Surface studies relevant to microbial adhesion and bioflotation of sulphide minerals
Abstract (Summary)Biomineral beneficiation concerns the way in which microorganisms bring about the enrichment of an ore matrix. It involves the selective removal of undesired mineral constituents from an ore through microbe-mineral interactions in the processes 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, Thiobacillus thiooxidans and Paenibacillus polymyxa are used in the present investigation. Mineral and bacterial cell surface is characterised by electro-kinetic measurements, XPS, FT-IR and FT-Raman spectroscopy, contact angle measurement, adhesion to organic solvents and surface energy evaluation. Thermodynamic approaches- Fowkes, Gemetric mean, Equation of state and Lifshitz-van der Waals Acid/base, for evaluating the surface energy from contact angles have been critically analysed using literature and measured contact angle data. Adhesion of microbial cells on mineral surface has been studied by constructing adsorption isotherms and DLVO potential energy diagrams. Single mineral Hallimond flotation tests are performed for chalopyrite and pyrite after interaction with microbial cells and in the presence and absence of collector. Microbial cells were able to successfully depress pyrite and not chalcopyrite. Hence, a separation among pyrite and chalcopyrite can be accomplished by bioflotation.
School:Luleå tekniska universitet
Source Type:Doctoral Dissertation
Date of Publication:01/01/2001