57 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 uranum from waste streams via proecipitation (as UO_2)~1. Such reductive precipitation has been demonstrated using anaerobic microorganisms in synthetic bicarbonate buffer solutions~2 and in bicarbonate maended ground waters~3. However, the chemical composition of process waste-water and soil decontaminated leachates containing uranium may be much more complex than those proeviously evaluated. For example, the presence of organic solvents used at radioactive material processing facilities and organic chelating materials used to resotre, uranium contaminated soils can alter uranium speciation~(4, 5) thereby impacting bioavailability. Although re-searchers have addressed degradation of lighands in organic-metal comples,~(6-8) little work has been done to evaluate biotransformation of metals in such complexes. Sucessful implementation of this novel treatment approach requires information regarding the capability of anaerobic microorganisms to initiate uranium precipitation in the pressence of various organic chelating agents.