Synergetic transformations of multiple pollutants driven by BiVO4-catalyzed sulfite under visible light irradiation: Reaction kinetics and intrinsic mechanism

Visible-light-driven photocatalysis has been widely employed as an efficient and environment-friendly technology for organic pollutants removal from wastewaters. Herein, a novel approach of BiVO4-catalyzed sulfite under visible light irradiation (BiVO4/sulfite/vis) was established to achieve the model contaminant methyl orange (MO) removal. About 92.06% of MO could be rapidly degraded within 50 min in this new catalytic system and the reaction rate was close to 105.29-fold as high as that of BiVO4/vis system. The effects of sulfite amount, catalysis dosage, MO concentration, inorganic anions and natural organic matters (NOMs) were deeply investigated and the correspondent mechanisms were also discussed. Interestingly, the coexisting Cr(VI) at certain concentration would accelerate MO removal and further demonstrated by phenol and atrazine degradation through the Cr(VI) + organic pollutants combined pollution system. The presence of HA in BiVO4/sulfite/vis also exhibited positive effects on the degradation of organic pollutants, attributable to more OH species generation. Three-dimensional excitation-emission matrix fluorescence spectra (3D EEMs) and liquid chromatography-mass spectrometer (LC-MS) were implemented to explore MO degradation pathway. The sulfite (SO3−) generation was confirmed by active species trapping experiments and electron spin resonance (ESR), and N2 purging reaction was also carried out to exclude the oxidative species of SO3−. The photoinduced holes played a direct role in the SO3− generation and the OH radical also contributed. This study provides new thoughts to improve the photodegradation of multiple organic pollutants by the introducing of sulfite or sulfite/Cr(VI).