Photocatalytic Degradation of Oxytetracycline by Ternary Mixed Catalyst and Toxicity Assessment Using Boar Sperm.

Response surface methodology was adopted to obtain ternary mixed catalysts of TiO2-loaded ZSM-5 zeolite and graphene. Oxytetracycline was used as challenged toxicant to evaluate the photocatalytic degradation efficiency of the composites. The optimal weight ratio of graphene, TiO2, and ZSM-5 was 1:8:1. The composites were characterized by ultraviolet-visible spectroscopy, X-ray diffraction, fourier transform infrared, N-2 adsorption-desorption isotherms, and transmission electron microscope with an energy-dispersive spectroscopy system, etc. Synthesized samples showed high stability and strong visible-light absorption efficiency. The optimal operating conditions of oxytetracycline photocatalytic degradation were achieved over a wide range of pH and temperature. With 0.1 g/L of optimal ternary mixed composite, the photocatalytic degradation of oxytetracycline was nearly reached completion within 150 min at all treatment temperatures at pH 7. Toxicity of degraded oxytetracycline solution was assayed by a boar sperm quality model using fluorescent staining and flow cytometry. During 180 min of photocatalytic treatment, the degraded oxytetracycline solution showed increasing biotoxicity and changed the morphology and function of boar sperm, despite not killing them.