Chemical Speciation and Interaction Mechanism of U in “Shewanella putrefaciens-Mineral-U” System

We constructed binary and ternary systems between U (VI) and Shewanella putrefaciens, kaolin, and nano-α-Fe2O3, and studied the interactions of mixtures in the systems to determine and describe the role of microorganisms in regulating the environmental mobility of U. Shewanella putrefaciens, kaolin, or nano-α-Fe2O3 was placed in U (VI) solution to form a binary system. In this system, the adsorption of U (VI) by Shewanella putrefaciens increased with the increase of time, while the adsorption of U (VI) by kaolin and nano-α-Fe2O3 was not obvious at low concentration. The mixture of bacteria, kaolin, or nano-α-Fe2O3 was placed in U (VI) solution to form a ternary system, in which the adsorption capacity of Shewanella putrefaciens to (VI) was significantly reduced after the addition of minerals. The results indicate that the combination of minerals and bacteria may affect the respiration of bacteria, thereby reducing the adsorption and reduction of (VI) by Shewanella putrefaciens. Fourier transform infrared spectroscopy (FTIR) was used to analyze the possible functional groups in the interaction between cells, minerals, and U. The results showed that the distribution of U on the cell surface was related to the carboxyl, amide, and hydroxyl groups of Shewanella putrefaciens.