Mechanisms involved in bioleaching of Collophanite by Acidithiobacillus thiooxidans

Mechanisms involved in bioleaching of the collophanite by Acidithiobacillus thiooxidans (A. thiooxidans) HY-01 were investigated, which took into account both direct and indirect mechanism. The reverse high performance liquid chromatography (HPLC) and Ion chromatography analyses of the A. thiooxidans-inoculated collophanite suspension were carried out for detecting acid components responsible for bioleaching. Furthermore, the surface feature and component changes of bioleached ore residues were analyzed by scan electron microscopy (SEM), Infrared spectroscopy (IR) and X-ray diffraction (XRD). On the basis of these studies, there are obvious bacterial direct contact and adhesion on the minerals via cellular surface proteins, and meanwhile bacterial metabolite sulfuric acids, rather than organic acids, are visualized to dissolve the phosphorous from collophanite matrix by proton attack. It is concluded that insoluble phosphorous Ca-5(PO4)(3)F, Ca-10(PO4)(5)CO3F1.5(OH0.5) and Ca(PO3)(2)center dot 2H(2)O within the collophanite was dissolved into soluble phosphorous CaHPO4 by a cooperative strategy, involving contact bioleaching with the mineral and simultaneous indirect bioleaching of the mineral via sulfuric acids.