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Waste printed circuit boards (WPCBs) are usually dismantled, crushed, and sorted to WPCB metal-enriched scraps, still containing an amount of non-metallic materials. This research used slurry electrolysis to refine these WPCB metal-enriched scraps and to examine if a standard ionic liquid, [MIm]HSO 4 , can replace H 2 SO 4 in the system. The impact of the refinement process on metal migration and transformation is discussed in detail. The results demonstrated that metals in WPCB metal-enriched scraps could be successfully refined using slurry electrolysis, and [MIm]HSO 4 can be used to replace H 2 SO 4 in the system. When 80% of H 2 SO 4 was replaced by [MIm]HSO 4 (electrolyte of 200 mL, 30 g/L CuSO 4 ·5H 2 O, 60 g/L NaCl, 130 g/L H 2 SO 4 , and 1.624 A for 4 h), the total metal recovery rate is 85%, and the purity, current efficiency, and particle size of cathode metal powder were 89%, 52%, and 3.77 μm, respectively. Moreover, the microstructure of the cathode metal powder was dendritic in the H 2 SO 4 -CuSO 4 -NaCl slurry electrolysis system, whereas at an 80% [MIm]HSO 4 substitution rate slurry electrolysis system, the cathode metal powder was irregular and accumulated as small-sized spherical particles. Thus, replacing inorganic leaching solvents with ionic liquids may provide a potential choice for the resources in WPCB metal-enriched scraps.

As an indispensable part of printed circuit boards (PCBs), central processing unit (CPU) slots contain a significant amount of precious metals which makes economic sense to recycle these materials. Slurry electrolysis is an attractive approach for electronic waste (e-waste) recycling. In this study, the effect of electrolyte reuse on the recovery of metals (Primarily aluminum, nickel, copper, lead, silver, palladium, platinum and gold), from waste CPU slots by slurry electrolysis is discussed in detail. These results show that metal recovery rate, more than 95% for all 13 cycles, was not affected by slurry electrolyte reuse during metal recycling from waste CPU slots, though the reuse of slurry electrolyte greatly impacted the distribution of metals in the anode residues, electrolyte and cathode metal powders. However, slurry electrolysis recovered metals from waste CPU slots and the effect of electrolyte reuse on the recovery of metals from waste CPU slots is discussed for the first time in this study. This could benefit the recycling process since it could improve cathode metal powders recovery rates by approximately 2 times. The acid usage could be significantly reduced by electrolyte reuse when compared to fresh electrolyte. Therefore, electrolyte reuse is demonstrated and slurry electrolysis is a feasible and potentially economically friendly choice for industrial e-waste recycling., (Copyright © 2019. Published by Elsevier Ltd.)

In this study, supercritical methanol (SCM) process was successfully used for the preparation of ultrafine copper materials from waste printed circuit boards (PCBs) after nitric acid pretreatment. Waste PCBs were pretreated twice in nitric acid. Sn and Pb were recovered by the first nitric acid pretreatment. The leach liquor with a high concentration of copper ions after the second nitric acid leaching was subjected to SCM process. The mixture of Cu and Cu 2 O with poor uniformity of particle size was formed due to the effect of ferric iron contained in the leach liquor of waste PCBs, while more uniform and spherical Cu particles with high monodispersity and smaller size could be prepared after the removal of Fe. The size of Cu particles increased obviously with the decline of SCM temperature, and particles became highly aggregated when the reaction temperature decreased to 300°C. The size of Cu particles decreased markedly with the decrease of initial concentration of copper ion in the leach liquor of waste PCBs. It is believed that the process developed in this study is simple and practical for the preparation of ultrafine copper materials from waste PCBs with the aim of recycling these waste resources as a high value-added product., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Rapid innovation in printed circuit board, and the uncertainties surrounding quantification of the human and environmental health impacts of e-waste disposal have made it difficult to confirm the influence of evolving e-waste management strategies and regulatory policies on materials. To assess these influences, we analyzed hazardous chemicals in a market-representative set of Waste printed circuit boards (WPCBs, 1996-2010). We used standard leaching tests to characterize hazard potential and USEtox® to project impacts on human health and ecosystem. The results demonstrate that command-and-control regulations have had minimal impacts on WPCBs composition and toxicity risks; whereas technological innovation may have been influenced more by resource conservation, including a declining trend in the use of precious metals such as gold. WPCBs remain classified as hazardous under U.S. and California laws because of excessive toxic metals. Lead poses the most significant risk for cancers; zinc for non-cancer diseases; copper had the largest potential impact on ecosystem quality. Among organics, acenaphthylene, the largest risk for cancers; naphthalene for non-cancer diseases; pyrene has the highest potential for ecotoxicological impacts. These findings support the need for stronger enforcement of international policies and technology innovation to implement the strategy of design-for-the-environment and to encourage recovery, recycling, and reuse of WPCBs., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

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., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

A number of efforts have been launched to solve the global electronic waste (e-waste) problem. The efficiency of e-waste recycling is subject to variable national legislation, technical capacity, consumer participation, and even detoxification. E-waste management activities result in procedural irregularities and risk disparities across national boundaries. We review these variables to reveal opportunities for research and policy to reduce the risks from accumulating e-waste and ineffective recycling. Full regulation and consumer participation should be controlled and reinforced to improve local e-waste system. Aiming at standardizing best practice, we alter and identify modular recycling process and infrastructure in eco-industrial parks that will be expectantly effective in countries and regions to handle the similar e-waste stream. Toxicity can be deleted through material substitution and detoxification during the life cycle of electronics. Based on the idea of "Control-Alt-Delete", four patterns of the way forward for global e-waste recycling are proposed to meet a variety of local situations.

Unlabelled: The plasma display panel (PDP) is rapidly becoming obsolete, contributing in large amounts to the electronic waste stream. In order to assess the potential for environmental pollution due to hazardous metals leached from PDP glass, standardized leaching procedures, chemical speciation assessments, and bioavailability tests were conducted. According to the Toxicity Characteristic Leaching Procedure (TCLP), arsenic in back glass was present at 4.46 ± 0.22 mg/L, close to its regulation limit of 5 mg/L. Zn is not available in the TCLP, but its TCLP leaching concentration in back glass is 102.96 ± 5.34 mg/L. This is because more than 90% of Zn is in the soluble and exchangeable and carbonate fraction. We did not detect significant levels of Ag, Ba, or Cu in the TCLP leachate, and the main fraction of Ag and Ba is residual, more than 95%, while the fraction distribution of Cu changes SEP by SEP. Ethylenediamine tetraacetic acid (EDTA)- and diethylenetriamine pentaacetic acid (DTPA)-extractable Ag, As, Ba, Cu, Zn, and Ni indicate a lower biohazards potential. These results show that, according to the EPA regulations, PDP glass may not be classified as hazardous waste because none of the metals exceeded their thresholds in PDP leachate. However, the concentrations of As and Zn should be lowered in the manufacturing process and finished product to avoid potential pollution problems., Implications: The plasma display panel is rapidly becoming obsolete because of the liquid crystal display. In this study, the leachability of heavy metals contained in the waste plasma display panel glass was first examined by standardized leaching tests, typical chemical speciation assessments, and bioavailability tests, providing fundamental data for waste PDP glass recovery, recycling, and reuse.

In this work, a Brønsted acidic ionic liquid, 1-butyl-3-methyl-imidazolium hydrogen sulfate ([bmim]HSO4), was used to leach copper from waste printed circuit boards (WPCBs, mounted with electronic components) for the first time, and the leaching behavior of copper was discussed in detail. The results showed that after the pre-treatment, the metal distributions were different with the particle size: Cu, Zn and Al increased with the increasing particle size; while Ni, Sn and Pb were in the contrary. And the particle size has significant influence on copper leaching rate. Copper leaching rate was higher than 99%, almost 100%, when 1g WPCBs powder was leached under the optimum conditions: particle size of 0.1-0.25 mm, 25 mL 80% (v/v) ionic liquid, 10 mL 30% hydrogen peroxide, solid/liquid ratio of 1/25, 70°C and 2h. Copper leaching by [bmim]HSO4 can be modeled with the shrinking core model, controlled by diffusion through a solid product layer, and the kinetic apparent activation energy has been calculated to be 25.36 kJ/mol., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Waste printed circuit boards (WPCBs) are resource-rich but hazardous, demanding innovative strategies for post-consumer collection, recycling, and mining for economically precious constituents. A novel technology for disassembling electronic components from WPCBs is proposed, using hot air to melt solders and to separate the components and base boards. An automatic heated-air disassembling equipment was designed to operate at a heating source temperature at a maximum of 260 °C and an inlet pressure of 0.5 MPa. A total of 13 individual WPCBs were subjected to disassembling tests at different preheat temperatures in increments of 20 °C between 80 and 160 °C, heating source temperatures ranging from 220 to 300 °C in increments of 20 °C, and incubation periods of 1, 2, 4, 6, or 8 min. For each experimental treatment, the disassembly efficiency was calculated as the ratio of electronic components released from the board to the total number of its original components. The optimal preheat temperature, heating source temperature, and incubation period to disassemble intact components were 120 °C, 260 °C, and 2 min, respectively. The disassembly rate of small surface mount components (side length ≤ 3 mm) was 40-50% lower than that of other surface mount components and pin through hole components. On the basis of these results, a reproducible and sustainable industrial ecological protocol using steam produced by industrial exhaust heat coupled to electronic-waste recycling is proposed, providing an efficient, promising, and green method for both electronic component recovery and industrial exhaust heat reutilization.

Rapid innovation in printed circuit board, and the uncertainties surrounding quantification of the human and environmental health impacts of e-waste disposal have made it difficult to confirm the influence of evolving e-waste management strategies and regulatory policies on materials. To assess these influences, we analyzed hazardous chemicals in a market-representative set of Waste printed circuit boards (WPCBs, 1996-2010). We used standard leaching tests to characterize hazard potential and USEtox® to project impacts on human health and ecosystem. The results demonstrate that command-and-control regulations have had minimal impacts on WPCBs composition and toxicity risks; whereas technological innovation may have been influenced more by resource conservation, including a declining trend in the use of precious metals such as gold. WPCBs remain classified as hazardous under U.S. and California laws because of excessive toxic metals. Lead poses the most significant risk for cancers; zinc for non-cancer diseases; copper had the largest potential impact on ecosystem quality. Among organics, acenaphthylene, the largest risk for cancers; naphthalene for non-cancer diseases; pyrene has the highest potential for ecotoxicological impacts. These findings support the need for stronger enforcement of international policies and technology innovation to implement the strategy of design-for-the-environment and to encourage recovery, recycling, and reuse of WPCBs.

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.

Due to rapid innovation in electronic industries, the average lifetime of electronic devices has been shortening drastically, leading to a massive electronic waste production (E-waste). As an essential part of E-waste, waste printed circuit boards (WPCBs) attract considerable concerns to seek a green and cost-effective recycling approach. In this study, a green chemical, [BSO 3 HPy]HSO 4 , was used to replace H 2 SO 4 in a slurry electrolytic system in order to recover valuable metal copper from WPCBs in one-step. The results indicate that as more H 2 SO 4 is replaced by [BSO 3 HPy]HSO 4 , copper recovery rate and current efficiency first increased and then decreased, while copper powders purity showed a reverse tendency: increases first and then decreases. The substitution of H 2 SO 4 by [BSO 3 HPy]HSO 4 could effectively reduce the particle size of the obtained powders. When 10% H 2 SO 4 was replaced by [BSO 3 HPy]HSO 4 , the recovery rate, current efficiency, purity and particle size of copper powders were 90.94%, 70.68%, 81.69% and 2.30 μm, respectively, thus reaching an optimal level. XRD results show that elemental Cu was the main mineral phase in the obtained powders. SEM and TEM results indicate that copper powders obtained in H 2 SO 4 -slurry-electrolysis system is dendritic and polycrystalline, whereas those obtained in an electrolytic solution with [BSO 3 HPy]HSO 4 were in form of scattered monocrystalline particles. [ABSTRACT FROM AUTHOR]

Waste Electrical and Electronic Equipment (WEEE) contain toxic metals and organic compounds, posing significant threats to human health and environmental quality. The risks vary according to equipment types and components that are influenced by innovations in technical configuration and regulatory policy. To disentangle the relative impacts of these influences in protecting health and environment, we investigated 13 WEEE and 14 components using a life cycle impact assessment procedure. Additionally, we analyzed Waste Mobile Phones (WMPs) and Waste Printed Circuit Boards (WPCBs) from computers manufactured between 2002 and 2010 to identify trends of toxic chemicals and potential adverse impacts associated with technological configurations and regulatory policies. The results show that, among WEEE, Cathode Ray Tube TV presented the highest carcinogenicity and non-carcinogenicity toxicity potential. Waste Air Conditioner posed the highest potential for ecotoxicity. Among electronic components, Waste Organic Light Emitting Diode displays posed the highest potential risk for carcinogenesis, whereas WPCBs from laptop computers posed the highest potential risk for non-cancer diseases. Solid State Drives posed the highest risks for ecotoxicity. Chromium was associated with risk of carcinogenesis and non-cancer diseases; whereas Al and Fe posed the highest potential for ecotoxicological impacts. During the period covered by the study, innovations in technological configurations and regulatory policies demonstrably reduced the potential toxicity risks posed by E-waste, attributable to reduction in the concentrations of toxic organic chemicals in WMPs/WPCBs. These results advance current understanding of strategies to reduce the risks posed by WEEE through coordination of technological innovations and regulatory policies. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Waste printed circuit boards (WPCBs) are considered as the most complicated and valuable component among e-waste. Slurry electrolysis can separate and recover metals from the extremely complex WPCBs. To promote its industrial application, a 5000 mL scale experiment was conducted to confirm industrial feasibility. Those results showed that copper and total metal recovery rates were 94.5 % and 75.2 % under the optimized conditions (30 g/L WPCBs, 10 g/L CuSO 4 ·5H 2 O, 30 g/L NaCl, 190 g/L H 2 SO 4 , 30 g/L H 2 O 2 , 298 K temperature, 250 r/min stirring speed, 300 A/m2 and 8 h). The copper purity was 92.9 %, and SEM-EDS analyses indicated the main dendritic metals recovered were copper and lead. USEtox toxicity potential evaluation results demonstrated human toxicity and ecotoxicity of WPCBs sharply decreased after treatment. A cost analysis of this process indicated that the $ 1.0 cost was partially offset by the $ 1.9 return from 1 kg WPCBs. Thus, slurry electrolysis has a promising industrial future for e-waste recycling/utilization. [ABSTRACT FROM AUTHOR]

Completely separating and recovering metals and nonmetals from waste printed circuit boards (WPCBs) is key to e-waste recycling. Here we proposed a novel approach, slurry or suspension electrolysis, to separate metals and nonmetals from WPCBs. The factors that impact the separation rate during the slurry electrolysis were discussed in detail. The results indicate that CuSO 4 ·5H 2 O, NaCl, H 2 SO 4 , WPCBs dosage, current and time could impact metals separating from WPCBs. Increasing NaCl and H 2 SO 4 concentration and extending electrolysis time could effectively increase the metal and nonmetal separation rate, while increasing WPCBs dosage and current have negative impacts on the metal and nonmetal separation rate. Slurry electrolysis could directly and completely separate and recover metals from WPCBs with a separation rate up to 97.79% under the conditions of 3 g WPCBs dosage in 100 mL electrolyte, 30 g/L CuSO 4 ·5H 2 O, 40 g/L NaCl, 150 g/L H 2 SO 4 , 0.5 A and 9 h. The separated micro-metal powders are mainly Cu, about 86.6%, without any nonmetal powders. Copper recovered is dendritic, with a copper recovery rate up to nearly 99%. Thus, slurry electrolysis shows a prospective future in e-waste reutilization, providing a way to enrich metals for all kinds of urban mines. [ABSTRACT FROM AUTHOR]

[Display omitted] • High-purity copper could be recovered from WPCB-MPs by ammonia slurry electrolysis. • Both copper current efficiency and recovery rate are higher than 90%. • Copper could be directly recovered at the cathode with a purity of 99.97%. Waste printed circuit boards (WPCBs) are identified to be the most complex recycling materials among waste electrical and electronic equipment (WEEE). Slurry electrolysis with acidic system can directly separate and recover copper from WPCBs while current efficiency and purity were generally reduced due to deposition of impurity metals and the hydrogen evolution during recovery process. In ammonia-based system, copper can be selectively extracted and copper (II) ammine complexes generally react with metallic copper to form copper (I) ammine complexes, promoting current efficiency and purity. Therefore, an efficient ammonia-ammonium carbonate slurry electrolysis system is proposed for high purity copper recycling from waste printed circuit boards of mobile phones (WPCB-MPs). The factors affecting copper current efficiency and recovery rate are systematically discussed. These results indicate that appropriate increasing NH 3 ·H 2 O, (NH 4) 2 CO 3 , Cu2+, NaCl concentration, solid-to-liquid ratio, current density and reaction time could effectively increase copper recovery rate and current efficiency. The current efficiency and recovery rate of copper are 95.2 and 90.4%, respectively under the optimum test conditions of 20 g/L Cu2+, 0.25 mol/L (NH 4) 2 CO 3 , 4 mol/L NH 3 ·H 2 O, 30 g/L solid-to-liquid ratio, 1 mol/L NaCl, 20 mA/cm2, 3 h. Moreover, copper could be recovered at the cathode with a purity of 99.97%. Compared with acidic system, this study provides an efficient approach to recover high purity copper from WPCB-MPs, showing a prospective future for WEEE resource recycling. [ABSTRACT FROM AUTHOR]