Photocatalytic degradation of sulfamethazine using a direct Z-Scheme AgI/BiVO photocatalyst: Mineralization activity, degradation pathways and promoted charge separation mechanism.

Z-scheme heterojunction can not only promote the separation of photogenerated carriers, but also retain the strong redox potential of the system, which would greatly improve the photocatalytic performance of catalyst. Herein, a Z-scheme AgI/BiVO heterojunction photocatalyst was prepared by a hydrothermal process combined with in situ coprecipitation process. Multiple techniques were employed to investigate the morphology, composition, chemical and electronic properties of the as-prepared samples. The obtained Z-scheme AgI/BiVO heterojunction photocatalyst exhibited remarkably enhanced photocatalytic performance towards sulfamethazine (SMZ) degradation under visible light irradiation. Especially, the 20 wt% AgI/BiVO composites exhibited the highest photocatalytic activity for sulfamethazine (SMZ) degradation and 91.47% SMZ would be eliminated within 60 min. In comparison with NO and SO, the presence of Cl and HCO presented more obviously inhibition effects on SMZ degradation. The possible degradation pathways of SMZ were speculated by identifying degradation intermediates. O, h and OH all involved in the photocatalytic degradation SMZ. The highly enhanced photocatalytic performance might be attributed to form Z-scheme junction between AgI and BVO, which are conducive to the efficient charges separation and maintain high redox potential. This work enriches BiVO-based Z-scheme heterojunction photocatalytic system and provides a reference for the preparation of effective Z-scheme junction photocatalysts.