Phosphoric Acid Network Induced by Surface Ligands Shifts the Selectivity for Uranium Extraction over Single Atom Modified TiO2 Catalysts

Abstract Photo-driven uranium extraction from fluorine-containing uranium wastewater is considered as a promising avenue to overcome the difficulty of uranium extraction in traditional uranium treatment technologies. Herein, we report a photocatalyst composed of Mn single atoms located at hollow TiO2 nanospheres with organophosphorus acid modification (Mn-SAs/TiO2@HEDP) for efficient uranium extraction from fluorine-containing uranium wastewater. Notably, the synergistic effect of the single-atoms and organophosphorus acid modification in the hollow TiO2 nanosphere significantly enhances the charge separation/transfer efficiency and photo-electron lifetime, thereby greatly boosting the photo-assisted uranium extraction activity. Accordingly, Mn-SAs/TiO2@HEDP show a considerable U(VI) removal rate of 94% in fluorine-containing uranium wastewater. By virtue of the reaction kinetics parameters and DFT calculation, we have confirmed that the phosphoric acid network induced by surface ligands over Mn SAC-TiO2 with Ti-O-P charge transfer channels can significantly enhance the selectivity and reaction kinetics for uranyl ions, relative to modifying inorganic phosphates. Relying on the X-ray absorption spectroscopy technique, we further confirm the dissociate uranyl ions were captured by the interlocking phosphate network to form the sturdy 2Oax-1U-4Oeq configuration, further verifying photo-driven fluorine uranium separation. This study provides a precedent for the design of advanced photocatalysts with specific recognition and a theoretical guide for the treatment of fluorine-containing uranium wastewater.