Gold Recovery from PCBs with Thiosulfate as Complexing Agent

Abstract:

Waste of electrical and electronic equipment (WEEE) is the fastest growing advanced type of solid waste streams in the urban environment worldwide and contains interesting amounts of precious metals. Hydrometallurgical technique is fast emerging as preferred process for the recovery of a variety of metals due to its lower energy consume and lower smelter emissions than conventional pyrometallurgical processes. In this work, a hydrometallurgical process for the recovery of gold and silver from electronic scraps was studied. In place of cyanide, thiosulfate was chosen as complexing agent for gold. Thiosulfate leaching can be considered a non-toxic process and the gold dissolution rates can be faster than conventional cyanidation. The electronic scraps, obtained from “end of life” mobile phones, were crushed and pre-treated with nitric acid before the leaching. Different parameters were studied: concentration of thiosulfate, temperature and reaction time. Moreover, the use of ultrasound to assist the hydrometallurgical gold extraction was investigated, as its application in ores leaching shows a greater metals release in shorter time and the advantage of working at lower concentration of reagents and at lower temperature. In this work, the use of ultrasound allowed a higher recovery of the precious metals than conventional leaching in all the conditions studied (different concentrations of reagents, temperature and reaction time). Moreover, the studied process allowed also the recovery of the other metals present in the waste (Cu, Sn and Ag).

• Periodical: Materials Science Forum (Volume 879)
• Pages: 289-294
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.879.289
• Online since: November 2016
• Authors: Pietrogiovanni Cerchier*, Manuele Dabalà, Katya Brunelli
• Keywords: Electronic Scrap, Gold Recovery, Hydrometallurgy, Thiosulfate, Ultrasound

References

[1] P. Tanskanen, Electronics Waste: Recycling of Mobile Phones, Post-Consumer Waste Recycling and Optimal Production, Edited by Prof. Enri Damanhuri, (2012) 129-150.

DOI: 10.5772/31530

[2] E.Y. L Sum, The recovery of metals from electronic scrap, JOM 43 (1991) 53-61.

DOI: 10.1007/bf03220549

[3] J.E. Hoffmann, Recovering precious metals from electronic scrap, JOM 44 (1992) 43-48.

DOI: 10.1007/bf03222275

[4] K.M. Swamy, K.L. Narayana, Ultrasonically assisted leaching - Advances in Sonochemistry, ed. by Elsevier Science B.V., (2001) 141-179.

DOI: 10.1016/s1569-2868(01)80008-5

[5] J.L. Luque - García, M.D. Luque de Castro, Ultrasound: A powerful tool for leaching, Trends in Analytical Chemistry 22 (2003) 41-47.

DOI: 10.1016/s0165-9936(03)00102-x

[6] K.S. Suslick, The Chemical Effects of Ultrasound, Scientific American, 260, (1989) 80-86.

[7] M.D. Luque de Castro, F. Priego Capote, Analytical applications of ultrasound, ed. Elsevier B.V., (2007) 99-137.

[8] C. Abruzzese, P. Fornari, R. Massidda, F. Veglio, S. Ubaldini, Thiosulphate leaching for gold hydrometallurgy, Hydrometallurgy 39 (1995) 265-276.

DOI: 10.1016/0304-386x(95)00035-f

[9] G. Hilson, A.J. Monhenius, Alternative to cyanide in the gold mining industry: what prospects for the future?, Journal of cleaner production 14 (2006) 1158-1167.

DOI: 10.1016/j.jclepro.2004.09.005

[10] S. Orgul, U. Atalay, Reaction chemistry of gold in thiourea solution for a Turkish gold ore, Hydrometallurgy 62 (2002) 71-77.

DOI: 10.1016/s0304-386x(02)00136-6

[11] S. Syed, Recovery of gold from secondary sources, Hydrometallurgy 115 (2012) 30-51.

DOI: 10.1016/j.hydromet.2011.12.012

[12] M.G. Aylmore and D.M. Muir, Thiosulfate leaching of gold- a review, Minerals Engineering, 14 (20011) 35-174.

DOI: 10.1016/s0892-6875(00)00172-2

[13] R.K. Rath, N. Hiroyoshi, M. Tsunekawa, T. Hirajima, Ammoniacal thiosulphate leaching of gold ore, The European Journal of Mineral Processing and Environmental Protection 3 (2003) 344-352.

[14] A.C. Grosse, G.W. Dicinoski, M.J. Shaw, P.R. Haddad, Leaching and recovery of gold using ammoniacal thiosulfate leach liquors (a review), Hydrometallurgy 69 (2003) 1-21.

DOI: 10.1016/s0304-386x(02)00169-x

[15] K. Brunelli, P. Cerchier, G. Zanmarchi, M. Dabalà, Ultrasound assisted leaching process for precious metals recovery from solid municipal waste, European Conference of Metallurgy, Düsseldorf, June (2015).

[16] Harunobu Arima, Toyohisa Fujita, and Wan-Tai Yen, Gold Cementation from Ammonium Thiosulfate Solution by Zinc, Copper and Aluminium Powders, Materials Transactions 43 (2002) 485-493.

DOI: 10.2320/matertrans.43.485