A preliminary techno-economic evaluation of the extraction of gold from a chalcopyrite concentrate using thourea

Abstract

This study involved thiourea leaching of gold contained in a chalcopyrite concentrate. The evaluated parameters included the method of adding thiourea, preleaching with acid, pH, thiourea concentration and granulometry. Thiourea leaching of the chalcopyrite concentrate performs better and is more selective than cyanidation. In fact, gold extraction rates of around 89% can be obtained with thiourea, compared to 71% for cyanidation (19kg/t cyanide). An analysis of the different control factors for thiourea leaching showed that optimum performance by the system requires the following conditions: preprocessing with sulphuric acid, leaching of gold for 72 hours at pH 3, while maintaining thiourea concentration between 3.7 – 5.0 g/L. The redox potential varied between 170 mV and 207mV (Ag, AgCl/KCl 4 M). The gold extraction rate was 88.8% and thiourea and acid consumption rates were 9.84 kg/t and 48.25 kg/t respectively. The amount of copper dissolved in a thiourea solution approximated 160 ppm, but the concentration was much higher for a cyanide solution, in which the copper content could exceed 5 g/L.