Biomass encapsulated ZIF-8-derived ZnO carbon aerogels for efficient uranium extraction by synergistic adsorption-photoreduction

Semiconductor-based photocatalytic materials have been widely used in photoreduction uranium systems. However, semiconductor-based materials still have some problems such as difficult recovery, few adsorption sites, poor stability, and large bandgap width. Based on this, we constructed 3D porous konjac glucomannanderived carbon-encapsulated carbon-doped ZnO carbon aerogels (KC@C-ZnO-X) for U(VI) adsorptionphotoreduction based on the gelling properties of Konjac glucomannan (KGM) and the unique structure of ZIF-8. The KC@C-ZnO-1.5 achieved the U(VI) removal rate of 93.5 % in 200 mg/L U(VI) solution and greatly weakened the photocorrosion of ZnO. And then the KC@C-ZnO-1.5 continued to maintain an outstanding U(VI) removal rate of 92.9 % after five cycles. Further characterization tests found that the role of 3D KGM-derived carbon aerogel (KC) encapsulation improves the stability of ZnO and carbon doping reduces the band gap width of ZnO. The mechanistic study showed that KC as the "skeleton" encapsulating C-ZnO not only enabled the catalyst to be recycled but also enhanced the photostability of ZnO. The synergistic effect of the C-ZnO and KC promoted photogenerated charge separation and facilitated the generation of center dot O-2(-), leading to the further formation of the stable (UO3 center dot NH3 center dot H2O) crystalline phase.