Leaching of metals from printed circuit boards using ionic liquids

Abstract

The rise in the electronics industry has impacted the environment through the large volumes of waste that are improperly disposed of and the growing demand for precious and rare metals from natural sources. Leaching of copper, cobalt, gold, and silver from printed circuit boards of waste cellular phone has been carried out using imidazolium cation-based ionic liquids (ILs). For the studied metals, the obtaining of selective leaching obtained is reported for the first time, where acidic ionic liquids ([Bmim]HSO 4 and [Hmim]HSO 4 ) leached copper and cobalt, while basic ionic liquids ([Bmim]Cl and [Bmim]Br) extracted gold and silver. The effect of temperature has been studied by testing at 60 and 80 °C, where the highest extraction was obtained at the lowest temperature. The concentration of the ionic liquid was also studied through a test without ionic liquid and then varying from 20 to 60%, where at higher concentration the extraction is more efficient ratifying the use of ionic liquids as leaching solutions for metals. Ionic liquids have demonstrated the ability to leach metal ions as the primary reagent in the leaching solution. The following extraction percentages were obtained for each metal: 86.2% copper, 99.5% cobalt, 40.8% gold, and 44.6% silver.

Environmentally friendly ionic liquid medium based on dicyanamide anion for leaching gold from e‐waste CPUs by iodination

“…A large amount of Cu(II) (approximately 550 mg on average) was leached from e‐waste by [HSO 4 − ] ILs using a 0.5 M leaching solution with the addition of H 2 O 2 , and the concentration of Cu(II) was approximately 10 mg/dm 3 30 . A process for leaching copper (86.2%), cobalt (99.5%), gold (40.8%), and silver (44.6%) from printed circuit boards using imidazolium‐cation‐based ILs ([Bmim]HSO 4 , [Hmim]HSO 4 , [Bmim]Cl, and [Bmim]Br) was also reported for the first time 31 . In addition, a novel technology was developed for the recovery of the precious metals platinum, palladium, rhodium, and gold from spent automotive catalysts by trihalide ILs, including [P 66614 ][Cl 3 ], [P 66614 ][Br 3 ], [P 66614 ][IBr 2 ], and [P 66614 ][I 3 ].…”

“…30 A process for leaching copper (86.2%), cobalt (99.5%), gold (40.8%), and silver (44.6%) from printed circuit boards using imidazolium-cation-based ILs ([Bmim]HSO 4 , [Hmim]HSO 4 , [Bmim]Cl, and [Bmim]Br) was also reported for the first time. 31 ] at a ratio of 50 mg•mL −1 and stirring at 300 rpm at 22.5 °C, the palladium concentration was selectively recovered to 58 ppm after 2 h. 32 Notably, ILs can be regenerated and reused, and their use is considered an environmentally friendly method for recovering metals from ewaste. 33 Abbott et al 34 investigated the selective oxidation and sequential recovery of Cu/Zn mixture components with iodine in a deep eutectic solvent (DES) IL.…”

Thiourea leaching of gold from processed municipal solid waste incineration residues

“…Therefore, over the past decades there have been several attempts to recover Au from secondary materials through leaching techniques using aqua regia, cyanide, ionic liquids, thiosulfate, or thiourea as lixiviants [27,30,68]. Among these commonly used lixiviants, thiourea is relatively effective in Au mobilization whilst having the least negative impacts on the environment [68,83,84]. Indeed, the application of different thiourea-based leaching systems is usually accompanied by a high yield of mobilized Au.…”

“…Thus more than 80% of Au can be mobilized by thiourea leaching from such wastes as activated carbon (2.9 µg/g of Au) [85], wastes of amalgamation and cyaniding processes (1.7-8.5 µg/g of Au) [86], and Cu smelting slag (0.44-0.46 µg/g of Au) [87]. Furthermore, thiourea-based leaching systems are often used for extraction of Au from electronic wastes [14,68,76,83,84,88,89]. For example, more than 90% of Au can be leached from dust generated during processing of electronic waste (141 µg/g of Au) or printed circuit boards (PCBs) (43 µg/g of Au) [88,89].…”

Leaching of Copper Contained in Waste Printed Circuit Boards, Using the Thiosulfate—Oxygen System: A Kinetic Approach

“…Acidic leaching solutions have led to the recovery of Cu, with interesting results. Some researchers have used nitric acid and obtained recoveries of up to 99.9% without dissolution of the gold involved and also using oxidants such as ozone or H 2 O 2 [ 32 , 33 , 34 , 35 ]. Others have used sulfuric and hydrochloric acids to recover Cu from WPCBs and have had adequate results [ 36 , 37 , 38 ].…”