Comparative thermodynamic analysis of gold dissolution in four organic carboxylic acid-catalyzed thiosulfate systems using Eh-pH and species distribution diagrams
The non-ammonia thiosulfate leaching system is considered to be an attractive and eco-friendly route for gold leaching without the usage of cyanide or ammonia.In this paper,the role of four organic carboxylic acids,named oxalic acid(Ox),malic acid(Mal),citric acid(Cit),and tartaric acid(Tart)in copper-thiosulfate system has been studied comparatively.Based on the available thermodynamic data,a series of Eh-pH and species distribution diagrams for copper-Ox/Mal/Cit/Tart-thiosulfate system under various conditions have been constructed from thermodynamic calculation.The results show that thiosulfate is the only effective complexing agent for aurous ions,while the organic carboxylic acids work as a copper ligand.The copper-Mal/Cit/Tart-thiosulfate system exhibits potential advantages over the traditional copper-ammonia-thiosulfate system,such as wider pH range and lower thiosulfate consumption.The calculation also indicates the redox potentials of Cu(Ⅱ)/Cu(Ⅰ)for the leaching systems are in the subsequence of E0[Cu(Ox)22-/Cu(S2O3)35-]>E0[Cu(NH3)42+/Cu(S2O3)35-]>E0[Cu2(Mal)2H-22-/Cu(S2O3)35-]≈E0[Cu2(Cit)2H-24-/Cu(S2O3)35-]>E0[Cu(Tart)2H-46-/Cu(S2O3)35-].Increasing thiosulfate concentration leads to a sharp decline in the content of copper-Ox/Mal/Cit/Tart complex,and the stability of the formed cupric complex follows the descending order of tartaric acid>citric acid>malic acid>oxalic acid.
NETL
NSTL
万方数据
