Biohydrometallurgical Processing of Flotation Tailings from Different Copper Mills

Two copper flotation tailings samples, one from the Almalyk Mining and Metallurgical Complex, Uzbekistan (sample designated AMMC) and the other from Whitehorse (WT), Yukon, Canada, were bioleached at laboratory scale. Acidophilic, iron- and sulphur-oxidizing cultures were enriched from the two tailings and these cultures were used for the testing. After 24 weeks of bioleaching in percolator columns 70-72% of the copper was leached from the AMMC tailings and 91-93% of the copper was leached from the WT tailings. The chalcopyritic nature of the copper and larger particle size of the AMMC tailings compared to the WT tailings were likely reasons that copper extraction was greater for the AMMC tailings. In-column, thiosulphate leaching of biooxidized residues yielded 90+% gold extraction for both tailings. In other testing the two cultures were subjected to an electromagnetic field during growth on ferrous iron. Compared to untreated controls, cultures subjected to the electromagnetic field oxidized iron more rapidly. Although magnetite, which exerts an electromagnetic field, was present in the AMMC tailings, there was no evidence that this magnetite had any effect on the bioleaching results. However, given the enhanced performance of the iron-grown cultures under the influence of an electromagnetic field, we believe that additional research should be performed to investigate this phenomenon