ca. '''''''' ''' (range: 1,000-10,000) tonnes of CO2e per year as a result of increased energy consumption compared to SD. As the SCB plant is not yet operational, it is not possible to fully update those calculations to adapt them to SCB’s plant.

Conclusion on suitability

Two-compartment cell technology would eliminate the use of SD without introducing chemical substances of notable concern, therefore, the technology may be considered to be a suitable alternative for SD in the applied for use. However, its use would require additional electricity thus would result in increased CO2 emissions.

5.4.5 Availability

In general, chlor-alkali technology is available on the open market, but technology specifically adapted to chlorate production is not. It would require significant R&D before it can become implementable; a pilot plant would be required to trial the use of two-compartment cells and optimise the conditions for sodium chlorate rather than chlorine production. If R&D were to be carried out successfully, this could not be done prior to the start-up date of the SCB plant (which cannot be delayed due to the need to continue to supply to Caffaro’s existing customers when Caffaro will be asked by the public authorities to close its plant).

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 106 In addition, the availability of membranes for a chlorate electrolyte is also crucial for this technology. In existing chlor-alkali plants, the technology is limited to chlorate concentrations of 15 g/L due to membrane quality. In the proposed technology, the electrolyte would contain up to 500 g chlorate/L.

5.4.6 Conclusion on suitability and availability for two-compartment electrolytic systems

The use of this alternative would most likely result in a reduction of risk to human health. However, it would result in increased electricity consumption and this would result in increased greenhouse gas emissions and associated environmental damage costs.

The two-compartment cell technology is not currently available in a form that can be implemented commercially and its technical feasibility is poor.

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 107 Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 108 6 Overall conclusions on suitability and availability of possible alternatives

6.1 Technical feasibility of shortlisted alternatives

The production of sodium chlorate has been carried out by industry since 1886 (Tilak & Chen, 1999)(Tilak & Chen, 1999) and has seen continual improvements over its long history of use but no realistic alternative to the use of SD has been found despite significant R&D efforts (see Section 4.2.3). According to the research undertaken, no technology or substance other than SD is used anywhere in the world as a process aid in the production of sodium chlorate. Given the inability to identify a suitable alternative or technology despite extensive research, the trend among sodium chlorate manufacturers such as SCB (who notably use the chlorate as a raw material in the onward generation of sodium chlorite) has been to maximise efficiency and therefore reduce the volume of Cr(VI) used, to minimise the release of Cr(VI) from the process and work towards a predominantly closed loop system to minimise the release of Cr(VI) to the environment.

Three potential alternatives have been considered in detail in this AoA:

 Alternative substance: Sodium molybdate;  Alternative technology: Molybdenum-based cathode coatings; and  Alternative technology: Two-compartment electrolytic systems.

A summary of the assessment of technical feasibility of the shortlisted alternatives is presented in Table 6-1. More specifically:

 Sodium molybdate: sodium molybdate has been studied by industry and academia but results have been poor and further development is required. The addition of the molybdate salt has shown issues with poor energy efficiency and pH buffering, the latter requiring the addition of phosphate buffers. The addition of such buffers, at considerably elevated concentrations, would cause major problems to the stability and durability of the anodes and would contribute to an increase in the generation of oxygen at plant scale. The evolution of increased concentrations of oxygen in hydrogen (above the limit of explosion) raises serious process safety concerns. Transition metal ions present in the chlorate electrolytic cells could be released into the chlorate solution fed to chlorite plant. These ‘impurities’ would adversely affect the stability of the gaseous chlorine dioxide generation in the first step of sodium chlorite production process. Overall, this technology has not been proven at the industrial scale, where continuous operation puts significant strain on the electrodes, and the very presence of high concentrations of phosphates makes this alternative technically unrealistic

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 109 Table 6-1: Summary of technical feasibility of shortlisted alternatives for SD (NB. grey cells show problematic areas, parentheses show areas of uncertainty) Technical feasibility criteria Threshold based on SD Sodium molybdate Molybdenum-based coatings Two-compartment systems performance Formation of protective film Similar to SD  () Not relevant that is permeable to hydrogen and impermeable to hypochlorite pH buffering and control of pH 6-6.5; <4% O2 in H2 by   () oxygen formation volume Poor buffering, phosphates Poor buffering, phosphates pH control required affect anodes affect anodes Oxygen evolution Oxygen evolution (?) Cathode protection Minimum cathode lifetime ? ? () (corrosion inhibition) ‘’’’’''''' ’’’’’’ Current efficiency and ‘’’’’’’’’''''' ’’’’’’’’’’’’’  ()  energy consumption 86%; 5,746 kWh/t theoretical 94%; 4,342 kWh/t 5,880 kWh/t (theoretical) theoretical Solubility in electrolyte Sufficient  Not relevant Not relevant Control of Impurities in the ‘’’’’’’’’’’’’’ ‘’’’’’’’’’’’’’ ‘’’’’’’’’’’’’’ ‘’’ ‘’’ ‘’’ NaClO3 solution in exit from ‘’’’’’’’’’’’’’''''' ’’’’’’’’’’’ ‘’’’’’’’’’’’’’ ‘’’''''' ’’’’’’’ ‘’’’’’’’’’’’’’ ‘’’''''' ’’’’’’’ ‘’’’’’’’’’’’’’ ‘’’’’''''' ’’’’’ the electrolytic cell and in ‘’’’’’’’’’’’’’ ‘’’’’’’’’’’’’’ ‘’’’’’’’’’’’’’ ‘’’’’’’’’’’’’’ ‘’’’’’’’’’’’’’ ‘’’’’’’’’’’’’’ ‘’’’’’’’’’’’’’ ‘’’’’’’’’’’’’’ ‘’’’’’’’’’’’’’ ‘’’’’’’’’’’’’’ ‘’’’’’’’’’’’’’ entrance in the ClO2 ‘’’’’’’’’’’’’’ ‘’’’’’’’’’’’’’ ‘’’’’’’’’’’’’’ ‘’’’’’’’’’’’’’ ‘’’’’’’’’’’’’’ ‘’’’’’’’’’’’’’ ‘’’’’’’’’’’’’’ ‘’’’’’’’’’’’’’ ‘’’’’’’’’’’’’’ generator

Current state of knowledge of technical parameters Not used, globally. Research Not used, globally. Not used, globally for chlorate past and ongoing; much R&D Research past and ongoing; production. still needed much R&D still needed Significant R&D required Expected time for achieving technical feasibility for Impossible to estimate; many years would be needed for R&D, pilot scale and commercialisation, if commercialisation at industrial scale R&D results are positive Conclusion and technical shortcomings  Poor energy efficiency  Poor pH buffering  Poor energy efficiency  Phosphate effects on  Phosphate effects on  Requires complete anode anode plant rebuild  Explosion hazards (O2)  ‘’’’’’’''''' ’’’  Not a feasible solution  Not a feasible solution  Not a feasible solution

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 110  Molybdenum-based coatings: claims have been made in relevant patent applications that this technology could lead to a reduction of cell voltage and, consequently, of energy consumption. This has not been proven at the industrial scale, as the lab tests described in the literature only lasted for a few hours. On the other hand, the new cathodes would also need the addition of high concentrations of phosphates, which would have a very detrimental effect on the anodes. As mentioned above for sodium molybdate, this technology has not been proven at the industrial scale, where continuous operation puts significant strain on the electrodes and the durability of the electrodes in the cell is a parameter on which little specific information is available; and

 Two-compartment electrolytic systems: such systems have been used industrially for the chlor-alkali process since the late 1800’s (IPPC, 2001)(IPPC, 2001). As a result of their long history, this technology is very well understood; the process has many similarities to the production of sodium chlorate and for the production of chlorine, hydrogen and caustic soda, but, here, a variation of the known technology would be required. The available information would suggest that this technology would result in a more expensive manufacturing process due to higher electricity consumption, more complex equipment and higher maintenance requirements. Its requirement for a complete rebuild of the sodium chlorate plants makes this a very unrealistic solution for the elimination of SD.

In conclusion, there is no certainty that any of the alternatives could demonstrate technical feasibility. 6.2 Economic feasibility of shortlisted alternatives

Due to a lack of technical feasibility, the shortlisted alternatives cannot have any immediate economic feasibility and the latter has not been investigated in detail. For completeness, we provide below the conclusions that were reached in the Caffaro AoA which are still valid for the SCB plant – these are slightly modified to reflect the fact that the SCB plant is not yet operational:

 “Sodium molybdate: sodium molybdate would be accompanied by notable investment costs, namely (…) the improvement of oxygen controls (to reduce the risk of explosion) (…). In terms of on-going costs, sodium molybdate would result in considerably increased energy consumption, increased maintenance and materials costs due to the adverse effect of phosphates on the stability and durability of the anodes and significant operating difficulties for the applicant’s ancillary operations that depend on high quality hydrogen gas. The economic feasibility of this alternative is very poor;

 Molybdenum-based coatings: as with sodium molybdate, the introduction of these coatings would be accompanied by notable investment costs, namely (…) the purchase and installation of new cathodes (…). In terms of on-going costs, molybdenum-coated cathodes would result in uncertain changes to energy consumption, possibly a reduction, according to a relevant patent application, increased maintenance and materials costs due to the adverse effect of phosphates on the stability and durability of the anodes and unclear impacts on ancillary operations (as it is not clear what oxygen controls would be required). The economic feasibility of the alternative is very poor, particularly in light of the significant investment costs; and

 Two-compartment electrolytic systems: for this alternative, the investment costs are far greater and, realistically, prohibitive, than the previously described alternatives, as demolition of the existing chlorate plant and erection of a new plant would be required at a cost of several millions of Euros. Even if such investment would be feasible, the new plants would have increased maintenance requirements (the periodic replacement of membranes and higher energy consumption is the most critical component of chlorate plant operating costs. Two-

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 111 compartment solutions are the most economically infeasible solution and cannot be considered as a realistic proposition”.

In addition, to-compartment solutions cannot be considered as a realistic proposition as the R&D that would need to be done to assess feasibility of commercialising this technology for use in the production of sodium chromate could not be undertaken in time for the planned start-up of the SCB plant, nor would it be feasible to redesign and/or rebuild the new plant adapted to this technology, before the new plant comes into operation. The timing of this is critical as SCB’s new plant must be up and running as to be able to continue to supply Caffaro’s water treatment customers when Caffaro will asked by the public authorities to cease production.

In general, alternatives have not come even close to being proven at the industrial, commercial scale; therefore, issues of economic feasibility are purely of theoretical nature, as these alternatives cannot possibly be implemented by the applicant given the planned timing of the new plant. Two important points need to made: (a) investment costs would be very high, and (b) electricity (primarily for electrolysis and for ancillary tasks) accounts for – by far – the largest proportion of the production cost. Therefore, profitability crucially depends on electricity prices and costs. SCB, being located in Italy, is subject to particularly high electricity process as a direct result of local taxes. Figure 6-1, taken from Eurostat, shows that electricity prices in Italy in the first half of 2018 were the second highest in Europe (higher than the EU-28 average). Taxes and levies other than VAT are also among the highest in the EU.

Against this backdrop, the use of an unproven technology that could increase electricity consumption is not a viable option for the applicant, as they cannot guarantee the profitability and long-term viability of the chlorate/chlorite operations.

Figure 6-1: Electricity prices for industrial consumers, first half 2018 (€/kWh) Source: Eurostat19

6.3 Reduction of risks from the use of shortlisted alternatives

There is a mixed picture with regard to the capacity of the shortlisted alternatives to reduce risks from the use of SD in the applied for use. Two-compartment systems do not use any replacement additives

19 https://ec.europa.eu/eurostat/statistics-explained/index.php?title=File:Electricity_prices_for_non- household_consumers,_first_half_2018_(EUR_per_kWh).png, accessed on 24 January 2019

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 112 and do not appear to introduce notable hazards; therefore, they could be considered capable of eliminating the risks from SD, and as such, perhaps potentially suitable alternatives for SD. However, this AoA confirms they have not been tested or scaled up, nor proven to be a commercially viable alternative technology for the production of sodium chlorate.

For molybdenum-based solutions, the use of sodium molybdate and sodium phosphate buffers results in a reduction of risks, as shown by the lower RCR values estimated for the Caffaro AoA. Therefore, the two molybdenum-based alternatives could be considered suitable alternatives for SD. However, past research has shown that some of the technical shortcomings of these alternatives can be addressed by the addition of SD into the electrolyte. Under such a condition, the two shortlisted alternatives would evidently not be considered suitable alternatives.

On the other hand, the use of the three alternatives would result in increased use of energy and this would in turn result in increased greenhouse gas emissions. 6.4 Availability of shortlisted alternatives

Table 6-2 summarises the previously presented discussion on the availability of the shortlisted alternatives. These technologies are not available at the industrial/commercial scale.

Table 6-2: Summary of availability of shortlisted alternatives for SD (NB. grey cells show problematic areas) Molybdenum-based Two-compartment Availability criterion Sodium molybdate coatings systems  () Small quantities Required reagents Quantity availability required, sodium available on the market Not relevant molybdate is REACH but coated cathodes not registered yet available   No issues identified with  Technology specifically the quality of the Technology not available adapted to chlorate Quality availability substance but for use at the industrial production not available technology not available scale for use at the industrial for use at the industrial scale scale  ?  3rd party patents have Uncertain; a 3rd party had Technology specifically been applied for but the Access to technology filed a relevant patent adapted to chlorate required technology that rights application but this was production not available would render this deemed to be withdrawn for use at the industrial alternative feasible, is in November 2015 scale not currently available Is the alternative available to the No No No applicant

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 113 6.5 Overall conclusion

The overall outcome of this analysis is shown in Table 6-3.

Table 6-3: Overall conclusions on suitability and availability of shortlisted alternatives for Caffaro Technical Economic Alternative Reduction in risk Availability Feasibility Feasibility HH:  Sodium molybdate    ENV:  Molybdenum-based HH:     coatings ENV: ? Two-compartment HH:     electrolytic systems ENV:  : better than SD; : worse than SD; -: no change compared to SD; ?: uncertain Parentheses indicate a degree of uncertainty

None of the shortlisted alternatives is a feasible alternative for SD that would eliminate the exposure of workers to the Cr(VI) species responsible for SD’s SVHC status, and this conclusion supports the applicant’s request for the Authorisation of the future use of SD in the manufacture of sodium chlorate, as is standard practice in the chlorate industry across the world.

SCB believes that the practical implementation at the industrial scale of the above or more novel solutions may lie many years into the future. A long review period for the Authorisation would not only allow time to attempt to overcome the limitations in the currently known technologies, but also to explore potentially better long-term solutions.

Use number: 1 Legal name of the applicant: Società Chimica Bussi SpA 114 7 Annex – Justifications for confidentiality claims

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'''''''''''''''''''''''''''' '''' ''''''' '''''''''''''''''' '''''''''''''' ''''''' ''''''''''''''''''''''' '''''''''''''''''''''''' ''''''' '''''' '''''''''' '''''''''''''''''''''''' '''' ''' ''''''''''''' '''''''''' ''''''' ''''''''''''''''' '''' ''''''''''''''''''''' '''''''' ''''''' ''''''' '''''''''' '''''''''''' ''' ''''''''''' ''''''' ''''''''''''''''' ''' ''''''''''''' ''' ''''''''''' '''''''''''''''''''''' '''''''''''' ''''''''''''' ''''''' '''''''''''' ''''''''''''''''''''' ''''''''''''''' '''''''''''''''''''' '''''''' ''''''''''''''''''' '''''''''''''''''''''''''''''' ''''''' '''''' ''''''''''' ''''' ''''' '''''''''''' ''''' ''' ''''''''''' ''''''''''' ''''''''''''''''''''''' '''' ''''''''''''''''''''''' '''''' ''''''' ''''''''' ''''''''''''''''' ''''' '''''' '''''''''''''''''' ''''''''''''''''''' ''''''''''''''''''''' ''''''''''''''''' ''''''' '''''''''' ''''''''''''''''' ''''''' ''''''''''''''''''' '''''''''''''''''' ''''''''' '''''' ''''''' '''' '''''''''''''''''''''''''' 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''''''''''''''''''''' '''''''' '' '' ''''''''''''''''' '''' ''''''''''''''''' ''''''''''''''' ''''''' '''''''''''' '''''''''''''''' ''''''''''''''''''' ''''''''' ''''''''''''''''' '''''''''''''''''''''' '''' '''''' ''''''''''''''''' '''''''''''' '''''''' '''''''''''' '''''''' ''''''''''''''''' ''''''''''''''' '''''''' '''''''' '''''''''''''''''''' ''''' ''''''' '''''''''''''' ''''''''''''' ''''''' ''''''''''''''''''' '''''''''''''''''''''' ''''' '''''' ''''''''''''''''' '''' '''''''''''''' '''' ''''''' '''''''' ''''''' '''''''''''''''''''' '''''''' ''''''''''''''' '''' ''''''' ''''''''''''' '''' '''''''''''''''''''''''' ''''''' '''''''' '''''''''''''''''' ''''''''''''''' '''''''''''' '''''''''''''''''' '''''''' '''''''' ''''' ''''''''''''''' ''''' ''''' '''' ''''''' ''''''''''''''''' '''' ''''''''''''''' '''' '''''''''''''''''''''' '''''''' '''''''''''''''''''''''''''''' ''''' '''''''''''''''''''' '''''''''''''''''''' ''''' '''''''' ''''''''''''''''''' '''''''' '''''''''''''''''''''' ''' ''''''' '''''''' ''''''''''''''''' ''''' ''''''' '''''''''' ''''' ''''' ''''''' '''''''' ''''''''''''''' ''''''' ''''''''''''''' ''''''''''''''''''' ''''''' ''''''''''' '''''' ''''''' ''''''' ''''''''''''''''' ''''''''''''''' '''''''''''''''''' ''''''' ''''''''''''' '''''''''''''' ''''' '''''''''''''' ''''''''''' ''''''''''''''''''''' ''''''''''''''''' '''' ''''''''''''' ''''''''' '''''' ''''''' ''''''''''''''''''''''' ''''''''''''''' ''''''' ''''''''''''''''' '''''''''''''''''''''' ''''' '''' '''''' ''''''''''''' '''''''''''''''''''''' '''' '''''''' ''''''''''''''''' '''''''''''' ''''''''''''' '''''''''''''''' ''''''''' ''''''''' '''''''''''' '''' ''''''' '''''''''''''''' ''''''''''''' ''''' '''''''''''''' ''''''''''''''' ''''''''''''''''''''''' '''''' '''''''' ''''''' ''''''''''''' '''''''''''' '''''''''''' '''' ''''''''''''''''''' ''''

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'''''''''''''''''''''''''' '''''''''''''''''''' '''' '''''' ''''''''''''''''' '''' '''''''''''' '''' '''''' '''''''''''''''''''' '''''''''''' ''''''' '''''''''''''''' ''''''''''''''''' '''''' ''''''' ''''''' ''''' ''''' '''' ''''''' ''''''''' '''''''''' ''''''' '''' ''''''''''''''''''''' ''''''''''''' ''''''''''''' '''' ''''''''''''''' ''''''' '''''''''''''''''''' ''''''''''''''''' '''''''''''''' ''''''''''' ''''' ''''''''''''''' '''''''''''' ''''''''''''''''' ''''' '''''' ''''''''''' ''''''''''' '''' '''''''''''' '''''''''' '''' ''''''''''''''''''' ''''''''''''''''''' '''''''''' '''''''' ''''''''''''''''''''' '''''''' '''''''''''''' '''''''''''''''' '''' ''' '''''''''''''' '''''''''''''''''''''''' '''''''' '''''' ''''''''''' '''''''''''''' '''' ''''''' ''''''''''''''''' '''''''' '''''''''''' '''''''''''''''' ''''''' ''''''''''''''''' '''' ''''''' ''''''''''''''''''''' '''' '''''' ''''''''''''''''' ''''''' ''''' ''''''' '''''''''''''''''''''' '''''' '''''''''''''' '''''''''''''''''''''' ''''''''''''''' '''''''' ''''''''''''''' ''''''''''''''''''' ''''''' ''''''' ''''''''''''''''''' ''''''''''''''' ''''''''''' '''' ''''''' ''''''''''''''''''''''' ''''''''' '''''''''''' ''''''' ''''''''''' '''' ''''''''''' '''''''' '''''' ''''''''''''' '''''''' ''''' '''''' '''''''''''''' '''' ''''''' '''''''''''''''' ''''''' ''''''''''''''''''' '''''''''''''' ''''''''''''''''' ''''''' '''''''''''''' '''''''''''' '' ''''''''''''''''''''''' ''' ''''''''''' '''''''' '''''''''''''''' ''''''''''''''''''''' '''''''' '''''''''''' '''' '''''' '''''''''''''''''' '''' ''''''''''' '''' ''''''' '''''''' '''''''''''''' ''''''''''''''''''''''''' '''''''''''''''' ''''''''''' '''' ''''''' '''' ''''' ''''''''' '''''''''' '''''''''''''' ''''''''' '''''''''''''''''''' '''''''' '''''''''' '''''''''''''''''' ''''''''''''''''''''' '''' ''''''''''''''''''''' ''''''''''''''''''''' '''''' '''''''''''''' ''''''''''' '''' '''''''''' '''''' ''''''''''''' ''''' '''''''''''' '''''''''' 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''''''' '''''''''''''' ''''''''''' ''''''''''''''''''''''''''' ''''''''''''''''' '''''''' ''''''''''''' '''' '''''''' ''''''' ''''''''''''' '''' '''''' '''''''''''''''''' '''' '''''''''' ''''' '''''''''''' '''''''''''''''''''''' ''''''''' ''''''''''' ''''''' '''''''''' '''' ''''''' ''''' ''''''''''''''''''' '''''''''''''''''''''' '''''''' '''''''''' ''''''''''''' ''''''''''''''''' ''''''' ''''''''''''''''''' ''''''''''''' '''''''''''''''''' ''''''''' '''''''''''''' ''''''''''' '''''' ''''''''''''''''''''''' '''''''''''''''''''''' ''' ''''''''''''' ''''''' '''''''''''''' '''''''''''''''''''''' '''''''''''''''''''''' ''''''' ''''' ''''''' '''' '''''''' ''''' '''''''''' ''''''''''' ''''''''' ''''''''''''''' ''''''''''''''''''''' ''''''''''''' '''''''' ''''''''''''''''' ''''''' ''''''' '''''''''''''''''' '''''''''''''''''' ''' ''''''''''''''''''''' ''''''''''''' ''''' '''''''''''' ''''' ''''' ''''''''''''''''''

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'''''''''''''' '''''' '''''''' '''''''''' '''''''''''' ''''''' ''''''''''''''''''''''' ''''''''''''''''' ''''''' '''''''''' '''' ''' ''' '''''''''''''''''' '''''''' '''''''''''''''''''''''' ''''' ''''''' ''''' ''''''''''''''''''''' ''''' ''''''''''''''''''''''' ''''''''''''' ''''''''' '''''''''''' '''''' '''''''''''''' '''''''''''' '''''''''''''''' ''''' ''''''''''''''' '''''''''''''' ''''' ''''''' ''''''''''''''''' ''''''''''''''''' ''''''''''''' '''' ''''''''''' '''''''''' ''''' ''''''' '''''''''''' '''''''''''''''''' '''''''''' '''''' '''''''''''''' ''''''''''''''''''''''''' ''''''' ''''''''''''''''''''' ''''''''''''''''' '''''''''''''' '''''''' ''''''''''''''''''''''' ''' ''''''''''''''''''''' '''' ''' '''''''''''''''''' '''''''''''''''''''''''' '''''''' '''''''''''''''''''''' '''''''''''''''''' ''''''' ''''''''''' ''''''''''''''''''' ''''' '''''''''''' ''''''''''''''''''''''''' ''' '''''''''''''' ''''''''''''''''' ''''' ''''''''''' ''''''''''''''''''''''' '''''''' 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