期刊
ELECTROCHIMICA ACTA
卷 399, 期 -, 页码 -出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.electacta.2021.139393
关键词
Gold; Thiosulfate leaching; Cobalt catalysis; Electrochemistry; Catalytic mechanism
资金
- National Natural Science Foundation of China [52104256, 52174271]
- Qingdao Postdoctoral Application Research Project
This study investigated the electrochemical behavior of gold leaching in ammoniacal thiosulfate solutions catalyzed by Co(NH3)6(3+), and found that Co(NH3)6(3+) is more efficient than Cu(NH3)4(2+). A new catalytic mechanism involving redox cycle between Co(NH3)6(3+) and Co(NH3)x(S2O3)(0) (x = 4, 5) was proposed for the leaching of gold with ammoniacal thiosulfate.
Thiosulfate is a green gold lixiviant that has promise to replace cyanide at the gold mining industry. Hex-aamminecobalt(III) (Co(NH3)(6)(3+)) is effective in catalyzing the thiosulfate leaching of gold from ores, but the electrochemical behavior and catalytic leaching mechanisms remain unclear. This paper reports an in-depth investigation into the electrochemical behavior of gold leaching in ammoniacal thiosulfate so-lutions catalyzed by Co(NH3)(6)(3+). The electrochemical results suggested that Co(NH3)(6)(3+) is more efficient than Cu(NH3)(4)(2+) in catalyzing the ammoniacal thiosulfate leaching of gold. Compared with Cu(NH3)(4)(2+), the coulombic efficiency of gold dissolution (QAu/QT) under the Co(NH3)(6)(3+) catalysis is much higher. In the presence of Co(NH3)(6)(3+), the QAu/QT was nearly 100% at 150-250 mV and higher than 78.9% at 250- 350 mV; at 250 mV, the QAu/QT was approximately 100% in the initial electrolysis of 300 s and remained basically unchanged at around 75% after 1200 s. Leaching results further showed that the catalysis of Co(NH3)(6)(3+) not only achieved a continuous leaching of gold with time, but also significantly decreased the consumption of thiosulfate from 36.5% (for Cu(NH3)(4)(2+)) to 20.9% after leaching 24 h. In the ammonia-cal thiosulfate solution, Co(NH3)(6)(3+) is likely reduced to mixed ligand Co(II) complexes of Co(NH3)x(S2O3)(0) (x = 4, 5), which are readily oxidized back to Co(NH3)(6)(3+). Thus, an improved catalytic mechanism of gold leaching is proposed that the redox cycle between Co(NH3)(6)(3+) and Co(NH3)x(S2O3)(0) (x = 4, 5) catalyzes the leaching of gold with ammoniacal thiosulfate. (C) 2021 Elsevier Ltd. All rights reserved.
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