Prediction of Dissolution of Copper from a Chalcopyrite Carbonatite Ore of South Africa

Chalcopyrite accounts for 70% of all copper bearing minerals and therefore has been studied closely to understand the dissolution kinetics in hope of overcoming the passivation film and increasing the extraction rates of copper. In this study carbonatite samples were obtained from a mining company in South Africa. The carbonatite samples were leached and the leachates were assessed for the metal ions content, pH, electrical conductivity (EC), RedOx potential (RP), acidity, major anions (sulphate, chloride) as well as iron ion concentration for speciation prediction. Speciation of metal ions was conducted through the use of PHREEQC modelling software. The main objective of the study was to determine the kinetic dissolution pattern of the run of mine (ROM) chalcopyrite samples from the carbonatite host rock over time as a varying factor. The mineralogical investigation showed that the ROM sample was dominated by calcite magnesium (Ca0.97 Mg 0.03 (CO3)). The elemental investigation showed that the sample was dominated by Ca and Fe with mass% of 49.81 and 26.31 respectively. The dissolution curve for copper displayed and overall decrease in dissolution rate of copper clearly showing the effects of passivation on the chalcopyrite mineral; a peak dissolution rate (22.8%) was observed after 7 hours of leaching. From the ICP data the major cation in the leachate of the ROM was determined to be Ca, Cu, Fe and Mg. The PHREEQC results showed that Ca, Cu and Mg was dominant as sulphate salt species while Fe was dominant as a free ionic species (Fe). Keywords— Carbonatite ores, Chalcopyrite, kinetic dissolution, pH, passivation, ORP, ROM, XRF, XRD.