The initial stages of the dissolution of chalcopyrite in chloride solutions: Validity of mixed potential model and comparison with sulfate solutions

Abstract

A relatively simple electrochemical method has been used to obtain accurate data on the rates of oxidative dissolution of chalcopyrite from well defined surface areas under ambient conditions using iron(III) or copper(II) (in chloride solutions) as the oxidants. The initial rates are approximately constant for extended (6 h) periods in chloride solutions but decrease with time in sulfate solutions.The rates of dissolution are not strongly dependent on the nature of the solution except in solutions of high chloride concentration for which the rates are higher. The rate is also slightly higher with copper(II) or with iron(III) + copper(II) as the oxidant. A limited study has shown the importance of temperature with an activation energy of 57 kJ mol−1 for dissolution in chloride solution.The chalcopyrite mixed potentials measured during dissolution vary over a limited range (less than 200 mV) depending on the conditions. Potentiostatic measurements in solutions without oxidants have shown that the rates calculated from the current densities at the mixed potentials agree quantitatively with those obtained from the chemical dissolution measurements. This correspondence confirms the validity of the mixed potential model for oxidative dissolution. Comparisons have been made with previously published data largely at elevated temperatures.