This work represents a study on the biological oxidation of molybdenite, MoS2. The principal objective of this study was to investigate the possibility of the biological oxidation of molybdenite, to determine the physical and chemical conditions under which the oxidative process occurs, and to develop a strain of bacteria or alter the activity of the microorganisms by acclimatization to increase their activity on sulfide minerals, in particular molybdenite. Minerals used in this study were pyrite (FeS2), chalcopyrite (CuFeS2), molybdenite concentrate, and molybdenite ore. The microorganisms used in this investigation were autotrophic bacteria obtained from the leaching streams of Bingham Canyon, Utah. The apparatus consisted of sixty-four airlift percolators containing Ottawa sand (SiO2) as a dispersing medium for the finely divided sulfide minerals. The studies were perfomed by inoculating the solutions in the percolators with active cultures and comparing the amount of soluble molybdenum and other desired components produced with the amount found in a controlled sample. The effect of the following ions in the nutrient requirements: phosphate, ferrous iron, cupric copper, and aluminum on the molybdenite oxidative process were studied. The result of mixing pyrite and chalcopyrite with molybdenite concentrate for oxidation was also determined. The effect of the molybdate ion and phosphate ion concentrations were determined on the biological oxidation of pyrite. Studies were performed on the biological oxidation of molybdenite ore and molybdenite ore mixed with pyrite to determine the percentage molybdenum solublized, also the relative oxidation states or the solublized molybdenum. The effect of repeated bacterial transfer and molybdenite ore particle size was determined upon the biological oxidation. There were no components found in the Bingham Canyon streams that would precipitate the molybdate ion. Although these results were obtained from a synthetic media under laboratory conditions, they have provided conclusive evidence that it is possible to oxidize molybdenite by the aid of soil microorganisms.



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Chemistry and Biochemistry



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