Adding Nano B-TiO₂ active cores to polyacrylic acid cryogel for boosting synergistic adsorptive-photocatalytic uranium capture

Efficient U(VI) capture and its catalytic reduction to U(IV) is of importance for both environmental protection and uranium resource recovery, whereas the available adsorbents and catalysts are still inefficient or expensive. The current study synthesizes an efficient and cost-effective polyacrylic acid (PAA) cryogel with B-doped TiO₂ nanoparticle photo-active cores (B-TiO₂@PAA) for adsorptive- photocatalytic capture and reduction of U(VI). The testing results show that the current B-TiO₂@PAA exhibits a 1.95-fold enhancement compared to that of the pristine PAA gel under simulated sunlight radiation with high stability and selectivity. A synergistic effect between the PAA substrate and the B-TiO₂ active cores for uranium capture is also revealed. B-TiO₂ serves as crosslinkers of the cryogel to improve the porous structure and stability. It reduces the proportion of the medium size pores (3–30 μm) for a lower mass transfer resistance, whereas those of both larger (> 30 μm) and smaller (< 3 μm) size pores are increased. The former provides a better mass transfer condition, and the latter a confinement effect for a fast uranium capture on the activated sites. Meanwhile, B-TiO₂ is also tested as a conductivity regulator of the cryogel to enable semiconducting behavior for an intensified photocatalytic performance. This study provides a novel “Nano-photocatalyst@Cryogel” strategy for the design of U(VI) capture materials from aquatic media.