Biologically enhanced dissolution of a pyrite‐rich black shale concentrate

Abstract

The acid leaching of a pyrite‐rich black shale concentrate (7% S) was tested in this study. The experiments were performed at 5–30% pulp densities and with inoculations of Fe‐ and S‐oxidizing thiobacilli (Thiobacillus ferrooxidans, and Thiobacillus thiooxidans,),. Cultures supplemented with S⁰ showed strong acid production, with final pH values of 0.9 in T. ferrooxidans, cultures and 0.4–0.5 in the presence of T. thiooxidans,. Fe dissolution was pronounced in the T. ferrooxidans, culture whereas T. thiooxidans, did not dissolve Fe from the black shale. Total dissolved Fe concentrations were 3 to 50 times higher in the cultures inoculated with T. ferrooxidans, when compared to T. thiooxidans, and sterile controls. The dissolution of Mo was enhanced in the inoculated cultures as compared with the chemical controls. With V, Si, and Al this effect was not as pronounced but was still discernible in solutions acidified by bacterial oxidation of S⁰. The leaching experiments suggested that the black shale was inhibitory to the inocula. The inhibition was related to the pulp density and was associated with the leach solution. The inhibition could be completely alleviated by replacing the leach solution.

Key words:

• Bioleaching
• iron oxidation
• pyrite oxidation
• sulfur oxidation
• Thiobacillus,

Notes

Present address: Institute of Molecular and Cell Biology at Tartu University, Riia 23, Tartu EE2400, Estonia.

Present address: Department of Biochemistry, Institute of Chemistry, São Paulo State University, P.O. Box 355, Araraquara, SP 14.800, Brazil.

Corresponding author. Mailing address: Department of Microbiology, Ohio State University, 484 West 12th Avenue, Columbus, OH 43210–1292, U.S.A. Phone: [phone]. Fax: [phone]. E‐mail: [email protected]‐state.edu.