Acid dissolution of uranophane and carnotite

Abstract

Uranium dissolution from rock samples containing uranophane or carnotite was tested in acid mineral salts solutions in the presence and absence of Fe‐ and S‐oxidizing bacteria (Thiobacillus ferrooxidans) and with FeSO₄ or S⁰ as the substrate. The addition of FeSO₄ enhanced the solubilization of uranium from uranophane. S⁰‐amendment was also effective, because uranium solubilization was enhanced at low pH resulting from the bacterial oxidation of S⁰. Uranium was readily dissolved from carnotite. However, the carnotite‐containing rock sample was predominantly composed of calcite that excessively consumed acid, increasing the pH and thereby reducing the concentration of uranium dissolved in leach solution.

Key words:

• carnotite
• iron oxidation
• leaching
• sulfur oxidation
• Thiobacillus ferrooxidans
• uranophane
• uranium dissolution

Notes

Present address: National Institute for Biotechnology and Genetic Engineering, P.O. Box 577, Jhang Road, Faisalabad, Pakistan.

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.