Microscopic and Spectroscopic Insights into Uranium Phosphate Mineral Precipitated by Bacillus Mucilaginosus

In this paper, we used spectroscopic and microscopic techniques to investigate the interaction mechanism between uranium and Bacillus mucilaginosus. According to scanning electron microscope couple with energy dispersive X-ray detector analysis, the lamellar uranium phosphate precipitation was only observed on the living B. mucilaginosus and the resting B. mucilaginosus. The Fourier transform infrared spectroscopy spectrum also indicated the important role of phosphate groups in forming U(VI)-phosphates precipitation. The X-ray diffraction analysis identified the phase of U(VI)-phosphate precipitation as H₃OUO₂PO₄·3H₂O. Batch experiment showed that biominerilization amount could be up to 195.84 mg/g when exposing living B. mucilaginosus to U(VI) aqueous solution at pH 5.0 for 1 h. The precipitate was further evidenced by extended X-ray absorption fine structure spectra based on the presence of U-P shell, which demonstrated that hydrogen uranyl phosphate became the main products on the living B. mucilaginosus with prolonged reacting time. After ashing and hydrothermal process, the precipitated U(VI) on B. mucilaginosus could be converted into UO₂ and K(UO₂)(PO₄)·3H₂O. Our findings have significant implications in elucidating the potential role of bacteria in the migration of uranium in geological environment.