Electrochemical Approaches for the Recovery of Metals from Electronic Waste: A Critical Review

Rai, Varun; Liu, Daobin; Xia, Dong; Jayaraman, Yamuna; Gabriel, Jean‐Christophe P.

doi:10.3390/recycling6030053

Cited by 65 publications

(35 citation statements)

References 133 publications

(156 reference statements)

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“…If, however, more purification or elemental separation must be performed, additional process steps are required such as: (i) chlorination using safer agents such as NH 4 Cl [220,221]; (ii) advanced leaching [222][223][224][225][226][227][228][229][230][231][232][233][234][235][236]; (iii) or even bioleaching using bacteria which avoids the use of strong acids [237]; (iv) hydrometallurgy (solid-liquid or liquid-liquid extraction) [15,210,[238][239][240][241][242][243][244]; as well as (v) electrodeposition at the reduction step, including in ionic liquids [245][246][247][248][249][250][251][252][253] and molten salts [254][255][256][257][258][259], with their wide electrochemical stability [260].…”

Section: Rare-earth Elementsmentioning

confidence: 99%

Dismantling of Printed Circuit Boards Enabling Electronic Components Sorting and Their Subsequent Treatment Open Improved Elemental Sustainability Opportunities

et al. 2021

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This critical review focuses on advanced recycling strategies to enable or increase recovery of chemical elements present in waste printed circuit boards (WPCBs). Conventional recycling involves manual removal of high value electronic components (ECs), followed by raw crushing of WPCBs, to recover main elements (by weight or value). All other elements remain unrecovered and end up highly diluted in post-processing wastes or ashes. To retrieve these elements, it is necessary to enrich the waste streams, which requires a change of paradigm in WPCB treatment: the disassembly of WPCBs combined with the sorting of ECs. This allows ECs to be separated by composition and to drastically increase chemical element concentration, thus making their recovery economically viable. In this report, we critically review state-of-the-art processes that dismantle and sort ECs, including some unpublished foresight from our laboratory work, which could be implemented in a recycling plant. We then identify research, business opportunities and associated advanced retrieval methods for those elements that can therefore be recovered, such as refractory metals (Ta, Nb, W, Mo), gallium, or lanthanides, or those, such as the platinum group elements, that can be recovered in a more environmentally friendly way than pyrometallurgy. The recovery methods can be directly tuned and adapted to the corresponding stream.

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Section: Rare-earth Elementsmentioning

confidence: 99%

Dismantling of Printed Circuit Boards Enabling Electronic Components Sorting and Their Subsequent Treatment Open Improved Elemental Sustainability Opportunities

et al. 2021

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“…The recovery of valuable metals from waste printed circuit boards, WPCBs is traditionally carried out using hydrometallurgy and pyrometallurgy with primary leaching with aqua regia, or other acids [ 1 , 2 , 3 ]. Electro-waste contains large amounts of valuable metals, such as copper, silver, palladium, nickel, aluminium, zinc, gold, iron, lead, and others [ 1 , 2 , 3 ]. It is well known that annually over 70 million tons of e-waste from various technological processes should be recycled based on pyrometallurgy, hydrometallurgy or solvometallurgy.…”

Section: Introductionmentioning

confidence: 99%

“…It is well known that annually over 70 million tons of e-waste from various technological processes should be recycled based on pyrometallurgy, hydrometallurgy or solvometallurgy. In hydrometallurgical processes, acid and alkaline leaching is generally employed to dissolve metals such as Cu, Au, Ag, and Pd from the spent e-waste [ 1 , 2 , 3 ]. Recent studies have proposed extraction with ionic liquids (ILs) by liquid-liquid extraction (LLE) and electrodeposition [ 4 ].…”

Section: Introductionmentioning

confidence: 99%

Recovery of Metals from Electronic Waste-Printed Circuit Boards by Ionic Liquids, DESs and Organophosphorous-Based Acid Extraction

et al. 2022

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The extraction of metals from waste printed circuit boards (WPCBs) with ionic liquids (ILs), Deep Eutectic Solvents (DESs) and organophosphorous-based acid (Cyanex 272) has been presented. The study was undertaken to assess the effectiveness of the application of the new leaching liquids, and the new method of extraction of metals from the leachate and the solid phase with or without the leaching process. Solvent extraction from the liquid leachate phase has been studied in detail with popular ILs, such as tetraoctylphosphonium bromide, {[P8,8,8,8][Br] and tributyltetradecylphosphonium chloride, [P4,4,4,14][Cl] using Aqueous Biphasic Systems (ABS) method. Trihexyltetradecylphosphonium bis(2,4,4-trimethylpentyl) phosphinate, [P6,6,6,14][Cyanex272], ([P6,6,6,14][BTMPP]), trihexyltetradecylphosphonium thiocyanate, [P6,6,6,14][SCN], methyltrioctylammonium chloride (Aliquat 336), as well as bis(2,4,4-trimethylpentyl)phosphinic acid (Cyanex 272) were also used in the extraction of metals from the leachate. Two DESs (1) {choline chloride + lactic acid, 1:2} and (2) {choline chloride + malonic acid, 1:1} were used in the extraction of metals from the solid phase. The extraction behavior of metals with DESs was compared with that performed with three new bi-functional ILs: didecyldimethylammonium salicylate, [N10,10,1,1][Sal], didecyldimethylammonium bis(2-ethylhexyl) phosphate, [N10,10,1,1][D2EHPA], and didecyldimethylammonium bis(2,4,4-trimethylpentyl) phosphinate, [N10,10,1,1][Cyanex272]. The [P6,6,6,14][Cyanex272]/toluene and (Cyanex 272 + diethyl phosphite ester) mixtures exhibited a high extraction efficiency of about 50–90% for different metal ions from the leachate. High extraction efficiency of about 90–100 wt% with the ABS method using the mixture {[P8,8,8,8][Br], or [P4,4,4,14][Cl] + NaCl + H2O2 + post-leaching liquid phase} was obtained. The DES 2 revealed the efficiency of copper extraction, ECu = 15.8 wt% and silver, EAg = 20.1 wt% at pH = 5 from the solid phase after the thermal pre-treatment and acid leaching. The solid phase extraction efficiency after thermal pre-treatment only was (ECu = 9.6 wt% and EAg = 14.2 wt%). The use of new bi-functional ILs did not improve the efficiency of the extraction of metal ions from the solid phase. Process factors such as solvent concentration, extraction additives, stripping and leaching methods, temperature, pH and liquid/solid as well as organic/water ratios were under control. For all the systems, the selectivity and distribution ratios were described. The proposed extraction processes can represent alternative paths in new technologies for recovering metals from electronic secondary waste.

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“…Considering the abundance of copper and precious metals in e-waste, which is higher than in ore deposits [6], the usual valorization methods are analogous to those in primary metal production, built on pyro-electro and/or hydrometallurgical bases [7]. The application and significance of the electrometallurgical approach in the production of metals from solution are given in a detailed review by Rai et al, emphasizing that there are limitations in e-waste processing due to the complexity of the material itself [8].…”

Section: Introductionmentioning

confidence: 99%

Influence of Electrolyte Impurities from E-Waste Electrorefining on Copper Extraction Recovery

Djokić

Radovanović

Nikolovski³

et al. 2021

Metals

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In order to reflect possible issues in future sole e-waste processing, an electrolyte of complex chemical composition reflecting system of sole e-waste processing was obtained by following a specially designed pyro-electrometallurgical method. The obtained non-standard electrolyte was further used for the purpose of comprehensive metal interference evaluation on the copper solvent extraction (SX) process. Optimization of the process included a variation of several process parameters, allowing determination of the effect of the most abundant and potentially the most influential impurities (Ni, Sn, Fe, and Zn) and 14 other trace elements. Moreover, comparing three commercial extractants of different active chelating groups, it was determined that branched aldoxime reagent is favorable for Cu extraction from the chemically complex system, as can be expected in future e-waste recycling. The results of this study showed that, under optimal conditions of 20 vol.% extractant concentration, feed pH 1.5, O/A ratio 3, and 10-min phase contact time, 88.1% of one stage Cu extraction was achieved. Co-extraction of the Fe, Zn, Ni, and Sn was under 8%, while Pb and trace elements were negligible. Optimal conditions (H2SO4 180 g/L, O/A = 2, and contact time 5 min) enabled 95.3% Cu stripping and under 6% of the most influential impurities. In addition, an impurity monitoring and distribution methodology enabled a better understanding and design of the process for the more efficient valorization of metals from e-waste.

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Electrochemical Approaches for the Recovery of Metals from Electronic Waste: A Critical Review

Cited by 65 publications

References 133 publications

Dismantling of Printed Circuit Boards Enabling Electronic Components Sorting and Their Subsequent Treatment Open Improved Elemental Sustainability Opportunities

Dismantling of Printed Circuit Boards Enabling Electronic Components Sorting and Their Subsequent Treatment Open Improved Elemental Sustainability Opportunities

Recovery of Metals from Electronic Waste-Printed Circuit Boards by Ionic Liquids, DESs and Organophosphorous-Based Acid Extraction

Influence of Electrolyte Impurities from E-Waste Electrorefining on Copper Extraction Recovery

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