Integrating surface functional modification and energy-level adapted coupling of photocatalyst with ultrafast carrier separation for uranium extraction

Abstract

Photo-assisted uranium extraction is recognized as a promising U-extraction method by turning soluble hexavalent uranium (U(VI)) into insoluble tetravalent uranium (U(IV)). However, efficient charge separation and abundant uranium confinement sites are two key factors for efficient uranium extraction. Herein, a facile and universal parallel strategy is reported to fabricate confinement-site-rich photocatalysts with ultrafast carrier separation by energy band-tailored coupled surface functional modification for photo-assisted extraction of uranium. As a proof-of-concept demonstration, Mn-doped mesoporous TiO2 microspheres with phosphoric acid modification (Mn-TiO2@PO4) are successfully synthesized, which enables accelerated carrier separation efficiency and enhances the U(VI) selectivity. By virtue of the theoretical simulation, in conjunction with other spectral analyses, we demonstrate that Mn doping efficiently modifies the band structure with improved electron-hole separation, and surface phosphoric acid modification can enhance the affinity for uranyl ions. Accordingly, the removal rate of Mn-TiO2@PO4 for U(VI) is up to 94%, which was 6.6 times as powerful as the pristine TiO2 microspheres. This study offers a valuable paradigm for the rational design of advanced photocatalysts with band-tailored coupled and surface functional modification for photo-assisted extraction of uranium.