Computer controlled pilot scale test of bioleaching of copper sulphides flotation concentrate

Abstract

The bioleaching is a biochemical process that is based on the capacity that certain microorganisms have to transform insoluble elements present in certain sulphide minerals in soluble elements and easy to be extracted from the lecheate in conventional downstream processes. The leaching microorganisms are characterized by a unique capacity to grow in environments virtually uninhabitable for the majority of microorganisms, as they live in places with extremely low pH and in temperature that can vary between 25 to 80°. In a process of leaching sulphide minerals it is used to obtain a flotation concentrate so as to recover a large part of the metal of interest bearing sulphide minerals. In the case of copper, for instance, its main sulphides are the chalcopyrite, bornite, chalcocite, enargite, tenantite and covelite, being chalcopyrite the most abundant copper sulphide and the most important economically. This research work aims at controlling in an orderly manner the biological processes that occur in a heap of copper sulphide minerals-bearing flotation concentrate. In a bioleaching heap without external control, it is observed that mesophile microorganisms are acting in the most external areas of the heap, i.e., in areas where there is more heat exchange, and the moderate and extreme thermophilic ones act in the inner parts of the heap, in their acting corresponding temperatures. The oxidative processes that occur have exothermic character and there is a trend of intense rising of temperature inside the heap, and, the result of this heat intensification, the death of part of these microorganisms may occur. However, with the temperature control, in combination with an up-flow of air can prevent the death of microorganisms and reach a significant extraction of those metals of interest, without mentioning the redox potential monitoring, which gives a quite reliable indication of the sulphide minerals oxidation process efficiency.