Design of Z-scheme UIO-66-NH2/BiOBr heterojunctions for efficient visible-light-driven selenite removal from water: Performance and mechanism studies

Excess existence of the selenite (Se(IV)) is hazardous to water resources. Therefore, a need still exists for the removal of Se(IV) from the wastewater in the renewable, environmentally friendly, and low-cost way. This paper presents a novel way to design a Z-type heterojunction of UIO-66-NH2/BiOBr using co-precipitation technology for efficiently removal of Se(IV) from wastewater using the adsorption-visible photocatalytic synergy. The UIO-66-NH2 presents an enhanced adsorption of Se(IV) due to the expose of abundant linker defects, as the active sites. The Z-type heterojunction (UB-2) showed 96.4% removal of Se(IV) at an initial concentration of 100 mg/L under visible light conditions due to its higher charge transfer capacity and electron-hole separation ability. The photocatalytic removal rate of UB-2 toward Se(IV) was 4.12 times and 9.93 times higher than that of UIO-66-NH2 and BiOBr, respectively. UB-2 could be reused and showed a good removal capacity in real-world water samples. The used UB-2 was superior to the nano-selenium in the scavenging of superoxide radical and DPPH, revealing a potential of biological antioxidant. This work will be beneficial for the efficient decontamination of Se(IV)-containing wastewater.