Copper Extraction from Chalcopyrite Through a Two-Step Non-Oxidative/oxidative Leaching Process

Abstract

Despite their challenges, hydrometallurgical methods can be successfully utilized to extract copper from copper sulfide minerals, and in particular, chalcopyrite (CuFeS2). A slow dissolution rate caused by passive film formation is considered to be the main challenge of low temperature hydrometallurgical processes. To overcome chalcopyrite passivation and enhance copper extraction from the mineral, several biological and chemical leaching methods have been developed over the last few decades. Nevertheless, among hydrometallurgical methods, the main focus has always been on the oxidation (oxidative leaching) of chalcopyrite since the other types of leaching, such as non-oxidative and/or reductive, would not be able to extract as much copper as oxidative leaching. In spite of this, from both thermodynamic and surface studies, it has been shown that chalcopyrite is more difficult to leach than the other copper sulfides such as chalcocite (Cu2S) and covellite (CuS), and the conversion of chalcopyrite to these forms of sulfide can be achieved through non-oxidative and/or reductive leaching methods. As a result, in this thesis a novel process was studied that takes advantage of both non-oxidative and reductive mechanisms to convert chalcopyrite into other sulfide/sulfate forms and improve copper extraction from the mineral. To achieve this, sulfuric acid leaching of chalcopyrite was carried out under conditions that the mineral could undergo non-oxidative and reductive mechanisms, followed by oxidative leaching using hydrogen peroxide as an oxidizing agent. Various key factors were identified and optimized to maximize copper dissolution throughout the process, including temperature, pulp density, stirring speed, leaching time, acid concentration, and particle size. After optimizing the parameters, a copper recovery of 82% was obtained through non-oxidative/oxidative leaching of chalcopyrite, while 93% copper recovery was achieved through a two-step consecutive leaching process.