Visible-light-driven Bi2WO6/biochar composite photocatalyst efficiently degrades 17α-ethinylestradiol (EE2) and 17β-estradiol (E2) under persulfate synergy

Biochar (BC) composite photocatalysts have attracted much attention by virtue of their high efficiency in removing endocrine disruptors (EDCs). However, there has been a lack of systematic research on the mechanism and constitutive relationship of BC on photocatalysts, which has seriously impeded the development process in this field. In this study, Bi 2 WO 6 –BC 2% composite photocatalysts were prepared by microwave-assisted hydrothermal method and used for degradation of 17α-ethinylestradiol (EE2) and 17β-estradiol (E2) in conjunction with persulfate synergy (PS). The removal rate of EE2 and E2 by Bi 2 WO 6 –BC 2% was as high as 99.41 % (12 min) and 97.84 % (15 min), respectively. Systematic studies have shown that BC enhances the catalytic activity mainly through the following ways, increasing the specific surface area of the photocatalytic system, enriching the types of functional groups, enhancing the separation ability of photogenerated electron–hole pairs, and promoting the concentration of active free radicals. The results of the phytotoxicity experiments showed that compared to the EE2 or E2 pollutant solutions, the stem and root lengths of V. radiata increased by 93.63 % and 389.58 % in EE2 metabolites, and by 117.35 % and 160.38 % in E2 metabolites. Similarly, the stem and root lengths of P. vulgaris increased by 80.08 % and 174.91 % in EE2 metabolites, and by 188.92 % and 345.75 % in E2 metabolites. This work not only fills the gap in the study of the mechanism of action of BC, but also provides a green catalyst with very excellent photocatalytic efficiency and detoxification properties.