Molecular Binding of Eu~(Ⅲ)/Cm~(Ⅲ) by Stenotrophomonas bentonitica and Its Impact on the Safety of Future Geodisposal of Radioactive Waste

摘要

Microbial communities occurring in reference materials for artificial barriers (e.g., bentonites) in future deep geological repositories of radioactive waste can influence the migration behavior of radionuclides such as curium (Cm~(Ⅲ)). This study investigates the molecular interactions between Cm~(Ⅲ) and its inactive analogue europium (Eu~(Ⅲ)) with the indigenous bentonite bacterium Stenotrophomonas bentonitica at environmentally relevant concentrations. Potentiometric studies showed a remarkably high concentration of phosphates at the bacterial cell wall compared to other bacteria, revealing the great potential of S. bentonitica for metal binding. Infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS) confirmed the role of phosphates and carboxylate groups from the cell envelope in the bioassociation of Eu~(Ⅲ). Additionally, time-resolved laser-induced fluorescence spectroscopy (TRLFS) identified phosphoryl and carboxyl groups from bacterial envelopes, among other released complexing agents, to be involved in the Eu~(Ⅲ) and Cm~(Ⅲ) coordination. The ability of this bacterium to form a biofilm at the surface of bentonites allows them to immobilize trivalent lanthanide and actinides in the environment.