Effect of Acid Leaching Pre-Treatment on Gold Extraction from Printed Circuit Boards of Spent Mobile Phones

Abstract

The effect of a preliminary acid leaching for the recovery of gold by thiourea from printed circuit boards (PCBs) of spent mobile phones, was investigated. Preliminary leaching is aimed to recover copper in the leachate that would compete with gold in the successive leaching of the residue with thiourea, thus preventing the formation of the gold-thiourea complex. Two hydrometallurgical routes were tested for the recovery of copper first, and gold after. The first one was based on a two-step leaching that utilizes sulfuric acid and hydrogen peroxide in the preliminary leaching and then thiourea for the recovery of gold in the successive leaching: A copper and gold recovery of 81% and 79% were obtained, respectively. In the second route, nitric acid was used: 100% of copper was recovered in the leachate and 85% of gold in the thiourea successive leaching. The main operative parameters, namely thiourea and ferric sulphate concentrations, leach time, liquid-solid ratio, and temperature were studied according to a factorial plan strategy. A flowsheet of the processes was proposed, and a mass balance of both routes was obtained. Finally, qualitative considerations on the technical and economic feasibility of the different routes were made.

Simultaneous Recovery of Precious and Heavy Metal Ions from Waste Electrical and Electronic Equipment (WEEE) Using Polymer Films Containing Cyphos IL 101

“…It is also important that in the described procedure of preparing e-waste samples for metals ion recovery, there is no need to use complex pre-treatments. For example, one alternative non-contaminating reagent used for gold leaching is thiourea [ 42 ], but as reported by Ippolito et al [ 43 ], recovering gold from printed circuit boards or spent cell phones “as is” for thiourea leaching was not feasible due to the low Au grade release and recovery of only 15%. Direct leaching of thiourea onto the plate failed due to the competition between copper and gold for thiourea to form the corresponding complexes.…”

Recovery of Metals from Heat-Treated Printed Circuit Boards via an Enhanced Gravity Concentrator and High-Gradient Magnetic Separator

“…The bare PCB is composed of metals, woven glass fiber and flame retardant [ 6 , 7 ], especially, as some metals are more abundant than in raw material sources [ 8 , 9 ], PCB recovery is called “urban mining” [ 10 , 11 ]. This is exemplified by studies showing that the copper content in PCBs is about 20%, much higher than the 0.2–0.7% found in copper ore [ 12 , 13 , 14 ].…”

Batch Reactor vs. Microreactor System for Efficient AuNP Deposition on Activated Carbon Fibers

“…The carbon fibers were selected for their high chemical resistance and easy separation from the solution. In addition, gold deposited on the carbon surface can be recovered by hydrometallurgical methods such as the leaching process used in the recycling sector [ 19 ].…”