Biotransformation of uranium complexed to organic ligands by desulfovibrio desulfuricans

摘要

Microbially mediated reduction of soluble hexavalent uranium (U~(6+)) to insoluble tetravalent uranium (U~(4+)) has recently been proposed as a possible mechanism for removing dissolved uranium from waste streams via precipitation (as UO_2)~1. Such reductive precipitation has been demonstrated using anaerobic microorganisms in synthetic bicarbonate buffer solutions~2 and in bicarbonate amended ground waters~3. However, the chemical composition of process waste-waters and soil decontaminated leachates containing uranium may be much more complex than those previously evaluated. For example, the presence of organic solvents used at radioactive material processing facilities and organic chelating materials used to restore uranium contaminated soils can alter uranium speciation~(4, 5) thereby impacting bioavailability. Although researchers have addressed degradation of ligands in organic-metal complexes,~(6-8) little work has been done to evaluate biotransformation of metals in such complexes. Successful implementation of this novel treatment approach requires information regarding the capability of anaerobic microorganisms to initiate uranium precipitation in the presence of various organic chelating agents.