Experimental Study On The Effect Of Microelectric Field On Uranium Adsorption/Immobilization By Bacteria

Nuclear energy is regarded as one of the most potential energy sources with its advantages of high energy density,stable output and cleanliness.The raw material of nuclear energy comes from uranium mining,but uranium mining will produce radioactive wastewater containing uranium,which will cause serious ecological problems and threaten human health if it is not treated into the natural environment.Therefore,the treatment of uranium-containing wastewater is one of the key research topics in today’s society.Microorganisms have certain advantages in the treatment of uranium-containing wastewater.The adsorption sites and functional groups on the surface of microorganisms can adsorb uranium in the solution,and the electrons generated by them can be transferred and used for metal ions to precipitate.Because microbes produce a finite number of electrons,the lack of electrons hinders the efficiency with which microbes can remove uranium.In this study,in order to improve the efficiency of microbial treatment of uranium-containing wastewater,combined with previous studies,a solid electrode was set in the solution and a micro electric field was applied to strengthen the ability of electron donor.The static experiment explored the influence of initial pH value,reaction contact time,initial uranium concentration and other factors on the removal of uranium by bacteria.Fluorescence materials were added into the reaction system to explore the effect of fluorescent materials on the removal of uranium.On the one hand,fluorescent materials as carbon sources can enhance the activity of bacteria,and on the other hand,they can make bacteria have fluorescence properties to facilitate the direct observation of the migration trajectory of bacteria.By means of X-ray photoelectron spectroscopy（XPS）,Scanning electron microscopy（SEM）,Fourier infrared spectroscopy（FTIR）and other detection&characterization means,the effect of removing uranium ions by bacteria under the action of micro-electric field was explored.The main research results are as follows:In the reaction system,the initial pH value,initial uranium concentration,contact reaction time and other factors have a great influence on the removal efficiency of uranium ions.When the initial pH value is 5,the initial uranium concentration is 10 mg/L,and the reaction time is 7 hours,the uranium removal rate reaches 93.8%.In the experimental group with fluorescent materials,the removal rate reached96.53%.Fluorescent materials enhance the activity of bacteria and improve the removal efficiency of uranium in the system.FTIR analysis showed that the groups interacting with uranium ion mainly included hydroxyl（-OH）,carboxyl（-COOH）,phosphate ion(-PO₄³⁺),amino（-NH）,etc.XPS analysis showed that the electrons supplemented by the microelectric field enhanced the reduction process of uranium and broke the U-O bond of uranyl ions.After the treatment of wastewater by bacteria,the valence states of uranium are quadruvalent and hexavalent,indicating that the removal of uranium consists of adsorption of the original valence state and precipitation reduced to quadruvalent state.