Microbial Induced Flotation Studies on Sphalerite Ore

High grade ore deposits in the world are fast depleting and the valuables in the low-grade ores are finely disseminated. The feed grades to flotation circuits are also declining. Attainment of suitable grind is preferred, which inevitably creates more fines of the gangue minerals to interfere with the flotation process because of the undue competition between the fines and the valuables for the collector ion adsorption. Moreover, the gangue minerals like graphitic carbon have the natural tendency to float and hence the use of polymeric or long chain hydrocarbon compounds as depressants is not very effective. Microbial induced flotation was found to be a potential alternative to float minerals selectively. Thiobacillusferroxidans and Thiobacillusthiooxidans adhere on the minerals to modify its surface properties and affect the minerals flotation acting as depressants. Hindustan Zinc Limited has conducted laboratory studies to understand the adhesion of microorganism on the mineral surfaces and its impact on the selective flotation. The experiments were further designed to reduce consumption of depressing reagents for graphitic carbon, pyrite and galena. Preliminary studies reveal that the desired quality of clean concentrates can be achieved with reasonable recovery.