Physico-chemical characterisation of microbial cell surface and bioflotation of sulfide minerals

Sammanfattning: Biomineral beneficiation concerns the way in which microorganisms bring about the enrichment of an ore matrix. It involves the selective removal of undesirable mineral constituents from an ore through microbe-mineral interactions in the process such as selective flotation and flocculation. Adhesion of microorganisms to minerals result in alteration of surface chemistry of minerals relevant to beneficiation process. Physico-chemical properties of microbial cell surface influence their adhesion behaviour therefore, the physico-chemical characterisation of microbial cell is essential in order to fully understand and control the biomineral beneficiation process. Thiobacillus ferrooxidans(T.f.) and Paenibacillus polymyxa (P.p.) are used in the study. Mineral and bacterial cell surface is characterised by electro-kinetic measurements, FT-IR and FT-Raman spectroscopy, contact angle measurement, adhesion to organic solvents and surface energy evaluation. Adhesion of microbial cells on mineral surface has been studied by constructing adsorption isotherms and DLVO calculations. Single mineral Hallimond tube flotation is performed for chalopyrite and pyrite after interaction with microbial cells and in presence and absence of collector. Microbial cells were able to successfully depress pyrite and not chalcopyrite. Hence, a separation among pyrite and chalcopyrite is possible by bioflotation.