Stable immobilization of uranium(VI) mediated by highly efficient indigenous microbes: dynamic behavior and mechanisms

Abstract

Indigenous microbial consortia were screened from uranium-contaminated sites to remediate subsurface water polluted by uranium with β-sodium glycerophosphate (GP) as the external carbon and phosphorous source. The results showed that the uranium removal ratio reached 98.34% at 228 h, and the stability of the immobilization product was also enhanced with prolonged reaction time. The remediation of uranium-contaminated wastewater involved two stages. In the early stage, soluble U(VI) was removed swiftly and mainly absorbed onto cell surfaces through electrostatic interactions and complexation. In the second stage, U(VI)-phosphate minerals appeared in various forms, including metaankoleite [K(UO₂)(PO₄)·3H₂O], chernikovite [H₂(UO₂)₂(PO₄)₂·8H₂O], and metanatroautunite [Na(UO₂)(PO₄)·3H₂O]. The crystallinity of U(VI)-phosphate minerals improved with increasing reaction time. Meanwhile, U(IV) was also detected as UO₂ in the crystalline state. Uranium precipitates were found inside cells at this stage, and these precipitates were dominated by metaankoleite. In the whole system, unclassified_f_Enterobacteriaceae played a major role, and Lysinibacillus, Dysgonomonas, Methylobacterium–Methylorubrum, Devosia, Petrimonas, Citrobacter, Microbacterium, and Paenibacillus also participated in the remediation process. This work confirmed that biosorption, biomineralization, bioaccumulation and bioreduction were all involved in the process of uranium immobilization. These findings have practical significance for the in situ remediation of uranium by indigenous microbes.