Concurrent leaching of copper and cobalt from a copper–cobalt ore using sulfuric and organic acids

Abstract

A study involving the leaching of Cu and Co from a CuCo ore in sulfuric acid (H2SO4), citric acid (CA) and oxalic acid (OA) using hydrogen peroxide (H2O2) as oxidant, was carried out. The ore was characterised by x-ray fluorescence (XRF), x-ray diffraction (XRD) and scanning electron microscopy coupled with energy-dispersive x-ray spectroscopy (SEM-EDX). The results obtained indicate that increasing the time, temperature, and concentration of the leaching agent/oxidant enhanced the leaching efficiencies of Cu and Co, while a reduction in particle size (large surface area) favours the leaching of Cu and Co. The highest leaching efficiencies of 99.2 % and 94.0 % were obtained for Cu and Co, respectively, in a leaching system constituted by 1.0 M H2SO4 and 3.0 M H2O2 within 4 h at 65 °C. In contrast, the 0.8 M OA leaching system demonstrated a 97.1 % efficiency for Cu and 100.0 % efficiency for Co. The estimated activation energy in the temperature range of 25–65 °C is 40.7 kJmol−1 for Cu, while that of Co is 64.0 kJmol−1, which implies that the leaching is controlled by a surface chemical reaction. A comprehensive analysis demonstrated that the reaction mechanism for Cu leaching is diffusion-controlled at lower temperatures (<35 °C) and surface chemical reaction-controlled at temperatures higher than 35 °C.