This study was prompted by the phenomenon of the optimal conditions for nickel and copper extractions were quite different in the bioleaching of a low grade complex nickel-copper concentrate. Response surface methodology (RSM) was firstly utilized to promote chalcopyrite oxidation under optimal condition of nickel recovery. The experiment results showed that a satisfactory second-order polynomial regression equation was achieved with a high coefficient of determination (R2=0.9522) which demonstrated that the model could be effectively applied for optimization of silver-catalyzed bioleaching process. Based on the model, the term of silver-bearing species and the interaction term of adding time and Ag+ concentration exhibited high contribution to copper extraction. The different effect of silver-bearing species on bioleaching was revealed by RSM. Besides, the addition time of silver was quite significant in silver-catalyzed bioleaching process, which has never been reported. The high copper extraction reached 0.814 under the optimal conditions of Ag2SO4 as silver-bearing species, adding catalyst after 7 d of bioleaching and Ag+ concentration 1.1 g Ag/kg of ore. Moreover, validation tests were performed and the results were very close to the predicted values.
Bioleaching, Nickel-copper concentrate, Box-Behnken design, Silver catalysis, Chalcopyrite
© The Author(s) 2014. Open Access. This article is distributed under the terms of the Creative Commons Attribution 4.0 International License which permits unrestricted use, sharing, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.