Abstract

This work represents a study of the biological oxidation of copper sulfide minerals. The principal objective of the study was to determine the extent of bacterial oxidation on copper containing sulfide minerals. It was also desired to determine if the bacteria could oxidize copper sulfides in the absence of iron. A better understanding of the nitrogen requirements of the organisms was desired. Minerals used in this study were Bingham Canyon Float Concentrate, chalcopyrite, covellite, calcocite, bornite, tetrahedrite, and reagent grade copper sulfide. The bacteria used were obtained from the mine waters of Bingham Canyon, Utah. To study the problem the apparatus used consisted of an air-lift percolator which contained the finely divided ore dispersed in Ottawa sand. A nutrient media was used to supply the ingredients necessary to support growth. The studies were conducted by comparing the amount of soluble copper produced in the presence of the organisms with that of a sterile control. The effect of the mine water bacteria was studied on all of the minerals listed above. The soluble copper in each was determined and recorded. A study on ammonium ion concentration was conducted and also the effect of acid concentrations on sterile leaching. The results of the experiments provided conclusive proof that the microorganisms are able to oxidize copper sulfide ores in the presence or absence of soluble iron. Nitrogen is essential for bacterial growth. By varying the ammonium ion concentration, the optimum was determined. Although the hydrogen ion concentration was found to have a positive effect upon the sterile leaching of chalcopyrite, the amount of soluble copper produced at the highest concentration was far less than that produced by the action of bacteria. Although these results were obtained from a synthetic media under controlled conditions, they have shown that the natural weathering and leaching action in the waste rock dumps in Bingham Canyon, Utah, is due largely to the action of iron-sulfur oxidizing microorganisms.

Degree

College and Department

Physical and Mathematical Sciences; Chemistry and Biochemistry

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