An Experimental Study On Remediation Of Uranium Contaminated Groundwater By ?-Glycerophosphate

Uranium pollution in groundwater is a major problem to be studied and solved in the field of uranium mining.The majority species of uranium were UO22+,UO2(OH)+,(UO)2CO3,UO2(CO3)22-,etc,in the uranium contaminated groundwater.These species of uranium have high solubility and could diffusion with the flow of groundwater.These uranium-contaminated groundwaters were potentially harmful to both the natural environment and human health.Its high solubility in uranium can easily migrate with the flow of groundwater and enter into the human body with the groundwater trajectory,which have great harm to human health.In the technique of remediation of uranium-contaminated groundwater,insitu bioremediation is currently a widely studied method.Compared with traditional physical and chemical methods,bioremediation has the advantages of high efficiency,low cost,and no secondary pollution.Enzymatic reactions are usually stimulated by the addition of electron donors to reduce the water-soluble U(?)to water-insoluble U(?),or activating microorganisms to metabolize SO42-,PO43-,CO32-,OH-and other ligands for uranium mineralization in solution.In this study,?-glycerophosphate was used as carbon source and phosphorus source to remediate uranium-contaminated groundwater.In this study,uranium contaminated sediments and groundwater were collected from a decommissioned uranium tailing impoundment in south China,and the microcosms of uranium contaminated aquifer under anaerobic conditions were constructed.To investigate the effect of ?-glycerophosphate as carbon source and phosphorus source on in situ remediation of uranium-contaminated groundwater,the changes of nitrate,sulfate,phosphate,p H and uranium concentrations in the microcosms were monitored.A modified sequential extraction technique and bicarbonate extraction technique were used to analyze the chemical forms of uranium and the ratio of U(?)in the sediments.The composition and uranium valence of the products were analyzed by SEM-EDS and XPS.It was found that,after 25 d incubation,the concentrations of uranium in liquids in the ?-glycerophosphate and glycerol amended groups decreased from 2.96 and 2.99 mg/L to 0.030 and 0.044 mg/L,respectively,which were lower than the limits of contaminants stipulated in the regulations on radiation and environment protection in uranium mining and milling in China.?-glycerophosphate worked as the carbon and phosphate sources and reduced the proportion of the uranium species in exchangeable and carbonate fractions in sediments and increased the proportion of the uranium species in Fe(Mn)oxides,organic matter and residual fractions in sediments.The proportion of U(?)in the sediment of ?-glycerophosphate amended group amounted to 91.79%,which was 28.82% higher than that of the glycerol amended group.After 45 d anaerobic incubation,the proportion of U(?)in the sediment of ?-glycerophosphate amended group almost remained unchanged,while that in glycerol amended group decreased by 7.98%.Therefore,?-glycerophosphate could work as carbon and phosphate sources and could immobilize uranium in-situ through bioreduction and biomineralization.The results provide the experimental basis for the in-situ bioremediation of uranium contaminated groundwater by ?-glycerophosphate.