Persulfate-assisted photodegradation of diethylstilbestrol using monoclinic BiVO₄ under visible-light irradiation

In this study, the photosynergistic performance of BiVO₄ with persulfate (PS) is demonstrated under visible light irradiation for the first time. Diethylstilbestrol (DES) was selected as a reluctant compound, and factors including dosages of PS and catalyst, solution pHs, initial concertration of DES, and inorganic anions were evaluated. The morphology and chemical state of bismuth vanadate (BiVO₄) was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive spectrometer (EDS), and ultraviolet-visible (UV-Vis) diffuse reflectance spectroscopy (DRS). It was found that the degradation of DES was promoted in either acid or alkaline solutions. The increase of PS and BiVO₄ dosages was beneficial to the reactions, while incremental concentration of DES showed the inhibiting effect. By scavenging h_VB⁺, Cl^- was able to make the promotion, differentiated from the exsiting HCO- 3. Moreover, the photocatalytic mechanism for the BiVO₄/PS/vis-light system was proposed by using several probe compounds (isopropanol, tert-butanol, and 1,4-benzoquinone), which consists of h+ VB/e- CB generation and recombination on the surface of BiVO₄ as well as free radical oxidation in the solutions. The study provides a distinctive method to treat organic contaminants using visible light in the aqueous environment.