Modeling the Kinetics of Anodic Dissolution of Chalcopyrite based on Electrochemical Measurements Conducted on Chalcopyrite Particle Electrodes

Abstract

Anodic dissolution of chalcopyrite was studied with an electrochemical technique that allows direct measurements of anodic dissolution current in small chalcopyrite particles. Experiments were conducted with a working electrode made of a monolayer of chalcopyrite particles pressed onto an adhesive conductive carbon tape. Potentiostatic anodic dissolution experiments of 8 hr duration were conducted in deoxygenated iron-free sulfuric acid solutions at pH 1.7 and 70 ºC, at potential values of 0.55, 0.6, 0.7, 0.8 and 0.9 V/SHE. Results showed that anodic dissolution of chalcopyrite involves two main reactions. First, chalcopyrite is anodically dissolved while reacting with protons through a 2 electron reaction which results in the formation of intermediate polysulphide compounds and dissolution of copper and iron. Secondly, the polysulphide intermediate layer is further oxidized to elemental sulfur or sulfate which involves a much larger number of electrons. The kinetics of both reactions is interdependent and controlled by the applied potential.