The synthesis of biotemplate‐based Bi₂WO₆/TiO₂ composite photocatalyst for degradation of microcystin

Abstract

Microcystin is a harmful hepatic toxin produced by cyanobacteria, is a serious threat due to its toxicity to water ecosystems, and it is found recently that TiO2 photocatalyst is effective in degradation of microcystin. In this study, hierarchical porous Bi2WO6/ TiO2 composite photocatalysts were synthesized with a novel hydrothermal method by using rice husk as the biological template. The results showed that the original micro‐ and nanopores of rice husk were efficiently replicated by the synthesized porous TiO2 photocatalyst with a specific surface area of 137.09 m2/g, which increased by nearly 100 m2/g over the surface area. SEM, TEM, XRD, and XPS spectra showed that heterogeneous structures were formed by Bi2WO6 and TiO2, with which process the crystal structures of both were not affected. In the meantime, we studied the effect of hierarchical porous TiO2 photo‐catalyst, pure TiO2 photo‐catalyst, Bi2WO6 photo‐catalyst, Bi2WO6/ hierarchical porous TiO2 photo‐catalyst on degradation of 1 mg/L MC‐LR, and the results showed that to use the unique silicon‐carbon structure of rice husk to prepare hierarchical porous TiO2 photo‐catalyst can have the degradation rate of 53.5%, which is higher than that of commercially available TiO2 photo‐catalyst by 13.8%. Compared with a single photo‐catalyst, the photo‐catalytic activity of Bi2WO6/ hierarchical porous TiO2 photo‐catalyst is significantly improved. The optimal mingling amount of Bi2WO6 is 0.2 mol/mol. At this time, the degradation rate of MC‐LR is 85.3%, and the main active substances for degradation are h+ and ·OH. In addition, the degradation process of MC‐LR fit well with the kinetic model of Quasi Primary Reaction. The insight of green synthesis of Bi2WO6/ TiO2 composite photocatalysts for degradation of microcystins was provided by this study.