Co-doped zinc oxide microspheres as photocatalysts for enhanced uranium extraction

Tailoring the band structure of photocatalysts by elemental doping to enhance redox ability and carrier separation kinetics is a promising strategy for designing high-efficiency catalysts for uranium (U(VI)) photoreduction. Herein, we report enhanced visible-light spectral absorption by tuning the energy bandgap of flower-like ZnO microspheres by doping Co. Accordingly, Co doping narrows the bandgap and increases the photogenerated carrier concentration, thereby promoting the U(VI) photocatalytic reduction. Especially, the removal ratio of U(VI) by Co-doped ZnO microspheres reaches 98.4% with a remarkable adsorption capacity of 1645 mg/g for U(VI) uptake in 400 ppm U(VI) solution. In addition, the Co-doped ZnO microspheres present desired U(VI) reduction ratio in a wide range of U(VI) concentrations, as well as excellent reusability, and resistance to ion interference during photocatalysis. This paper provides a feasible strategy for enhancing the photocatalytic reduction of uranium by introducing metal element doping on the metal oxide surface. Graphical abstract