An Experimental and DFT Study on Using the Thiosulfate-Glycine Complex as an Alternative Agent of Cyanide in the Gold Leaching Process

This study aims to comprehensively investigate the role of glycine (GL) in gold dissolution with thiosulfate (TS), utilizing both experimental and density functional theory (DFT) approaches. Three different leaching systems, namely AM-TS-Cu2+, GL-TS-Cu2+, and AM-GL-TS-Cu2+, were examined and compared using the response surface methodology at 25 & DEG;C and pH 9.5 for 24 h. The results indicated that under optimal conditions, the GL-TS-Cu2+ system had a 27% lower gold dissolution content (7.49 mg/l) compared to AM-TS-Cu2+ (10.27 mg/l). However, GL substitution resulted in higher dissolution in the first hour and a 20 times lower dose of chemicals. A detailed cost-benefit analysis may favor GL due to its lower consumption and environmental impact compared to AM. Furthermore, the concurrent utilization of AM and GL in the AM-GL-TS-Cu2+ system caused a complete disruption in the dissolution process due to negative interactional effects between AM and GL molecules at the intra-atomic level. This occurred as some copper tetraamine complexes were converted into copper amino acid complexes, limiting the role of copper oxidation and catalysis, and reducing the gold dissolution rate sharply (3.57 mg/l).

Automated summary

This study investigates the role of glycine in gold dissolution with thiosulfate through experimental and density functional theory approaches. Three different leaching systems were compared and the results showed that the GL-TS-Cu2+ system had lower gold dissolution content compared to AM-TS-Cu2+ system. GL substitution resulted in higher dissolution in the first hour and lower chemical dose. The concurrent utilization of AM and GL disrupted the dissolution process due to negative interactional effects between AM and GL molecules.