Catalytic degradation mechanism of sulfamethazine via photosynergy of monoclinic BiVO4and microalgae under visible-light irradiation

Abstract

To improve the efficiency of antibiotic degradation, the photosynergistic performance of bismuth vanadate (BiVO4) with a microalga, Dictyosphaerium sp., was demonstrated under visible-light irradiation for the first time. Sulfamethazine (SM2) was selected as a representative sulfanilamide antibiotic, and the photocatalytic degradation mechanism of SM2 was evaluated in media via the BiVO4–algae system. The hydrothermally synthesized sample was characterized using X-ray powder diffraction, X-ray photoelectron spectroscopy, ultraviolet–visible diffuse reflectance spectroscopy, transmission electron microscopy, Brunauer–Emmett–Teller surface area, and Fourier transform infrared spectroscopy techniques. The results demonstrated that the prepared photocatalyst corresponded to phase-pure monoclinic scheelite BiVO4. The synthesized BiVO4 showed superior photocatalytic properties under irradiation with visible light, and more than 80% of photocatalytic degradation efficiency was obtained by the BiVO4–algae system. Based on quenching experiments, the photocatalytic degradation of SM2 in the BiVO4–algae system was primarily accomplished via the generation of triplet state dissolved organic matter, and hydroxyl radicals played a small role in the degradation process. The direct oxidation of holes made no contribution to the degradation. Metabolomics data showed that a total of 91 metabolites were significantly changed between the two comparison groups (algae–SM2 group vs algae group; algae–BiVO4–SM2 group vs algae–BiVO4 group). The glycometabolism pathways were increased and the tricarboxylic acid cycle was activated when BiVO4 was present. The study provides a distinctive approach to remove antibiotics using visible light in the aqueous environment.