Electrochemical behaviors of gold and its associated elements in various complex agent solutions

Abstract

Thermodynamic properties and electrochemical behaviors of gold and its associated elements, such as silver, copper, nickel and iron, in various complex agent solutions were studied. Within CS(NH₂)₂, S₂O₃²⁻ and SCN⁻ systems, alkaline thiourea is the optimal nontoxic lixiviating agent substituting cyanide from the viewpoint of thermodynamics. The electrochemical study indicates that the anodic dissolution current densities of gold are 2.616, 1.805, 1.267, 1.088, 0.556, and 0.145 mA · cm⁻² respectively in the solutions of cyanide, alkaline thiourea containing Na₂SiO₃, SCN⁻, acidic thiourea, alkaline thiourea and thiosulfate at the potential of 0.500 V. Comparing various lixiviating agents, the alkaline thiourea solution containing Na₂SiO₃ is of prominent selectivity in leaching gold, in the potential range from 0.500 to 0.600 V, which is most efficient for leaching gold selectively instead of cyanide. The effect on leaching gold is similar to that in the cyanide system.

Keywords

gold / associated element / complex agent / electrochemical behavior