Evaluation of the inhibition process effect “Preg-robbing” for gold recovery (AU)

Abstract

Currently, the National Society of Mining, Petroleum and Energy (SNMPE) states that in recent years the production of gold in Peru has reduced, since in 2016 there was a production of 153 MT, compared to 2005 with a production of 208 MT. Until 2018, a production decrease of 5.4% was established and in 2017 a decrease of 11.3%. Currently there is a need to develop research on gold extraction processes in low recovery minerals with traditionally used processes, due to the complex structure of gold that prevents their extraction. It is necessary to evaluate new processes that are environmentally friendly and that are sustainable in the environmental and economic aspects. In the present work, the applicability of leaching with NaCl and KNO3 in acid medium in a sulphurous gold mineral was evaluated, through the process of leaching with oxidizing salts, which allows to process hydrometallurgy the various forms of gold minerals present in nature. The sample is composed in percentages by Quartz 24%, Carbonates Dolomite 22%, Calcite 6%, Arsenopyrite 19%, Pyrite 5%, Galena 4% and clays associated with traces of Native Au-Electrum, which were interfering with the process of leaching of the sample. A pretreatment by gravimetric concentration was carried out using the Falcón equipment, with the aim of releasing the encapsulated gold and eliminating the interfering agents, facilitating the leaching action of the oxidizing salts. When testing the concentrations of the oxidizing salts, it was found that for the concentrations of 86.86 g/l of NaCl, 21.96 g/l of KNO3 and 125.93 g/l of H2SO4, a maximum recovery of 26.62% gold was obtained. Based on the results from the factorial design, an increase in gold extraction performance was observed; obtaining a maximum recovery of 29.31% of the gold; in the process it was determined that dissolved gold is affected by the presence of clays, producing the "Preg-robbing" effect of the valuable metal and consequently decreasing the recovery of gold after 8 leaching hours. According to the results, it is concluded that the leaching process with oxidizing salts in acidic medium for the type of mineral used, is mainly affected by the presence of coarse gold and electrum associated with clays, establishingconditions of degree of release according to the granulometry in the gold leaching process.