Interference of coexisting copper and aluminum on the ammonium thiosulfate leaching of gold from printed circuit boards of waste mobile phones

Nowadays there is a wide variety of models, sizes and configurations of mobile phones available for consumption. After the life cycle of this equipment, the recycling and reuse of the precious metals found in the printed circuit boards (PCB) of the mobile phones are principal objectives. Thus, the objective of this work was to characterize the gold and silver present in a PCB and develop a recycling route using alternative reagents for cyanide, such as sodium and ammonium thiosulfate. These reagents are less harmful to the environment and worker health. The first characterization of gold and silver was performed with aqua regia. The results show 86.26g Au/ton of PCBs and 123.85g Ag/ton of PCBs. The second characterization was performed with a commercial cyanide-based reagent and 112.02g Au/ton of PCBs and 26.13g Ag/ ton of PCBs were obtained. A leaching study with solutions based on thiosulfate was performed and an extraction of 9.02g Au/ton of PCBs and 33.88g Ag/ton of PCBs was obtained, compared to characterization results using a cyanide-based reagent.

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Recovery of high purity copper from waste printed circuit boards of mobile phones by slurry electrolysis with ammonia-ammonium system

Separation and Purification Technology ◽

10.1016/j.seppur.2021.119180 ◽

2021 ◽

pp. 119180

Author(s):

Jiqin Wang ◽

Shuyuan Chen ◽

Xiangfei Zeng ◽

Jinfeng Huang ◽

Qian Liang ◽

...

Keyword(s):

Mobile Phones ◽

High Purity ◽

Printed Circuit Boards ◽

Circuit Boards ◽

Printed Circuit ◽

Waste Printed Circuit Boards ◽

Purity Copper

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

Materials ◽

10.3390/ma14020362 ◽

2021 ◽

Vol 14 (2) ◽

pp. 362

Author(s):

Nicolò Maria Ippolito ◽

Franco Medici ◽

Loris Pietrelli ◽

Luigi Piga

Keyword(s):

Mobile Phones ◽

Printed Circuit Boards ◽

Acid Leaching ◽

Economic Feasibility ◽

Circuit Boards ◽

Gold Extraction ◽

Printed Circuit ◽

Solid Ratio ◽

Thiourea Complex ◽

Pre Treatment

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.

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