Silver vanadium oxide materials: Controlled synthesis by hydrothermal method and efficient photocatalytic degradation of atrazine and CV dye

Silver vanadium oxides have received remarkable attention in recent years because of their stability, suitable band gaps, and relatively superior photocatalytic abilities. This study reports the synthesis of silver vanadates by the hydrothermal method and the investigation of their photocatalytic abilities for removing crystal violet (CV) and atrazine pollutants under visible-light irradiation. The as-prepared silver vanadates are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and UV-vis diffuse reflectance spectra (DRS). Crystal violet and atrazine could be successfully degraded in the presence of the silver vanadate catalyst under visible-light irradiation. The obtained results show complete degradation of crystal violet after 24 h of treatment and over 97% degradation of atrazine after 72 h. The as-prepared silver vanadate materials show extremely high catalytic stability and maintain stable activity after three catalytic cycles. The scavenger studies indicate that O2− radicals are the main active species in the degradations of CV and atrazine, while OH and h+ play an assistant role in these processes. Liquid chromatography coupled with electrospray ionization mass spectrometry is used to analyze the samples obtained from the photocatalytic degradation of CV and atrazine. The degradation pathways of atrazine are evaluated suggesting two different routes including dechlorination-hydroxylation and alkylic-oxidation-de-alkylation. On the other hand, the degradation of the CV takes place via N-de-methylation in a stepwise manner generating the various N-de-methylated intermediate CV species. The excellent activity and photostability reveal that silver vanadates (including Ag4V2O7) are promising visible-light-responsive photocatalysts for water and wastewater treatment.