CeOx-coupled MIL-125-derived C-TiO2 catalysts for the enhanced photocatalytic abatement of tetracycline under visible light irradiation

The overuse of antibiotics triggered a serious environmental crisis, stimulating the development of feasible technologies for removing antibiotics from wastewater. Herein, a set of CeOx@C-TiO2 composites with varying amounts of CeOx from 1% to 15% were synthesized and applied for the photodegradation of tetracycline (TC) for the first time. It was found that the composites exhibited excellent performance for TC removal by degradation and mineralization under visible-light irradiation. The uniform distribution of CeOx nanoparticles in C-TiO2 permitted the surface contact of particles, enhancing their visible light absorption with a reduced band gap of 2.39 eV and electron-transfer efficiency through the formation of heterojunctions. The amount of CeOx played a predominant role in the photocatalytic properties. The 10% composite exhibited high removal rates of 99.1%, 98.2%, and 83.5% for 10, 20, and 40 mg/L TC, respectively. Characterization experiments proved that Ce mainly existed in its +3 and +4 valence states in the composites. The interchange of these two valence states accelerated the transfer of electrons and promoted the production of superoxide anion radicals and hydroxyl radicals responsible for TC degradation. These findings provide valuable guidelines for exploiting high-performance MOF-derived photocatalysts for the abatement of contaminants.