A kinetic study of the electro-assisted reduction of chalcopyrite

The electro-assisted reductive leaching of chalcopyrite was studied in an undivided electrochemical cell in order to explore a low temperature, low pressure hydrometallurgical alternative to convert chalcopyrite to a less refractory phase, chalcocite. The most probable active reducing agent was presumed to be a reactive monatomic hydrogen species, which is formed in the electrolysis of acid solutions as an intermediate species, proceeding the generation of hydrogen gas. The results of this study show that the chalcopyrite reduction velocity is affected by an intricate interrelation of the cathodic, anodic and bulk phase heterogeneous reactions which take place simultaneously in the reactor (cell). The parameters that were found to have the greatest influence on the conjugate system are the current density, percentage of solids and the solution pH and temperature. Cathodic polarization curves were used to elucidate the nature of reactive hydrogen species production on an aluminum cathode and its dependence on the solution conditions. Through the analysis of the Tafel slopes, potential ranges for the reactive hydrogen species formation were determined as a function of the solution parameters. It was also observed that the mechanism by which the reactive hydrogen species is consumed (electrochemical desorption) changes to chemical desorption in the presence of an elevated ferrous ion concentration and at higher temperatures. (c) 2008 Elsevier B.V. All rights reserved.