Electrochemical bioleaching of high grade chalcopyrite flotation concentrates in a stirred bioreactor

The main objective of this study is to improve the basic understanding of electrochemical bioleaching as an advanced hydrometallurgical process suitable for the treatment of high grade complex sulfide ores and to use this understanding for analyzing the potential of this process for copper recovery from high grade chalcopyrite ores and flotation concentrates. Using a typical flotation concentrate from the Sarcheshmeh copper processing complex (located in the south-east of Iran) and mixed mesophilic as well as moderately thermophilic microorganisms, leaching experiments were performed in a stirred bioreactor. The emphasis was given on the comparison between the results of bioleaching and that of electrochemical bioleaching tests. From the results of this study, it can be pointed out that compared to the conventional bioleaching; the electrochemical bioleaching of chalcopyrite flotation concentrate leads to about 35% more copper recovery. It seems that the main reason for increasing copper recovery by electrochemical bioleaching is the control of redox potential between 400 and 425 mV. Under this condition, the precipitation of iron oxy-hydroxides on the surface of chalcopyrite, which can act as a diffusion barrier and prevents chalcopyrite dissolution, is significantly reduced. This leads to a higher electrochemical reduction of chalcopyrite and its improved dissolution.