Bioleaching of a complex mixed sulphide ore as a remedy for chalcopyrite disease

摘要

Europe is increasingly looking at its own mineral reserves as a route to supply independence. However, given extensive historic mining activity, many remaining ore deposits tend to be complex and low grade. Therefore, increasingly sophisticated processing options are required. A complex sulphide ore containing arsenopyrite in tight association with sphalerite was targeted. Fine grain chalcopyrite was disseminated within the sphalerite matrix, a condition known as chalcopyrite disease. A copper concentrate (CuF) could be produced but it still contained high concentrations of arsenic. This concentrate was amenable to bioleaching at 70°C but losses of copper to the tailings during flotation were unacceptably high. Therefore, bioleaching tests were done on a bulk sulphide concentrate (BSF) at 30°C, 45°C and 70°C in order to determine the effect of temperature on the relative dissolution rates of arsenic, copper and zinc. The aim was to selectively bioleach the zinc at low temperatures and then subsequently bioleach the copper at high temperature. The copper dissolution rates were low at low temperatures with little of the copper being recovered. However, zinc leaching rates were also low, suggesting this may not be a suitable process option. As expected with chalcopyrite, significantly faster copper dissolution rates were achieved at 70°C. Moreover, the arsenicxopper concentration ratio in the leachate was significantly lower at this temperature, probably due to precipitation with iron. For these reasons, a more suitable bioprocessing option for this ore may be the production of a bulk sulphide concentrate followed by high temperature bioleaching for the recovery of copper and zinc in a single step.