Thiosulfate is a green gold lixiviant that has promise to replace cyanide at the gold mining industry. Hexaamminecobalt(III) (Co(NH₃)₆³⁺) 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 solutions catalyzed by Co(NH₃)₆³⁺. The electrochemical results suggested that Co(NH₃)₆³⁺ is more efficient than Cu(NH₃)₄²⁺ in catalyzing the ammoniacal thiosulfate leaching of gold. Compared with Cu(NH₃)₄²⁺, the coulombic efficiency of gold dissolution (Q_Au/Q_T) under the Co(NH₃)₆³⁺ catalysis is much higher. In the presence of Co(NH₃)₆³⁺, the Q_Au/Q_T was nearly 100% at 150–250 mV and higher than 78.9% at 250–350 mV; at 250 mV, the Q_Au/Q_T 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)₆³⁺ not only achieved a continuous leaching of gold with time, but also significantly decreased the consumption of thiosulfate from 36.5% (for Cu(NH₃)₄²⁺) to 20.9% after leaching 24 h. In the ammoniacal thiosulfate solution, Co(NH₃)₆³⁺ 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)₆³⁺. Thus, an improved catalytic mechanism of gold leaching is proposed that the redox cycle between Co(NH₃)₆³⁺ and Co(NH₃)_x(S₂O₃)⁰ (x = 4, 5) catalyzes the leaching of gold with ammoniacal thiosulfate.

硫代硫酸盐是一种绿色黄金浸出剂，有望在金矿行业取代氰化物。六氨合钴(III) (Co(NH ₃ ) ₆ ³⁺ ) 可有效催化硫代硫酸盐从矿石中浸出金，但其电化学行为和催化浸出机制尚不清楚。本文报道了对 Co(NH ₃ ) ₆ ³⁺催化的氨硫代硫酸盐溶液中金浸出电化学行为的深入研究。电化学结果表明Co(NH ₃ ) ₆ ³⁺比Cu(NH ₃ ) ₄ ²⁺更有效催化氨硫代硫酸盐浸出金。与Cu(NH ₃ ) ₄ ²⁺相比，Co(NH ₃ ) ₆ ³⁺催化下金溶解的库仑效率( Q _Au / Q _T )要高得多。在 Co(NH ₃ ) ₆ ³⁺存在下，Q _Au / Q _T在 150-250 mV 时接近 100%，在 250-350 mV 时高于 78.9%；在 250 mV 时，Q _Au / Q _T在 300 s 的初始电解中约为 100%，在 1200 s 后基本保持在 75% 左右。浸出结果进一步表明，Co(NH ₃ ) ₆ ³⁺的催化不仅实现了金随时间的连续浸出，而且硫代硫酸盐的消耗量从36.5%（对于Cu(NH ₃ ) ₄ ²⁺）显着降低到浸出 24 小时后为 20.9%。在氨硫代硫酸盐溶液中，Co(NH ₃ ) ₆ ³⁺很可能被还原为 Co(NH ₃ ) _x (S ₂ O ₃ ) ⁰ ( x = 4, 5)，它们很容易被氧化回 Co(NH ₃ ) ₆ ³⁺。因此，提出了一种改进的金浸出催化机制，即 Co(NH ₃ ) ₆ ³⁺和 Co(NH ₃ ) _x (S ₂ O ₃ ) ⁰ ( x  = 4, 5)之间的氧化还原循环催化了金的浸出用氨硫代硫酸盐。