Bio-leaching effects of Leptospirillum ferriphilum on the surface chemical properties of pyrite

Leptospirillum ferriphilum cultured using different energy sources (either soluble ferrous ion or pyrite) changed the surface properties of pyrite. Cell adsorption, zeta-potential, hydrophobicty, FT-IR spectra and surface morphology were investigated. Adhesion of bacterial cells to the pyrite surface is a fast process. Furthermore, the adsorption of cells grown in pyrite is greater than of cells grown in soluble ferrous ion. The Iso-Electric Point (IEP) of pyrite treated with L. ferriphilum approaches that of the cells themselves. The contact angle of the pyrite surface was observed to decrease due to the surface formation of some hydrophilic substances during bio-leaching. Changes in pyrite surface properties after bacterial treatment support the idea that ferric ion plays an important role and that indirect bio-oxidation is the principal mechanism of pyrite bio-leaching.