An Alkaline Glycine-Based Leach Process of Base and Precious Metals from Powdered Waste Printed Circuit Boards
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Electronic waste (E-waste) is accumulating rapidly globally and pose a significant environmental challenge. One of the ways to cover the cost of waste processing (in addition to reducing the costs associated with landfill) is through recovery of metals. In addition, toxic and dangerous metals can and must be removed prior to repurposing, incineration or pyrolysis of the plastic substrates. E-waste is usually either transported to landfills or processed by pyrometallurgical and hydrometallurgical processes. Recently, a number of hydrometallurgical approaches have been considered in metals recovery from different electronic components. In this study, glycine (amino acetic acid) or its salts is considered as a lixiviant in an alkaline environment for base and precious metals recovery from shredded and ground printed circuit boards (PCBs). It was found that alkaline glycine solutions selectively dissolve copper, zinc, and lead over precious metals. Gold and silver were then recovered in a subsequent leaching step using glycine and small amounts of cyanide (at starvation levels, implying no free cyanide is present). The leach system remains alkaline throughout both stages of processing. In the two-stage glycine leaching system, gold, silver, zinc, lead and copper recoveries were 92.1%, 85.3%, 98.5%, 89.8%, and 99.1% respectively. The recoveries of precious and base metals by direct cyanidation, single stage glycine–cyanide leaching, and ammonia leaching were lower than the recoveries of these metals using the two-stage glycine and glycine–cyanide systems.
KeywordsGlycine E-waste Printed circuit boards Leaching Metal recovery
The authors would like to thank Dr Hatem El-Borai at Vilytics Company, Egypt for providing the PCB powder and related details and information of the PCB production. Mr. Huan Li gratefully acknowledge the financial sponsorship by Curtin University and the China Scholarship Council (CSC). Curtin University funded the working costs of this research.
Compliance with Ethical Standards
Conflict of interest
Messrs Oraby and Eksteen are listed co-inventors on patents that includes the use of glycine in alkaline environments to leach precious and chalcophile metals from materials bearing these metals.
- 1.Wang, Z., Zhang, B., Guan, D.: Take responsibility for electronic-waste disposal. Nature 536, 4 (2016)Google Scholar
- 4.Lin, C., Chi, Y., Jin, Y.: Experimental study on treating waste printed circuit boards by molten salt oxidation. Waste Biomass Valori. 8:2523–2533 (2017).Google Scholar
- 5.Baldé, C.P., Forti, V., Gray, V., Kuehr, R., Stegmann, P.: The global e-waste monitor—2017. https://www.itu.int/en/ITU-D/Climate-Change/Documents/GEM%202017/Global-E-waste%20Monitor%202017%20.pdf Accessed 10 June 2018
- 9.Shuey, S., Vildal, E., Taylor, P.: Pyrometallurgical processing of electronic waste. In: SME Annual Meeting 2006, pp. 06–037Google Scholar
- 20.Ficeriová, J., Baláž, P., Gock, E.: Leaching of gold, silver and accompanying metals from circuit boards (PCBs) waste. Acta Montan. Slovaca 16(2), 128 (2011)Google Scholar
- 21.Montero, R., Guevara, A., Torre, E.: Recovery of gold, silver, copper and niobium from printed circuit boards using leaching column technique. J. Earth Sci. Eng. 2(10), 590 (2012)Google Scholar
- 23.Sahin, M., Akcil, A., Erust, C., Altynbek, S., Gahan, C.S., Tuncuk, A.: A potential alternative for precious metal recovery from e-waste: iodine leaching. Sep. Sci. Technol. 50(16), 2587–2595 (2015)Google Scholar
- 24.Oraby, E., Eksteen, J.: A process for precious metals recovery. PCT Patent, PCT/AU2014/000877 (2014).Google Scholar
- 33.Aliyu, H.N., Na'Aliya, J.: Potentiometric studies on essential metal (II) amino acid complexes. Int. Res. J. Pharm. Pharmacol. 2(2), 76–80 (2012)Google Scholar
- 34.Eksteen, J.J., Oraby, E.A., Lombard, L., Di Prinzio, L.: Leaching of cobalt bearing nickel sulfide and furnace converter mattes with alkaline glycine, and subsequent SX and IX. Paper presented at the Proceedings of ALTA Hydrometallurgy Conference 2018, Perth, Australia, 19–26 MayGoogle Scholar