Investigation of leaching behaviour of pre-concentrated copper ore using ammonium chloride solution

Investigation of the leaching behaviour of near infrared sensor-based pre-concentrated and classified copper ore samples in ammonium chloride solution was studied to understand the trend in copper extraction. The mineralogical and chemical content of the ore was evaluated using QEMSCAN® and ICMPMS techniques. The effects of leaching parameters such as NH4Cl concentration, particle size, temperature, solid-to-liquid ratio and stirring speed on the leaching were determined. Results mineralogical analysis indicated that the copper bearing mineral in the ore is Chrysocolla with the product containing more copper content than the middling and waste. The middling ranked very high in hematite content than the other fractions while the waste contained significant quartz indicating higher gangue content than the product and middling. Copper extraction and elemental analysis of residue suggested that the rate of copper recovery in the product fraction was more significant than the middling which is in line with the mineralogical and NIR classification of the ore samples. The leaching parameters studied revealed that increasing temperature and NH4Cl concentration with decreasing particle sizes and solid-to-liquid ratio led to increase in the rate of copper extraction up to 86.4 % and 67.3 % in the product and middling groups, respectively. Kinetic analysis revealed the activation energy to be 48.3 kJmol-1 and 71.3k Jmol-1 , this suggests the dependence of the leaching process on surface chemical reaction.