Silver catalyzed IBES process: Application to a Spanish copper-zinc sulphide concentrate

The Indirect Bioleaching with Effects Separation process (IBES process) has been applied to a chalcopyrite/sphalerite concentrate from Rio Tinto, In this paper the chemical stage of the process (ferric sulphate leaching) has been studied in agitated batch reactors, Two stages of ferric sulphate leaching are required at atmospheric pressure: primary leaching and catalytic leaching, the second one using silver ion as a catalyst for chalcopyrite dissolution, The effect of the variables such as pulp density, pH, ferric and ferrous iron concentrations, temperature and amount of catalyst have been investigated. The recovery amounts to 95% for both zinc and copper under the following experimental conditions: 70 degrees C, 12 g/l Fe3+, pH 1.25, 8 h of primary leaching and 8 h of catalytic leaching with 2 mg silver/g concentrate, It has been proved that, after solid/liquid separation, the ferrous iron in the leaching liquor can be bio-oxidized with Thiobacillus ferrooxidans for ferric iron regeneration (the biological stage of the IBES process) and the silver can be recovered from the residue and thus recycled to the process.