Experimental Study On The Performance And Mechanism Of Removal Of U (â…¥) By

Development of uranium mining and metallurgical processes often produce largeamounts of radioactive waste with a higher concentration of uranium and residualcontaminants. They migrate with water infiltration, posed a significant ecologicalrisks to soil and water migration. How to reduce or eliminate the toxicity of heavymetals is the key point to reduce pollution. Humus and humus substances reducingmicroorganisms can occur a strong complexing and binding activity with metal ions,thus affect their form in the environment, migration, transformation and biologicaltoxicity. Bioremediation is one of the effective methods of uranium contaminatedwater governance. While metal-reducing microorganism, with a heavy metalresistance and accumulation capacity, shows a very broad prospect in the field oftreatment of heavy metal pollution.In this study, Shewanella oneidensis MR-1co-processing with humic substancemodel anthraquinone-2-sulfonate(AQS) is used to reduce uranium. Characteristicsand reaction conditions of anaerobic reduction by the Shewanella oneidensis MR-1inthe presence of anthraquinone-2-sulfonate(AQS) were evaluated in this study．Theeffects of the initial concentration of uranium, biomass dosage, coexisting ions,anthraquinone-2-sulfonate and toxic organic compounds were investigated throughstatic batch experiments.The results showed that U(VI) could be efficiently reduced by Shewanellaoneidensis MR-1utilizing AQS as a electronic shuttle vector and various organicacids as electron donors under anaerobic environment. AQS in low concentration cansignificantly enhanced reduction of U(VI), while the high concentration of AQSweakened. When the concentration of AQS was0.5mmol/L, U(VI) concentrationreduced from30mg/L to0.41mg/L, the reduction rate reached98.61%; When theconcentration of AQS was5mmol/L, AQS competed electrons with U (VI) whichcaused a diminished role in promoting. When the initial concentration of U(VI) was30mg/L,Uranium reduction rates were95.37%,92.41%and95.65%using the formate,acetate and lactate as the sole electronic donor of strain MR-1after7d, respectively. Metal ions(Cu2+,Mn2+,Ca2+)and toxic organics impact on the reduction of U(VI).Ca2+acted as a weak role in promoting the reduction, on the contrary, equal concentrationsof Cu2+and Mn2+could cause varying degrees of inhibition of U(VI) reduction. Sometoxic organic compounds, such as toluenes, trichloroacetic acid and maleic acid, areavailable to reduce U(VI) efficiently by Shewanella oneidensis MR-1and getdegraded at the same time. Characterizations with Scanning Electron Microscope(SEM) and other modern analytical tools indicated the deposition of U element on thecell of Shewanella oneidensis. in cell U (VI), associated hydroxyl group, phenolichydroxyl group, P-O, amide group and other group is the main role in the reductionprocess of U(VI).