Abstract

---

With continuous industrial demands and as the market potential of purified copper in Nigeria and around the world is on the increase, the development of cheap and eco-friendly methods for the processing of mixed and lower grade copper ores become paramount. Consequently, this study examines the effect of ammonia-ammonium chloride concentration, temperature and particle size on the extent of covellite ore dissolution for predicting optimal copper extraction conditions. The results of the dissolution rates were found to be influenced by ammonium ion concentration, reaction temperature and particle size. At optimal leaching conditions, 82.9% of the initial 10 g/L covellite ore reacted within 120 minutes. The un-leached products (~17%) examined by X-ray diffraction was found to contain siliceous impurities that could be processed further to serve as a by-product for some defined industries. In all, the dissolution data was accordingly analysed and found to follow the shrinking core model for the diffusion controlled reaction. The calculated activation energy of 31.16 kJ/mol supported the proposed mechanism, assumed to be first order relation.

Keywords: Covellite ore, Leaching; Ammonia-ammonium chloride; Dissolution kinetics.