INFLUENCE OF URANIUM EXTRACTANTS ON PYRITE OXIDATION ABILITY OF Thiobacillus ferrooxidans

Abstract

Microbiological leaching as applied to uranium ores involves the metabolic oxidation by Thiobacillus ferrooxidans of associated pyrite to sulfuric acid and ferric sulfate. The sulfuric acid and ferric sulfate generated are effective leachants for common uranium minerals. Dissolved uranium can be recovered from the aqueous leach solutions by solvent extraction or ion exchange techniques. The present study explored the effects of potential solvent extraction reagents for uranium on pyrite oxidation ability of Thiobacillus ferrooxidans. For the solvents studied it was found that in all cases the dissolved organic matter decreased the pyrite oxidation activity of the bacteria, the surface tensionof the leach solutions and the oxygen saturation concentration. The following order of inhibition was established for the solvents and modifiers studied: aliquat 336 > nonyl phenol > kerosene 140 > alamine 310 > adogen 381 > di (2-ethylhexyl) phosphoric acid > adogen 365 > tri-n-butyl phosphate > ¥sodecanol > alamine 308 > alamine 336 > alamine 304. Suggestions to integrate solvent extraction and bacterial leaching for uranium by treating the recirculating raffinate are described.