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The copper ion reduction and oxidation cycle during the cathodic process of gold thiosulfate leaching
Author(s) -
Zhang Canyu,
Wang Qiang,
Nie Yanhe,
Han Zhiguo,
Su Yifan
Publication year - 2020
Publication title -
asia‐pacific journal of chemical engineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.348
H-Index - 35
eISSN - 1932-2143
pISSN - 1932-2135
DOI - 10.1002/apj.2568
Subject(s) - thiosulfate , copper , redox , chemistry , inorganic chemistry , cyclic voltammetry , electrochemistry , leaching (pedology) , dissolution , cathodic protection , diffusion , standard electrode potential , rotating disk electrode , electrode , sulfur , organic chemistry , environmental science , soil science , soil water , physics , thermodynamics
Abstract The copper ion reduction and oxidation cycle during the cathodic process of gold thiosulfate leaching was studied using a rotating disc electrode and cyclic voltammetry, and the dynamic characteristics of the system were discussed. In a copper ammonium solution, the redox reactions of CuNH 3 4 2 +were reversible and controlled by substance diffusion. The rotating disc electrode and the reduction method with a constant potential showed that the CuNH 3 2 + generated during the reduction process was easily oxidized by O 2 to CuNH 3 4 2 + . In the copper ammonium and thiosulfate system, the reversibility of the redox reactions of CuNH 3 4 2 +became worse, and the reduction process was still controlled by material diffusion and had a higher diffusion coefficient than that in the copper ammonium solution. However, under this condition, the oxidation reaction of the generated Cu(I) species was complicated. The reduction method with a constant potential showed that the rate‐determining step for the cathodic process was the oxidation step of the Cu(I) species. In addition, some amount of Cu(I) species in solution could not be oxidized in time under the experimental conditions. This part of Cu(I) species may be included during the oxidation decomposition of thiosulfate, thus affecting the dissolution of gold.