Degradation of tetracycline by visible light over ZnO nanophotocatalyst

ZnO material can only absorb ultraviolet light. However, tetracycline (TC) can sensitize semiconductors to produce visible light activity. The application of intrinsic ZnO for visible light degradation of TC is a new discovery. The ZnO nanostructures were synthesized by the precipitation method with sodium dodecyl sulfate (SDS) as the structure guide. The catalytic activity of intrinsic ZnO to degrade high concentrations of TC under visible light irradiation was investigated. The addition of SDS changed the morphology of ZnO and reduced its average size to 55.5 nm. In the visible light photocatalytic degradation, SDS also enhanced the adsorption of TC on the surface of ZnO and promoted the formation of TC-SDS/ZnO surface complexes at the defects. The results showed that the degradation rate of TC by SDS/ZnO is 49.0%, which is 2.51 times that of commercial ZnO. UV-Vis DRS proves that TC-SDS/ZnO has visible light response, TC as a photosensitizer absorbs visible light and excites ZnO with visible light response. Radical trapping experiments combined with ESR tests jointly proved that •O2− and •OH play vital roles in the degradation of TC, finally the degradation mechanism was proposed.