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 hVB+, 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.