Kinetics improvement of high-grade sulphides bioleaching by effects separation

Abstract: The kinetics of bioleaching of sulphide concentrates by Thiobacillus ferrooxidans can be improved by performing separately the two operations relating the two effects involved in the indirect contact mechanism, (1) chemical leaching and (2) biological oxidation of the Fe2+ produced in the chemical stage (IBES: Indirect Bioleaching with Effects Separation). This scheme permits the separate enhancement of each stage. On the one hand, the chemical attack of the ferric iron to sulphides can be performed at a higher temperature. On the other hand, the biological oxidation stage is more effective when biofilm models are applied. At the same time, inhibitory phenomena produced as a result of the bacterial breaking caused by the abrasion of the solid particles on microorganisms are prevented. In this work the 1BES process has been applied to a Spanish copper-zinc and a copper sulphide concentrate. The objective has been to selectively dissolve zinc, which may be recovered by solvent exraction, the remaining residue being a copper concentrate suitable for pyrometallurgical treatment. The attributes of moderate temperature, atmospheric pressure, low cost of the leaching agent, flexibility and effectiveness make the process very attractive from an economic point of view.