The Reduction Of U(?) By Iron Oxide/Silicate Mineral-Shewanella Oneidensis Combined System

With the continuous development of civilization,society's demand for energy is also constantly increasing.As thermal power generation has an obvious negative effect on the ecological environment,nuclear energy as a clean energy source has begun to be continuously valued.However,in the process of nuclear energy mining,it will cause a certain amount of uranium pollution in the surrounding area.Among them,U(?),due to its high water solubility and strong mobility,has a greater impact on the environment.In order to reduce the solubility of U(?)in water,alleviate the harm caused by uranium pollution to biological health,and reduce the migration range of uranium pollution.In this study,montmorillonite and beidellite were transformed into iron oxide/clay minerals and formed a combined system with Shewanella oneidensis MR-1 to achieve the biological reduction of U(?)under anaerobic conditions,and finally used Specific surface area,Zeta potential,Fourier infrared spectroscopy and other technologies have explored the electron transfer mechanism of the U(?)biological reduction pathway in this combined system.The main results are as follows:(1)Preparation and characterization of iron oxide/clay minerals.In this study,montmorillonite and beidellite were used as base minerals,and a total of 6 iron oxide/silicate minerals were synthesized.They were lepidocrocite/montmorillonite,hematite/montmorillonite,goethite/Montmorillonite,lepidocrocite/bedelite,hematite/bedelite,and goethite/bedelite.The iron oxide/silicate mineral composite presented an irregular spherical structure;among them,the particle size of montmorillonite-based was about 1?3?m,and the particle size of beidellite was about2-6?m;The content of Fe in lepidocrocite was higher than other mines,and the relative content of Fe in lepidocrocite/beidelite was 89.31%respectively.(2)The construction of the combined system of iron oxide/clay minerals and Shewanella oneidensis MR-1,and a preliminary study on the biological reduction ability of U(?).The results showed that the cell growth rate of Shewanella oneidensis MR-1 was the highest at 12 h;when six iron oxide/silicate minerals were combined with Shewanella oneidensis,all of them could reduce the U(?)content in the system.,And reach equilibrium at 12 h;the lepidocrocite/montmorillonite system had the highest reduction capacity for U(?).In the 50 mg·L^-1uranium treatment group,the reduction rate of U(?)is 85.8%;The reduction kinetic constant k of lepidocrocite was significantly higher than that of hematite and goethite.(3)The effect of humic acid on the reduction of U(?)by the combined system of iron oxide/clay minerals and Shewanella oneidensis MR-1.The results showed that the effect of humic acid on the reduction of U(?)in the combined system was represented by three phenomena:"complete promotion","low promoting high inhibition"and"high promoting low inhibition";humic acid had an effect on Fe(?)in the combined system.The effects of Fe(?)were mainly divided into two types:inhibition and promotion;Most cases of humic acid ccould significantly increase the reduction kinetic constant of the mineral-microbe combined system on U(?),but lepidocrocite/beide There was a significant negative correlation between the k value of stone and the concentration of humic acid treatment;in the 200 mg·L^-1humic acid treatment group,the k value in the hematite/montmorillonite combined system was compared to In the control group,it increased by nearly 10 times.(4)The mechanism of the U(?)reduction pathway of the combined system of iron oxide/clay minerals and Shewanella oneidensis MR-1.The results showed that the specific surface area of clay minerals was greatly increased after being synthesized into iron oxide/clay minerals;it was added to the combined system of lepidocrocite/beidelite,Shewanella oneidensis MR-1 and U(?)After humic acid,the specific surface area of the mineral decreased by 16.8%;the Zeta potential in the lepidocrocite/montmorillonite-humic acid combined system was-11.39 m V;the main absorption peak of MR-1 in different systems was 3400 cm^-1.The NH stretching vibration at 2500 cm^-1,the absorption peak of carboxylic acid hydrogen bond at 2500,and the C=O stretching vibration at 1660 cm^-1(amide I).In summary,the combined system composed of iron oxide/silicate minerals and Shewanella oneidensis MR-1 could achieve the biological reduction of U(?)under anaerobic conditions and reduce the water solubility of uranium;in addition,The addition of electronic shuttles such as humic acid could enhance the reduction ability of the combined system to U(?);finally,three ways to reduce U(?)in the combined mineral-microbe system are proposed,which can provide guidance for the in-situ remediation of soil uranium pollution.