Recovery Of Base Metals Research Articles

Utilisation of acid-tolerant bacteria for base metal recovery under strongly acidic conditions.

Hydrometallurgical bioprocesses for base metal recovery in environmentally friendly electronic device waste (e-waste) recycling are typically studied under neutral pH conditions to avoid competition between metals and hydrogen ions. However, metal leachate is generally strongly acidic, thus necessitating a neutralisation process in the application of these bioprocesses to e-waste recycling. To solve this pH disparity, we focused on acid-tolerant bacteria for metal recovery under strongly acidic conditions. Four acid-tolerant bacterial strains were isolated from neutral pH environments to recover base metals from simulated waste metal leachate (pH 1.5, containing 100 or 1000 mg L-1 of Co, Cu, Li, Mn, and Ni) without neutralisation. The laboratory setting for sequential metal recovery was established using these strains and a reported metal-adsorbing bacterium, Micrococcus luteus JCM1464. The metal species were successfully recovered from 100 mg L-1 metal mixtures at the following rates: Co (8.95%), Cu (21.23%), Li (5.49%), Mn (13.18%), and Ni (9.91%). From 1000 mg L-1 metal mixtures, Co (7.23%), Cu (6.82%), Li (5.85%), Mn (7.64%), and Ni (7.52%) were recovered. These results indicated the amenability of acid-tolerant bacteria to environmentally friendly base metal recycling, contributing to the development of novel industrial application of the beneficial but unutilised bioresource comprising acid-tolerant bacteria.

Leaching of base metals in PCBs and copper cementation by iron powder

When dealing with electronic waste, printed circuit boards (PCBs) are some of the most important materials in terms of recovery possibilities, because of their high content of precious metals and base metals, notably copper (> 20% w/w), in addition to organic resins and ceramic materials. Efficient hydrometallurgical metals recovery from electronic waste is an important on-going research topic, and the present study consisted in the development of a process for the concentration of precious metals by leaching and recovery of major base metals mainly copper.A fraction of crushed PCBs concentrated in metals with more than 50 % copper was used for the leaching tests for two types of components: processor cards and mobile phone cards. For the leaching process, two steps were carried out. A first step consisted in leaching the concentrate three times with sulfuric acid and hydrogen peroxide, a second step consisted in lead removal by nitric acid leaching.The obtained results exhibit that, for processor cards, the first stage of leaching allowed the extraction of about 98 % of copper. Other base metals, zinc (99.8 %) and nickel (96 %) were also significantly leached. Precious metals were less leached except Ag with 88 % of release. The second stage of leaching with nitric acid allowed significant removal of lead (66 %). For mobile phone cards, the first stage of leaching led to an almost complete extraction of Cu (>98 %) and some other base metals (Fe, Ni, Sn, and Zn > 90 %). Al, Co and Mn were also extracted at 76 %, 78 % and 81 % respectively. Precious metals remained in the residue, except Pd which was leached at 16 %. The second stage of leaching with dilute nitric acid solution was not necessary for mobile phone cards, as it was responsible of an important Ag release from residue (80 %).

Multi-Objective Optimization of the Recovery of Base and Precious Metals from Waste Printed Circuit Boards by Two-Stage Hydrometallurgical Process Using Taguchi-Based Grey Relationship Analysis

This study focused on determining the optimum conditions for the maximum recovery of base and precious metals from printed circuit boards of end-of-life desktop computer motherboards using Taguchi-based grey relation analysis. In the first stage of the two-stage study, optimum conditions were investigated for the dissolution of base metals (copper and zinc) in waste printed circuit boards under high-pressure leaching. The dissolution of base metals was performed based on the L25 orthogonal array designed by Taguchi method. In the second step, designed according to Taguchi L9 orthogonal array to recover gold and silver from the solid remaining from the pressure-leaching process. Optimum combinations of parameters in both stages were determined using the multi-criteria optimization technique grey relationship analysis. In the experiments carried out in the determined optimum combinations, 99.62% of copper, 98.76% of zinc, 99.15 of silver and 85.82% of gold in waste printed circuit boards were recovered.Graphical

The hydrometallurgical recovery of critical and valuable elements from WEEE shredding dust: Process effectiveness in a life cycle perspective

Waste electrical and electronic equipment (WEEE) recycling stands as a crucial opportunity to get critical resources while managing a waste stream in accordance with the circular economy principles. Recently, a two-step hydrometallurgical process has been successfully investigated to treat the dust originating from the mechanical processing of WEEE. The best operating conditions selected in this study were used to further investigate the recovery of precious metals and critical elements, achieving extraction yields of approximately 77.7 % and 53.1 %, respectively; base metals (i.e. aluminum, zinc, copper, ..) were also leached from dust up to 96 %. A life cycle approach was also applied to preliminary assess and compare the potential environmental impact of the proposed process with respect to the manufacturing process of the virgin material. The analysis focused on standard environmental indicators (i.e. global warming potential, acidification, …), human toxicity and eco-toxicty and a set of five different characterisation models for abiotic depletion of resources. Four scenarios, differing for allocation criteria (mass/economic) and the possible recovery of metals along with REEs, were compared. Among the recovered products, the greates potential benefits were found in the case of rare earth elements, in the scenario considering the complete recovery of base and precious metals and performing an economic allocation. Impacts on abiotic depletion and toxicity account for the highest benefits from maerial recovery. Nevertheless, the recovery of sulphuric acid would allow a further reduction also in other impacts, strengthening the potential competitiveness of REE recovery against the manufacturing of virgin materials.

Microbial immobilisation and adaptation to Cu2+ enhances microbial Fe2+ oxidation for bioleaching of printed circuit boards in the presence of mixed metal ions

A circular economy requires effective re-use of finite resources, such as metals from waste electrical and electronic equipment (WEEE). Bioleaching for extraction and recovery of base metals from printed circuit boards (PCBs) before recovering precious metals has potential to increase metal circularity. However, inhibition by base metals released from the PCBs and accumulated in PCB leachates on microbial Fe2+ oxidation, a critical bioleaching sub-process for Fe3+ regeneration, can limit this approach. Here, we explore the potential of microbial immobilisation on polyurethane foam (PUF) and adaptation to cupric ions to minimise inhibition by mixed metals released from PCBs, particularly zinc, nickel, and tin, and enhancing Fe2+ oxidation rates in PCB bioleaching systems. A mixed mesophilic culture dominant in Leptospirillum ferriphilum, Acidiplasma cupricumulans and Acidithiobacillus caldus was immobilised on PUF and adapted to 6 g/L Cu2+. Tolerance of Cu-adapted immobilised cells to the inhibitory metal ions Zn2+, Ni2+, and Sn2+, as individual (0–10 g/L) and mixed metal ions at concentrations typically leached from PCBs at solids loadings of 0–20% (mass/volume) was compared to that of non-adapted immobilised cells. Further, the impact of solutes from PCB leachates was evaluated. Inhibition by individual metal ions decreased in the order Sn2+ > Ni2+ > Zn2+. Inhibition of ferrous iron oxidation by mixed metal ions was synergistic with respect to individual metal ions. PCB leachates were more inhibitory than both mixed and individual metal ions even where metal concentration was low. Cu-adapted immobilised cells exhibited higher tolerance to increasing concentrations of inhibitory metal ions than non-adapted cells. These results are promising for the application of Cu-adapted cells in the bioleaching of PCBs and multi-metal concentrates.

A Comprehensive and Sustainable Recycling Process for Different Types of Blended End-of-Life Solar Panels: Leaching and Recovery of Valuable Base and Precious Metals and/or Elements

The production of photovoltaic modules is increasing to reduce greenhouse gas emissions. However, this results in a significant amount of waste at the end of their lifespan. Therefore, recycling these solar panels is important for environmental and economic reasons. However, collecting and separating crystalline silicon, cadmium telluride, and copper–indium–gallium–selenide panels can be challenging, especially in underdeveloped countries. The innovation in this work is the development of a process to recycle all solar panel waste. The dissolution of all metals through the leaching process is studied as the main step of the flowchart. In the first step of leaching, 98% of silver can be recovered by 0.5 M nitric acid. Then, the second and third step involves the use of glycine for base metal dissolution, followed by the leaching of valuable metals with hydrochloric acid. The effect of parameters such as the initial pH, acid concentration, solid/liquid ratio, and hydrogen peroxide concentration is studied. The results show that up to 100% of Cu, Pb, Sn, Zn, Cd, In, Ga, and Se can be recovered under optimal conditions. The optimal conditions for the dissolution of Cu, Zn, and Cd were a glycine concentration of 0.5 M, a temperature of 25 °C, a solid/liquid ratio of 10 gr/L, and 1% of hydrogen peroxide. The optimized glycine concentration for the leaching of lead and tin was 1.5 M. Indium and gallium were recovered at 100% by the use of 5 M hydrochloric acid, S/L ratio = 10 gr/L, and T = 45 °C. Separation of selenium and tellurium occurred using 0.5 M HCl at a temperature of 60 °C. Additionally, for the first time, a general outlook for the recycling of various end-of-life solar panels is suggested.

Techno-economic analysis of an integrated bio- and hydrometallurgical process for base and precious metal recovery from waste printed circuit boards

Electronic waste (e-waste) is one of the fastest-growing waste streams and is often referred to as an urban mine due to its high base and precious metal content. Printed circuit boards (PCBs) have been the focus of numerous studies investigating bio- and hydrometallurgical pathways to extract and recover metals of value. This study evaluated the economic feasibility of an integrated bio- and hydrometallurgical process for extracting and recovering base and precious metals from PCBs. The process consisted of collecting and processing PCBs, extracting and recovering base metals using biogenic sulfuric acid and ferric iron, and extracting and recovering precious metals using hydrometallurgical pathways. A preliminary techno-economic analysis (TEA) was conducted to examine the potential costs of a plant that can process 1,000 tons per year of PCBs in Australia. The key factors that influence the economic feasibility were identified, and the effects of various factors, such as process efficiencies and market conditions, on the plant's profitability were evaluated. This assessment provided insight into the economic aspects of the process and assisted in identifying critical research pathways. Based on this analysis, the proposed process is profitable under optimised conditions and can address many challenges associated with e-waste processing in Australia.

A comparative study on metal pollution from surface dust of informal and formal e-waste recycling sectors in national capital region of New Delhi and associated risk assessment

Electrical and electronic waste (e-waste) is considered as resource and secondary source of metals, and is being recycled for recovery of precious and base metals. But the processes of recycling and the waste generated during e-waste recycling in informal and formal sectors contribute toxic metals in to the environment. This work aimed to compare the environmental and health impacts of informal and formal e-waste recycling facilities at New Delhi and Bhiwadi Industrial area in India, respectively. Here, concentrations of Ba, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Sn, V, Zn, and Ag, and As in surface dust collected from informal and formal recycling sectors and their associated pollution, human health and ecological risk are presented. Metal concentrations were higher than the background levels in both sectors. Contamination factor (Cf), contamination degree (Cdeg), pollution load index (PLI), geo-accumulation index (Igeo) and enrichment factor (EnF) of metals indicated severe pollution levels in both sectors. However, contamination in informal sector was comparatively higher than the formal sector. Sampling sites in both sectors had very high ecological risk. Storage, dismantling/shredding and recycling techniques were contributors of metals in surface dust in formal sector whereas fumes deposition, re-suspension, and dried by-products during acid bath treatments were additional sources in informal sector. Metal pollution depends on metal(s), e-waste type(s) and recycling sector(s). Total non-carcinogenic health risk due to metals was 6.5E+00 and 6.0E+01 and 6.2E+00 and 5.5E+01 in adult and children in informal and formal sectors, respectively. Total carcinogenic risk was 3.3E-03 and 7.2E-03 in informal and formal sectors, respectively. Ingestion was major pathways of metals followed by dermal and inhalation and children were more prone to risk compared to adults. Formal sectors too cause metal pollution but to lesser degree compared to informal. More effective pollution control measures are required in formal sector to control environmental pollution.

Recovery of base and precious metals from scrap TV boards using zig-zag air separator

Waste of Electrical and Electronic Equipments (WEEE) is one of the fastest growing waste streams in the world. The treatment of WEEE with high content of precious metals (Au in particular) has received the most attention due to their high economic potential. The development of simple, environmentally friendly and cost-effective methods for the recovery of metals from “low-value” WEEE (e.g., <100 g/t Au) is important from the circular economy perspective. In this study, the separation of base (Cu) and precious (Ag) metals from scrap TV boards (STVBs) by using a zig-zag air separator was investigated. Size-reduced scrap STVBs (-1 mm) were subjected to separation tests after the removal of the fine fraction (-0.1 mm). The sized scrap material (-1 +0.1 mm) was determined to have a metal content of 15.4% Cu, 47 g/t Ag and 0.05% Fe, with no gold. In the air separation tests, the effect of air flow rate (4-16 m/s) on the recovery of metals was studied. Increasing the air flow rate resulted in low metal recoveries with concurrent high metal grades in the concentrate. Separation efficiency (%) calculations showed that the most efficient separation is obtained at the highest air flow rate of 16 m/s. At this flow rate, 15.4% of the material was recovered in the concentrate which contains 62.3% Cu and 198 g/t Ag with recoveries of 63.3% Cu and 73.9% Ag. The findings indicated that zig-zag air separators can be used to obtain a metal-rich fraction under suitable conditions of the flow regime.

Eco-friendly recovery of base and precious metals from waste printed circuit boards by step-wise glycine leaching: Process optimization, kinetics modeling, and comparative life cycle assessment

Glycine as a green alternative to cyanide for gold leaching is a promising reagent to put a curb on the environmental footprints of conventional hydrometallurgical processes. This work was designed to investigate the step-wise glycine leaching of the base and precious metals from waste printed circuit boards (WPCBs) as one of the most dominant and problematic e-wastes in today's world. Using response surface methodology, selective copper extraction reached 99.96% recovery at the optimum condition of 0.5 M glycine, 1% v/v H2O2, 20 g/l pulp density, and ambient temperature. Copper sulfide was then recovered from the leach solution via precipitation by sodium hydrosulfide. Gold leaching in the glycine + permanganate system was thoroughly studied with an emphasis on the process's kinetics mechanisms. It was revealed that gold leaching in the glycine and permanganate system starts with a rapid phase followed by a slower chemically controlled phase. At the optimum condition of 4 g/l glycine, 2 g/l potassium permanganate, and room temperature, 96.17% of the gold was selectively extracted. By using 3 g/L activated carbon, about 100% of the gold was separated from the leach solution. Comparative life cycle assessment revealed that in the proposed process, the main contributor to most of the environmental impact categories is glycine. Replacing the first step of glycine copper leaching with nitric acid can substantially reduce the environmental footprints of the process to a lower level than many other proposed recycling routes.

Evaluation of acid mine drainage (AMD) from tailings and their valorization by copper recovery

Recent investigations have found that the mining industry generates approximately 10 billion tons of tailings per year, tending towards doubling this amount by 2035. For this reason, a systematic method is needed to study acid mine drainage (AMD) potential, as well as determining the dissolution of potentially toxic elements (PTEs). Furthermore, the possible recovery of base or precious metals could transform the tailings into value-added materials. In the present investigation, the potential for the generation of acid mine drainage in a sample of mine tailings was evaluated, as well as an analysis of the dissolution of PTEs through a sequential extraction of appropriate chemical solutions with increasing strength of reactivity to identify base or precious metals that can be recovered through a metallurgical process consisting of leaching, solvent extraction and electrolysis, operating at moderate pressure and temperature. The results of this research showed that these tailings contain approximately 3.7% of pyrite occluded in silicates and therefore are not a high risk for generating acid drainage and PTEs dissolution. On the other hand, a process for obtaining metallic copper was proposed, which resulted in a leaching liquor with 1226 ppm using 0.21 M H2SO4 and a pulp density of 300 g/L. Solvent extraction in a single stage allowed the leach liquor to be concentrated at 9200 mg Cu/L, recovering the majority of the copper in metallic form by electrolysis.

Separation of base metals from reduction smelt-alloy of spent lithium-ion batteries by ferric sulfate leaching, cementation, solvent extraction and oxidative precipitation

We propose a hydrometallurgical process to recover Ni, Co, Cu, Mn, and Fe from ferric sulfate synthetic leaching solution whose composition was similar to the real leach liquor of spent lithium-ion batteries (LIBs). Copper(II) was completely separated by cementation with iron powder at room temperature for 20 min. Afterward, H2O2 was added to the raffinate to oxidize Fe(II) to Fe(III). Multi-stage cross-current extraction with 2.0 M D2EHPA and stripping with 60% aqua regia completely removed iron from the solution. The separation of Mn(II) over Co(II) and Ni(II) was carried out by oxidative precipitation, in which Mn(II) was oxidized to MnO2 at the molar ratio NaClO to Mn(II) of 4.0 at pH 3.0. Following this, most of Co(II) together with 11% of Ni(II) were coprecipitated from the Mn(II) free filtrate at the molar ratio of NaClO to Co(II) of 7.0. From the filtrate containing Ni(II) of pH 3.0, the Ni(II) ions were completely recovered using Na2C2O4 as a precipitant at the same molar ratio of oxalate to Ni(II). Continuous experiments at the optimum condition of each step verified that Cu(II), Fe(III), and Mn(II) were completely separated by cementation, solvent extraction, and oxidative precipitation. The proposed process for base metal recovery from spent LIBs offers several advantages, such as low energy requirements and products with high purity.

Enhanced selectivity of platinum group metals concentrates at Kola MMC’s chemical and metallurgical shop

An upgrade of the nickel refining circuit realized in 2019 by Kola MMC when the plant adopted an electrowinning process for extracting nickel from sulphate-chloride solutions resulting from chlorine dissolution of tube furnace nickel powder, led to a considerable decrease in the amount of nickel sludge generated. The latter is treated at the Chemical and Metallurgical Shop by liquid phase sulphation in the presence of sulphuric acid. Other materials containing precious metals are now used in the sulphation process. For example, the concentrate obtained as a result of flotation of the tube furnace nickel powder chlorine dissolution residue. The main purpose of sulphation is to obtain selective concentrates of platinum group metals. The products include platinum-palladium concentrate and a concentrate of concomitant metals that contains at least 20 % of rhodium. The qualitative and quantitative characteristics of the concentrates define the process to be applied, as well as the recovery of base metals during further refining. A change in the feedstock supplied to the Chemical and Metallurgical Shop affected the distribution of rhodium between the target concentrates leading to a greater loss of concomitant metals in the refining process. The high demand for platinum group metals at the global market, the drawbacks of the current process, as well as the new type of feedstock supplied created a need for the process parameters to be studied and adjusted. The paper examines the process flowsheet and looks at ways to raise the selectivity of the final products by means of liquid phase sulphation in the presence of sulphuric acid.Contributors to this paper include M. A. Lastochkina, who oversees the precious metals section at the Hydrometallurgical Laboratory of Gipronikel Institute.

Biohydrometallurgical Recovery of Metals from Waste Electronic Equipment: Current Status and Proposed Process

Electronic waste (e-waste) is an emerging health and environmental burden due to the toxic substances present within e-wastes. To address this burden, e-wastes contain various base, rare earth and noble metals, which can be recovered from these substances, thus serving as secondary sources of metals. Pyrometallurgical and hydrometallurgical processes have been developed to extract metals from e-waste. However, these techniques are energy-intensive and produce secondary wastes, which will add to the operating costs of the process. However, the biohydrometallurgical approach has been deemed as an eco-friendly, cost-effective, and environmentally friendly process that does not produce large quantities of secondary waste. However, research has focused chiefly on one-stage bioprocesses to recover the metals of interest and majorly on base metals recovery. Hence, this review proposes a two-stage bio-hydrometallurgical process where the first stage will consist of acidophilic iron and sulphur oxidising organisms to extract base metals, followed by the second stage which will consist of cyanide-producing organisms for the solubilisation of rare earth and precious metals. The solid waste residue that is produced from the system can be used in the synthesis of silica nanomaterials, which can be utilised for various applications.

Development of an integrated glycine-based process for base and precious metals recovery from waste printed circuit boards

The present study developed an integrated glycine-based process to recover metals from waste printed circuit boards at high solid contents (10–15%). A novel glycine-ammonia leaching was used to selectively extract >99% copper, >85% zinc and around 50% lead at room temperature. Ammonia played a key role, increasing the copper solubility in solution (>40 g/L), shortening leaching time from 72 to 24 h, and also acting as a pH modifier. The 2nd leaching step utilised cyanide-starved glycine where extractions of 70–90% for gold and silver, and >50% for palladium were obtained. The remaining metals from the previous steps were removed by ferric sulfuric acid leaching, with/without thiourea. In the presence of thiourea, 70–95% of remaining base and precious metals were removed. Overall, the metals with major economic value were all extracted at >99% for copper, >80% for gold, >90% for silver and >85% for palladium.

Comprehensive utilization of bauxite residue for simultaneous recovery of base metals and critical elements

The growing stockpiles of bauxite residue and associated environmental hazards require a sophisticated recycling system for complete utilization and value recovery. The current application is limited as a raw material for building and construction applications. Considering the association of multiple elements (Fe, Al, Si, Ca, Ti, V, Sc) within bauxite residue, metal extraction is of prime interest with respect to the economic value of the final product. The following study presents a hydrometallurgy-based process flowsheet for the sustainable recovery of base metals and critical elements within bauxite residue. Major elements present in bauxite residue are recovered as materials for industrial application, including high purity magnetite, alumina, titania, silica, and calcium carbonate. Trace elements are recovered in the liquid stream generated after the recovery of base metals.

Valorization of copper smelter slag through the recovery of metal values by a synergistic bioprocess system of bio‐flotation and bio‐leaching

AbstractSlag sample generated as solid waste from a copper plant in Southern Africa contains strategically important base metals like copper, nickel and cobalt. X‐ray diffraction and X‐ray fluorescence analysis confirmed the presence of fayalite (Fe2SiO4), silica (SiO2) and alumina (Al2O3) as the major mineral phases in the slag sample. The presence of alumina and silicate minerals in copper slag are the major obstacles in the recovery of base metals in mineral processing industries. The copper slag may be hazardous if abandoned to the environment but it may be a valuable resource if the metal values can be recovered. Hence, the present study focused on the application of a bio‐surfactant extracted from Lactobacillus fermentum bacterium as a bio‐collector in the flotation of the slag sample to reduce its silica and alumina content. Subsequently, the slag sample was subjected to bio‐leaching by Acidithiobacillus ferrooxidans bacterium for recovery of the metal values. Flotation batch experiments were conducted in 1 L scale Denver flotation cell and during the process, about 37.90% of silica and 22.82% alumina were removed from the slag sample. The findings from this study further revealed the effectiveness of the bio‐surfactant‐assisted flotation process on the bio‐leaching of base metals from the slag sample. Flotation of silica and alumina from the slag improved bio‐leaching performance and recovered about 74.0% of copper, 60.0% of nickel and 33.4% cobalt in the bio‐leaching process conducted at laboratory scale.

Recovery of Platinum Group Metals from Leach Solutions of Spent Catalytic Converters Using Custom-Made Resins

Platinum group metals (PGMs) play a key role in modern society as they find application in clean technologies and other high-tech equipment. Spent catalytic converters as a secondary resource contain higher PGM concentrations and the recovery of these metals via leaching is continuously being improved but efforts are also directed at the purification of individual metal ions. The study presents the recovery of PGMs, namely, rhodium (Rh), platinum (Pt) and palladium (Pd) as well as base metals, namely, zinc (Zn), nickel (Ni), iron (Fe), manganese (Mn) and chromium (Cr) using leachates from spent diesel and petrol catalytic converters. The largest amount of Pt was leached from the diesel catalytic converter while the petrol gave the highest amount of Pd when leached with aqua regia. Merrifield beads (M) were functionalized with triethylenetetramine (TETA), ethane-1,2-dithiol (SS) and bis((1H-benzimidazol-2-yl)methyl)sulfide (NSN) to form M-TETA, M-SS and M-NSN, respectively, for recovery of PGMs and base metals from the leach solutions. The adsorption and loading capacities of the PGMs and base metals were investigated using column studies at 1 M HCl concentration. The loading capacity was observed in the increasing order of Pd to be 64.93 mmol/g (M-SS), 177.07 mmol/g (M-NSN), and 192.0 mmol/g (M-TETA), respectively, from a petrol catalytic converter. The M-NSN beads also had a much higher loading capacity for Fe (489.55 mmol/g) compared to other base metals. The finding showed that functionalized Merrifield resins were effective for the simultaneous recovery of PGMs and base metals from spent catalytic converters.

Recovery of base and precious metals from PCBs (Printed Circuit Boards) in waste electrical and electronic equipment (WEEE)

Natural minerals are a powerful tool in politics when some have a major role in production. Its depletion is now a hot topic worldwide. Thus, the safety of the environment, natural surface water, groundwater and the protection of soils from chronic contamination by metallic and inorganic elements is a global concern. Indeed, industrialization and development have led to the generation of huge and varied amounts of waste, including electronic waste (e-waste), which is released into the environment. Although e-waste is classified as hazardous, most of it is not recycled and developed countries with strict environmental protection legislation send most of their e-waste to developing countries where regulations are lax. These electronic devices and components after being used are simply dumped into the environment due to lack of treatment and recycling strategy. As a result, they become a threat to the environment, ecosystems and humans. African countries are among the most vulnerable nations. But they are unfortunately ignored and underestimated. To date, there is no e-waste recycling unit (factory) in most African countries and mainly in the Republic of Benin. In response to this challenge, this study explored the different techniques used for the recycling of waste electrical/electronic equipment in order to develop a new environmentally friendly approach in future work, for the extraction and recycling of the usual and valuable metallic elements contained in electronic waste (printed circuit boards) released into the environment. For this purpose, a bibliographic research was carried out from 20 April to 16 October 2021. The results obtained allowed us to identify the advantages and disadvantages of existing recycling methods.

Recovery of base and precious metals from PCBs (Printed Circuit Boards) in waste electrical and electronic equipment (WEEE)

Recovery of base and precious metals from PCBs (Printed Circuit Boards) in waste electrical and electronic equipment (WEEE)