Gold recovery from electronic scrap waste by low-temperature chloridizing roasting

Е. Е. Zholdasbay, А.А. Аргын, Н. К. Досмухамедов, V. A. Kaplan

2024

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DOI 10.17580/nfm.2024.01.04
Data confidence 70 medium
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Abstract

In the work the scientific and technical analysis of modern methods of E-waste processing is carried out. It is shown that on the territory of Kazakhstan there are no E-waste recycling technologies. The relevance and importance of collection and processing of E-waste increases with the fact of lack of application of rational technology of their processing. Many valuable, technologically recoverable metals are lost irretrievably. The results of the chemical composition of the crushed product — computer boards of computers, which were used as an object of research for gold extraction from them, are presented. The results of studies of qualitative assessment of initial E-waste showed a wide range of changes in metal compositions. Precious metals in the studied E-waste are represented by Au, Ag and Pd, the average content of which is 225, 425 and 15 ppm, respectively. The paper presents the scheme of the laboratory installation and the methodology of low-temperature chloridizing roasting of E-waste with gaseous chlorine. Comprehensive studies of the chemical and phase composition of the solid residue obtained after the experiment using the SEM instrument (Leo Supra Carl Zeiss AG, Germany) and Agilent 7700 Series ICP-MS (Agilent Technologies, USA), Rigaku, Ultima III (Rigaku Corporation, USA) showed the presence of metal chlorides and amorphous phase representing unburned parts of plastic and other organic compounds in them. The quantitative ratio of solid and amorphous phase in the obtained solid residue is 31.5% and 69.5%, respectively. The phase composition of the solid residue was determined: 5.4% CuCl2; 7.8% FeClO and 17.2% Cu2Cl(OH)3. As a result of the experiments, the optimal process parameters were established: temperature — 250 оC, duration — 30 min, chlorine consumption —150 ml/min. It is established that at optimum firing parameters high up to ~98% ofgold extraction from E-waste in the form of gaseous sublimate of gold chlorides is achieved. The research was conducted under the grant financing of the Committee of Science of the Ministry of Science and Higher Education of the Republic of Kazakhstan for 2023-2025 on the priority direction “Rational use of water resources, fauna and flora, ecology” project: AP19576638 “Development of innovative technology of accumulated E-waste utilization with obtaining pure gold and non-ferrous metals”.