Removal of oxytetracycline by Fe₂O₃–TiO₂/modified zeolite composites under visible light irradiation

A series of Fe₂O₃ and TiO₂ immobilized on NZVI modified zeolite composites ((n)Fe₂O₃–TiO₂/FeZ) were synthesized by a one-pot hydrothermal method combined with calcination for oxytetracycline (OTC) removal. Some of the zero valent iron particles (NZVI) were impregnated into the framework of zeolite X by hydrothermal method and others were oxidized to Fe₂O₃ through calcination. The TiO₂ and Fe₂O₃ particles were immobilized on the surface of zeolite X. Compared with pure Fe₂O₃–TiO₂, the OTC adsorption and photocatalytic degradation efficiency of (n)Fe₂O₃–TiO₂/FeZ increased sharply. As the weight ratio of NZVI to TiO₂ was six and four, the sample had the highest adsorption efficiency (95%) and showed the highest total efficiency (98%) via adsorption and visible light—driven photocatalytic activity for the degradation of OTC, respectively. The materials also had good cyclic stability and the removal efficiency reached up to above 80% after four runs. In addition, the photocatalytic mechanism was proposed. The improved photocatalytic activities and stabilities of (n)Fe₂O₃–TiO₂/FeZ for OTC degradation were ascribed to the enhanced adsorption capacity of FeZ, the strong absorbance in the visible light region and improved photo-induced charge carriers separation.