Effect of Oxidative Pretreatment and Lead Nitrate Addition on the Cyanidation of Refractory Gold Ore

Cyanidation is the main process in gold leaching. There are several parameters that affect gold recovery and cyanide consumption. In this paper, the effect of the oxidative pretreatment and lead nitrate addition on the cyanidation of Zarshuran refractory gold ore containing 3.32 ppm Au, 1.09% As, and 0.5% sulfur were investigated. Au recovery was increased from 79.4% to 89.4% in the presence of 500 g/t lead nitrate. Results of pretreatment experiments showed that lead nitrate had little effect on the Au recovery in comparison to the direct leaching condition. Cyanide consumption in the direct leaching tests was about 2.5 times higher than that of pretreatment-leaching tests. The amount of arsenic in the pretreatment solution was dramatically decreased and hence the cyanide consumption was decreased. Thermodynamic calculations showed that the precipitation of arsenic as Ca3AsO42·6H2O\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ {\text{Ca}}_{3} \left( {{\text{AsO}}_{4} } \right)_{2} \cdot 6{\text{H}}_{2} {\text{O}} $$\end{document} is the main reason for lower cyanide consumption in the pretreatment-leaching tests. The results showed that cyanide consumption is still high (about 2 kg/t sodium cyanide), and that copper ions could be considered as one of the cyanide consumers that needs further investigation.