Abstract
— The aim of this study was to determine the effect of pH during the reductive leaching of chalcopyrite with activated carbon. Leaching chalcopyrite is generally slow when using sulphuric acid as a leaching reagent, limiting its potential as an alternative to pyrometallurgical methods. Reductive leaching is used to improve copper extraction by breaking down passivation layers of the mineral using reducing agents like AC, making it easier to dissolve copper. Additionally, AC helps to improve the rate of leaching, especially working in sulphate solutions. The experiment had two leaching stages, first stage being the effect of pH (1.5, 2, 2.5 and 3) at constant temperature of 50ºC. Optimum pH of 1.5 was found in first stage and used in the second leaching stage as a constant where the temperature was varied (25, 35, 45, 55, 65ºC). For both stages time was varied from 2,3,4,5,6,7, to 8 hours and sulphuric acid was the leaching reagent. It was observed that using activated carbon as a catalyst minimized the effect of passivation during leaching, as the highest recovery without the use of AC yielded 2.3% at 1.5 pH and with activated carbon yielded 7.4% at 2pH after 2 hour. Optimal condition at 45ºC for 8hours at the pH of 1.5 yielded 35.26%. Kinetics studies showed the rate limiting factor attributed to the dissolution of Cu to CuFeS2 to be the chemical reaction mechanism. This experimental model was mathematically validated with the near correlation of 0.817. Additionally, activation energy was found to be 25.42 KJ/mol which means that diffusion controlled is the rate limiting step.