Research On The Action Mechanism Of Soil Bacterial Extraction Polymeric Substances To U(?) In Solution

Uranium is an important strategic resource and has important applications in many fields.As the nuclear industry expands,so do the environmental problems of the soil.Uranium in the soil can enter the human body through various channels and endanger human health.Soil bacterial extracellular polymeric substances(SB-EPS)is a biological macromolecular mixture secreted by soil bacteria in life activities and released when the bacteria lysis.It has complex interactions with metal ions in the soil and may affect uranium activities and morphological changes in the soil layer.In order to explore the action mechanism of SB-EPS to U(VI)in solution,a series of single-factor experiments and characterization analyses were performed.High-throughput sequencing of the 16 S rRNA of the cultured soil bacterial flora showed that the population structure and pedigree development of the bacterial flora sample performed well,with a coverage rate of 99.9%,indicating that the results can reflect the true flora status.The soil bacterial flora metabolic abundance was measured in the following order:carbohydrates > amino acids and amino acid derivatives(proteins)> cofactorsand vitamins > terpenoids and ketones > lipid compounds > nucleotides.The ultrasonic method combined with high-speed centrifugation was used to extract extracellular polymeric substances produced by soil bacteria.The yield experiments on SB-EPS showed that the soil bacterial flora should be cultured at 30 ?.The single factor experimental results of SB-EPS and U(VI)under different conditions of pH,temperature,contact time and initial U(VI)concentration show that the optimal pH value of the reaction is 5,and the optimal reaction temperature was 40 ?.The reaction proceeded to near dynamic equilibrium at about 120 min,and was basically completely balanced at 140 ~ 160 min.When the initial U(VI)concentration was 50mg/L,the pH was 5,the reaction temperature was 40 °C,and the contact time was 120 min,the adsorption capacity and rate of U(VI)in the solution by SB-EPS were 8.75 mg/g and 58.36%,respectively.Kinetic analysis and isotherm analysis show that pseudo-second-order kinetic model,Elovich model and double constant model and Freundlich isotherm model are all suitable for describe the adsorption of U(VI)in solution by SB-EPS.The particle diffusion model has a good fit for the reactions at 30 ? and 35 ?.It shows that this process is a complex multi-molecular layer reaction mainly based on chemical mechanism,and U(VI)diffuses in a non-uniform manner on SB-EPS.SEM,EDS-Mapping,FTIR and XPS analysis were used to explore the mechanism of interaction between SB-EPS and U(VI).The analysis results indicate that SB-EPS to U(VI)in solution has physical adsorption,chemical complexation,and biological reduction.U(VI)can bind to hydroxy,carboxyl,amino,amido and phosphate genes on SB-EPS,and also affect the molecular conformation and properties of SB-EPS.The thesis can provide some references for studying the Migration of uranium in soil environment and using microbial method to solve uranium pollution in soil.