Silver, gold and palladium leaching from electronic scrap using bromine- bromide solution
DOI:
https://doi.org/10.31643/2019/6445.36Keywords:
gold hydrometallurgy, computer scrap, thermodynamics and kinetics of noble metal dissolution with bromine, phosphate buffer solution.Abstract
This study investigated the thermodynamics and kinetics of gold and accompanying noble metals, such as silver, palladium and platinum, leached from the electronic scrap by bromine-bromide solutions. Theoretical and practical analysis of the behavior of gold in the traditional Br2 - Br- - H2O system confirmed the fact that in a neutral and slightly acidic medium, when bromine hydrolysis proceeds slightly, a bromine in bromide solution can be used to leach gold. In this case, bromine-bromide leaching compared with cyanidation is more favorable in terms of kinetics and selectivity. In particular, when brominated in a neutral medium as a result of the formation of a passivating copper monovalent copper (Cu2O) film on the surface of copper particles, copper does not go into solution, while copper forms stable soluble anionic complexes with cyanide. For the first time in order to stabilize the pH in the alkaline area the conditions for gold leaching in the presence of a phosphate buffer solution (NaH2PO4) were investigated. The effect of the pH of the leach solution, the concentration of active bromine, bromide ions and the concentration of the buffer solution on the leaching kinetics of gold was studied. It was established experimentally that a noticeable dissolution of gold begins at pH ≤ 8, and at pH 6, almost all gold passes into the solution. A sufficient concentration of active bromine under these conditions can be considered 6.6 g · dm-3 Br2 at a bromide concentration of 20 g · dm-3 NaBr. Leaching with the productive solution turnover made it possible to reduce the consumption of bromine from 89-95 to 20-32 kg Br2 per ton of scrap and raise the concentration of gold from 76 to 195 mg · dm-3. In this paper, it was first shown that silver and palladium in the system under study (pH = 5-6) begin to dissolve noticeably only at high concentrations of bromide ions. Complete dissolution of palladium is achieved with an excess of bromide ions and pH values of 1.5-2.0. Platinum turned out to be more resistant to bromine-bromide leaching because of the formation of a sparingly soluble platinum dibromide on its surface.
Downloads
References
Balde C., Forti V., Gray, V. et al. The Global E-waste monitor 2017, United National University (UNU), International Telecommunication Union (ITU) & International Solid Waste Association (ISWA), Bonn / Geneva / Viena;(In Eng.).
Kogan V.S., Reichman G.O. Povedeniye metallsoderzhashchikh i nemetallicheskikh poleznykh komponentov pri fiziko-mekhanicheskoy utilizatsii i gidrometallurgicheskoy dovodke elektronnogo skrapa // KompleksnoeIspol’zovanie Mineral’nogo Syr’a (Complex Use of Mineral Resources).-2015, No. 4-S. 67-74(In Rus.); https://doi.org/10.31643/2018/166445
Cieszynska A., et al. Waste Electronic and Electric Equipment (WEEE) –scrap of valuable source of precious metals // Towaroznawcze Problem Jakosci, v.4 (49) 2016- P.43-53 (In Eng.). https://doi.org/10.19202/j.cs.2016.04.04
Ashiq A., Kulkarni J., Vithange M. et al. Hydrometallurgical Recovery of Metals from E-Waste // Electronic Waste Management and Treatment Technology, January 2019, P. 225-246 (In Eng.). https://doi.org/10.1016/B978-0-12-816190-6.00010-8
Cui J., Zhang L. Metallurgical Recovery of Metals from Electronic Waste: A Review // Journal of Hazardous Materials. V.158. 2008. P.228-256 (In Eng.). https://doi.org/10.1016/j.jhazmat.2008.02.0
Hageluken C. Recycling of Electronic Scrap at Umicore’s Integrated Metals Smelter and Refinery // World of Metallurgy-Erzmetall V. 59 (3), 2006. P.152-161; (In Eng.).
Sousa et al. Bromine leaching as an alternative method for gold dissolution // Minerals Engineering 118: 16-23- March 2018- P. 16-23 (In Eng.). https://doi.org/10.1016/j.mineng.2017.12.019
Complex Use of Mineral Resources. No4. 2019 ISSN-L 2616-6445, ISSN 2224-5243 (Print) 47
Melashvili et al. Study of gold leaching with Bromine and bromide and influence of sulfide minerals on the reaction // COM 2014- Conference of Metallurgists Proceedings ISBN: 978-1-926872-24-7; (In Eng.).
Kellsall G., Welham N., Diaz M. Thermodinamics of Cl- -H2O, Br- - H2O, I-H2O, Au-Cl- - H2O, Au-Br-H2O, Au-I-H2O systems at 298 K // J. Electrochemical Chem., V. 361, 1993. P.13-24; (In Eng.).
Ksenzenko V.I., Stasinevich D.S. Khimiya i technologiya broma, ioda I ih soideneniy. M. Khimiya. 1995. 432S.(In Rus.);
Dadgar A. Extraction and Recovery of gold from concentrate by bromine process // Precious Metals’89, 1989. P. 227-240; (In Eng.).
Pesic B., Sergent R. Reaction mechanismof gold dissolution with bromine // Metallurgical and Materials Transactions B, Juny1993. V.24. Iss.3.- PP.419-431; (In Eng.).
Pesic B., Sergent R. A rotation disk study of gold dissolution by bromine // JOM, December 1991. V.43. Iss. 12. P.35-37; (In Eng.).
Fleming C.A. Hydrometallurgy of Precious Metals recovery // Hydrometallurgy, 30 (1992) P.127-162;
Cotton F., Wilkinson D. Sovremennaya neorganiczeskaya khimiya (Part 3. Chemistry of transition metals) M .: Mir, 1979. S. 457-479 (In Rus.).
Kenzhaliyev B. K. Innovative technologies providing enhancement of nonferrous, precious, rare and rare earth metals extraction // Kompleksnoe Ispol’zovanie Mineral’nogo Syr’a (Complex Use of Mineral Resources). – 2019. – No3 (310). -Page: 64-75. (In Eng.). https://doi.org/.10.31643/2019/6445.30
Kogan V.S., Berkovich I.V. Silver, gold and palladium leaching from pre-preparedelectronic scrap using bromine-bromide solution // Kompleksnoe Ispol’zovanie Mineral’nogo Syr’a (Complex Use of Mineral Resources). –2019. –No3 (310). – P. 55-63 (In Eng.). https://doi.org/10.31643/2019/6445.29
Downloads
Published
How to Cite
Issue
Section
License
Copyright (c) 2022 Complex use of mineral resources
This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 Unported License.
