Study On The Performance And Mechanism Analysis Of U(Ⅵ)Treated By Pseudomonas Cepacia

A large amount of uranium-contaminated wastewater is produced during the mining of uranium,which poses a potential hazard to the ecological environment and human safety,and wide attention has been attracted for finding suitable treatment methods.Microorganisms have a good treatment effect on uranium-containing wastewater.It is a hot research topic to explore the performance and mechanism of bacterial treatment of uranium.In this paper,the indigenous Pseudomonas cepacia isolated from the soil of a uranium tailings pond in Hunan Province was used to test its performance in the treatment of low-concentration uranium-containing wastewater.The effects on the adsorption of U（VI）by the cells were investigated in bacterial dry wet dosage,initial pH,initial concentration of U（VI）and time.Heavy metal ions such as Cu²⁺,Pb²⁺and Zn²⁺have a great influence on the removal of U（VI）.The effects of different concentrations of the above ions on the removal of U（VI）are investigated.Extracellular polymer（EPS）plays an important role in the adsorption of U（VI）by bacteria.The changes of bacterial extracellular polymer content and its effect on uranium treatment were investigated under different culture time.The reaction mechanism of uranium-bacteria interaction was elucidated by modern analytical methods such as SEM-EDX（scanning electron microscopy-energy spectroscopy）,FTIR（infrared spectroscopy）and XRD（X-ray diffraction spectroscopy）.The results showed that the maximum equilibrium adsorption capacity of U（VI）was 160.4 mg/g when U（VI）concentration was 10 mg/L,pH 6.0,and 30°C,.The static test results showed that the adsorption of U（VI）by the cells reached equilibrium at 4 h,and the removal rate of U（VI）reached 95.0%.When Cu²⁺,Pb²⁺,and Zn²⁺plasmas were added,the efficiency of removing U（VI）by bacteria was reduced.When the concentration of heavy metal ions is 100 mg/L,Cu²⁺and Pb²⁺have obvious inhibitory effects on U（VI）,while the effect of Zn²⁺is weak.As the culture time increased,the content of extracellular polymer gradually increased,reaching a maximum of 66.1 mg/g（DW）in 3 days.Compared with the adsorption of U（VI）by the original cells,the adsorption rate of the extracellular polymer showed a certain decrease,indicating that the extracellular polymer of the bacteria involved in the adsorption of U（VI）.The results of SEM-EDX,XRD and FTIR analysis showed that U（VI）was deposited on the cell surface with flocculent uranium phosphate compound,and the functional groups such as hydroxyl,amide and phosphate groups played an important role in the binding of uranium.The sediment on the surface of the bacteria is mainly phosphorus-containing uranium oxide(UO₂P₆O₁₇),uranium hydrogen phosphate compound UO₂H（PO₃）₃ and uranium hydrogen phosphate hydrate（UO₂（H₂PO₄）₂.3H₂O）.Native Pseudomonas cepacia has good removal performance for U（Ⅵ）containing wastewater,and can survive well from toxicity of U（Ⅵ）and other heavy metal and mineralize U（Ⅵ）,which plays a significant role in the treatment of low concentration uranium wastewater.