Quantitative leaching of a Nigerian chalcopyrite ore by nitric acid
Due to increasing uses of copper nitrate, Cu(NO3)2, as catalysts, textile and polishing agents for other metals, experiment on the leaching of a Nigerian chalcopyrite ore by nitric acid for possible production of copper nitrate was examined. The effects of acid concentration, temperature and particle size on the dissolution rates of chalcopyrite ore have been investigated. Distribution of elements, compounds present within the ore particle size -90 + 75 μm was initially determined by X-ray Fluorescence (XRF), X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) to provide basis for explaining the dissolution process. It was observed that dissolution rates were greatly affected by acid concentration, temperature and particle diameter. Kinetic data analysis showed that the dissolution mechanism followed diffusion as the rate controlling step. The reaction order was calculated to be 0.51 while the activation energy was deduced to be 29.99 kJmol-1 from the dissolution data. The X-ray diffraction analysis of the unleached residue at optimal leaching showed that it contains α-quartz (α-SiO2) and Tin oxide (SnO2).
Keywords: Chalcopyrite ore, Nitric Acid, Leaching, Dissolution Kinetics, Copper Nitrate.