Assessment of toxic metals in waste personal computers

Application of plasma technology for treating e-waste: A review

This review details the current information on e-waste treatment using plasma technology. The current status of e-waste treatment via plasma technology from the scientific literature is presented herein, namely, moist paste battery, galvanic sludge, resin, printed circuit board, and semiconductor industries. The concept of plasma technology, classification of e-waste, contaminants of e-waste (metals, metalloids, and VOCs), and vitrification of the final product are presented herein. This review paper focuses on fusing flux agents to vitrify e-waste. Furthermore, this paper covers laboratory-scale investigations, plasma technology benefits, and reuse of material from plasma post-treatment. The use of plasma technology combined with flux agents could be recommended to eliminate contaminants from e-waste. Materials from plasma post-treatment may also be applied in environmental reuse applications.

Recovery of gold from waste mobile phone circuit boards and synthesis of nanomaterials using emulsion liquid membrane

In recent years, waste mobile phones have become popular as electronic waste due to the huge amount, serious pollution with improper disposal and high resource value. It is imperative to realize the recycling of resources in waste mobile phones. The application of emulsion liquid membrane in the recovery of gold and synthesis of nanomaterials from waste mobile phone printed circuit boards (WMPCBs) was studied. The components of the emulsion liquid membrane, effects of 7 factors on the extraction rate and the morphology of the synthesized nanomaterials were explored. The results show that it is possible to extract 99.79% of Au(III) from WMPCBs leachate with kerosene as diluent, Span80 as surfactant, methyl isobutyl ketone(MIBK) as carrier, ascorbic acid solution as stripping agent and liquid paraffin as membrane stabilizer. The external phase pH and the internal phase concentration had a greater influence on the extraction efficiency of Au(III) among 7 factors. The morphology of the synthesized product was affected by the concentration and type of the surfactant. It provides a new idea to connect recovery from waste with deep processing, extending the waste mobile phone recycling process chain and achieving high-value utilization of waste mobile phone secondary metal resource products.

Economic and environmental evaluation of flux agents in the vitrification of resin waste: A SWOT analysis

Flux agents play an important role in the pyrolysis treatment of vitrifying hazardous wastes. Among these is plasma jets, a cost-less flux agent derived from shell powder which can be used to create vitrification. It is a promising option to be applied in the vitrification of elements and to remove the VOCs of hazardous waste, namely, resin from PCB scrap in an atmospheric-pressure microwave plasma reactor. In this study, a laboratory scale experiment was conducted. The experiment was performed in the pyrolysis of resin which was added with flux agents. The economic evaluation of the flux agents, and the circular economy concept of the final residue derived from the plasma pyrolysis was then analyzed post treatment. To test the strength and weakness of the experiment, the SWOT analysis was performed. The outcome helped in the understanding of the cost-less flux agent used in the pyrolysis treatment of hazardous waste. Results showed that fusing shell powder in resin was better for improving the removal efficiency of VOCs, such as benzene and toluene as well as toxic metals than compared to other flux agents such as limestone and quartz sand. Moreover, the final residue of resin was found to fulfil the concept of circular economy where it could be reused as an absorbent of methyl blue, thereby indicating good absorption performance, from 1 ppm-100 ppm. The twelve strategies that were derived from the SWOT analysis could be used as information outlining the current internal and external condition for the development and application of shell powder. Shell powder, as a cost-less flux agent, has the potential for enhancing waste management and circular economy when used in the pyrolysis treatment of future hazardous wastes.

Optimized indium solubilization from LCD panels using H2SO4 leaching

Spent liquid crystal displays (LCDs) are a secondary source of precious/strategic metals, including indium (In). The present study involved optimizing the solubilization of this strategic element from samples of indium tin oxide (ITO) glass prepared from LCD screens of computer monitors and laptop screens. The influence of operating conditions on In solubilization, as well as optimum conditions for sulfuric acid leaching were defined by a Box-Behnken-type experimental design methodology. Optimum operating conditions include a leaching step for 30 min at a temperature of 70 °C in the presence of 0.4 N H₂SO₄ and a pulp density of 50% (w/v). Under these conditions, the quadratic model established to predict the solubilization of In from ITO glass samples provided an In solubilization efficiency of 89.7%, which was validated experimentally (99.5%). The analysis of direct operating costs and capital costs for the implementation of such a leaching process revealed that the process is conceivable for a high-capacity plant processing ~100 t/day of ITO glass.

Effect of shell powder on removal of metals and volatile organic compounds (VOCs) from resin in an atmospheric-pressure microwave plasma reactor

Resin has been widely used for thermosetting printed circuit boards (PCBs) and is a key part of e-waste from scrap PCBs. It requires appropriate treatment because of its harmful elements (metals and metalloids) and organic compounds that are toxic to human health and the environment. The purpose of this study is to eliminate volatile organic compounds (VOCs) and elements (metals and metalloids) in resin via the use of powdered snail shell (Babylonia formosae) in an atmospheric-pressure microwave plasma reactor. Shell powder plays a significant role in the destruction of benzene and toluene with removal efficiency 98.8 % and 100 %, respectively, compared to quartz sand with removal efficiency 44.9 %. A high ratio of shell powder increases the inertization of metals and metalloids by more than 96 %. The crystalline structures of these materials are dominated by calcite formations (CaCO₃), confirming the elimination of metals and metalloids. Raman spectroscopy shows that the shell powder vitrifies these elements. The use of shell powder is thus recommended to degrade hazardous substances and to vitrify elements from resin in plasma pyrolysis.

A review of sustainable e-waste generation and management: Present and future perspectives

Studies on sustainable management of waste from electrical and electronic equipment (or e-waste) have gained increasing attention from researchers around the world in recent years, with investigations into various aspects of e-waste management were investigated. Studies on e-waste generation by previous papers have been reviewed to provide an overview of the current research progress and recommendations for future research. The relevant existing studies were collected from various databases. Using content analysis, three main aspects of the existing studies were evaluated: the distribution and trends of the publications, the scope and boundaries of the studies, and the current research practices and research applications. Although there was a significant increasing trend of the amount of research on the evaluation of e-waste generation, however, the number of publications based on the countries of origin was still small. Another limitation was found related to the differences in the selection of research subjects and the level of analysis resulted in variations in the scopes and boundaries of the existing studies. Various other research areas were investigated further based on their research findings, but the analysis of various methodological aspects was complicated due to the increasing number of newly developed methodologies and the lack of comprehensive and up-to-date reviews on this research area. Additionally, there was also a need to evaluate emerging and/or older technology, which led electrical appliances to be overlooked. We found that comprehensive and up-to-date reviews of the methodological aspects of e-waste generation are still lacking. Based on the research gaps and limitations discussed, recommendations for future research were made.

Comprehensive elemental analysis of consumer electronic devices: Rare earth, precious, and critical elements

Over the past few decades, electronic devices of all kinds, and especially consumer electronics, have evolved in function and composition, in parallel to increasing manufacture and use. There is great potential for recovering economic value and reducing environmental impact by recycling devices and extracting various elements. However, there are few studies that comprehensively identify the elemental content of electronic devices or electronic waste. In the present study, consumer electronics and components (hard drives, ethernet hubs, portable media players, printers, answering machines, mobile phones, Digital Versatile Disc (DVD) players, computer wiring, and printed circuit boards) and electronic waste (low-grade scrap from one commercial recycling facility) were analyzed for rare earth, precious and critical metals. The overall procedure included size reduction, microwave assisted digestion, and Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES) analysis. Fifty-six elements were quantified or detected in these devices: 14 rare earth elements, six platinum group metals, 20 critical metals, and 16 other elements, including some precious metals. A single device could include a wide range of elements: 48 metals were quantified in the computer hard drives. The estimated economic value of the metals in each device ranged from $12.94 USD (computer wiring) to $454 USD (hard drives). The variety of metals in electronic devices suggests that end-of-life management strategies should focus on recycling and recovery, which also decreases the overall environmental impacts of the devices, especially associated with mining and refining metals.

Recycling of the scrap LCD panels by converting into the InBO3 nanostructure product

Preparation of the value-added products from e-waste resources is an important step in the recycling process. The present paper aims to propose a methodology for the recovery of In from scrap LCD panel via preparation of InBO₃ nanostructure. Discarded LCD panel was subjected to a recycling process through crushing, milling, and oxalic acid leaching to prepare In₂(C₂O₄)₃·6H₂O. Through the leaching process, B(OH)₃ from glass part (alumina borosilicate) has been leached out along with indium oxalate hydrated. Further thermal treatment on these extracted materials at 600 °C could result in the formation of InBO₃ nanostructures with an average particle size of 20 nm. A multistep mechanism based on thermodynamic calculations for the recycling of the InBO₃ form extracted precursors was proposed. Graphical abstract.

End-of-Life Liquid Crystal Display Recovery: Toward a Zero-Waste Approach

End-of-life liquid crystal displays (LCD) represent a possible source of secondary raw materials, mainly glass and an optoelectronic film composed of indium (90%) and tin (10%) oxides. A strong interest for indium, classified as critical raw material, pushed research towards the development of high-efficiency recycling processes. Nevertheless, a deepened study of the technological innovation highlighted that only a small number of treatments included use of whole waste. Furthermore, these processes often need high temperatures, long times, and raw materials that have a significant environmental impact. In this context, this article shows an approach developed in accordance with the “zero waste” principles for whole, end-of-life LCD panel recycling. This process includes preliminary grinding, followed by cross-current acid leaching and indium recovery by zinc cementation, with efficiencies greater than 90%. A recirculation system further increases sustainability of the process. To enhance all waste fractions, glass cullets from leaching are used for concrete production, avoiding their disposal in landfill sites. Considering the achieved efficiencies, combined the simple design suitable for real-scale application (as confirmed by the related patent pending), this process represents an excellent example of implementing circular economy pillars.

Heavy Metals in the Glass and Enamels of Consumer Container Bottles

The glass and enameled decorations of bottles of alcoholic beverages sourced from retailers in the U.K. were analyzed by X-ray fluorescence spectrometry for various heavy metals. In the glass substrate, lead, cadmium, and chromium were present at concentrations up to about 1100, 1100, and 3000 μg g^-1, respectively, but their environmental and health risks are deemed to be low significance. Of more concern from an environmental and, potentially, occupational exposure perspective are the concentrations and mobilities of Pb and Cd in the enamels of many bottles. Thus, Pb concentrations up to about 100000 μg g^-1 were found on the décor of various wine bottles and a beer bottle, and Cd concentrations of up to 20000 μg g^-1 were measured in the decorated regions on a range of spirits, beer, and wine bottles. Moreover, maximum concentrations that leached from enameled glass fragments according to a standard test that simulates water and other liquids percolating through a landfill were about 1200 and 3200 μg L^-1 for Pb and Cd, respectively, with several fragments exceeding the U.S. Model Toxins in Packaging Legislation and, therefore, defined as "hazardous". Given that safer decorative alternatives are available and that a precautionary principle should be adopted for toxic heavy metals, the pervasive use of Pb and Cd in the enamels of consumer bottles is brought into question.

Thermal treatment of liquid crystal display panel scraps: The metals migration and potential environmental risk in solid residue

Thermal treatment has been proved to be an efficient and promising method for organics removal from LCD panels and for resource recycling. Considering with the toxic metals contained in LCD panels and their potential risk, it is necessary to study and evaluate the metals behavior and potential risk associated with the thermal treatment of LCD panels. In this study, the migration and transformation behavior of ten metals (Cr, As, Al, In, Ni, Cu, Zn, Cd, Fe, Sn) in LCD panels were investigated during thermal treatment, as well as their potential environmental risk and leaching toxicity in solid residue were evaluated. Results showed that Cr, Ni, In, Cu and Fe exhibit obvious migration behavior from solid into gas phase/fly ash during thermal treatment, with the maximum migration rate of 52.8%, 54.7%, 37.7%, 30.8%, and 34.9% respectively under the experimental condition. Speciation transformation for the metals of Cr, Ni, In, Cu, Fe and Zn was also observed in solid residue after thermal treatment, which leads to the ecological risk increase of Cu, In and contamination risk increase of Fe. Meanwhile, the leachable concentration and leaching toxicity of Cu and Ni in solid residue showed increasing trend after thermal treatment. The results indicate that attentions should be paid on the emission control of Cr, Ni, In, Cu, Fe during thermal treatment of LCD panel scraps. Environmental risk of Cu, In, Fe and the leaching toxicity of Ni in solid residue after thermal treatment should also be concerned.

An assessment of achievements of the WEEE Directive in promoting movement up the waste hierarchy: experiences in the UK

Rapidly developing technology and an increasing number of products containing electrical or electronic functions, has led to discarded electrical and electronic equipment (EEE) being one of the fastest growing waste streams. The European Union (EU) has enacted several iterations of the Waste Electrical and Electronic Equipment (WEEE) Directive to address this complex waste stream. However, recycling dominates treatments for e-waste, despite the established 'waste hierarchy' showing waste prevention and reuse are generally preferable to recycling. This paper reports on 30 semi-structured interviews, undertaken across the EEE value chain, examining the impact of the WEEE Directive in the UK. The interviews confirmed that reuse takes place for a limited number of product types, mostly on a small scale. Additionally, whilst legislation has prompted innovation in recycling and higher capture rates, resource recovery is in practice limited to easily salvageable materials, whilst recovery of critical raw materials is often neglected. Furthermore, there is confusion around available collection networks, particularly for small WEEE, which consistently appears in residual waste streams. The waste hierarchy remains the key component of EU waste strategy and moving to the higher levels of the waste hierarchy is an essential part of achieving sustainable waste management and moving towards a circular economy. The paper proposes a series of measures to this end: promoting recovery routes and practices that facilitate reuse of suitable products, adapting recycling technology to increase recovery of critical raw materials and targeted policies to encourage the application of the waste hierarchy within a resource efficiency-oriented framework.

Evaluation and comparison of pre-treatment techniques for recovering indium from discarded liquid crystal displays

Over the last years, emerging incentives for secondary production of high tech-metals, found in e-waste, are created because of their increasing demand and economic issues associated with their primary production. Due to the very low share of these metals in e-waste, pre-treatment methods can result in an output fraction rich in the metals of interest and may, therefore, be essential. To this scope, the present article evaluates and compares the efficiency of four different pre-treatment approaches containing various steps for recovering indium (In) from liquid crystal displays (LCDs) in laptop computers. The pre-treatment steps, used in various combinations, are (a) dry mechanical crushing and sieving, (b) pyrolysis, (c) thermal shock and (d) gravimetric process. Also, in all approaches, liquid crystals were removed from the samples, before applying the mechanical crushing step, as these are toxic and potentially harmful to human health and the environment. The removal was achieved by ultrasonic irradiation or mild agitation and optimized in terms of time, temperature and solvent type and concentration. Then, the feasibility of each pre-treatment approach was evaluated based on two parameters: (a) the content of In in the resulting sample after pre-treatment and (b) the separated mass share (%) with larger indium content as compared to the original LCD panel. The results showed that In is highly liberated in the fractions consisting of finest particles (<25 μm and <53 μm) after dry mechanical crushing and sieving with a maximum content of 234 mg/kg, which is twice as much as in the raw material. However, these particles represented only about 14 wt% of the original LCD panel mass. On the contrary, thermal shock results indicated that this was the most efficient pre-treatment approach, as both the content of In and the separated LCD mass (%) remained in high levels. Finally, some economic aspects associated with the processes are presented.

Physical-chemical treatment of rainwater runoff in recovery and recycling companies: lab-scale investigation

Scrap material recovery and recycling companies are producing wastewater in which common pollutants (such as COD, nutrients and suspended solids), toxic metals, polyaromatic hydrocarbons (PAH) and polychlorinated biphenyls (PCB) frequently can exceed the discharge limits. Lab-scale optimisation of different possible physical-chemical treatment techniques was performed on the wastewater originating from three different companies in view of further testing at pilot-scale testing and implementation at full-scale. The lab-scale tests demonstrate that sedimentation or hydrocyclone treatment as stand-alone technique cannot be used for proper treatment of this type of wastewater. Dual bed filtration or coagulation/flocculation proved to be more promising with removal efficiencies of about 71-95% (dual bed filtration) and 61-97% (coagulation/flocculation) for the above-mentioned pollutants (metals, PAH and PCB).

Concentrations and Migratabilities of Hazardous Elements in Second-Hand Children's Plastic toys

About 200 second-hand plastic toys sourced in the UK have been analyzed by X-ray fluorescence spectrometry for hazardous elements (As, Ba, Cd, Cr, Hg, Pb, Sb, Se) and Br as a proxy for brominated flame retardants. Each element was detected in >20 toys or components thereof with the exception of As, Hg, and Se, with the frequent occurrence of Br, Cd, and Pb and at maximum concentrations of about 16000, 20000, and 5000 μg g^-1, respectively, of greatest concern from a potential exposure perspective. Migration was evaluated on components of 26 toys under simulated stomach conditions (0.07 M HCl) with subsequent analysis by inductively coupled plasma spectrometry. In eight cases, Cd or Pb exceeded their migration limits as stipulated by the current EU Toy Safety Directive (17 and 23 μg g^-1, respectively), with Cd released from yellow and red Lego bricks exceeding its limit by 1 order of magnitude. Two further cases were potentially noncompliant based on migratable Cr, with one item also containing >250 μg g^-1 migratable Br. While there is no retroactive regulation on second-hand toys, consumers should be aware that old, mouthable, plastic items may present a source of hazardous element exposure to infants.

Effect of temperature on copper, iron and lead leaching from e-waste using citrate solutions

E-waste is a potential source of large quantities of metals. The ability of citrate solutions to recover base metals from these materials has been demonstrated. In the present study, the effect of the temperature on base metal leaching capacity by the citrate solutions is determined. The material employed consisted of a mechanically prepared, gravity concentrated e-waste, with a metallic content greater than 90%. The leaching conditions were selected based on previous research performed by the authors (0.5 M sodium citrate, pH 4.5 and 20 g per liter e-waste concentrate). Leaching tests were performed at temperatures between 0° and 70 °C. The initial leaching rates for the three metals increased with temperature. However, these tapered off with time for temperatures above 30 °C, which can be associated to citrate destruction.

Recycling of indium from waste LCD: A promising non-crushing leaching with the aid of ultrasonic wave

The tremendous amount of end-of-life liquid crystal displays (LCDs) has become one of the prominent sources of waste electrical and electronic equipment (WEEE) in recent years. Despite the necessity of safe treatment, recycling indium is also a focus of waste LCD treatment because of the scarcity of indium. Based on the analyses of the structure of Indium Tin Oxide (ITO) glass, crushing is demonstrated to be not required. In the present research, a complete non-crushing leaching method was firstly adopted to recycle indium from waste LCDs, and the ultrasonic waves was applied in the leaching process. The results demonstrated that indium can be leached efficiently with even a low concentration of chloride acid (HCl) without extra heating. About 96.80% can be recovered in 60mins, when the ITO glass was leached by 0.8MHCl with an enhancement of 300W ultrasonic waves. The indium leaching process is abridged free from crushing, and proves to be of higher efficiency. In addition, the ultrasonic wave influence on leaching process was also explained combing with micron-scale structure of ITO glass.

The social benefits of WEEE re-use schemes. A cost benefit analysis for PCs in Spain

One goal of the new European legislation set out in WEEE Directive 2012/19/UE is the promotion of WEEE re-use schemes. However, some authors are rather sceptical about the contribution of WEEE re-use schemes to improve resource efficiency. In order to evaluate and to design adequate policy instruments, some authors recommend the cost-benefit analysis (CBA) as a compulsory first step. In this context, the main contribution of this paper is to enlarge the empirical literature by providing a CBA of re-use schemes versus recycling processes of PCs. The analysis is made for Spain by quantifying in monetary terms the social damages of environmental impacts such as climate change, human toxicity, particulate matter formation, metal depletion, etc. Our results suggest that promoting re-use against recycling (and consequently the need for manufacturing a new PC from raw materials) may reduce environmental costs by 45.20€ per PC. Those social benefits are mainly generated in the re-use preparation process and distribution activities, whereas the re-use scenario displays a worse performance in energy consumption. The difference in the distribution stage during the second life cycle originates from the fact that the ready to re-use product is produced locally, while the brand new product is manufactured and distributed from abroad, mainly Asia. These results provide valuable information to policymakers and think tanks willing to design support schemes for re-use over recycling operations.

Closed circuit recovery of copper, lead and iron from electronic waste with citrate solutions

An integral closed circuit hydrometallurgical process is presented for base metal recovery from electronic waste. The leaching medium consists of a sodium citrate solution, from which base metals are retrieved by direct electrowinning, and the barren solution is recycled back to the leaching stage. This leaching-electrowinning cycle was repeated four times. The redox properties of the fresh citrate solution, as well as the leach liquors, were characterized by cyclic voltammetry to determine adequate conditions for metal reduction, as well as to limit citrate degradation. The leaching efficiency of electronic waste, employing the same solution after four complete cycles was 71, 83 and 94% for copper, iron and lead, respectively, compared to the original leach with fresh citrate solution.

Toxicity assessment and feasible recycling process for amorphous silicon and CIS waste photovoltaic panels

End-of-Life (EoL) photovoltaic (P/V) modules, which are recently included in the 2012/19/EU recast, require sound and sustainable treatment. Under this perspective, this paper deals with 2nd generation P/V waste modules, known as thin-film, via applying chemical treatment techniques. Two different types of modules are examined: (i) tandem a-Si:H/μc-Si:H panel and, (ii) Copper-Indium-Selenide (CIS) panel. Panels' pretreatment includes collection, manual dismantling and shredding; pulverization and digestion are further conducted to identify their chemical composition. A variety of elements is determined in the samples leachates' after both microwave-assisted total digestion and Toxicity Characteristic Leaching Procedure (TCLP test) using Inductively Coupled Plasma Mass Spectroscopy (ICP-MS) analysis. The analysis reveals that several elements are detected in the two of panels, with no sample exceeds the TCLP test. Concentrations of precious and critical metals are also measured, which generates great incentives for recovery. Then, further experiments, for P/V recycling investigation, are presented using different acids or acid mixtures under a variety of temperatures and a stable S/L ratio, with or without agitation, in order to determine the optimal recycling conditions. The results verify that chemical treatment in P/V shredded samples is efficient since driving to ethylene-vinyl acetate (EVA) resin's dissolution, as well as valuable structural materials recovery (P/V glass, ribbons, cells, P/V intermediate layers). Among the solvents used, sulfuric acid and lactic acid demonstrate the most efficient and strongest performance on panels' treatment at gentle temperatures providing favorably low energy requirements.

Environmental impact assessment of different end-of-life LCD management strategies

The strong growth of the electrical and electronic equipment production combined with its short lifespan are causing the production of a significant amount of waste to treat. In particular, the present paper focuses on end-of-life liquid crystal displays (LCDs) for their significant content of valuable materials, like plastic, glass and metals that could be recovered after dismantling. In the recent literature, traditional LCD recycling processes are combined with innovative treatments, which allow to recover critical raw materials, such as indium. In this context, we have evaluated the environmental impact of four different strategies of end-of-life LCD management: the disposal in landfilling sites, the incineration, the traditional recycling treatment and an innovative process also addressed to the recovery of indium. The traditional recycling treatment resulted to be the best scenario for the environment. Indeed, a life cycle assessment study gave following environmental burdens (if negative they are credits): 18, 81, -68, -60kg CO₂-equiv. and 0.08, 0.01, -0.25, -0.18mol H⁺-equiv., for the four scenarios in the categories of global warming and acidification, respectively. The limit of the variability of LCD composition was overcome including additional literature data in the study. In order to improve the innovative process sustainability, a system of water recirculation was optimized with a consequent impact decrease of 35% in the global warming category. Nevertheless, this action should be combined with an increase of indium concentration in the panel because the low metal content represents the bottleneck of the overall approach. In this regard, a sensitivity analysis showed that an increase of at least five times in indium concentration in the waste is needed to observe an advantage of the innovative vs the traditional recycling process, when the impact category of climate change is considered. As a whole, the life cycle assessment was confirmed as a key tool for the choice of the best option of WEEE management.

Beneficiation and recovery of indium from liquid-crystal-display glass by hydrometallurgy

Considering indium scarcity, the end-of-life (EOL) LCD, which accounts for up to 90% of market share can be a feasible secondary resource upon successful recycling. In the preferred hydrometallurgical process of such critical metals, leaching is the essential primary and essential phase has been investigated. In this process, LCD was mechanically separated along with other parts from EOL TVs through a smartly engineered process developed at our institute, Institute for Advanced Engineering (IAE), the Republic of Korea. After removing plastics and metals from the LCD, it was mechanically shredded for size reduction. The mechanically shredded LCD waste was leached with HCl for recovery of indium. Possible leaching parameters such as; effect of acid concentration, pulp density, temperature and effect of oxidant H₂O₂ concentration were investigated to identify the best conditions for indium extraction. Indium (76.16×10^-3g/L) and tin (10.24×10^-3g/L) leaching was achieved at their optimum condition, i.e. lixiviant of 5M HCl, a pulp density of 500g/L, temperature 75°C, agitation speed of 400rpm and time for 120min. At optimum condition the glass, plastic and the valuable metal indium have completely been separated. From indium enriched leach liquor, indium can be purified and recovered through hydrometallurgy.

Two-step bioleaching of copper and gold from discarded printed circuit boards (PCB)

An effective strategy for environmentally sound biological recovery of copper and gold from discarded printed circuit boards (PCB) in a two-step bioleaching process was experimented. In the first step, chemolithotrophic acidophilic Acidithiobacillus ferrivorans and Acidithiobacillus thiooxidans were used. In the second step, cyanide-producing heterotrophic Pseudomonas fluorescens and Pseudomonas putida were used. Results showed that at a 1% pulp density (10g/L PCB concentration), 98.4% of the copper was bioleached by a mixture of A. ferrivorans and A. thiooxidans at pH 1.0-1.6 and ambient temperature (23±2°C) in 7days. A pure culture of P. putida (strain WCS361) produced 21.5 (±1.5)mg/L cyanide with 10g/L glycine as the substrate. This gold complexing agent was used in the subsequent bioleaching step using the Cu-leached (by A. ferrivorans and A. thiooxidans) PCB material, 44.0% of the gold was mobilized in alkaline conditions at pH 7.3-8.6, and 30°C in 2days. This study provided a proof-of-concept of a two-step approach in metal bioleaching from PCB, by bacterially produced lixiviants.

Recent development of recycling lead from scrap CRTs: A technological review

Cathode ray tubes (CRTs) contain numerous harmful substances with different functions. Lead is found in the funnel glass of CRTs. Improperly treated toxic lead may pose significant risks to human health and the environment. This paper reviews and summarizes existing technological processes on the recycling of lead from waste CRTs, including pyrometallurgy, hydrometallurgy, and product-regeneration. The present situation, advantages, and disadvantages of these techniques are described in detail. Generally, pyrometallurgy shows better practicability in recovery lead from waste CRT than hydrometallurgy and hydrometallurgy, in view of environmental impact, energy-consumption, product formats and safety and maturity of technology. Moreover, the gaps in the existing technologies were identified and recommendations for future research were provided.

Resource recovery from waste LCD panel by hydrothermal transformation of polarizer into organic acids

Based on the significant advantages of hydrothermal technology, it was applied to treat polarizer from the waste LCD panel with the aim of transforming it into organic acids (mainly acetic acid and lactic acid). Investigation was done to evaluate the effects of different factors on yields of organic acids, including the reaction temperature, reaction time and H2O2 supply, and the degradation process of polarizer was analyzed. Liquid samples were analyzed by GC/MS and HPLC, and solid-phase products were characterized by SEM and FTIR. Results showed that at the condition of temperature 300 °C and reaction time 5 min, the organic materials reached its highest conversion rate of 71.47% by adding 0.2 mL H2O2 and acetic acid was dominant in the products of organic acids with the yield of 6.78%. When not adding H2O2 to the system, the yields of lactic and acetic acid were respectively 4.24% and 3.80% at a nearly equal degree, they are suitable for esterification to form ethyl lactate instead of separating them for this case. In the hydrothermal process, polarizer was first decomposed to monosaccharides, alkane, etc., and then furfural and acids are produced with further decomposition.

Forecasting waste compositions: A case study on plastic waste of electronic display housings

Because of the rapid succession of technological developments, the architecture and material composition of many products used in daily life have drastically changed over the last decades. As a result, well-adjusted recycling technologies need to be developed and installed to cope with these evolutions. This is essential to guarantee continued access to materials and to reduce the ecological impact of our material consumption. However, limited information is currently available on the material composition of arising waste streams and even less on how these waste streams will evolve. Therefore, this paper presents a methodology to forecast trends in the material composition of waste streams. To demonstrate the applicability and value of the proposed methodology, it is applied to forecast the evolution of plastic housing waste from flat panel display (FPD) TVs, FPD monitors, cathode ray tube (CRT) TVs and CRT monitors. The results of the presented forecasts indicate that a wide variety of plastic types and additives, such as flame retardants, are found in housings of similar products. The presented case study demonstrates that the proposed methodology allows the identification of trends in the evolution of the material composition of waste streams. In addition, it is demonstrated that the recycling sector will need to adapt its processes to deal with the increasing complexity of plastics of end-of-life electronic displays while respecting relevant directives.

Mechanical pre-treatment of mobile phones and its effect on the Printed Circuit Assemblies (PCAs)

The recycling of Waste Electrical and Electronic Equipment (WEEE) has attracted a notable amount of interest during the last few decades due to the high metal concentrations and substantial increase in the growth rate of WEEE. In addition, higher recovery and recycling rates required by the European Union demand more comprehensive treatment of WEEE. However, complex product design and the presence of harmful substances together with low concentrations of special metals present challenges for processing. This study examines the effect of mechanical treatment of mobile phones on metal concentrations in the printed circuit assembly (PCA) fraction compared to manual dismantling. The designed mechanical treatment process including crushing, sieving, magnetic-, eddy current- and sensor-based separation was able to separate plastics, ferrous metals, PCA and stainless steel for further treatment. The process separated PCA with an efficiency of 85%. However, the quality of the separated PCAs was poor compared with "pure" manually dismantled PCAs. The primary crushing of mobile phones destroys PCAs thus resulting in the loss of especially precious metals used in the connector coatings and in the surface-mounted components. As a result, the theoretical value of the produced PCA fraction is only half compared to using manual dismantling. However, high labour costs in western countries and low capacity may hinder the feasibility of hand dismantling.

Leaching capacity of metals-metalloids and recovery of valuable materials from waste LCDs

The purpose of Directive 2012/19/EU which is related to WEEE (Waste Electrical and Electronic Equipment), also known as "e-waste", is to contribute to their sustainable production and consumption that would most possibly be achieved by their recovery, recycling and reuse. Under this perspective, the present study focused on the recovery of valuable materials, metals and metalloids from LCDs (Liquid Crystal Displays). Indium (In), arsenic (As) and stibium (Sb) were selected to be examined for their Leaching Capacity (R) from waste LCDs. Indium was selected mainly due to its rarity and preciousness, As due to its high toxicity and wide use in LCDs and Sb due to its recent application as arsenic's replacement to improve the optimal clarity of a LCD screen. The experimental procedure included disassembly of screens along with removal and recovery of polarizers via thermal shock, cutting, pulverization and digestion of the shredded material and finally leaching evaluation of the aforementioned elements. Leaching tests were conducted under various temperatures, using various solid:liquid (S/L) ratios and solvents (acid mixtures), to determine the optimal conditions for obtaining the maximum leaching capacities. The examined elements exhibited different leaching behaviors, mainly due to the considerable diversity in their inherent characteristic properties. Indium demonstrated the highest recovery percentages (approximately 60%), while the recovery of As and Sb was unsuccessful, obtaining poor leaching percentages (0.16% and 0.5%, respectively).

Comparative study on copper leaching from waste printed circuit boards by typical ionic liquid acids

Waste printed circuit boards (WPCBs) are attracting increasing concerns because the recovery of its content of valuable metallic resources is hampered by the presence of hazardous substances. In this study, we used ionic liquids (IL) to leach copper from WPCBs. [BSO3HPy]OTf, [BSO3HMIm]OTf, [BSO4HPy]HSO4, [BSO4HMim]HSO4 and [MIm]HSO4 were selected. Factors that affect copper leaching rate were investigated in detail and their leaching kinetics were also examined with the comparison of [Bmim]HSO4. The results showed that all six IL acids could successfully leach copper out, with near 100% recovery. WPCB particle size and leaching time had similar influences on copper leaching performance, while IL acid concentration, hydrogen peroxide addition, solid to liquid ratio, temperature, showed different influences. Moreover, IL acid with HSO4(-) was more efficient than IL acid with CF3SO3(-). These six IL acids indicate a similar behavior with common inorganic acids, except temperature since copper leaching rate of some IL acids decreases with its increase. The results of leaching kinetics studies showed that diffusion plays a more important role than surface reaction, whereas copper leaching by inorganic acids is usually controlled by surface reaction. This innovation provides a new option for recovering valuable materials such as copper from WPCBs.

An investigation of used electronics return flows: a data-driven approach to capture and predict consumers storage and utilization behavior

Consumers often have a tendency to store their used, old or un-functional electronics for a period of time before they discard them and return them back to the waste stream. This behavior increases the obsolescence rate of used still-functional products leading to lower profitability that could be resulted out of End-of-Use (EOU) treatments such as reuse, upgrade, and refurbishment. These types of behaviors are influenced by several product and consumer-related factors such as consumers' traits and lifestyles, technology evolution, product design features, product market value, and pro-environmental stimuli. Better understanding of different groups of consumers, their utilization and storage behavior and the connection of these behaviors with product design features helps Original Equipment Manufacturers (OEMs) and recycling and recovery industry to better overcome the challenges resulting from the undesirable storage of used products. This paper aims at providing insightful statistical analysis of Electronic Waste (e-waste) dynamic nature by studying the effects of design characteristics, brand and consumer type on the electronics usage time and end of use time-in-storage. A database consisting of 10,063 Hard Disk Drives (HDD) of used personal computers returned back to a remanufacturing facility located in Chicago, IL, USA during 2011-2013 has been selected as the base for this study. The results show that commercial consumers have stored computers more than household consumers regardless of brand and capacity factors. Moreover, a heterogeneous storage behavior is observed for different brands of HDDs regardless of capacity and consumer type factors. Finally, the storage behavior trends are projected for short-time forecasting and the storage times are precisely predicted by applying machine learning methods.

Leaching behaviour of different scrap materials at recovery and recycling companies: full-, pilot- and lab-scale investigation

Scrap material recovery and recycling companies are confronted with waste water that has a highly fluctuating flow rate and composition. Common pollutants, such as COD, nutrients and suspended solids, potentially toxic metals, polyaromatic hydrocarbons and poly chlorinated biphenyls can exceed the discharge limits. An analysis of the leaching behaviour of different scrap materials and scrap yard sweepings was performed at full-scale, pilot-scale and lab-scale in order to find possible preventive solutions for this waste water problem. The results of these leaching tests (with concentrations that frequently exceeded the Flemish discharge limits) showed the importance of regular sweeping campaigns at the company, leak proof or covered storage of specific scrap materials and oil/water separation on particular leachates. The particulate versus dissolved fraction was also studied for the pollutants. For example, up to 98% of the polyaromatic hydrocarbons, poly chlorinated biphenyls and some metals were in the particulate form. This confirms the (potential) applicability of sedimentation and filtration techniques for the treatment of the majority of the leachates, and as such the rainwater run-off as a whole.