Abstract:To address the issues of high toxicity in traditional cyanidation gold leaching processes and the significant environmental hazards posed by cyanide-containing wastewater and tailings, there is an urgent need to develop an environmentally friendly cyanide-free leaching technology. The thiosulfate method has emerged as the most promising non-toxic gold extraction process to replace cyanidation. This study focuses on a quartz vein-type gold ore from Inner Mongolia, employing thiosulfate leaching to systematically investigate the effects of total ammonia concentration, ammonium salt types, ammonia/ammonium ratio, thiosulfate concentration, copper ion concentration, leaching temperature, duration, and liquid-to-solid ratio on gold leaching behavior. A comprehensive kinetic analysis of the leaching process was conducted. The results demonstrate that ammonium sulfate can partially substitute ammonia water during gold leaching, thereby mitigating adverse environmental impacts from ammonia volatilization. Under optimal leaching conditions, a gold extraction rate of 94.23% was achieved with initial ammonia concentration and sodium thiosulfate consumption reduced to merely 0.8 mol/L and 46.98 kg/t, respectively. Kinetic analysis revealed a two-stage leaching process: during the initial 20 minutes, the leaching was governed by mixed diffusion control with an activation energy of 13.19 kJ/mol, while in the subsequent stage beyond 20 minutes, the process transitioned to internal diffusion control with a lower activation energy of 4.84 kJ/mol.