Thesis/Dissertation Sheet

Surname/Family Name O'Hara Given Name/s TobyY Abbreviation for degree as give in the University calendar MMatTech Faculty Science School Materials Science and Engineering Recovery of Copper Rich Fractions from Waste Printed Circuit Boards of Th esis Title Mobiles

Abstract 350 words maximum: (PLEASE TYPE) A significant innovation of the 20th century, the printed circuit board (PCB), and its components, i.e. printed wiring board (PWB) plus integrated circuits (ICs), are ubiquitous, even if they are not always visible, but are instead tucked away inside of useful gadgets. From very small segments for simple computations in children's toys, to dense, multi ;;�ye red, highly complex arrays of PCBs present housed in stacks of black boxes in server rooms all over the world, these workhorses of the modern world are produced to meet the technological needs of billions of businesses, government organisations, and individuals. In a world of rapid technological innovation, toys, personal devices, and business machines are all upgraded and improved on a regular basis. It is well established that e-waste, or Waste Electrical andElect ronic Equipment (WEEE), is an increasing waste stream. According to the United Nations Environment Programme (UNEP), the life span of computers in 1997 was on average six years, but more recently, in 2005, the life span of a computer is just two years. This estimate is likely to have worsened rather than improved since 2005. Research has characterised the electronic waste (e-waste) stream, and has proposed various recovery methods. It is also worth noting that characterising the waste stream and making discoveries towards better recovery clearly demonstrate the value proposition inherent in doing so. This paper discusses recovering copper from waste Printed Circuit Board (PCB), a common component of e-waste, specifically PCB from mobile phones (MPCB), which have been demonstrated to have a short lifespan. Additionally, mobiles are increasingly common, by some estimates production has exceeded the quantity of one smart phone per person worldwide. Processing of mobile phones using heat treatment has been proven effectivein recovering materials from waste MPCB, this paper discusses options for recovery of copper at differenttemperatures.

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Date ……………………………………………...... Faculty of Science School of Materials Science and Engineering

Recovery of Copper Rich Fractions from Waste Printed Circuit Boards of Mobiles

A thesis in Materials Science and Engineering

By

Toby O’Hara

Submitted in Partial Fulfilment of requirement for the degree of MASTER by Research

December 2019

1 ACKNOWLEDGEMENTS

Without my supervisors, this present study would never have been possible: Professor Veena Sahajwalla and Farshid Palevani.

A big thank you to Ravindra Rajarao, for assistance, Irshad Mansuri, lab manager, and other technical staff like Mohannand Mayyas, Rasoul Nekouei for their assistance, including Anne Rich, Rabeya Akter, and Simon Hager.

My family and close friends were there for me when I felt like giving up, I owe them big time.

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ABSTRACT

A significant innovation of the 20th century, the printed circuit board (PCB), and its components, i.e. printed wiring board (PWB) plus integrated circuits (ICs), are ubiquitous, even if they are not always visible, but are instead tucked away inside of useful gadgets. From very small segments for simple computations in children’s toys, to dense, multi layered, highly complex arrays of PCBs present housed in stacks of black boxes in server rooms all over the world, these workhorses of the modern world are produced to meet the technological needs of billions of businesses, government organisations, and individuals. In a world of rapid technological innovation, toys, personal devices, and business machines are all upgraded and improved on a regular basis.

It is well established that e-waste, or Waste Electrical and Electronic Equipment (WEEE), is an increasing waste stream. According to the United Nations Environment Programme (UNEP), the life span of computers in 1997 was on average six years, but more recently, in 2005, the life span of a computer is just two years. This estimate is likely to have worsened rather than improved since 2005.

Research has characterised the electronic waste (e-waste) stream, and has proposed various recovery methods. It is also worth noting that characterising the waste stream and making discoveries towards better recovery clearly demonstrate the value proposition inherent in doing so. This paper discusses recovering copper from waste Printed Circuit Board (PCB), a common component of e-waste, specifically PCB from mobile phones (MPCB), which have been demonstrated to have a short lifespan. Additionally, mobiles are increasingly common, by some estimates production has exceeded the quantity of one smart phone per person worldwide.

Processing of mobile phones using heat treatment has been proven effective in recovering materials from waste MPCB, this paper discusses options for recovery of copper at different temperatures.

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TABLE OF CONTENTS

ACKNOWLEDGEMENTS 2

1 Introduction 8

2 Literature review 9

3 Experimental 43

3.1 Research Questions 43

3.2 General Methodology and Scope 43

3.3 Risks 44

3.4 Material collection and preparation 45

3.5 Instruments 48

4 Analysis 53

5 Conclusions 77

References 79

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LIST OF TABLES

Table 2-1 Consumption of inputs for processing different concentrations of copper (Reproduced from Norgate and Haque 2010)...... 15 Table 3-1 Temperatures for PCB selective thermal transformation ...... 44 Table 4-1 Composition of droplet from iPhone PCB after heat treatment at 1050°C ...... 55 Table 4-2 Composition of droplet from iPhone PCB after heat treatment at 1150°C ...... 57 Table 4-3 Composition of droplet from iPhone 4 after heat treatment at 1250°C ...... 59 Table 4-4 Composition of droplet from iPhone PCB after heat treatment at 1350°C ...... 62 Table 4-5 Composition of droplet from Nokia WPCB after heat treatment at 1150°C ...... 67 Table 4-6 Summary results for iPhone 4 and Nokia N3210 at different temperatures ...... 77

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LIST OF FIGURES

Figure 2-1 Concentrations of copper ...... 13 Figure 2-2 Processing diagram for end of life appliance (Hieronymi, Kahhat et al. 2012)..... 25 Figure 2-3 Electrorefining of copper ...... 38 Figure 3-1 Disassembled iPhone 4 with selected labels ...... 46 Figure 3-2 Disassembled Nokia N3210 ...... 47 Figure 3-3 Milled Nokia N3210 printed circuit board ...... 48 Figure 3-4 Diagram of Thermo-gravimetric analyser (TGA) ...... 48 Figure 3-5 Untreated PCB from iPhone 4 placed in alumina crucible ...... 49 Figure 3-6 Post heat treatment PCB from iPhone 4 in alumina crucible ...... 49 Figure 3-7 High Temperature Furnace ...... 50 Figure 3-8 Sample in the cold zone of a horizontal high temperature furnace ...... 50 Figure 3-9 Sample in the hot zone of a horizontal high temperature furnace ...... 51 Figure 3-10 SEM-EDS ...... 52 Figure 4-1 Heat treatment of iPhone PCB before and after photo ...... 53 Figure 4-2 SEM image of iPhone after heating at 850C ...... 54

Figure 4-3 iPhone PCB heat treated at 1050C ...... 55 Figure 4-4 Metal droplet from iPhone heat treated at 1050°C, showing copper (Cu) in pale green, nickel (Ni) in yellow, tin (Sn) in pale blue, silver (Ag) in purple...... 56 Figure 4-5 Point analysis of iPhone PCB heat treated at 1150°C ...... 57 Figure 4-6 Element mapping for iPhone PCB treated at 1150°C, showing calcium (Ca) in purple, aluminium (Al) in green, carbon (C), in pink, and copper (Cu) in yellow...... 58 Figure 4-7 iPhone printed circuit board heat treated at 1250C ...... 59 Figure 4-8 Points measured on metal droplet from iPhone 4 after heat treatment at 1250°C . 60 Figure 4-9 EDS analysis of iPhone droplet after heat treatment at 1250°C, showing copper (Cu) in purple, iron (Fe) in pale green, tin (Sn) in pink...... 60 Figure 4-10 iPhone printed circuit board heat treated at 1350C ...... 61 Figure 4-11 Elemental analysis of points on iPhone WPCB following selective thermal transformation at 1350°C ...... 62 Figure 4-12 EDS of iPhone WPCB following selective thermal transformation at 1350C, showing tin (Sn) in pale blue, alumininm (Al) in pink, phosphorus (P) in yellow, copper (Cu) in red...... 63

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Figure 4-13 Nokia PCB after selective thermal transformation at 850°C and EDS analysis of copper (Cu) content (in bright green)...... 64 Figure 4-14 Nokia PCB after selective thermal transformation at 950°C with EDS analysis, showing copper (Cu) in blue, silicon (Si) in pink, calcium (Ca) in bright green...... 65 Figure 4-15 Nokia PCB fragment following heat treatment at 1050°C with EDS analysis, showing a composite image, and separated images for carbon (C) in teal, oxygen (O) in purple, fluorine (F) in pink, aluminium (Al) in olive, silicon (Si) in blue, calcium in red, copper (Cu) in pale green...... 66 Figure 4-16 Nokia PCB following selective thermal transformation at 1150°C...... 67 Figure 4-17 Nokia PCB under SEM/EDS following selective thermal transformation at 1150°C, showing copper (Cu) in pink, silicon (Si) in green, calcium (Ca) in purple...... 68 Figure 4-18 Nokia PCB fragment following selective thermal transformation at 1250°C ..... 69 Figure 4-19 Nokia PCB heat treated at 1350°C, showing silicon (Si) in blue, copper (Cu) in orange, magnesium (Mn) in yellow...... 70 Figure 4-20 Nokia PCB after selective thermal transformation at 1350°C, showing carbon (C) in green, copper (Cu) in orange, silicon (Si) in red, tin (Sn) in purple...... 71 Figure 4-21 Percentage weight loss during selective thermal transformation of Nokia PCB . 72 Figure 4-22 iPhone PCB weight loss during selective thermal transformation...... 72 Figure 4-23 IR Gas analysis of MPCB off gasses during heat treatment ...... 73 Figure 4-24 iPhone PCB after heat treatment, viewed with FTIR ...... 73 Figure 4-25 Nokia N3210 quantitative ICP analysis raw material prior to heat treatment ..... 74 Figure 4-26 iPhone 4 quantitative ICP analysis raw material prior to heat treatment ...... 74 Figure 4-27 Semi quantitative ICP analysis post heat treatment at 1350℃, visually separated into char (X), silvery coloured metal (Y), and copper coloured metal (Z)...... 75

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1 Introduction A significant innovation of the 20th century, the printed circuit board (PCB), and its components, i.e. printed wiring board (PWB) plus integrated circuits (ICs), are ubiquitous, even if they are tucked away inside of useful gadgets. From very small segments for simple computations, to dense, multi layered, highly complex arrays of PCBs, these workhorses of the modern world are produced to meet the technological needs of billions of businesses, government organisations, and individuals. In a world of rapid technological innovation, toys, personal devices, and business machines are all upgraded and improved on a regular basis.

It is well established that e-waste, or Waste Electrical and Electronic Equipment (WEEE), is an increasing waste stream. According to the United Nations Environment Programme (UNEP), the life span of computers in 1997 was on average six years, but in 2005, the life span of a computer is just two years. Since 2005 estimates vary between two and three years.

Research has characterised the electronic waste (e-waste) stream, and has proposed various recovery methods. These efforts to characterise the waste stream and discover better recovery methods clearly demonstrate the value proposition inherent in doing so. This paper discusses recovering copper from waste Printed Circuit Board (PCB), a common component of e- waste, specifically PCB from mobile phones (MPCB), which have been demonstrated to have a short lifespan. Additionally, mobiles are increasingly common, by some estimates production has exceeded the quantity of one smart phone per person worldwide.

Processing of mobile phones using heat treatment has been proven effective in recovering materials from waste MPCB, this paper discusses options for recovery of copper from two different common mobile phone models, each disassembled and processed at five different medium to high temperatures.

This paper finds at least two options for recovery that should be considered, that of low selective thermal transformation, and that of high selective thermal transformation, each with benefits and drawbacks, as described below.

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2 Literature review 2.1 Waste printed circuit boards (PCBs) From small segments for simple computations in children’s toys, to dense, multi layered, highly complex arrays of PCBs present housed in stacks of black boxes in server rooms all over the world, these workhorses of the modern world are produced to meet the technological needs of billions of businesses, government organisations, and individuals. In a world of rapid technological innovation, toys, personal devices, and business machines are all upgraded and improved on a regular basis (Williams, 2011) (Ogunseitan et al., 2009). When the PCB component, or the entire product becomes end-of-life, it contributes to the growing problem of electronic waste (e-waste).

2.1.1 Form While these technological wonders were at one time chunky and easily decipherable to the casual observer, PCBs have long since become highly heterogeneous and microscopic facilitators of computation (Gilleo et al., 2000). Early Printed Circuit Boards (PCBs) were single layered, with only one layer of metal circuitry on a polymer substrate, referred to as FR-2 type. Many modern units, including mobile phones utilise PCBs that are multi-layered FR-4, which is alternating layers of some form of polymer/fibreglass/resin layer with a conductive metal layer, usually copper. The polymer layer is often mixed with a brominated flame retardant, hence the appellation ‘FR’ (Kasper et al., 2011). While most circuitry is sandwiched between layers, some circuitry printed on the outside for interactivity, such as buttons (Ghosh et al., 2015; Hadi et al., 2015). The wiring board itself, FR-2 and FR-4 type boards are then soldered with components of all different types. These components are what give a significantly greater level of material complexity to a PCB (Kasper et al., 2011).

2.1.2 Material The materials and alloys have become increasingly specialised, which has had the effect of making components smaller and less resource intensive, reducing dependency on a particular metal, increasing the speed of manufacture, reducing hazardous materials used in the end product, reducing hazardous or toxic by-products, and/or accelerating the functionality and speed of the unit itself (DeSantis, 1993). As an example of the shrinking size and increasing capability, compare the first Motorola mobile phones introduced in the early 1980’s, with a chunky interface, large size, and weight, which were approximately 790 g and 25 cm high (Hanafi et al., 2012), and capable of doing one thing: wireless calls (Geraldes 2010), to the 9 smart phones we use today, around 100 g and 15-17 cm with built in Wi-Fi, Bluetooth, camera, gyro, speakers, microphones, lights, and more apps than any one person might need.

Material composition of waste from mobile phone printed circuit boards (MPCB) provides particular insights into what is reasonably expected for recovery. A number of studies have characterized MPCB, and a number of published papers have provided rules of thumb when estimating the expected materials for extraction from the end of life material. This is an important challenge because of the large variety of compositions potentially present in MPCB for a resource recovery operation to estimate or try to characterize in advance what material would reasonably be expected as an output, and the implications of having these particular materials closely bound and commingled during processing for materials recovery. The processing may need to adjust for interaction between materials, and may need to adjust in order to minimise by products and wasted energy. E-waste as a whole has been characterized by weight as 60% metal 30% plastic and 10% ceramics (Tuncuk et al., 2012). Of these elements, 2.7% can be considered hazardous or toxic (Widmer et al., 2005). Of the total e- waste, about 3.1% is printed circuit board (Tuncuk et al., 2012). Just PC’s 32% Ferrous metal, 23% plastic, 18% Non-ferrous metal, 15% Glass, and 12% PCB (Baker, E. et al., 2004). To characterize the PCB only, across a range of WEEE products, Ghosh et al (2015) and Zhou and Qiu, (2010).estimate 28% metals, 23% plastics, and the remainder being a combination of glass, ceramics, silica, or other material.

For a mobile phone, however, the ratios are slightly different, the PCB is closer to 21% of the total mass of the mobile phone. This is inferred from Kasper et al (2011), Yamane et al (2011) which places Cu at 30% of the MPCB and Niera et al (2006) which places Cu at 14% of the entire mobile phone, on average.

Mobile phone PCB (MPCB) are said to contain, or have the potential to contain, over 40 different elements (Schulep et al., 2009). This includes common elements one might expect, such as Iron (Fe), Copper (Cu), Silver (Ag), Lead (Pb), and Gold (Au), but also less common elements such as Indium (In), Antimony (Sb), and Cobalt (Co). Lead is considered a toxic substance, and so is Arsenic (As), Bromine (Br), and Cadmium (Cd), some present in batteries, some present in solder, and some present in polymers (IPMI, 2003). MPCB are also known as rich boards. The circuit boards in a mobile phone are ‘richer’ due to the large number of components, number of processors, much fewer capacitors, and being thinner, due to thin layers and less polymer being used, as opposed to ‘poor’ circuit boards with large

10 capacitors, thicker polymer layers, and few or no processors (Abrantes 2009) (Kasper et al., 2011). This idea of value is further reinforced when it is considered that the content of a PCB which is precious metals accounts for more than 80% of the material’s saleable value but the amount by weight is less than 1% (Park et al., 2009). MPCB are composed of polymers, ceramics, and metals (Yamane et al., 2011). The materials distribution within a MPCB looks like this: by weight, approximately polymers 30%, refractory oxides 30%, and metals 40% (Jianzhi et al., 2004; Kasper et al., 2011). Polymers include polymer films such as polyimides, then polyethylene terephthalate or polyethylene naphthalate, which are not as common, and then glass fibre composites and thermoset resin (Hall et al., 2007). The refractory oxides are silica, alumina and rare earth oxides. The metals are most usually iron, copper, tin, nickel, lead, aluminum, silver, gold, and others. These materials are closely associated with three basic segments of the PCB: the polymers act as structural support, nonconducting substrate or laminate; metals often act as the circuit conductors on top of and in between the substrate layers (the substrate and the metal tracks form the printed wiring board) as well as the solder itself; and the refractory oxides are often found in the mounted components that have been soldered to the printed wiring board. The components are what provide the greatest variety of elemental material to the MPCB (Jianzhi et al., 2004). Of the total For MPCB, the highest metal content is copper, and according to Yamane et al (2011) MPCB contains roughly 33% by weight. Kasper et al (2011) suggest between 25-45% by weight.

2.2 Importance of recycling PCBs

2.2.1 Increased consumption It is also well established that humanity’s consumption of increasing numbers of electronic devices (EC, 2015) (UNU, 2013) (MM, 2015) (Economist, 2015), particularly personal devices such as smart phones exceeding 1 device per person in 2013, and personal computers (PC’s) expected to reach 1 device for every 2 people by 2017 (Economist, 2015), demands an equal response to mitigate the expansion of technological availability.

2.2.2 Increasing waste stream It is well established that e-waste, or Waste Electrical and Electronic Equipment (WEEE), is an increasing waste stream (EIU, 2015) (Global 2012) (Huisman, 2013).

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What has been less demonstrated is how best to divert the waste stream into recycling efforts. As of 2008, less than 4% of mobile phones, and less than 1.5% of computers, and less than 1% of televisions were recycled (Angel et al., 2009).

Recycling is also important when considering the fact that many consumers ignorantly discard their useless electronics into the bin (Cucchiella et al., 2015). Without further processing, these wasted materials end up in landfill, uselessly deteriorating over long periods of time. The digging, hauling, and processing energy required to obtain more of the same material, the by products from mining processes, and the refining and manufacturing energy to create new products are likewise thrown away and wasted (Menikpura et al., 2014). It is a better solution if the material present in end of life (EOL) electronics could instead be sent upstream, ready to be made into new products (Bigum et al., 2012; Cucchiella et al., 2015). This would prevent the waste of digging, hauling, processing, and by-products that are created in the mining process.

Industrial recycling usually lags behind industrial production, and can be considered a cost to the business, in the form of storing, reworking, and remaking products from unwanted offcuts, dust, turnings, and other debris from manufacture. Some businesses prefer to dispose of unwanted material to landfill or similar routes (Desrochers, 2002).

The next sections will describe the significant energy expenditure and environmental impact for extraction of metals from natural rock. Because of this, it makes sense to use refined metals for as long as possible and not send them to landfill. This includes using manufactured goods for as long as possible. For example, making products durable, and of high quality. As another example, designing for repairability, making a product easy to disassemble, and making parts swappable. Another example includes addressing capability upgrades, both from a hardware and software perspective. With good engineering and design, electronics and technology devices can last quite a while, or be repaired and updated many times before reaching end of life (Arnette et al., 2014).

2.2.3 Depletion Considering that the life span of a computer is becoming shorter, and the needs for computers in everyday life is continuing to increase with the convenience and speed they offer, one should ask where the material is obtained for the manufacture of more units more often. Most commonly the answer is extraction of natural resources. However, for many decades now 12 concern has been growing over the depletion of natural resources and the increasing need to recover material from the growing pile of our end of life products (Bonczar, 1976) (Carrillo et al., 1974) (Slade, 1980). Here recycling comes into play because metals that are extracted from natural sources have the potential to infinitely provide their properties to products of various types (Bigum et al., 2012), as long as that material is not sent to landfill, sent to a degraded use such as construction material, or dissipated through processing.

Not only is demand increasing, but in many instances, the availability of natural resources is shrinking with respect to ready extraction. As an example, copper is considered fairly abundant in the earth’s crust, however, the concentrations found in active and proposed mines have steadily decreased from 16% in 1860 to 2% in 2010, not counting mine tailings (EcoInfo, 2014). Also focused on copper, a study published in 2013 showed the diminishing concentration of Cu (Mudd, 2013), reproduced in simplified form in Figure 1-1 below. The trend can only continue downwards as the most viable and lucrative concentrations are exhausted.

Figure 2-1 Concentrations of copper Today’s copper mines can have ore grades up to 0.7%, for instance Chile’s Chuquicamata mine, according to the website Mining Technology (MT, 2018) . The target mineral, not counting overburden (meaning rock and soil above the target mineral deposit), one megatonne from the Chuquicamata mine only yields about 7.14 grams. If the US copper

13 penny (pre 1982) is 3.11 grams, this is just over 2 cents worth for every megaton. Entire mountains of soil and rock must be, and have been, removed in order to make the mine profitable. Regarding the exploitation of natural resources, the figures speak for themselves.

Also worth noting was the examination of diminishing ore grades within available resources. A study carried out by Norgate (2012) looked at gold, demonstrating the consumption of available resources and impact on the environment, and it is highly likely that similar curves exist for metals such as copper. The environmental impacts included embodied energy (GJ/t

Au), greenhouse gasses (t CO2 e / t Au) for refractory ore, greenhouse gasses (t CO2 e / t Au) for non-refractory ore, and water consumption (t/t Au). The authors examined the values provided at different ore grades, based on their own work, looking at other similar studies as a comparison. In each case, the graphs are parabolic, rising sharply as the ore grades diminish beyond 2 g/t Au. As an example, water consumption at 2 g/t Au was approximately 400,000 t/t. Water consumption at 1 g/t Au was approximately 800,000 t/t Au, and water consumption at 0.5 g/t Au was 1,800,000 t/t Au. It is clear to see that as ore grades diminish, an exponential amount of resources are required to extract the target virgin metal.

A study by Norgate and Haque (2010) analysed the effects of changing the amount of copper concentrate grade used for electricity generation from fuel. The study found an inverse relationship for recovery and the grade of the concentrate in all concentrating processes. A lower grade ore results in greater recovery under this model. The authors then point out that a reduction in concentrate grade is not expected to any significant effect on power consumption when compared to ore tonnes. The energy per tonne of concentrate, however, and the energy per tonne of copper ore, however, does go down, because the tonnage of concentrate per kWh is increasing.

The study also examined leach energy, leach oxygen and neutralisation requirements, leach recovery and grinding energy, smelting energy, smelting flux and oxygen. For each of these axes it was attempted to determine the effect of reduced ore grades. The most striking was the smelting energy consumption. The table provided in the paper is reproduced below, in Table 1-1Error! Reference source not found.. As the ore grade declines by 10% from 25% to 1 5%, the electricity consumption goes up 37%. Also telling, the Oxygen consumption more than doubles, from 834 kg/t to 1702 kg/t.

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Table 2-1 Consumption of inputs for processing different concentrations of copper (Reproduced from Norgate and Haque 2010).

Concentrate grade (% Cu)

25 20 15

Electricity (KWh/t Cu) 1143 1314 1562

Limestone (kg/t conc) 21 22 23

Silica (kg/t conc) 130 137 144

Oxygen (kg/t Cu) 834 1162 1702

As for the consumption of fuel used, and the effects of changing the fuel, the model compares natural gas with black coal. Black coal is a more common fuel source for electricity generation, but is less efficient than natural gas, and therefore has a higher greenhouse gas intensity. Most processes achieved a reduction of 25-30% environmental impact (GWP and AP) in modelling the use of natural gas generated energy inputs. The environmental implications of obtaining natural gas was not included, and is worth bearing in mind, considering that in many cases, natural gas is obtained through fracking, which is considered by some to be damaging to the environment and unethical (Marquis et al., 2014).

2.2.4 Processing intensity The process for recovery from end of life material goods is different from the extraction of resources from natural sources. No matter which end of life product is presented to the recycler, there are usually other structures around the target material that must be dismantled first. The sheer variety of product shapes, sizes, and configurations, of electronics, makes it difficult to take a one size fits all approach. Additionally, glues, magnets, and toxins like cadmium and lead all present particular problems that must be managed when recycling. On the plus side, the metal is not in mineral form, and therefore concentrating and liberation methods do not need to be repeated. Often wires and circuitry are pure copper and / or gold. Even alloyed iron, silver, lead, tin, gallium are not in mineral form, and present less intensive processing requirements. Some recovery processes can quickly separate the pure metal.

After a product does reach end of life, recycling and resource recovery address the requirement for resources to be extracted from end of life material goods and returned to the manufacturing process. There is a significant benefit to doing this, compared against 15 extraction from natural sources. Keeping in mind the significant energy for equipment, machinery, and transportation from mining sites, as well as the energy and chemical requirements for refining, and the waste and pollution that results, recycling is much less intensive. According to the European Copper Institute (ECI, 2018) and Norgate et al (2010), recovery from EOL products requires up to 85% less energy than the energy required to refine copper from natural resources.

Some Life Cycle Assessments (LCA) have been carried out to characterise the life cycle cost of a commodity metal, such as copper. LCA is a standard approach to characterising the consumption of raw materials, and the resultant waste, that is used and generated in manufacturing (and packaging and transporting) a particular item. The international standard for LCA is ISO 14040:2006. Taking a standardized approach, LCAs provide a clear view of levels of water consumption, energy consumption, waste, and pollution. LCAs have the potential to influence decision makers to address perceived issues.

LCA can be an important tool in the mining industry for at least two reasons. One, increased demand for products, manufactured using raw materials extracted from natural resources. Two, as natural resources are depleted in locations where high concentrations exist, producers explore areas of low concentration. The combination of these two factors means that more raw material is needed from declining resources (Ndilila et al., 2014). The implication is that when lower concentrations are mined, water and energy inputs and the resulting waste will increase. Below are two LCAs which are herein summarised.

Song et al (2014) and Wang and Chandler (2010) evaluated the environmental burdens of Chinese copper production. They used a standard approach to LCA and developed a methodology within the limits of information available, either from primary sources, their own investigation, or from secondary sources, in the literature. An important point that is made in the report, is that China supply does not meet demand. In 2009, only 37% of demand was met through Chinese mining, despite the fact that Chinese mining produced 3.8 million tons in 2008 and 4.05 million tons in 2009. The report was limited to the environmental impacts of producing copper within China, and did not cover the environmental impacts of copper produced overseas, with major suppliers located in Chile, Europe, and Japan. As with all LCA, a functional unit is required, to clearly define what unit is produced, and then determine what inputs and outputs are created in producing that functional unit. This study

16 chose the recovery of 1 tonne of refined copper (meaning cathode copper) as the functional unit.

Song et al discussed the kinds of production that provides copper supply. Of the more than four kmt produced within China, 67.9% consisted of pyrometallurgical production systems, 31.7% consisted of production processes utilizing secondary production copper, and then 0.4% consisted of production processes utilizing hydrometallurgical methods. As discussed above, pyrometallurgical methods, which already have been discussed in the present study previously (Song 2014). Hydrometallurgical production includes processes as follows: leaching, solvent extraction, and electrowinning (Song 2014). Through these production processes, pollutants are created, which form a significant part of the assessment for environmental impact. Off-gasses, acidic wastewater, and solid waste, are the main pollutants from mining production.

The study identified feedstock, ancillary materials, energy resources, and emissions (usually pollutants), and quantified each in the production of copper from pyrometallurgical, and secondary production processes. Pyrometallurgical processes analysed included flash smelting and bath smelting, the two main production methods that are used in China. Feedstock was copper ore for primary production, and copper wire for secondary production. Ancillary materials included limestone (providing Ca and O), quartz sand (providing Si and O), oxygen gas, sulfuric acid, and steam. The energy consumed was divided into AC electricity (assumed to be provided from coal fired generators), DC electricity, coal, coke, diesel oil, and heavy fuel oil. The emissions from the process that were listed and counted included CO2, SO2, Chemical Oxygen Demand (COD), dust, slag. The data collected was summarised in a table, which listed all the quantities consumed, or emitted from in the process of producing refined copper. As an example, to produce 1 tonne of copper, flash smelters require 128,977 kg of copper ore, bath smelters require 106,064 kg of copper ore, and secondary production (recycling) requires 4,302 kg of waste wire (Song 2014). Primary production requires 32 times more raw material than secondary production. As another example, AC electricity input is 14,890.57, 18,398.27, and 925.2 respectively. Between 16 and 19 times more electricity is required in primary production. Additional analysis was carried out to quantify what phase of the production process created the most environmental burden, for the flash smelting data, the bath smelting data, and the secondary recovery data. In the case of primary production, was rated at or near 1,000 units per tonne, and secondary production was at or near 500 units per tonne. 17

In another study, Norgate et al (2012) examined the environmental impact of primary gold production. The authors examined, in addition to the data available on gold, some comparisons with other metals. The authors also examined, the results of diminishing ore grades within available reserves.

In comparing different metals against one another, the following environmental measures were used: water consumption (m3/t metal), global energy consumption (PJ/y), solid waste burden (t/t metal), and gross energy requirement (GER) (MJ / g metal). GER was further divided by what portion for mining and mineral processing, and what portion for metal extraction and refining. Reading from a graphical representation, for water consumption, copper (pyro process) under 100 l/t, copper (hydro process) was also under 100 l/t. Gold, however was much more, at 500,000 l/t. Also reading from a graphical chart, for global energy consumption, copper rated more than gold at 2,000 PJ/y, and gold was 1,000 PJ/y. Solid waste burden for copper (pyro process) was around 100 t/t and for copper (hydro process) was around 200 t/t. Gold was much higher near the 1,000,000 t/t mark. In terms of GER, copper (pyro process) consumed 60 MJ/t for mining and mineral processing, and consumed 10 MJ/t for metal extraction and refining. For copper (hydro process) the comparative quantities are inverted, with mining and mineral processing consuming 40 MJ/t and metal extraction and refining consuming 70 MJ/t. Gold on the other hand, by comparison, consumed more energy during mining and mineral processing, at 135 MJ/t and for metal extraction and refining it came in at 70 MJ/t, comparable to copper hydrometallurgical processing. Not only are the numbers interesting by comparison, but also on their own, the numbers assist in understanding the environmental cost.

Another LCA, also by Norgate (2001), published for CSIRO and commissioned by Intec Ltd, compares several copper production processes against a new Intec process, which is more hydrometallurgical in nature, whereas most copper processing is pyrometallurgical in nature, or was at the time of the study (2001). In this study it was clearly demonstrated that the Intec process has a much reduced environmental impact when compared to other copper production. This study measured the greenhouse effect, acidification, ozone layer depletion, eutrophication, and smog. It was not able to include two other important measures, eco- toxicity, and human toxicity, which were demonstrated in an earlier study of the Intec process. The study also provided data comparing the consumption of important inputs, such as heat and pressure. In the same table, it was also identified which copper recovery processes used oxygen vs air, whether an autoclave leach was used, whether a lime boil was 18 required, and whether cyanidation was performed (Norgate 2001). It is unknown whether other data was available which cast a less favorable light on the Intec process. The study is also interesting because it outlines all in one paper the process flow charts and the inputs and outputs of a number of (competing) processes, including the CESL, Activox, Dynatec, Total pressure oxidation, BacTech, BioCOP, and Flash smelting. In the results, flash smelting rated lower on total energy and Global Warming Potential (GWP), between 4% and 13% lower, explained by the fact that flash smelting uses the generated heat to smelt and to melt, whereas the Intec and other hydrometallurgical processes require more inputs of electricity to generate the heat required for melting. That said, the acidification potential was the lowest in the Intec process. Similar results were presented in a conference paper presented to Green Processing in May 2002 (Sammut et al., 2002).

2.2.5 Hazardous waste It is necessary to address the hazardous elements that are often inside e-waste, and could leach into the environment, whether deposited to land, disposed at sea, or burned and dissipated to the atmosphere (Kummer Peiry, 2014). These hazardous elements include lead, often found in circuit boards as soldering, and often found in cathode ray tube (CRT) monitors as leaded glass; mercury, found in the backlight of liquid crystal display (LCD) units; and cadmium, found in batteries (Alabi et al., 2011; Muniyandi et al., 2014). Within the polymer of the circuit board is often found a brominated flame retardant, and furans, mixed in to control for elevated temperatures while it is computing, these additives are also hazardous to human health.

The hazardous nature of the materials present in e-waste means that it should be handled, processed, and managed responsibly(Angel et al., 2009). Recent history has shown that there is a risk that transboundary shipments of this kind of waste has a tendency to shift higher concentrations of the hazardous material onto poorer or less developed countries (Lepawsky, 2015) (Brigden et al., 2005). It was not until a significant and catastrophic incident occurred, with the dumping of highly toxic waste into the ocean, that significant steps were put in motion towards greater control, proscriptive processing, and ultimately increased recycling of manufactured products which contained hazardous substances. In 1986, when a cargo ship called the Khian Sea set sail from Philadelphia, Pennsylvania, USA loaded with more than 14,000 tons of ash from incinerators in that region. The neighboring state of New Jersey had taken waste from Pennsylvania up until 1984, and would not accept this shipment. The cargo ship spent 16 months trying to offload the hazardous ash, even changing its name, and trying 19 different countries, but was turned away. Some 4,000 tons was illegally dumped at Haiti, the remaining 10,000 was dumped at sea, in the Indian and Atlantic Oceans. As a result, heightened attention was given to the transboundary shipment of hazardous material (Alter, 1997). This led to discussions that culminated in an international treaty created during the Basel Convention on the Control of Transboundary Movements of Hazardous Wastes and Their Disposal in 1989. This is relevant to the present study because resource recovery from computing and computer products was greatly assisted by the increased regulation, because inside of these products are many components made from hazardous materials. By controlling these substances, many of the other components subsequently become controlled, managed, and recycled as well. Another result was the creation of the Basel Action Network, a group that identifies potential breaches in transboundary movements. Their recent study highlighted the need for further investigation of electronics being donated for recycling (BAN, 2016).

2.2.6 Conflict minerals Another reason for recycling electronic waste is conflict minerals. Computers, mobile phones, and other electronic devices, have become increasingly sophisticated, and use increasingly exotic materials, some of which may have been classified as a conflict mineral. Conflict minerals have been defined in the United States by the Dodd Frank Wall Street Reform Act (HR 4173) as Tin, Tantalum, Tungsten, and Gold, all of which are abundant in the Democratic Republic of Congo (DRC), and which may contribute to ongoing conflict and violence in that country. By simply requiring public companies to report whether they are using conflict minerals, a level of scrutiny, and a level of due diligence is introduced where there was none previously. From May 2014, when the first filings were made, till now, many companies have chosen to use recycled material because of the provenance (Thomas, 2015).

2.2.7 Green Economy and Value Recovery Recycling, including e-waste recycling, is a growing market that can also be considered part of the green economy, meaning economic activity that benefits the environment, reduces hazardous pollution, and/or combats climate change (Bozkurt et al., 2016). The green economy is a growing sector that recognizes the value to the economy for providing jobs, technology, and trade and at the same time is environmentally responsible, reduces hazardous substances, reduces waste, generates resources from waste, and educates and changes the behavior of everyday citizens (Raghupathy et al., 2013). The more that science and experimentation can make e-waste recycling a viable investment, the greater chance that 20 environmentally responsible activities such as this will be developed and thrive as an economic market (Delaney, 2016). While Australia does what many developed countries do in collecting e-waste from businesses and consumers, and to some extent, dismantling or separating, which creates jobs, it is also worth considering the jobs and productivity inherent in all parts of recycling, including crushing, separation, transformation, smelting, and hydrometallurgical methods for recovery, which can contribute to the green economy and at the same time limit environmental impacts from transportation (Bergqvist et al., 2019), increase responsible recycling practices (Morris et al., 2016), and retain recoverable material (Ciacci et al., 2017) inherent in shipping EOL waste material overseas.

The Australian EPA estimates that in 2016 metal recycling was 88%, which is commendable and demonstrates that value recovery happens at a significant level (Brulliard et al., 2012). E- waste is a subsection of metals recycling, but more complex because in addition to valuable metals as discussed above, it is also valuable for ceramics, glass, and plastics. In 2014, the total Australian e-waste was 587Mt or about 25 kg per capita (Golev et al., 2017). In 2013 the Australian Bureau of Statistics estimated 10% was recycled (ABS, 2013). Of the recycled e- waste, some can be refurbished and resold, and some is broken down for materials recovery. While numerical figures of e-waste export are hard to come by for Australia, anecdotally, according to an article in ABC News, at least 5 shipping containers per month arrive in Accra, Ghana for processing (LeTourneau, 2017). According to an EPA report (EPA, 2010), a majority of Australia’s e-waste is shipped overseas, and that Australia lacks commercial- scale facilities for e-waste precious metals recovery. It is worth noting that since this report, Umicore / Nystar has added capacity for processing PCB in Port Pirie, SA, see section 1.3.3 below. A report from UNEP in 2015 discussed the fact that much of the processing of e- waste goes over seas, including Australian e-waste (Rucevska et al., 2015). The same report added a case study from UK, whereby of the expected 1.5 million tonnes of on shore processing was projected as part of the economy in 2009, 1 million tonnes of it was shipped overseas, resulting in an estimated loss in value over GBP 4.7 million. For discussion on how the value is recovered via the supply chain, see section 1.3.1 below.

2.3 Current methods proposed in literature to recycle PCBs Research has characterised the electronic waste (e-waste) stream, and has proposed various recovery methods. As discussed above, benefits to the environment and the economy constitute a significant value proposition inherent in this kind of research. This section

21 discusses the recovery of materials from waste Printed Circuit Board (PCB), a common component of e-waste, and where possible the kind of PCB recovered from mobile phones (MPCB), due to the fact that mobile phones are the topic of the present study, and have been demonstrated to have a short lifespan. Additionally, they are increasingly common, by some estimates production has exceeded the quantity of one smart phone per person worldwide (Wang, C.-H., 2015).

2.3.1 Looking back From the first use of metal going back more than 10,000 years, industrious metallurgists and fabricators have seen the potential for metal to be reused, resmelted, and reborn as a new product, useful and valuable once again. The metal for recycling, referred to as scrap, can be categorised as old scrap, and new scrap. New scrap is by products, such as millings and off cuts created during fabrication, and old scrap is the used goods that are obsolete, damaged, or otherwise never going to be used again in its present form (Bonczar, 1976).

Using copper as an example, in 1922, non-brass copper alloy scrap amounted to 193,200 short tons (175,268 metric tonnes) in the United States (WSJ, 1924). In 1963 the secondary supply of copper in the United States was 382,700 t old scrap, 629,300 t new scrap, and for the rest of the world total copper scrap was 1,328,900 t, not counting Eastern Bloc countries (Fisher et al., 1972). To give one more statistic, from 1972, in the United States, 42% of all copper metal was from scrap, roughly half new scrap and half old scrap (NTIS, 1972) in (Bonczar, 1976).

New scrap is the easier scrap to re-process. It has consistent composition, and correct specifications for the manufacturing process where it is generated. This makes it relatively easy to characterise the scrap, and reclaim it for other high value applications, either in the same plant, or characterised and shipped to a recycler. Copper scrap is rated according to value. New copper scrap is usually Number 1 copper, the most valuable, because it has high purity and can be sent directly to refiners. Number 2 scrap is less valuable and usually gets smelted as mixed alloys and then sent for refining to pure copper (Carrillo et al., 1974).

Old scrap, copper that has been reclaimed from products that are no longer in use is often rated Number 2 and is worth less as a commodity. The old scrap presents a different challenge, because it needs to be characterized and valued according to the purity of the metal, the associated material that is stuck to it, and any other dismantling, stripping, or 22 separation needed. As described in Carrillo (1974), Old scrap will go to a dismantler and separator company and then, once the copper is isolated, separated, or otherwise consolidated, it is sent to smelters for melting into pure copper or mixed alloy ingots, a practice which is still common today.

Most old copper scrap up to the 1980’s originated with vehicles, such as passenger cars and large transport vehicles, wire, appliances, industrial waste, and brass recycling. The copper present in vehicles can be recovered through dismantling and selectively removing the relevant parts for scrap. Some of the scrap is rated Number 1, but often not, due to being attached to other parts, or being coiled around other material, or being housed inside a larger part. As an example, many radiators of that period are copper, but may contain fluids, residues, and attached to hoses, brackets that are not copper. Insulated wiring is stripped of its insulation, the copper purity is high, and is readily remade into new wire or other copper applications. Industrial waste also provides copper to scrap yards, after which it is recycled through regular channels. Brass, either as new scrap, but particularly in the form of old scrap, is another source of alloyed copper, and is readily recyclable. Not only is it separable based on colour and density, but also brass continues to be in demand as a feedstock for multiple manufacturing processes. Brass is typically recycled separately to copper and sent for brass smelting. One difficulty, in addition to the difficulties of recycling old scrap because of co- materials being present, is the unknown quantity of copper to zinc ratios, and as such old scrap brass is best suited to applications that are compatible with a wide range of options. Also discussed in Carrillo (1974) is the recycling of demolition waste. At that time, in the 1970’s, recycling demolition waste was seen as uneconomic, the cost of disposal to landfill, on the face of it, was at that time much less than the cost of paying personnel to pick, separate, and transport loads of separated waste to scrap yards and other recovery processes and companies. This mentality prevailed prior to items of legislation requiring recovery of material from demolition sites, standards like Leadership in Energy and Environmental Design (LEED) standards pertaining to demolition, and deterrents in the form of landfill levies which make the prices of recovery more attractive by increasing the price of landfill. The next section about legal framework discusses how good policies and laws can make landfill less attractive and recycling more attractive.

Even before the Basel Convention, some saw that the manufacture of computers, with high purity metals, presented opportunities for recycling., but the focus on recycling copper and other metals including precious metals from waste electronic equipment has historically been 23 quite minimal, but the studies and investigations into what was possible still existed. As an example, in a patent in 1973, US Pat No 3,736,239, a ‘waste plus waste’ method, to be used by manufacturing companies. One of the examples present in the patent was the recovery of etchant used in creation of circuit boards, which was spent chromic acid solution. Recovery of this nature closes the loop, creates less waste, and reduces cost.

2.3.2 Legal Framework While the science and proposed options for metals recovery are not new, the economic feasibility may limit widespread uptake. This is why a legal framework is necessary to drive industry and for-profit businesses to implement good waste management and resource recovery practices.

In the European Union, e-waste is differentiated into ten categories. The categories are set up in such a way that characteristics and material composition are more easily handled and addressed together (Widmer et al., 2005) (EU, 2012), which means that e-waste gets sorted appropriately in accordance with the legislation. It is also worth mentioning the Restriction on Hazardous Substances (RoHS) legislation which also provides a framework for handling, processing, and disposing e-waste due to the hazardous substances inside and out (EUR-Lex, 2011).

In Japan, the home recycling law demonstrates a progressive view on claiming and recycling WEEE. Comprehensive policy mechanisms mean good news for recyclers because it takes the guess work out of minimum standards for safe and reliable processing of the WEEE. (METI, 2013)

In Australia, some measures have been enacted to promote the recycling of WEEE and by extension the PCBs that are inside. Chief among these is the National Television and Computer Recycling Scheme (NTCRS), which continues to expand in success from year to year, in the 2014-15 year, it was estimated that out of the 121,866.3 t of televisions and computers were end-of-life in Australia that year, a total of 44,730.5 t of recycling occurred, which was above the target of 35% (DoEE, 2016). In the state of Victoria, a consultation

24 process throughout 2017 resulted in the state committing to banning e-waste from landfill by July 2019, and providing funding for upgrading e-waste collection and storage facilities1.

2.3.3 Process Overview With appropriate legislation or legal framework in place, it is important to choose an appropriate processing method, from the many which have been proposed for materials recovery from MPCB. To understand recovery processes, it is worth discussing a process overview. There are a number of stages that most recovery operations follow. The diagram below gives a general grouping for recycling steps, which can be arranged and broken down further, depending on product design, such as a computer, a printer, or a mobile phone.

Figure 2-2 Processing diagram for end of life appliance (Hieronymi, Kahhat et al. 2012) The diagramme above Figure 2-2 from (Hieronymi et al., 2012) identifies three major steps for processing.

1 https://www.environment.vic.gov.au/sustainability/e-waste-in-victoria 25

(i) Testing, sorting and dismantling (ii) Mechanical crushing, grinding, separation of visible elements (iii) Recovery of the target material, such as copper, gold and plastics, using hydrometallurgical and pyrometallurgical means.

In Menikpura et al (2014) multiple sources agree (e.g. Cui and Forssberg, 2003; Eichert et al., 2008; Kang and Schoenung, 2005; Lee et al., 2007) that waste electrical and electronic equipment (WEEE) recycling processes can be broken into the following seven major steps.

1. de-pollution 2. disassembly 3. shredding 4. magnetic separation 5. air separation 6. eddy-current separation 7. compression of residuals

Taking these two different process steps, one from Hieronymi et al and the other from Menkipura et al, it’s easy to see that there are different ways to demarcate what part of the recycling chain will be the focus. The WEEE recycling process in Mekipura addresses a part of the very first steps, such as disassembly, and then focuses on mechanical sizing and separation processes. The present study is focused on step three recovery, recovery of the target material. In this case, the target material is copper obtained from the mobile phone printed circuit board (MPCB). The collection from waste streams, testing, disassembly, and sizing are assumed to have been completed. It is also worth noting that due to the highly heterogenous nature, the microscopic circuitry and integrated components of most MPCB, mechanical sizing and separation processes must be evaluated for their usefulness. The next few sections provide some discussion regarding methods proposed for recovery from PCB, through mechanical, pyrometallurgical, or hydrometallurgical means. 2.4 Supply Chain and Reverse Logistics Before any processing can occur, and assuming the legal framework is in place as discussed above, the end of life (EOL) material must make its way to processing centres via the supply chain. When commodity trading occurs in recycling it is by way of reverse logistics. (Bedo, 2018; King et al., 2019). This is well established for many metals such as steel, copper (from

26 construction, vehicles, etc), and aluminium, and should be developed to greater detail for e- waste.

How this best occurs has been the subject of considerable debate (Cao et al., 2018; Favot et al., 2017; Nowakowski, 2016; Rodrigues et al., 2016). Chief among the controversial issues besides legal and policy framework are: security for EOL technology products, education of EOL asset holders, availability of infrastructure and logistical systems, accessibility of service providers and locations, accountability within the waste stream, and of course cost reductions and who pays (Carvalho, 2016; Nowakowski, 2017; Xue et al., 2014). Cost and who pays can be a considerable barrier to pitching the need for recycling infrastructure, education, and supply chain.

Australia’s e-waste supply chain, though still in development, does provide for the collection and accumulation of e-waste, including mobiles, PC’s, monitors, laptops, bulbs, batteries, TV’s, and other types, through the National Television and Computers Recycling Scheme (NTCRS), and through a number of e-waste companies such as SIMS Metal Management and MRI. Recently, China has restricted its intake of recycled material also creates pressure to develop on shore processing (APC, 2018). Additionally, there are continual reports from various watchdogs which highlight the ongoing need for responsible processing of e-waste rather than dumping or irresponsibly shipping e-waste to less developed countries (Rucevska et al., 2015). This, and other factors, create an opportunity to further develop the supply chain and increase the recycling infrastructure.

While the present study is primarily focused on later stage processing such as copper recovery, analyzing treatment options can most directly inform infrastructure and logistical questions, and prove that a treatment option is viable within a specified cost model, either through cost reductions by being less resource or labor intensive, that processing is viable at small or large scales, and/or that certain processing can be carried out within an existing legal framework, given restrictions on stockpiles, emissions, and recovery standards. New concepts are needed to make the supply chain and processing (discussed below) easier to adopt and implement. As an example for emerging green economy, see section 2.8 below, about a new microfactory concept. 2.5 Mechanical separation For printed wiring boards, particularly low value FR2 boards from Radios, Televisions, and larger appliances, mechanical separation is entirely possible, through shredding and then 27 vibration. Before shredding, the integrated components are either milled at the point of solder, or heated to the solder’s melting point, and then removed from the wiring board. What remains is the plastic board (fiberglass, polymer, and/or resin) and the copper integrated wiring. On some boards, if there remains gold contacts, shredding is unlikely to separate the much more valuable gold (Jianzhi et al., 2004).

With just the wiring board, the next steps in the process are to cut, shred, and then pulverize the boards to <1 mm (Huang et al., 2009). The shreddings are then added to a vibrating machine, which vibrates and bounces the lighter fiberglass to one side, and the heavier copper shreddings to the opposite side, resulting in shredded copper fines. This copper may then be shipped to refineries with no further processing required2.

An innovative approach to mechanical separation has been investigated by Duan et al (2015) and Zhao et al (2015) whereby high voltage electrical pulses separate WPCB, breaking plastics from metals as the electrical current passes through multiple times per second.

Mechanical separation can also occur as a post treatment step, wherein heat treatment is applied to MPCB in order to change the form of the organic polymers, to facilitate the liberation of the metals. Shokri et al (2017) demonstrated that most of the polymer has degraded after 10 minutes, and that a temperature of 350C is sufficient to accomplish this.

Milling can be an important mechanical separation step, starting coarse and proceeding to progressively finer milling of the PCB. Nekouei et al (2018b) demonstrated step by step milling processes, with samples analysed each step of the way. The results showed that the milled samples successfully created separated Cu, Zn, Fe, and Ni metal fractions within the first two sizing and separating processes. Ceramic oxides, such as CaO, SiO2, and Al2O3 were also separated from the metal fractions through the second process of milling and separation, as the metal and refractory elements had sufficiently different physical and mechanical properties. Selective thermal transformation of the milled sample was also investigated in this paper, and showed that greatest weight loss, through selective thermal transformation of the polymeric, organic fraction was occurred within the first 10 minutes, and showed a reduction of 25% in weight.

Milled PCB can be converted into a useful product on its own. In a related study, Nekouei et al (2018a) investigated what milling and mixing parameters were needed to create a useful

2 https://www.youtube.com/watch?v=n6E7PzJgU_A 28 homogenized powder. This study found that following cutting, coarse milling, and sieving, and the metal rich fraction required 10 hours milling and mixing in order to produce a sample that was homogenous, in this case a homogenous nanostructured alloy sample of

Cu79Zn13Fe3Sn3Ni1. The authors suggest that this is a useful product with no further processing, and could be used in deionized water to elevate the conductivity of the water by ten times. 2.6 Smelting Turning back to MPCB, the FR4 high value kind, with extremely small components, multiple layers, microscopic circuitry, and connectors like a millipede, some mechanical means can be used for sizing such as cutting, shredding, grinding, and pulverizing, however, an approach is needed to separate minute amounts of copper sandwiched between thin layers of fiberglass, and the minute amounts of gold, silver, lead, tin, nickel, arsenic, palladium, iron, including more exotic elements (Cui et al., 2003). This paper focuses less on the recovery of carbon, such as polymers and resins, but carbon recovery is certainly useful for a number of applications.

Pyrometallurgical methods have limitations such as toxic residues, clean up required, and further processing required (Wang, J. et al., 2015), however, it has some usefulness in the early stages, and could serve to speed the process for separating carbon-based polymers, metals at low melting point, and metals of high melting point. Some metals will be miscible at certain melting points, and some will remain separate.

There are likely parallels between metals recovery from MPCB and metals refining from natural sources. While the MPCB has a different composition, and properties, the target metal, such as Cu or Zn, has the same physical and chemical properties.

2.6.1 Smelting in industry The following examples discuss real life industrial processes for smelting scrap that includes waste printed circuit board (WPCB) and recovery of non ferrous and precious metals. The following examples are not intended to be a comprehensive list, but each are interesting in their own way.

Noranda – Quebec facility

As reported in Veldbuizen and Sippel (1994) and Caymuil et al (2014), the Noranda smelting process, primarily for smelting ores from natural sources, has successfully incorporated e-

29 waste for recovery of copper and other metals. The Noranda site in Quebec, Canada is reported to process 100,000 tons of copper per annum as of 1993, with an estimated 86% of that volume being virgin copper concentrates, and the remainder being e-waste. The process, in a nutshell, is to add the fines from both virgin and recycled sources to a reactor, where supercharged air, of up to 39% oxygen, reacts with the mixture, and forms oxides in slag. These oxides will include Fe, Pb, Zn, and Si. Other metals such as Au, Ag, Pd, stay in solution with the molten Cu. The reaction is assisted by the presence of any plastics, as the combustion of these plastics provides energy for maintaining a molten mixture of 1250°C. The molten mix is transferred to a second furnace, a converter, where sulphur (from the virgin ore) is removed. After this conversion, a third furnace refines the copper again, into blister copper of 99.1% Cu, and 0.9% other precious metals, which is poured into anode shapes and shipped for electrolytic refining (Cui et al., 2008).

Boliden – Rönnskar facility

As reported in Theo (1998) and Caymuil et al (2014), Boliden operates a smelter at Rönskar, Sweden. The site is reported to process 130,000 tons of Cu and 43 tons of Pb per annum as of 1997. The feedstock for the smelter included 4.7% scrap (a combination of scrap some of which was e-waste) 20.9% recycled ash, and the remainder as ore concentrates. This process uses a patented Kaldo furnace for recovering plastics, particularly from low grade e-waste (Leirnes et al., 1983), because, as stated in the patent, the scrap going to a cupola furnace will not tolerate organic content above 4-5%, which is always present in PCB. The Kaldo furnace charges a combination of PCB and Pb at 600-800°C, with a lance to provide oxygen for combustion of the organics, and the result is a semi molten mix of metals, with organic content converted to gas, which is burned off, and amorphous carbon, oxides, and silicates separated from the semi molten mixture. From the Kaldo furnace, the remaining mixture is then added to the copper refining process of furnaces, converters, and then refining to blister copper. At the Rönnskar site, Pb, Zn, Se, Au, Pd, and Au slime, as well as nickel sulphate are created (Cui et al., 2008).

Umicore – Hoboken facility

As reported in Hagelüken (2006) and Caymuil et al (2014), Umicore operates a resource recovery facility in Hoboken, Belgium. Total processing is 250,000 tons per annum, which includes a wide variety of primary and secondary scrap, locally and internationally. Since 2005 Umicore has focused this facility on processing scrap with less focus on processing ore

30 concentrates. It has become the largest smelter in the world for precious metal scrap including e-waste. Their operations are largely divided into precious metal operations (PMO) (including gold and silver; the platinum group metals platinum, palladium, rhodium, iridium, ruthenium; and special metals selenium, tellurium, indium; secondary metals antimony, arsenic, tin, bismuth) and base metal operations (BMO) (copper, lead, and nickel). In this process, the first melt is done in an IsaSmelt furnace. The furnace’s heat, atmosphere, fuel mix, and duration are all optimised based on the composition of the feedstock. The IsaSmelt reactor employs a deep cylinder shape, with feedstock scrap and coke at the very top, and the molten mix at the bottom, with a lance feeding oxygen and natural gas for fuel into the liquid mixture, thus creating a turbulent agitation that speeds up the separation process. The base metals function as collectors for the precious metals, Cu binding with Ag, Au, Pd, Ir, Ru, Rh, Pt, Se and with Pb binding with Te, In, Bi, Sn, As, Sb. The third base metal, Ni, assists this process through interactions with Pb and Cu. The smelted copper bullion is drained and formed ready for electro winning. The oxidised lead slag is treated in the base metals operation for removal of Pb metal and then refines the Pb. With the Pb removed, the result is nickel speiss, copper matte, returned for copper processing, and depleted slag, which is further processed in the special metals plant (Cui et al., 2008).

SIMS Recycling Solutions Franklin Park, IL, USA

Another example of successful industrial e-scrap recycling, albeit on a much smaller scale, is the SIMS Recycling Solutions facility in Franklin Park, IL, USA. Started in 1950 as United Refining & Smelting Company, a full service, secondary refiner, refining precious metals, such as gold, silver, platinum, palladium and rhodium. Diversified Industries, Inc. bought the company in 1968 and Sims Recycling Solutions bought Diversified Industries in 20073, acquiring the technology and licence to smelt and refine precious metals. According to the SIMS website4 the facility is dedicated to primarily processing e-waste, including home, office, industrial computers, and medical equipment. Of interest, circuit boards are specifically mentioned as eligible for processing5. According to Recycling Today (2014), the

3 http://allengelhard.com/item/10oz-ag-ingot-united-refining-15428/ 4 http://www.simsrecycling.com/locations/chicago-il-refining 5 http://www.simsrecycling.com/Services/Responsible-Recycling/Specialized-Recycling/Circuit-Board- Recycling

31 facility processes scrap through two rounds of shredding. “Once shredded, the precious metal components are roasted, melted and assayed before continuing on in the refining process.” According to United States EPA reports, in 2016 the facility processed 941,661 pounds (427 tonnes) of copper compounds, 13,752 pounds (6.2 tonnes) of lead compounds, and 31,810 pounds (14.4 tonnes) silver compounds6.

Nyrstar Port Pirie, SA, Australia

The facility at Port Pirie, South Australia is among the largest in the world for smelting lead and zinc, and has been in operation for over 120 years (Kutlaca, 1998), with a throughput of 185,000 tonnes per year (Regan, 2016). The refinery also has the ability to recover precious metals from e-scrap (Watt, 2015) estimated at 3,000 tonnes per year by 2018 (Linnenkoper, 2017). The facility uses a Top Submerged Lance (TSL) IsaSmelt furnace, which is capable of varying the conditions according to the feedstock coming in. Feedstock includes residues from other Zn smelters, third party residues, Pb concentrates, complex waste streams, and e- waste. From the TSL, off gasses are processed for recovery of Se, Slag is processed in a blast furnace which separates the Zn and Pb. The Pb goes to a refinery for recovery of Pb and Sb, and the slag from the lead refinery is sent for precious metals recovery such as Au, Ag, and Te. From the blast furnace the separated Zn heads to a slag fumer where ZnO is produced. From the IsaSmelt TSL and from the blast furnace is also produced copper matte, which is sent to the copper plant to create blister copper which is poured into sheets for electrolytic recovery offsite (Watt, 2015).

Aurubis, Hamburg and Lünen, Germany

Another relatively small scale but important processor of e-scrap in the industry are the Aurubis facilities in Hamburg Germany, which is heavily focused on recycling7. These facilities use the proprietary Kayser Recycling System (KRS), and KRS-Plus. The facility recycles a range of materials, such as copper-bearing shredded material, copper-processing

6 https://iaspub.epa.gov/triexplorer/facility_profile_charts?p_tri=60131NTDRF3700N&p_VAR=WST_PROD&p _LABEL=Total+Waste+Managed%20(Pounds) 7 https://www.aurubis.com/en/products/recycling/technology

32 industry residues, consumer scrap, meaning electrical and electronic type scrap. The Lünen facility, after being upgraded to KRS-Plus in 2011 has an expected output of 350,000 tpa8. According to Aurubis, the “KRS-Plus is an extension of the existing KRS facility, incorporating a so-called Top Blown Rotary Converter (TBRC), as well as a slag separator and a holding furnace.”9 The process produces a zinc oxide dust that itself contains the target metals. The zinc oxide is further processed into zinc sulfate by another company, and the metals remaining from the conversion is returned to Aurubis for precious metal refining (PMR).10

2.6.2 Smelting in the lab Vacuum metallurgy separation (VMS) is proposed by Zhan and Xu (2011) for recovery of Pb from Cu rich and Sn rich particles following processing of WPCB. In this process, 1 and 2 gram samples are added to a vacuum chamber that is vacuum pumped to 1 Pa. The sample is heated and then analysed. Because of the different vapour pressure of the Pb, it evaporates and then condenses outside of the alloy. In Sn rich particles, 23.4% of the total Pb residue was not evaporated. In Cu rich particles, 1.5% of the Pb residue was not evaporated.

Copper recovery by smelting includes work by Zhou et al (2007). In this experiment, NaOH was used to encourage slag formation, which separates impurities from copper during selective thermal transformation. The addition also decreased the melting temperature to 1200°C. Heating WPCB at the lower temperature with NaOH added at 12%wt was successful in recovering more than 99% of copper.

Molten salts NaOH and KOH were used in a similar way to the work by Zhou et al above. The team at Université Joseph Fourier, led by Flandinet (Flandinet et al., 2012) found that the molten salts were effective in dissolving the glasses and oxides without oxidising the target metals. The authors used a ratio of 49/51 NaOH to KOH, in a selective thermal transformation environment, heated to 300°C, with a ratio of 2:1 molten salt mixture and WPCB pieces for 1 hour. The result was a metallic fraction with fiberglass, resins and plastics completely removed, and a brown powder, which is the residue after the organics dissolve in the hydroxide melt. A similar study was carried out by Stuhlpfarrer et al (2016).

8 http://www.aurubis-stolberg.com/englisch/download/070711_krs-plus-einweihung_en.pdf accessed July 2018. 9 ibid 10 http://www.circulary.eu/project/aurubis-and-grillos-metal-loop/ accessed July 2018. 33

Another pyro-metallurgical study demonstrated the separation behaviour of metals from the WPCB. Khanna et al (2014), heated WPCB in a pyrolysed environment, 20 minutes at different temperatures between 1150 – 1350°C. The metallic results showed that at those temperatures, copper rich and tin rich metallic balls formed, each with a mixture of Cu, Sn, and Pb present. Other minor elements also separated, including Al, Fe, Mg, Ni, Pd, Pt and Zn. This study discussed the evaporation and shrinking amounts of Pb through increased temperatures, and also showed that with increased temperature, Cu was more distributed to different metallic droplets. Looking at precious metals, and under similar conditions to the study just discussed, Caymuil et al (2016) discussed the presence of precious metals such as Ag, Au, Pd, and Pt, were present in the base metals Cu, Sn, Pb. The affinity of Cu for these precious metals meant that they dissolved and alloyed with Cu rather than remaining in the non-metallic fraction (NMF).

Another heat treatment approach included the separation of Sn rich and Cu rich alloys at different temperatures. The Sn fraction being often the solder of the PCB and the Cu fraction often being the wiring and printed circuitry. Hossain et al (2018) demonstrated that Sn alloy, including Pb, Ag, and Zn is formed above 500C, noting that Cu can raise this melting point, depending on the available material within a given PCB. This paper also noted that above 1000C there formed Cu droplets that were 80% of IACS (International Annealed Copper Standard) conductivity. From these results it can be inferred that a two step process would obtain Sn alloys first, and then Cu alloys.

Looking more closely at the energy requirement for smelting based recovery, Ulman et al (2018) showed that recovery of metallic products at 500C is possible. The resulting metallic residue, after heat treating the hydrocarbon content and removing it, was found to be 94% pure with no oxides present and 78% conductive against the international standard. Obtaining this result at a lower temperature has implications in saving energy and therefore cost in recovery operations.

2.6.3 Limitations of Smelting Smelting, or pyro metallurgy, has limitations. It will only recover metals to an approximate purity. For example, blister copper is generally between 98-99% pure copper. Blister copper is transferred to an anode furnace and refined to 99% copper, and then the anode copper is poured into anode moulds ready for electrolytic refining (Khaliq et al., 2014). This is an 34 example with copper, but the same holds true for other metals. Smelting also has the potential for the target metal to be lost to slag, where the chemistry or process is insufficiently tuned. Smelting also usually requires significant energy inputs, in the form of fossil fuels, such as coke and natural gas, in the form of reactive feedstock such as oxygen or sulphur, in the form of renewables, such as natural gas from plant matter, or in the form of electricity from various sources. With ever increasing technological demands and with ever increasing scarcity, thermal treatment alone is not sufficient. Much has been done to explore and advance the available methods for hydro metallurgy, the art of dissolving and leaching the target metals, and then capturing and forming the target metal ions into useable metal. 2.7 Leaching The process of selective leaching, common in mining processes, can also be used for materials recovery processes. Leaching uses a corrosive substance, in air or liquid, and selectively converts a particular element out of solid state into liquid or gas state

(Vandersloot, 2002). Leaching usually utilises mineral acids and oxidants such as HNO3,

H2SO4, HCl, H2O2, HClO4 and NaClO, and other acids such as aqua regia, thiourea, cyanide, halides or thiosulfate. Capturing the target metal from solution occurs in several ways, through forming salts and chelates in a series of steps (hydrometallurgy) which may include cementation and adsorption, through electrochemical deposits, and through biological means (bio metallurgy) of capturing ions with organisms (Pradhan et al., 2014). According to Tuncuk et al (2012) PCB leaching includes two stages. The first stage recovers base metals, and the second stage recovers precious metals.

2.7.1 Leaching in industry EnviroLeach

A proprietary non-cyanide solution has been adopted by the EnviroLeach company, and licenced to various industrial processing companies. EnviroLeach extracts precious metals in the context of mining, including concentrates and tailings; and e-waste, including new scrap and old scrap (Dow Jones 2017a) . It provides leach activity similar to cyanide or acid based lixiviants, is safe, eco-friendly, and operates at ambient temperature and near neutral pH, without poisonous off gasses. A recent study from June 2017 took place at Mineworx in Coquitlam, BC, Canada. It used waste PCB, and showed Gold recovery up to 90% in less than 120 minutes, using the proprietary leaching method (Financial Services Monitor 2017) . The facility in Canada also recently announced that on the back of the success of the trial, a

35 new facility will be constructed to recover precious metals from PCB at a rate of 2,500 t per year (Gileage, 2017) . Another partnership with MineWorx has been established, for the process to be used at Jabil’s facility in Memphis Tennessee, processing scrap batteries to recover lithium and rare earth metals (Canada, 2017) (NASDAQ 2017).

2.7.2 Hydro metallurgy Acid leaching

Mecucci and Scott (2002) investigated the leaching of waste printed circuit boards (WPCB) using nitric acid. The experiment demonstrated copper and lead selectively leached from

WPCB, and tin precipitated out as H2SnO3 (metastannic acid) when nitric acid was above 4 mol dm-3. The study also evaluated the effects of electrodeposition at different concentrations of the acid. By covering the cathode with copper and lead on the anode in the form of lead dioxide. By varying the current efficiency, they were able to achieve 99.8% copper on the cathode, and exclusively lead (oxides), on the anode.

Kinoshita et al (2003) also used nitric acid to leach base and precious metals from waste printed wiring boards (WPWB). Their first step process was to leach the base metals and release the surface gold, which occurred successfully. Next, they addressed the extraction of nickel and copper. Nickel was extracted with a weak HNO3 solution of 0.1 M and copper was extracted with a stronger solution of 1.0 M HNO3. Then lixiviant LIX984 was used to remove the copper from solution, and then the copper was stripped from the lixiviant with 4.0 M nitric acid, resulting in a solution of only copper ions.

Leaching of cuprous ions out of WPCB using HCl and electro generated chlorine was investigated by Kim et al (2008). In their study, they found that while electrically generating chlorine, copper ions leached into solution in a linear fashion. They then controlled the current density and observed the behaviour of the copper accumulation on the anode. When there was enough copper on the anode, the supplied charge ceased to generate chlorine, but instead affected the copper to generate cuprous and cupric oxide.

Starting from WPCB, investigators Oh et al (2003) found a multi step process that recovered metals, using varying concentrations and durations of H2SO4 and H2O2 in step one,

(NH4)2S2O3, CuSO4, and NH4OH in step two, and NaCl in the final step to leach out Pb. First, the authors prepared the PCB from scrap, by sizing, electrostatic separation, and magnetic separation. Then, in the first leaching step, a combination of 0.2 M H2O2 (dilute amounts) and

H2SO4 (more concentrated amounts), removed greater than 95% of Cu, Fe, Zn, Ni, and Al 36 base metals after 12 hours. In the next step precious metals Ag and Au were removed using

0.2 M (NH4)2S2O3, 0.02 M CuSO4, and 0.4 M NH4OH, the result after 24 hours was 100% of the Ag and after 48 hours 95% of the Au. Next the residues were exposed to 2 M NaCl solution to separate Pb, which occurred at room temperature within two hours.

2.7.3 Supercritical fluids Using supercritical fluids is a relatively recent innovation that is being studied, due to some important environmentally friendly possibilities, such as low viscosities, high mass transport coefficient, high diffusivity, and high solubility of organic materials. Supercritical fluid is liquid that is heated beyond its boiling point, and would ordinarily evaporate, but by increasing the environmental pressure, it remains in liquid form. Li and Xu (2015) decomposed memory modules (similar to PCB) using supercritical water, by placing the water and the material into a heat and pressure chamber. Temperatures were between 350 to 550 °C, pressures were between 25 to 40 MPa, and reaction times were between 120 to 360 min. The authors used response surface methodology (RSM) to determine that the optimal parameters were 495 °C, 33 MPa, and 305 min, for maximum recovery of the metallic and glass fraction, with organics and brominated flame retardants being dissolved into the supercritical water. Examples of supercritical methanol for PCB recovery is found in (Xiu et al., 2010). Examples of supercritical CO2 for waste recovery found in (Sanyal et al., 2013)

2.7.4 Cementation The process of cementation involves precipitating a metal ion with a more active metal. For example, precipitating / cementating copper from an iron rich solution, or precipitating / cementating copper from a zinc-copper solution (Demirkıran et al., 2007). This has been used for industrial wastes and mining processes, and could be used for recycling.

Cementation was also used in a study by Birloaga et al (2014). After WPCB was leached for Zn, Cu, and Fe, the solution was used for cementation with Au as the less active metal, and then evaluated whether Au precipitated or cemented out. The experiment showed that Zn and Cu solution resulted in Au cementing out. The Fe solution did not completely cement out the Au.

2.7.5 Adsorption A common form of adsorption is the use of activated carbon, originally in a mining scenario, described by Stalker and Sandberg (1987). Another study looked at a similar method, only

37 the carbon was provided by barley straw for some experiments and rice husk for similar experiments (Chand et al., 2009) and wheat husk (Farooq et al., 2010).

2.7.6 Electricity Electrowinning, the process of accumulating a target metal onto a cathode, originated with mining recovery process, and was an important improvement, after flotation and solvent extraction. For example, the smelter at Port Pirie, South Australia, built a solvent extraction and electrowinning (SX–EW) plant in 1985 to recover copper out of the tailings of the lead smelting operations (Donaldson et al., 2003). The process leaches the copper from the copper matte with an acidic chloride–sulfate solution, then solvent extraction for copper recovery from the leachate. Electrowinning was then performed, dipping a lead alloy anode and a starting sheet copper cathode into a solution of CuSO4 -H2SO4 electrolytes. Cathodes are copper or stainless steel (see also IsaKidd process) (Wiechmann et al., 2016). A potential of only 0.2–0.4 volts is used. After copper metal accumulates at the cathode, arsenic and zinc can be recovered subsequently and separately using higher voltages.

Figure 2-3 Electrorefining of copper11

Electro refining is a much more common process than electrowinning12. For a simplified diagram, see Figure 2-3. Electrolytic refining is the process of submerging an anode comprised of the target metal with some impurities, into ionic solution, and dissolving the target metal, and then attracting the ions to a cathode sheet. It is different to electro winning, where the metal is already dissolved and the anode does not collect material, or attracts impurities. The anodes poured from blister copper usually are large and flat, with a handle on

11 http://www.chemguide.co.uk/inorganic/extraction/copper.html 12 http://www.ct.ufrgs.br/ntcm/graduacao/ENG06631/5-b_copper.pdf 38 top, and then dipped into copper sulfate approximately 3-4% and sulfuric acid approximately sulfuric acid. When that happens the following reactions occur:

2+ − Anode reaction: Cu(s) → Cu (aq) + 2e

2+ − Cathode reaction: Cu (aq) + 2e → Cu(s)

According to P J Wand in Woodcock et al. (1980) pp. 335–340 Other impurities, such as Zn, Pb, Au, and Ag also dissolve. The Zn stays in solution, Ag, Pb, and Au form a salt and precipitate out of solution, dropping to the bottom of the tank. The free Cu+ ions are attracted to the cathode, thus producing 99.99% copper sheet in accordance with the ASTM B 115-00 standard, ready for electronics manufacturing.

Electro Refining usually occurs with hundreds of cells, housed in large tankhouses. The tank houses are large enough to hold a quantity of approximately 100,000 cathodes. Those cathodes are organized into groups of cells and cathodes. Six groups, consisting of 100 cells, and 55 cathodes, comprise a typical modern set up. Twelve pulse transformer-rectifiers supply electricity to the cells (Morales et al., 2010). A tank house containing copper refining cells can consume around 2,000 kWh to obtain one tonne of grade-A copper (Lanktree, 2012).

Bio metallurgy

Use of organisms living or dead, or its by products, is often referred to as bio leaching, bio sorption, or bio metallurgy. Using bio metallurgy to capture metal ions has become of interest in recent years, because organisms have the ability to select very specifically the target metal in very low concentrations (Tasdelen et al., 2009). Some various types of bio metallurgy includes adsorption using biological materials, chelation using biological forms and organisms, phytomining, and mycoremediation, This applies to waste water, electroplating residuce, rinse water, as well as dissolved mixed materials with trace amounts of a target metal, and mine tailings (Kuyucak et al., 1988). This also applies to e-waste, because e-waste can contain trace amounts of precious and rare metals, particularly after extraction of base metals like copper (Das, 2010). For some informative summary tables showing the effectiveness of recovering metals such as Cu and Au using a variety of organisms, look no further than Zhang and Xu (2016).

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2.7.7 Bio Leaching As an example of bio leaching Arshadi and Mousavi (2015) studied simultaneous extraction of gold and copper using bacteria Bacillus megaterium and A. ferrooxidans, varying the pH, pulp density, particle size, and glycine concentration. In this experiment B. megaterium was selected because it produces cyanide, which reacts with Cu and Au as in a typical recovery scenario. The study found that 36.81% Au was extracted when maximising simultaneous extraction of metals. Then, the authors ran a second series using A. ferrooxidans to remove Cu first, and then B. megaterium to remove Au. The second series resulted in 63.8% Au recovery. In another example bioleaching from waste printed circuit boards (WPCB) was carried out using Pseudomonas chlororaphis by a team at Sun Yat-Sen University, Guangzhou, People’s Republic of China. The results showed that P. chlororaphis in a solution of Cu and Au, absorbed Au, leaving Cu in solution, with only trace amounts of Au remaining. The study also showed that optimal conditions were pH 7.0, temperature 22.5°C, and rotation speed 80r/mi (Jujun et al., 2015).

2.7.8 Phytomining Another form of bio metallurgy is phytomining, whereby plants absorb and transport a target metal up through the roots and into its own plant structure (Baker, A. J. M. et al., 1989). The plants are then burned, and the ashes treated for metal recovery. An example of this is found in Qu et al. (2012) where Brassica juncea L. hyperaccumulated Cu and Zn into recoverable as Cu0.05Zn0.95O nanoparticles. Another example of phytomining, in a natural occurring setting, but near an e-waste recycling site Ma et al (2013) investigated the uptake of phthlic acid esters into alfalfa, Medicago sativa L., perennial ryegrass, Lolium perenne L., and tall fescue, Festuca arundinacea from the contaminated site surrounding a large e-waste processing facility in China. Another type of phytomining, using fungi, is referred to as mycoremediation. While there were a number of studies showing mycoremediation of soils containing base and precious metal contamination, there were not found studies where this was accomplished in an e-waste recovery context. 2.8 Microfactory concept While challenges still exist with processing e-waste, there are small scale innovations that must be considered due to important advantages such as lower start up cost and production of multiple end products. The Smart Centre at UNSW, led by Scientia Professor Veena Sahajwalla, has developed the world’s first e-waste microfactory, capable of producing a

40 number of useful quality materials13. According to an article in the Australian Quarterly (Sahajwalla, Veena, 2018), the microfactory has the potential to pay for itself within three years. The set up fits within 50 square meters, and it is modular, consisting of several stations, or steps that break down, separate, and then process various components of e-waste. Glass, metal, and plastics are separated, with the plastic filament product being the most instantly useful and saleable item produced, due to its application in 3D printing.

Underpinning the development of this microfactory was a significant amount of original work and research to test, model, and bring this technology to life. As examples, Mohammed et al. (2017) proposed a method for shredding and exruding plastic waste from e-waste, and Maroufi et al. (2018) demonstrated smelting of SiMn/FeMn from mixed e-waste. As another example, Gaikwad et al. (2018) studied the polycarbonate (PC) plastics available from shredded e-waste to characterise the viability of PC in a 3D printer, and then test the tensile strength of the resulting printed product, in this case a dog-bone shape for use in the testing machine. Noting that acrylonitrile butadiene styrene (ABS) is more commonly in use, the experiments demonstrated the characteristics of printed products made with recaptured PC filament compared to products made from virgin ABS. What this study found was that PC printed parts had 83% of the tensile strength of the ABS printed parts, and that the tensile strength reduced more rapidly than ABS when re-extruded and reused.

Looking at small scale solutions can provide significant advantages to an existing waste management or recycling industry, because barriers include available space for processing, and available funds to build additional processing capability. As schemes such as NTCRS are expanded, and as e-waste becomes banned from landfill, such as it is in Victoria starting June 2019, it is anticipated that the increasing waste stream will convert to an increasing need for material recovery. Starting small demonstrates the viability of the recovery efforts, and then subsequently expanding the same technology into more than one cluster of processing is also entirely possible.

13 https://newsroom.unsw.edu.au/news/science-tech/world-first-e-waste-microfactory-launched-unsw 41

2.9 Limitations of current recycling techniques Recycling mobile phone printed circuit boards (MPCB) is challenging for at least two reasons.

Being able to accurately cost and implement a recovery operation depends on technologies that can be implemented at an industrial scale, within legal constraints. There are plenty of companies that are making it work, but lowering the barriers to entry makes good sense if those benefits, outlined in the above discussion of how important recycling is, are to be realized. Lower barriers to entry include where possible to reduce energy requirements, shorten preparation time, reduce preparation steps, speed up reactions or transformations, reduce harmful or pollutive substances, and/or reduce dissipation of the available material.

The other reason is that mobile phone printed circuit board (MPCB) circuitry is becoming even more miniature and complex. The layers are increasing and becoming more sophisticated. The demands of technology are driving manufacturers to implement complex materials and alloys for greater performance. Tiny amounts of Pd, Pt, Ge, Te, and more, added to base metals like copper, facilitate very specific desirable functionality in the MPCB. There is a need to keep pace with current technology, in addition to understanding PCB from personal computers and gaming consoles, and simpler PCBs present in radios, appliances, and toys, by studying recovery efforts and experimental effects on more recent technology. No studies were found which focused on PCBs present in newer technologies such as the iPhone 4, manufactured as recently as 6 years ago and now nearly obsolete.

An important limitation to keep in mind is as always, cost. This includes the investment cost, and the ongoing cost of the operation. Costs are often acceptable to larger businesses due to security needs and secure destruction (Davis et al., 2008). For the average consumer, however, it costs nothing to put it in the waste collection bin. Costs are often covered in disposal fees, product stewardship schemes (a form of producer pays), and other subsidies or incentives (Golev et al., 2017). Looking at two extremes, high investment cost presents challenges because of an uncertain waste stream, but has greater processing power and results in a compelling channel for waste processing. Low investment cost presents challenges in attracting sufficient returns on investment, but is less sensitive to fluctuations in the waste stream, if it is scaled to the low, but likely volume of input EOL e-waste material. From a supply chain perspective, Khaliq et al. (2014) list a number of challenges for increasing e- waste recycling in Australia, namely: insufficient facilities for collection, transportation cost

42 and distance, insufficient facilities for separating metals, technical and knowledge barriers, and no smelting or refining facility. The same study also pointed out that in Australia is a lack of efficiency and optimization, which amounts to an economic barrier, and last but not least, Australia does not have much in the way of manufacturing, which means that demand for the smelted metal is still overseas.

On a small scale, lab-on-a-chip (Mohammed et al., 2015) is a concept that discusses available technology for processing various materials by combining the components of the processing procedure and programming the necessary instruments within a central computer controller and the limitations of same. Limitations include the high cost of specialist knowledge and the necessity for expertise equivalent to much larger scale operations, in order to perform fine tuning, or troubleshooting in the event that unexpected results do occur.

3 Experimental

3.1 Research Questions This research will analyse the effect of selective thermal transformation at various temperatures on the composition of the metal fractions from the PCB inside two common mobile phones. At various temperatures, the research will evaluate how separate or mixed the copper fraction is, both physical separation from layers and substrates, as well as material purity. Will separation occur by reducing surrounding elements, or by melting and viscous movement, and will metals become more mixed or alloyed with the interaction of the metals under heat treatment. This research will also evaluate whether there are effects due to the wide variety of material elements used to manufacture mobile phone PCB (MPCB).

3.2 General Methodology and Scope To discover the effect of selective thermal transformation as in the stated objective, and to better recover materials from end of life mobile phone printed circuit boards (MPCBs), this experiment will demonstrate the behavior of copper and related metals following selective thermal transformation in an inert atmosphere. Different temperatures are used, in order to understand the behaviour and interactions of the elements. Because MPCB is a highly complex manufactured product consisting of numerous elements due to rapid technical advances in mobile phone technology, modelling is difficult, experimentation is required.

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This will assist future developments in separating materials, reclaiming materials, particularly metals, from end of life MPCB.

Selective thermal transformation facilitates the recovery of materials from end-of-life MPCB, using heat to reduce organic compounds and free up metallic elements. During heat treatment, the interactions of the materials will result in some transformations, such as being reduced, alloyed, and / or separated.

The samples will be FR-4 (complex) printed wiring board (PWB) and electronic components (EC) with no separation of EC’s, due to complexity and miniaturization. To be able to recover materials without having to separate the EC's as a prior step, would be ideal. The samples will be cut into pieces, to facilitate experiments in the test environment.

The experiment will vary temperature, with inert atmosphere, and consistent sample weight and consistent heating duration. Six different temperatures are used as in Table 3-1 Temperatures for PCB selective thermal transformationTable 3-1 below.

Temperature 850℃ 950℃ 1050℃ 1150℃ 1250℃ 1350℃

Phone 1 iPhone 4 iPhone 4 iPhone 4 iPhone 4 iPhone 4 iPhone 4

Phone 2 Nokia Nokia Nokia Nokia Nokia Nokia N3210 N3210 N3210 N3210 N3210 N3210

Table 3-1 Temperatures for PCB selective thermal transformation The material is analysed and conclusions drawn about the effects of temperature on whether materials have removed away from the target metal, or metals have become alloyed to the target metal. Some information about the off gasses and weight loss will also be obtained.

3.3 Risks Through the experimentation process, there are a number of risks. Preparation of the samples will likely result in some loss of material, due to the difficulty of some components on the circuit board to not be included due to size or due to irregular breakages. It is anticipated that the losses will be acceptable. Post heating, the process of separating organic and metal components will also potentially pose issues due to visual limitations of the material. It is anticipated that the blackened Carbon component, and the copper coloured, and the other silvery coloured metals will be separable by sight.

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From a safety perspective, it will be important to obtain correct training, and follow safety procedures. Safety risks during preparation include, handling sharp objects for cutting the MPCB, and operation of rapidly moving grinding equipment. Safety risks during heating include handling equipment and materials at high temperatures, and avoiding toxic fumes resulting from melting, evaporation, and transformation of organics, which are already known to be toxic, due to having brominated flame retardants. Safe operation of equipment and handling of material is also proscribed during analysis.

3.4 Material collection and preparation A number of mobile phones were collected from various sources to discover available end of life mobile phones. Five phones were collected from a local retailer, JB Hifi, which at the time was collecting e-waste and discarded mobile phones as part of the National Television and Computer Recycling Scheme. Two phones were collected from colleagues whose relatives had an old phone for donation. Additional phones and parts were also available within the UNSW Smart Centre, which were previously collected.

Two common mobile phones were selected, Nokia N3210 (manufactured in 1999) and Apple iPhone 4 (manufactured in 2010). It was also decided that at least one well known ubiquitous phone could be used, the iPhone, manufactured by the Apple company. A total of four second hand iPhones and two iPhone motherboards were obtained through the auction website eBay. Also, the Nokia N3210 was selected, because of the available phones collected from various donation sources, there were three of this model which provided sufficient material for the experimentation. The other phones and parts were returned to UNSW Smart Centre for other investigations or for recycling.

The selected phones were disassembled by hand, with helpful instructions from http://ifixit.com, a website dedicated to disassembly and reassembly instructions for the purpose of repairing electronics that may not have shipped with repair instructions. Each circuit board was disassembled one more step, to remove the thin metallic shields, presumably ferrous, protecting the transistors and processors. All other circuit board components remained in situ.

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Figure 3-1 Disassembled iPhone 4 with selected labels

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Figure 3-2 Disassembled Nokia N3210

The separated parts are pictured in Figure 3-1 and Figure 3-2. All parts besides the main circuit boards were set aside. The circuit boards were identified as FR-4 multi layer circuit boards.

Milling

Though copper is present through most of the PCB, in the form of circuits, there may be other materials that will interact in a unique way; so a representative sample would be ideal. The sample is not crushed smaller than this however, because the separation of metallic, non- metallic, and un-melted samples will be achieved during selective thermal transformation before analysis is carried out.

One circuit board from each phone type was selected and then milled using a knife mill sized to < 1mm using a 1mm internal sieve. Several larger pieces, up to 3 mm, were still inside the grinder, and still collected and included. The resulting powder was then shaken to create a representative homogenous sample for testing and analysis. Another option, not used, is to use a cryomill, which involves significantly reducing the temperature of the PCB to make it more brittle, then milling to smaller particle sizes. The result of milling appears in Figure 3-3

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Figure 3-3 Milled Nokia N3210 printed circuit board

3.5 Instruments TGA

Some of the milled material was used for slow selective thermal transformation and thermo gravimetric analysis (TGA). The machine used was a ThermoGravimeric Analyser, Perkin Elmer Pyris 1. Thermo gravimetric analysis exposes characteristics of materials reacting under heated selective thermal transformation over time. From the milled fraction, a 50 mg sample was measured into a hanging crucible and lowered into the unit (see Figure 3-4).

Figure 3-4 Diagram of Thermo-gravimetric analyser (TGA)

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The temperature was increased from room temperature approximately 30C to 1250C at the heating rate of 30C per minute, and then cooled. The sample was heated in a nitrogen gas atmosphere at a flow rate of 20 mL/min. As the temperature increased, and the sample experienced selective thermal transformation, the organic fraction produced off gasses, resulting in a reduction in weight over time. The weight loss was recorded by sensor and data logging device embedded in the unit. For this experiment the off gas from the TGA was not analysed.

Furnace

Figure 3-5 Untreated PCB from iPhone 4 placed in alumina crucible

Figure 3-6 Post heat treatment PCB from iPhone 4 in alumina crucible

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Another circuit board was cut using hardware scissors and/or tin snips into rough segments between 5-10 mm to a side making segments approximately 1 cm2 to be used for heat treatment. For heat treatment, approximately 1 gram ± 10 mg of cut circuit board was measured into an alumina crucible (see Figure 3-5 and Figure 3-6). No fuel nor reagent were added. The crucible was placed onto a graphite rod, fashioned with a paddle at one end. The rod, with the alumina crucible at one end, with the WPCB in it, was slid into a horizontal tube furnace, tube 1 m length, 5 mm thickness, 5 cm internal diameter. Different samples were heated at various temperatures for 10 minutes at a time.

Figure 3-7 High Temperature Furnace

Figure 3-8 Sample in the cold zone of a horizontal high temperature furnace

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Figure 3-9 Sample in the hot zone of a horizontal high temperature furnace First, the WPCB was placed into a cold zone near the entrance of the furnace (Figure 3-7 and Figure 3-8), approximately 250ᵒC, for 10 minutes, to ready the sample for heat exposure and expedited reactions at higher temperatures, then added to the furnace at the designated temperature for 10 minutes (Figure 3-9), and then held in the cold zone again for 10 minutes to limit thermal cracking and oxidation reactions while the sample was still at high temperature. The designated temperatures were 850, 950, 1050, 1150, 1250, and 1350ᵒC, with one or two samples from each temperature kept and preserved for analysis. During heat treatment, pure inert Argon gas flowed through the horizontal furnace at a rate of 1 L/m to maintain a selective thermal transformation atmosphere. The off gas flow was captured by an FTIR device as it left the furnace, in order to measure quantity of airborne organic residue that flowed away from the sample as the polymers changed form and released gasses in the heat. Recorded off gasses were CO2, CO, and CH4.

Sample analysis

Before and after heat treatment, samples were analysed to reveal the composition and morphology of the metallic fraction. Following heat treatment, samples were collected and then visually separated into metallic and non metallic fractions (NMF). Grey-silvery (Pb/Sn) droplets are separated from the reddish (Cu) droplets. A selection of metallic droplets are evaluated to understand the composition of the fractions and the droplets. For the purpose of this study, emphasis remains with the composition and morphology of the metallic fraction. Other studies have characterised the NMF from PCB before and after heat treatment and its uses, see Sahajwalla, V. et al. (2015), Saini et al. (2017), Rajagopal et al. (2016).

ICP

Milled samples were taken prior to heat treatment and analysed using laser induced Inductive Coupled Plasma Mass Spectrometry (ICP-MS) to determine composition and relative quantities of metallic fractions. Heat treated samples were also analysed using ICP-MS

51 technique, by visually separating the heat treated samples into metallic and non-metal fragments, and testing metallic quantities or metallic residues of each. Semi quantitative measures were taken and then full quantitative analysis was completed, based on selected elements of interest.

SEM EDS

Following heat treatment, the metallic fraction (MF) and non-metallic fraction (NMF) were analysed using Hitachi S3400X Scanning Electron Microscope (SEM) to view the morphology of the metals and the residue. Morphology prior to heat treatment was not examined, due to opaque top / outer layer. Each sample from each temperature level was analysed separately. The energy dispersive spectrum (EDS) analysis was completed at the same time, for selected fragments, to measure the elemental composition of points of interest and map elemental composition of relevant conflated morphologies. Figure 3-10 shows the combined SEM-EDS instrument.

Figure 3-10 SEM-EDS

FTIR

For analysis of the WPCB following heat treatment, Fourier-transform infrared (FTIR) spectroscopy was used to determine compounds and possible molecular structures remaining 52 in the material. It is expected that carbon molecules will have degraded during selective thermal transformation.

4 Analysis

4.1 Physical 4.1.1 Visual Visual observation of the samples post heating shows changes in morphology as a result of selective thermal transformation in an inert atmosphere (see Figure 3-6 and Figure 4-1). Polymeric surfaces appeared to shrink and turn black. Metallic fractions appeared to form small and very small spheres. Carbonaceous residue was brittle upon transfer from the crucible, and metallic components separated relatively easily. Layers of carbon or silicon substrate were easily crumbled and separable. Carbon based polymers and silica based fiberglass substrates were visually indistinguishable, as the carbonaceous resin char was uniformly black. It was also observed that metal welds and metal attachment points tended to bead in place, held there by the substrate. Where temperatures reached the melting point of copper, exposed copper and layered copper tended to form spherical beads, also held in place. No analysis was done to determine what quantity and what types of metals reached evaporative / gas state, such as those with relatively low boiling points like Hg (357C) and Zn (906C).

Figure 4-1 Heat treatment of iPhone PCB before and after photo

4.1.2 Surface analysis SEM analysis of the appearance of the resulting metallic fraction.

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4.1.3 iPhone SEM-EDS iPhone heat treated at 850C shows transformations as viewed in Figure 4-2. Photograph A shows the presumably silica based fiberglass substrate intact and slightly warped through heat treatment, and presumably carbon polymer dusty residue following selective thermal transformation. Photograph B shows the metallic fraction with polyps forming at the surface of the metal as it melts and begins to cohere to itself.

A B

Figure 4-2 SEM image of iPhone after heating at 850C

iPhone heat treated at 1050C shows transformations as viewed in Figure 4-3. The substrate (A) shows some cracking has occurred during selective thermal transformation. The metallic fraction (B) has begun to show surface changes, but remains largely in place. Separately, a silvery bead (C) has formed, presumably from lower melting point metals as found in solder. The surface of the silvery sphere is shown in (D), which has the appearance of agglutinated blobs of metal, variation likely due to changes in the alloy mix and response to heat at the surface versus heat inside the sphere.

C

A B D

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D

Figure 4-3 iPhone PCB heat treated at 1050C

The material pictured in Figure 4-3 was analysed by EDS and shows the following composition in Table 4-1. It shows morphologically indistinguishable elements, in alloy, with predominantly copper content, followed by tin, nickel, and silver, most likely the result of copper circuits and tin/nickel/silver solder liquefying and amalgamating.

Table 4-1 Composition of droplet from iPhone PCB after heat treatment at 1050°C

Element Percentage Cu 81.54 Sn 10.83 Ni 4.03 Ag 1.57

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The composition is visually represented in Figure 4-4.

Figure 4-4 Metal droplet from iPhone heat treated at 1050°C, showing copper (Cu) in pale green, nickel (Ni) in yellow, tin (Sn) in pale blue, silver (Ag) in purple.

The figure below, is the EDS analysis of the SEM image following selective thermal transformation at 1150C. The next image, Figure 4-5 and in Table 4-2Error! Reference source not found.Error! Reference source not found., shows percentage quantities of particular elements as indicated by point analysis in 2 different areas on the surface. The analysis shows that the metallic structure in the image is Cu (Point 1), and the unordered material around the metallic structure is C / Si (Point 2).

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Table 4-2 Composition of droplet from iPhone PCB after heat treatment at 1150°C

Percentage Element Point 1 Point 2 Cu 66.36 0.98 C 24.07 70.42 Si 2.94 12.52 O 2.73 8.59 Al 2.05 1.04 Mg 1.85 5.10 P 1.13 Fe 0.24

Figure 4-5 Point analysis of iPhone PCB heat treated at 1150°C

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Figure 4-6 Element mapping for iPhone PCB treated at 1150°C, showing calcium (Ca) in purple, aluminium (Al) in green, carbon (C), in pink, and copper (Cu) in yellow.

iPhone heat treated at 1250C shows transformations as viewed in Figure 4-7. The substrate (A) shows an ashy surface, presumably from the reduction of polymers during selective thermal transformation, and the angular shapes of the cut substrate appear to have held their form. On the surface there is some formation of pits and blobs, presumably metal. Billowing out from between the layers appear to be metallic spheres (B), showing that the metal between the layers has melted and is leaking out the sides. This is presumed to be copper circuitry melting and flowing outward where the circuit board was severed, and the wire was cross cut. A closeup of the surface of the copper sphere (C) shows some alloying behavior as well as flattened and flowing metal.

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A C

B C

Figure 4-7 iPhone printed circuit board heat treated at 1250C

The EDS multi point analysis of the SEM image as seen in Figure 4-8, below. The multi point analysis shows percentage quantities of particular elements as indicated by 4 different areas on the surface. The analysis shows that the overall metallic structure in the image is 82% and 83% Cu (Point 3 and Point 4), with small heterogeneous features such as Fe, O, and Cu (Point 2) and 79% Fe (Point 1).

Table 4-3 Composition of droplet from iPhone 4 after heat treatment at 1250°C

Percentage Element Point 1 Point 2 Point 3 Point 4 Cu 1.58 18.20 82.18 83.22 Fe 79.25 20.79 4.16 7.79 O 6.27 53.48 9.19 Cr 1.13 0.93 Al 1.11 Ag 0.56 1.14 2.72 Si 3.70 1.99 1.14 Sn 2.34 1.36 4.85

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Figure 4-8 Points measured on metal droplet from iPhone 4 after heat treatment at 1250°C

Figure 4-9 EDS analysis of iPhone droplet after heat treatment at 1250°C, showing copper (Cu) in purple, iron (Fe) in pale green, tin (Sn) in pink.

iPhone heat treated at 1350ᵒC shows transformations as viewed in Figure 4-10. Non metallic surfaces show more significant changes, particularly carbon, having the appearance of yeasty 60 bread, showing that reactions in the carbon substrate are forming gaseous bubbles and escaping through a liquid or semi liquid substrate. The metallic fraction is forming spherical blobs as in the previous heat treatment at 1250ᵒC, however in contrast the metals are more homogenous in appearance, with fewer distinct features on the surface.

A D

B C C E

E

Figure 4-10 iPhone printed circuit board heat treated at 1350C

EDS analysis reveals the composition as follows (Figure 4-10 and Figure 4-11)

The EDS analysis shows percentage quantities of particular elements as indicated by point analysis in 3 different areas on the surface. The analysis shows that the surface is a mix of Cu and Sn (Point 1), with a C / Al region (Point 2), and bits of Si and P scattered throughout (Point 3).

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Table 4-4 Composition of droplet from iPhone PCB after heat treatment at 1350°C

Point 1 Point 2 Point 3 Copper 52.61 5.99 28.71

Aluminium 21.43 Tin 39.34 21.62 63.25

Magnesium 0.90

Phosphorus 2.58 0.53

Silicon 5.02 6.05

Oxygen 27.47 1.45

Figure 4-11 Elemental analysis of points on iPhone WPCB following selective thermal transformation at 1350°C

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Figure 4-12 EDS of iPhone WPCB following selective thermal transformation at 1350C, showing tin (Sn) in pale blue, alumininm (Al) in pink, phosphorus (P) in yellow, copper (Cu) in red.

4.1.4 Nokia SEM-EDS This next series of images and elemental analysis are related to Nokia N3210 PCB material.

The figures below show morphology of Nokia WPCB after heat treatment at 850°C as shown in Figure 4-13.

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Figure 4-13 Nokia PCB after selective thermal transformation at 850°C and EDS analysis of copper (Cu) content (in bright green).

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The figures below show morphology of Nokia WPCB after heat treatment at 950°C as shown in Figure 4-14.

Figure 4-14 Nokia PCB after selective thermal transformation at 950°C with EDS analysis, showing copper (Cu) in blue, silicon (Si) in pink, calcium (Ca) in bright green.

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The figures below show morphology of Nokia WPCB after heat treatment at 1050°C as shown in Figure 4-15.

Figure 4-15 Nokia PCB fragment following heat treatment at 1050°C with EDS analysis, showing a composite image, and separated images for carbon (C) in teal, oxygen (O) in purple, fluorine (F) in pink, aluminium (Al) in olive, silicon (Si) in blue, calcium in red, copper (Cu) in pale green.

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The figures below show morphology of Nokia WPCB after heat treatment at 1150°C. In Figure 4-16, the area marked A appears to be a metallic fraction, already liberated from its component part and showing signs of changing shape, as indicated in area B. Area C gives the appearance of being a nonmetallic fragment, such as Carbon.

B B C

A

Figure 4-16 Nokia PCB following selective thermal transformation at 1150°C.

The following table shows percentage quantities of particular elements as indicated by point analysis in 3 different areas on the surface. The analysis shows that the metallic structure in the image is Cu (Point 1 and Point 2), and the unordered material around the metallic structure is C / Si (Point 3), most likely substrate fragmented during the process of breaking up the board for heat treatment. The figure below, Figure 4-17, is the SEM evaluation.

Table 4-5 Composition of droplet from Nokia WPCB after heat treatment at 1150°C

Point 1 Point 2 Point 3

Copper 82.10262 76.14921 1.78467

Carbon 6.62756 16.86959 18.42106

Silicon 11.69855 0.899304 18.73041

Oxygen 3.535165 3.5446 51.52036

Aluminium 1.044122 #N/A 6.91280

Calcium 0.647046 #N/A 12.23982

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Point 1 Point 2 Point 3

Manganese #N/A #N/A 1.55556

Barium #N/A #N/A 3.76268

Figure 4-17 Nokia PCB under SEM/EDS following selective thermal transformation at 1150°C, showing copper (Cu) in pink, silicon (Si) in green, calcium (Ca) in purple.

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The figure below, Figure 4-18, is Nokia PCB following selective thermal transformation at 1250°C. What is interesting is the accumulation of smaller metallic droplets against a fairly intact substrate.

Figure 4-18 Nokia PCB fragment following selective thermal transformation at 1250°C

In Figure 4-19 the SEM image of spherical material following selective thermal transformation at 1350°C shows beading and collecting of other material on the outside of a mainly Cu droplet.

B

A

B

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Figure 4-19 Nokia PCB heat treated at 1350°C, showing silicon (Si) in blue, copper (Cu) in orange, magnesium (Mn) in yellow.

In Figure 4-20 Nokia PCB heat treated at 1350°C the substrate, primarily of C and Si has started to melt.

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Figure 4-20 Nokia PCB after selective thermal transformation at 1350°C, showing carbon (C) in green, copper (Cu) in orange, silicon (Si) in red, tin (Sn) in purple.

4.1.5 Weight changes TGA analysis of the weight changes during heating. The weight changes were expected to be the result of combustion and burn-off of organics, due to heating and selective thermal transformation of organic carbon based material used as substrate and structure for the PCB. Weight changes from evaporating metallic particles were also possible; however, the off gasses were not analyzed.

The Nokia waste printed circuit board (WPCB), milled to <1mm, mixed by hand, to form a representative sample, was exposed to increasing temperature to analyze the effect of heat in a selective thermal transformation atmosphere on the decomposition and evaporation of the heterogeneous material. Starting at 30ᵒC and continuing through 1000ᵒC at 20ᵒC per minute, a total of 48.5 minutes to complete the event. The experiment was completed twice, once with 32.7g and again with 36.5g. The two results were compared and shown shown below.

As shown in Figure 4-21, 1% weight loss occurs at 317°C, and 20.2% weight loss at 1000°C, the greatest change in weight occurred between 400 and 600°C.

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Figure 4-21 Percentage weight loss during selective thermal transformation of Nokia PCB

The iPhone WPCB was milled to <1mm, mixed by hand to form a representative sample. From the representative sample, 25.4g was used and heated in selective thermal transformation atmosphere from 30°C to 1200°C at a rate of 10°C per minute, for a total time of 118 minutes. The sample achieve 1% weight loss at 377°, 35.8 minutes, and 17.4% weight loss at at 1200°C. As shown in Figure 4-22 the greatest amount of change (DTG) occurred between 300 and 500°C.

Figure 4-22 iPhone PCB weight loss during selective thermal transformation.

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4.2 Compositional 4.1.6 IR Gas Analysis During heating of the MPCB, the off gasses were analysed for three common molecules, CO,

CO2, and CH3. The result, averaged over 4 experiments with the Nokia MPCB (2x 1350°C,

2x 1250°C) is shown below in Figure 4-23. It is noted that most CO2 and CH3 is produced within the first 40s, and most CO is produced within the first 70s.

Figure 4-23 IR Gas analysis of MPCB off gasses during heat treatment

4.1.7 FTIR Analysis A sample of char from heating Nokia WPCB at 1350°C was collected to conduct FTIR analysis. Sample was mixed with KBR 1:1. As viewed in Figure 4-24, the peaks coincide with amorphous, matte carbon (Ferrari et al., 2004).

Figure 4-24 iPhone PCB after heat treatment, viewed with FTIR

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4.1.8 ICP Analysis ICP analysis of the material after grinding MP-PCB to obtain a mixed homogenous representative sample of 1g. A semi quantitative analysis was run, to identify materials of interest, and then a full quantitative analysis was also conducted. The representative quantities are below in Figure 4-25, Figure 4-26, and Figure 4-27.

Figure 4-25 Nokia N3210 quantitative ICP analysis raw material prior to heat treatment

Figure 4-26 iPhone 4 quantitative ICP analysis raw material prior to heat treatment

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Figure 4-27 Semi quantitative ICP analysis post heat treatment at 1350℃, visually separated into char (X), silvery coloured metal (Y), and copper coloured metal (Z).

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4.3 Summary The various experiments are summarized in Table 4-6 Summary results for iPhone 4 and Nokia N3210 at different temperatures . It shows the effect of increasing selective temperatures on the morphological characteristics of the WPCB fragments.

iPhone 4 Nokia N3210

Temperature Copper Silvery Non Metallic Copper Silvery Non Metallic fraction fraction Fraction fraction fraction Fraction

850℃ Nanowires Silvery Unordered Nanowires Silvery Unordered and beading Carbon and beading Carbon embedded present relevant to embedded present relevant to circuits <1 mm polymer circuits <1 mm polymer unchanged max substrate and unchanged max substrate and 950℃ diameter unordered diameter unordered Silicon, Silicon, 1050℃ Nanowires Nanowires Silvery Calcium, Calcium, not visible not visible beading Silvery Oxygen Oxygen and and present 3 beading relevant to relevant to embedded embedded mm max present 3 integrated integrated circuits circuits diameter mm max components components increasingly increasingly diameter 1150℃ ductile ductile

Embedded Silvery Embedded circuits and circuits flowing at coppery flowing at edges beading edges present 3.5 mm max 1250℃ diameter

Circuitry not Silvery As above, Circuitry not As above, found; copper beading, however, found; copper (gaseous beading up to 3.5 mm carbon beading up to bubbles not 3 mm; max became semi 3 mm; observed) metallic diameter, liquid with metallic bonding to copper gaseous bonding to other metals not bubbles other metals 1350℃ not observed. observed not observed.

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Table 4-6 Summary results for iPhone 4 and Nokia N3210 at different temperatures

5 Conclusions Current and existing work in processing WPCB shows a high degree of thermal processing for natural extraction, and a high degree of chemical processing for materials recovery. In this study it is demonstrated that copper recovery from MPCB is facilitated by the application of heat in a thermal transformation environment with at least two novel conclusions regarding heat levels applied and the effect it has on processing options.

The first is that the application of heat facilitates transformation of the substrate from its manufactured state into an unordered and brittle state, which may facilitate the separation of the substrate from copper and other metals through additional processing. Additional processing may include crushing or grinding, and then separation of the resultant material. Separation may be done by flotation, eddy current, or some other readily available technology. As demonstrated by TGA, the carbon reactions into a more brittle state appear to be most active in the range of up to 600C and limited change thereafter. The drawback of this approach is that the metal is not yet fully liberated from between the PCB layers. The advantage of this approach is limited copper transformation and alloying.

The second is that melting the copper causes it flow out from between the layers of WPCB and form metallic beads. Melting in situ occurs at temperatures above 1250C and a duration of 10 minutes. The advantage of this approach is reduced processing requirements and metal separation into beads. A disadvantage is that higher temperatures carry a higher energy requirement, not only in terms of processing cost, but in terms of environmental cost where energy is provided by fossil fuels.

Between the two options, emissions of toxic and greenhouse gasses, were not significantly different. As noted in other papers, some emissions of zinc or lead occurs at higher temperatures.

As a standalone process for material recovery, choosing a method with lower heat threshold has the potential to carry lower processing cost. Additionally choosing a method that preserves the existing copper purity has the potential to require fewer or less intensive processing steps.

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Potential applications exist for a combined process with natural resource extraction. As described earlier, natural resource extraction and heat treatment processes are already existent globally and in Australia, and could potentially be leveraged for copper recovery from WPCB. Where the cost of heat is absorbed in an existing mineral processing operation, WPCB has the potential to benefit from waste heat or mixed batch processing, thus providing justification for a processing model that melts and collects the metal. This is proposed for the Nyrstar smelter in Port Pirie, South Australia.

From a policy and legal perspective, a government has a duty to listen to the science behind climate change, and encourage materials recovery over landfill and natural resource extraction. This finding clarifies at least three points for consideration in policy making, including the duty of processors to balance the benefit of copper recovery with the cost of preventing pollution to air, the benefit and viability of encouraging secondary metals processing, and the potential for copper recovery regardless of scale. This study demonstrates successful recovery at a small scale, with on demand selective thermal processing. This is important in a country such as Australia where hurdles may exist due to questions of scale and economic viability.

This paper, and other similar works drive sustainability forward by providing new knowledge in support of recovery operations. Ongoing recovery operations, particularly in the field of electronic waste (e-waste) continue to evolve in response to the ongoing and increasing e- waste problem. This negative impact to the environment is manifested in ongoing destruction through resource extraction, ongoing energy and water demand, and ongoing greenhouse gas emissions through haulage and transport of raw minerals. Selective thermal treatment, and other viable options, have the potential to keep valuable copper and other materials in circulation for the creation of new and more useful products.

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