Emrah Pesman1), Evren E. Kalyoncu2), Perborate Usage instead of Hüseyin Kirci2) for the Reinforcement of Delignification

1) Artvin Çoruh University, Faculty of Forestry, Abstract The Department of Forest Industrial Engineering Oxygen has always been an attractive oxidant for the pulp and paper industry due to it being cheap and harmless for the environment. However, it has lower lignin-cellulose se- 2) Karadeniz Technical University, lectivity, therefore the degree of delignification achieved at the oxygen stage is ultimately Faculty of Forestry, limited by its industrial pulp strength – 45-50% . In this study, to enhance the degree of The Department of Pulp and Paper Tech. 61080, delignification, the addition ofsodium perborate and hydrogen peroxide at the oxygen stage Trabzon, Turkey was examined. At the same active oxygen (approximately 0.5%) content, the degree of del- E-mails: [email protected]; ignification increased from 45.56% to 49.42% using hydrogen peroxide and to 52.96% [email protected]; [email protected] with sodium perborate. For the same selectivity parameter with control, the delignification degree can be increased to 57.59% with the addition of sodium perborate, which includes * Author to whom correspondence should be addressed; 1% active oxygen. Moreover, the costs of using sodium perborate and hydrogen peroxide E-mail: [email protected] were compared with respect to commercial employability. It was determined that the use of sodium perborate was more effective than that of hydrogen peroxide for delignification of the oxygen stage. Key words: oxygen delignification, sodium perborate, selectivity, active oxygen, hydrogen peroxide.

Introduction tion leads to weaker pulp fibers and limits perborate monohydrate (NaBO3.H2O) single stage delignification to ~50% [3]. contains 16% active oxygen, and it does During the kraft pulping process, exten- Several researches, such as the pretreat- not have a specific melting point. When sive lignin fragmentation and degradation ment of pulp prior to oxygen delignifica- heated, it decomposes by releasing oxy- occurs, leading to the generation of new tion and the reinforcement of oxygen del- gen and water. Sodium perborate mono- free phenolic hydroxyl groups. Under ignification with a reactant, have been un- hydrate is preferred to tetrahydrate due the alkaline conditions employed, these dertaken to try and overcome this handi- to its higher oxygen content and faster hydrophilic groups are ionised, resulting cap. The first study about combining the dissolution rate. In addition, monohy- in approximately 90% of the lignin being effects of hydrogen peroxide and oxygen drate is more stable than tetrahydrate in dissolved in the cooking liquor [1]. By for the bleaching of chemical pulp was storage [7]. the end of the cooking, the majority of undertaken in 1980’s, and a synergy was β-aryl ether structures have been cleaved, determined between oxygen and perox- Meshcherova and coworkers conducted and consequently the ability to generate ide [4,5]. Parthasarathy and coworkers laboratory studies on the use of sodium new phenolic sites decreases, making the showed that peroxide with oxygen had and potassium perborates for bleaching residual lignin more resistant to dissolu- additional effects on the delignification softwood kraft pulps. They compared the tion. The remaining lignin is more re- of pine kraft pulps, resulting in improved physico-chemical and mechanical prop- sistant to hydrolytic degradation, requir- selectivity and delignification efficiency. erties of the bleached pulps and conclud- ing oxidative degradation over several The addition of 0.5% hydrogen peroxide ed that it is more advantageous to stages to be removed [2]. Traditionally, at the oxygen delignification stage caused kraft pulp with potassium perborate than chlorine and/or chlorine dioxide can be a 60% reduction in the kappa number as hydrogen peroxide [8]. Varennes and utilised, but environmental regulations compared to a conventional oxygen del- coworkers used sodium perborate tet- are increasingly mandating the replace- ignification stage [6]. Parthasaraty and rahydrate for bleaching thermomechani- ment of such chemicals. The major alter- coworkers also examined the peroxide cal pulp, reaching a brightness as high as natives currently employed are oxygen- reinforcement of the double-stage oxy- 75% ISO with the addition of 6.5% sodi- based chemicals such as molecular oxy- gen delignification process. Using the um perborate tetrahydrate [9]. Moreover, gen and hydrogen peroxide [2]. (PO)(PO) process, the kraft pulps delig- by using sodium perborate monohydrate nified showed a kappa number of about for the bleaching of SGW (Stone Ground At present, oxygen delignification is 73% of the original, as compared to 61% Wood) pulp, the brightness of the pulp widely used for lignin removal in pulp- for the double oxygen stage with an ad- increased from 49.64% to 64.74% ISO ing and bleaching. The chemical cost dition of 0.5% hydrogen peroxide to the with a 1% active oxygen dosage [10]. savings realised by displacing chlorine or oxygen delignification media [6] . Based the information above, we used chlorine dioxide with oxygen and caus- sodium perborate for the reinforcement tic, as well as the ability to recycle the fil- Besides hydrogen peroxide, similar of oxygen delignification. trate in the recovery furnace are the main oxidising agents such as sodium per- advantages of oxygen delignification. can be utilised for the reinforce- In this study, the effects of sodium perbo- However, the capital costs and lower ment of oxygen delignification. Sodium rate monohydrate reinforcement on oxy- lignin-cellulose selectivity compared to perborate monohydrate is used in the gen delignification was investigated as chlorine dioxide bleaching are handicaps formulation of concentrated detergents an alternative to hydrogen peroxide for of the oxygen delignification stages. The as well as in certain medical, disinfect- enhancing the delignification capacity of lower selectivity of oxygen delignifica- ant, and cleaning preparations. Sodium the oxygen stage.

106 Pesman E., Kalyoncu E. E., Kirci H.; Sodium Perborate Usage instead of Hydrogen Peroxide for the Reinforcement of Oxygen Delignification. FIBRES & TEXTILES in Eastern Europe 2010, Vol. 18, No. 6 (83) pp. 106-109. Methodology Results and discussion cate test result with peroxide and sodium perborate added. For comparison, the Eastern Spruce (Picea orientalis L.) kraft Determination of the optimum alka- charges of the reagents were calculated pulps were used for experiments, which line charge for the oxygen delignifica- as active oxygen on oven dry pulp. had the following properties: tion stage n Kappa Number – 33.2 Eastern Spruce (Picea orientalis L.) kraft However, both reagents increased the del- pulp was exposed to oxygen delignifica- ignification, and sodium perborate caused n 3 Pulp viscosity – 917 cm /g tion with a varying alkaline content, from significant delignification augmentation. n Screened pulp yield – 47.2% 1% to 5%. Other process parameters With an addition of (as active oxygen to were similar to those in conventional o.d. pulp) peroxide of 0.5%, the delig- Oxygen delignification was carried out mill scale application (Pulp consistency – nification degree rose from 45.56% to in a 15 L stainless steel reactor heated 12%, reaction temparature – 90ºC, reac- 49.41% in comparison with the control. electrically, the temperature of which tion time – 60 minutes, oxygen pressure Furthermore, with a sodium perborate ad- was controlled by an OMRON 55 CK – 690 kpa, MgSO4 addition – 0.02%). dition of 0.5%, the delignification degree digital process controller to within Pulp properties subjected to oxygen del- rose to 52.96% (Figure 1 – see page 108). ±0.2°C. Loading of the reactor was done ignification are shown in Table 1. At an manually, and 100 g o.d. of the spruce alkaline charge of 2% and delignification Hydroperoxide anion (HOO-) is an active kraft pulp was used in each experiment. degree of 45.6%, the minumun relative species and is responsible for the bleach- The pulp was diluted to a consistency of degredation of the pulp was determined. ing action of hydrogen peroxide under 12% with 0.2% MgSO4 and 2% NaOH When other parameters were kept con- alkaline conditions. On the other hand, added to the pulp. For reinforcement of stant at a conventional mill-scale level, and hydroxyl radicals gen- the oxygen delignification, peroxide and the optimal alkaline charge for oxygen erated by the decomposition of hydrogen sodium perborate with a charge varying delignification was selected as being 2%. peroxide are responsible for delignifica- from 0.25% to 1.5% was used as active (Table 1) tion [6]. Hydroxyl radicals are capable of oxygen on oven dry pulp. The constant attacking practically all types of organic temperature was set at 90°C and the Effects of peroxide and sodium perbo- structures, including those containing hy- process time at 60 minutes. An oxygen rate on delignification, viscosity and droxyl and ether linkages [6]. Similar re- pressure of 690 kPa was used in each selectivity parameters actions occur with sodium perborate, but experiment. For comparison, the charg- In optimum oxygen delignification con- its alkalinity is higher than that of hydro- es of the reactives were selected accord- ditions, a number of experiments were gen peroxide; in this respect sodium per- ing to the active oxygen content. The conducted with peroxide and sodium borate has significant effects on delignifi- active oxygen content of peroxide and perborate added to the reaction media. cation at the same active oxygen charge. sodium perborate monohydrate is 47% Table 2 gives the average of the dupli- Parthasarathy and coworkers showed and 15%, respectively.

Following oxygen delignification, the Table 1. Properties of oxygen delignified eastern spruce kraft pulp. pulp was washed twice with distilled, Scan Relative Alkaline Kappa General Process Delignification deionised water at a consistency of 1% viscosity, degradation charge,% Number yield, % yield, % degree, % and then pressed to a high consistency cm3/g (Δη/Δk) (>25%) for yield determination. Pulp 33.3 917 47.2 – – – 1% 24.6 839 46.8 99.1 26.1 9.01 The kappa numbers of the pulps were de- 2% 18.1 793 46.4 98.4 45.6 8.20 termined according to the TAPPI method 3% 14.1 752 46.2 98.0 57.5 8.65 T236. The viscosity of the pulps were 4% 13.1 713 45.5 96.4 60.7 10.1 determined according to the standard 5% 12.4 697 45.4 96.1 62.6 10.6 method SCAN cm 15:88. Correlation be- tween the SCAN viscosity and DP was made using formula (1): Table 2. Properties of the hydrogen peroxide and sodium perborate reinforced oxygen delignification stages.

1.105 DP = (0.75* [ηscan]) (1) Charge of Pulp Viscosity, Brightness Delignification Reactives Kappa Number cm3/gr (ISO), % In order to expose the selectivity to oxy- (active oxygen, %) gen delignification, selectivity parameter 0.00 793.00 18.10 37.10 Hydrogen 0.25 816.34 16.87 37.78 S, developed by Van Heinengen et al. peroxide was calculated as follows [3]: reinforced 0.50 814.40 16.82 39.83 oxygen 1.00 796.40 16.48 40.53 ∆K delignification S = c (2) 1.50 790.00 15.74 41.96 (1/ DPt −1/ DP0 0.00 793.00 18.10 37.10 Sodium 0.25 790.35 16.67 39.41 ΔKc – Difference in Kappa number, perborate reinforced 0.50 784.53 15.64 39.93 DPt – Polymerisation degree of Oxygen oxygen 1.00 766.61 14.10 42.55 delignified pulp, delignification 1.50 726.26 13.69 44.88 DP0 – Polymerisation degree of the pulp

FIBRES & TEXTILES in Eastern Europe 2010, Vol. 18, No. 6 (83) 107 Sodium perborate monohydrate Hydrogen peroxide Sodium perborate monohydrate Hydrogen peroxide -4 Delignification, % Selectivity x 10

Charge of Agents, % Active Oxygen Charge of Agents, % Active Oxygen

Figure 1. Effects of sodium perborate and hydrogen peroxide Figure 2. Effects of sodium perborate and hydrogen peroxide charges on the delignification degree of the oxygen stages. charges on the selectivity of the reaction during oxygen delignification.

that hydrogen peroxide with oxygen has effective than hydrogen peroxide for the higher than peroxide reinforced oxygen an additional effect on the delignifica- reinforcement of oxygen delignification. delignification without selectivity loss. tion of kraft pulps. Hydrogen peroxide In other words, to obtain a delignifica- charges of 0.2-0.5% applied at the oxy- Cost parameters of sodium perborate tion ratio of 52.5%, a peroxide charge of gen stage resulted in pulps with a lower and hydrogen peroxide reinforced 1.5% (as active oxygen to o.d. pulp) was kappa number and higher viscosity [6]. oxygen delignification needed, whereas with perborate mono- In this study the viscosity of the pulp and The costs of the chemical agents used in hydrate only an active oxygen charge of the selectivity of the reaction increased this work are summarised in Table 3 with only 0.5% was enough. Consequently, with the addition of hydrogen peroxide. respect to commercial employability. So- peroxide reinforcement increased the Nonetheless, with sodium perborate, the dium perborate is more expensive than oxygen delignification cost to $ 37.983 viscosity of the pulp decreased, whereas hydrogen peroxide because of the use of (Table 4) for a higher delignification ra- peroxide during perborate production. tio (52.5%) Table 3. Cost of the chemical agents [9,11,12]. On the other hand sodium perborate in- cludes extra alkaline, and consequently it Chemical agent Cost US$/kg needs less alkaline charge than hydrogen Conclusions Oxygen 0.0600 peroxide for oxygen delignification. The effects of sodium perborate and hy- Magnesium sulfate 0.3527 drogen peroxide reinforcement on the to 50% 0.3478 For an active oxygen charge of 0.5%, 21.2 delignification ratio and selectivity of the Hydrogen peroxide to 50% 0.3500 kg of hydrogen peroxide (50%) per ton of oxygen stage have been demonstrated. Sodium perborate tetrahydrate 0.4200 pulp, a 33.3 kg of sodium perborate mono- Both reactants increased the degree of Sodium perborate monohydrate 0.7100 hydrate, and 49.02 kg of sodium perborate delignification without selectivity loss. tetra hydrate per ton of pulp were needed. Sodium perborate was more effective the selectivity of the reaction increased than hydrogen peroxide at a high delig- up to a 1% charge. This situation can be As shown in Table 4, sodium perborate nification ratio, which is because of the explained by detailed examination of the reinforced oxygen delignification is $ increase in the alkalinity of the oxygen delignification and selectivity parameters 16.2 more expensive than hydrogen per- delignification media, as compared with all together. As can be seen in Figures 1 oxide reinforced oxygen delignification hydrogen peroxide. Nevertheless sodium and 2, with an addition of peroxides of for the same active oxygen charge; how- perborate is expensive because of the use 0.5% (active oxygen) , the selectivity in- ever, the delignification gained is 3.55% of peroxide during perborate production creased from 11.86 to 15.99 and the del- ignification – from 45.56% to 49.41%. Table 4. Cost of the reinforced oxygen delignification stages per ton of pulp. On the other hand, with a 0.5% addition of (active oxygen) sodium perborate, Charge, % Sodium perborate the selectivity increased to only 12.77, Component Hydrogen peroxide Hydrogen peroxide monohydrate reinforced OD reinforced OD whereas the delignification increased to reinforced OD 52.99% (Figures 1 & 2). Oxygen 2.49 (7 Bar) 2.49 (7 Bar) 2.49 (7 Bar) Magnesium sulfate 0.05 0.05 0.05 In fact, with a 0.5% addition of sodium Sodium hydroxide 2 2 2 perborate, a delignification ratio of 7.43% Hydrogen peroxide 0.5 (activated oxygen) 1.5 (activated oxygen) – was achieved without a loss of selectiv- Sodium perborate – – 0.5 (activated oxygen) ity. For the same selectivity value with Cost, US$/ODMT 23.00 37.98 39.22 control (11.9), a 1% addition of sodium According to the Control, Delignificaton and Selectivity Augmentation of Reinforced .O D. perborate increased the delignification Delignification, % 49.41 52.66 52.96 degree from 45.56% to 57.59%. These results clearly indicate that, because of ΔDelignification, % 3.85 7.10 7.40 -4 extra alkalinity, sodium perborate is more ΔSelectivity, Sx10 4.13 1.49 0.91

108 FIBRES & TEXTILES in Eastern Europe 2010, Vol. 18, No. 6 (83) and the increase in the cost of oxygen stage. In addition to this, more residual INSTITUTE OF BIOPOLYMERS lignin can be removed by sodium per- borate instead of hydrogen peroxide. In AND CHEMICAL FIBRES this respect, the cost of the oxygen stage or the chemicals for following bleaching stage can be decreased by using sodium LABORATORY OF ENVIRONMENTAL PROTECTION perborate . Moreover, it is a good alterna- tive for peroxide because it is more stable The Laboratory works and specialises in three fundamental fields: and can be stored in a solid form. n R&D activities: n research works on new technology and techniques, particularly envi- ronmental protection; n evaluation and improvement of technology used in domestic mills; References and Notes n development of new research and analytical methods; 1. Gellerstedt G., Lindfors E. L., ‘Structural n Changes in Lignin during Kraft Pulping’ research services (measurements and analytical tests) in the field of en- Holsforschung, 38, 151-158 (1984). vironmental protection, especially monitoring the emission of pollutants; 2. Kadla J.F., Chang H.M., ‘Reactions of Lignin with Cyanamide Activated Hydro- n seminar and training activity concerning methods of instrumental anal- gen Peroxide Part 3 The Degradation of ysis, especially the analysis of water and wastewater, chemicals used in Pine Kraft Lignin’ Holzforschung, 56, 76- paper production, and environmental protection in the paper-making in- 84, (2002). dustry. 3. Van Heiningen A., Violette, S., ‘Selectiv- ity Improvement during Oxygen Deligni- Since 2004 Laboratory has had the accredi- fication by Adsorption of a Sugar-Based tation of the Polish Centre for Accreditation Polymer’ Journal of Pulp and Paper Sci- ence, 29(2), 48-53 (2003). No. AB 551, confirming that the Laboratory 4. Lachenal D., De Choudens; C., Bourson meets the requirements of Standard PN-EN L., ‘Reinforcement of Oxygen-Alkali Ex- ISO/IEC 17025:2005. AB 388 traction with Hydrogen Peroxide or Hy- pochloride’ Tappi J., 69(7), 90-93, (1986). 5. Klein R.J., Meng T.Y.; Jameel H., Investigations in the field of environmental protection technology: n Sundaram V.S.M., ‘Hydrogen Peroxide Research and development of waste water treatment technology, the Reinforced Extraction Lowers Chlorin- treatment technology and abatement of gaseous emissions, and the utili- ated Organics and Color in Bleach Plant sation and reuse of solid waste, Effluent’ Tappi Pulping Conference Pro- n Monitoring the technological progress of environmentally friendly technol- ceedings, 2, 829-835, (1990). ogy in paper-making and the best available techniques (BAT), 6. Parthasarathy V.R., Klein R., ‘Sundar- n Working out and adapting analytical methods for testing the content of pol- am, V.S.M.; Jammel, H. and Gratzl, J.S. lutants and trace concentrations of toxic compounds in waste water, gase- Hydrogen Peroxide Reinforced Oxygen ous emissions, solid waste and products of the paper-making industry, Delignification of Southern Pine Kraft n Monitoring ecological legislation at a domestic and world level, particu- Pulp and Short Sequence Bleaching’ larly in the European Union. Tappi J., 73(7), 177-185 (1990). 7. Kocakuşak S., Köroğlu H.J., Akçay K., A list of the analyses most frequently carried out: Savaşçı Ö.T., Tolun R., ‘Production of n Global water & waste water pollution factors: COD, BOD, TOC, suspended Sodium perborate monohydrate by Flu- solid (TSS), tot-N, tot-P idized-Bed Dehydration’ Ind.Eng.Chem., n Halogenoorganic compounds (AOX, TOX, TX, EOX, POX) 36(7), 2863-2865 (1997). n Organic sulphur compounds (AOS, TS) 8. Meshcherova N.A., Stromskii S.V., Chup- n Resin and chlororesin acids ka E.I., ‘Bleaching Softwood Kraft Pulp n Saturated and unsaturated fatty acids with Perborates’ Khim. Drev., 3:36 (1982). n Phenol and phenolic compounds (guaiacols, catechols, vanillin, veratrols) 9. Varennes S., Daneault C., Parenteau, n Tetrachlorophenol, Pentachlorophenol (PCP) M., ‘Bleaching of Thermomechanical n Hexachlorocyclohexane (lindane) Pulp with Sodium Perborate’ Tappi Jour- n nal. 79(3):245-250 (1996). Aromatic and polyaromatic hydrocarbons n 10. Peşman E., Kırcı H., Kalyoncu E.E., Benzene, Hexachlorobenzene ‘Bleaching of Stone Ground Wood Pulp n Phthalates n Polychloro-Biphenyls (PCB) with Sodium Perborate’ Proceedings of n Carbohydrates n Glyoxal 3rd International Symposium An- n Glycols n Tin organic compounds kara, 75-79 (2006). 11. Yiğitoğlu Chemical Industry and Com- merce. Ltd. Corporation, The Price of Contact: Hydrogen Peroxide (2006). 12. Etibor Corporation, The Prices of So- INSTITUTE OF BIOPOLYMERS AND CHEMICAL FIBRES dium Perborate Monohydrate and Tet- ul. M. Skłodowskiej-Curie 19/27, 90-570 Łódź, Poland rahydrate (2006). Małgorzata Michniewicz Ph. D., tel. (+48 42) 638 03 31, e-mail: [email protected]

Received 18.03.2009 Reviewed 25.02.2010

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