Construction of activated biochar/Bi2WO6 and /Bi2MoO6 composites to enhance adsorption and photocatalysis performance for efficient application in the removal of pollutants and disinfection

Abstract

To synergistically enhance the adsorption and photocatalytic performance of Bi₂WO₆ and Bi₂MoO₆, using activated biochar (ACB) as substrate, ACB-Bi₂WO₆ and ACB-Bi₂MoO₆ composites were facilely prepared by hydrothermal synthesis. Their adsorption-photocatalytic degradation effects on rhodamine B (RhB), tetracycline (TC), and norfloxacin (NOR) were comparatively investigated. Additionally, the effects of environmental factors, wastewater treatment tests, and disinfection were systematically studied, and the enhancement mechanisms and reasons for the degradation differences were highlighted. The results showed that ACB-Bi₂WO₆ and ACB-Bi₂MoO₆ were confirmed to form intimately contacted heterojunctions by various advanced characterization techniques. The introduction of ACB narrowed the band-gap energy of Bi₂WO₆ and Bi₂MoO₆, and improved the visible light absorption range and specific surface area. The optimal loading ratios of ACB-Bi₂WO₆ and ACB-Bi₂MoO₆ were 1:1.06 and 1:0.58, respectively. The removal rate of ACB-Bi₂WO₆ for high concentrations of RhB (200 mg·L^-1), TC and NOR (50 mg·L^-1) were 89.15%, 87.27%, and 72.17%, respectively, which were higher than those of ACB-Bi₂MoO₆ and significantly stronger than those of Bi₂WO₆ and Bi₂MoO₆. This was attributed to the more effective inhibition of photogenerated carrier recombination, higher absorbance, and uniform morphology via ACB-Bi₂WO₆. ·OH and holes were dominant active species in photocatalysis, and the possible photogenerated carrier transfer path is type II heterojunction. Furthermore, ACB-Bi₂WO₆ possessed good reusability, and the removal of RhB and TC from the actual wastewater exceeded 80.63% and 58.54%, respectively. The sterilization rates of ACB-Bi₂WO₆ reached 99% and 95% for E. coli and S. aureus within 24 h, respectively. Therefore, ACB-Bi₂WO₆ was more recommended for environmental applications.

Keywords: Composite photocatalysts; Degradation effects; Disinfection; Heterojunction; Mechanisms; Wastewater treatment.