Effect of pretreatment prior to leaching on a chalcopyrite mineral in acid media using NaCl and KNO3

Abstract

Chalcopyrite is the most abundant copper ore mined in Chile. Hydrometallurgical plants are currently changing to concentration by flotation-matte smelting deposits when oxide minerals run out and chalcopyrite appears in deposits. The change from hydrometallurgical processing to flotation is mainly dependent on whether comminution costs can be absorbed given the copper grade. It is important to develop alternative technologies to work profitably with low-grade copper sulphide ores. One alternative that has been recently studied is the pretreatment of low copper grade sulphide minerals, especially chalcopyrite, to improve leaching efficiency. The curing time, as pretreatment, improves dissolution kinetics and shortens leaching time. This study used a pure sample of chalcopyrite mineral with 28.5% copper. Chalcanthite (copper sulphate) represented 9% of total copper in the sample. The effect of curing time as a function of copper extraction prior to leaching was evaluated using different concentrations of sodium chloride (NaCl), potassium nitrate (KNO3) and sulphuric acid (H2SO4). A 23% copper dissolution was obtained prior to leaching using 25 kg/t NaCl, 15 kg/t H2SO4 and 15 days of curing time. The ANOVA analysis reported that curing time was the most important variable (56.4 and 54.7% of contribution) in tests with NaCl and KNO3. According to the results, KNO3 does not have a significant effect on copper extraction prior to leaching.