KINETIC STUDY OF CHALCOPYRITE PASSIVATION DURING ELECTROCHEMICAL AND CHEMICAL LEACHING

摘要

A series of electrochemical and chemical leaching experiments has been carried out to clarify the role of solution potential and temperature under a variety of experimental conditions similar to those found during bioleaching of chalcopyrite. Electrochemical measurements showed that iron was preferentially dissolved at low potential and low temperature. A ratio of dissolved copper to iron of 1:3 was obtained at a constant potential of 450 mV vs. SCE. At higher temperature, the opposite effect was observed, i.e., copper was preferentially dissolved with a molar copper to iron ratio of about 3:2. Based on these results a systematic kinetic study was then conducted with fine chalcopyrite grains by controlling the solution potential of the slurry via the addition of hydrogen peroxide. Our results indicated that the oxidation of chalcopyrite was strongly dependent upon the solution potential. Maximum chalcopyrite dissolution occurred for a ferric to ferrous ratio of about 1:1. At higher ratios, the leaching rate was markedly reduced. The analysis of the data showed the contribution of elemental sulphur in the passivation of chalcopyrite.