Thermodynamic analysis of gold leaching by copper-glycine-thiosulfate solutions using Eh-pH and species distribution diagrams

Abstract

Glycine and thiosulfate, as alternatives to cyanide, are all considered to be one of the most promising lixiviants for gold. In this paper, a novel copper-catalytic glycine thiosulfate collaborative system of gold leaching was proposed. Based on the available thermodynamic data, a series of Eh-pH and species distribution diagrams for gold/copper-glycine-thiosulfate system under various conditions were constructed using thermodynamic calculations. The analysis results for thermodynamic diagrams indicated that the copper-glycine-thiosulfate system had many potential advantages over the copper-ammonia/citrate-thiosulfate system, such as wider pH range and lower thiosulfate consumption. The electrochemical models for the copper-catalytic mechanism of gold leaching with glycine-thiosulfate were also proposed in this study. Moreover, the relevant results obtained in this study provide a theoretical basis for the optimization of gold leaching with copper-catalytic glycine thiosulfate system.