Sonocatalytic degradation of diclofenac with FeCeO_x particles in water

This paper studies the sonocatalytic degradation of diclofenac in water using FeCeO_x-catalyzed ultrasound. The effects of pre-adsorption and gas addition were investigated. Nitrogen adsorption/desorption, SEM, XRD, Raman and XPS analyses of FeCeO_x before and after sonication were characterized. The proposed mechanism was based on the microstructure changes of FeCeO_x and reactive-species-scavenging performances. The results show that FeCeO_x has excellent performance in catalyzing an ultrasonic system in water, and 80% of diclofenac was removed in 30min ([Diclofenac]=20mg/L, FeCeO_x amount=0.5g/L, pH=6, ultrasonic density=3.0W/cm³, ultrasonic frequency=20kHz, temperature=298K). The Fe, Ce, and O elements remained highly dispersed in the structure of FeCeO_x, and the solid solution structure of FeCeO_x remained stable after the reaction. Ce (III) was gradually oxidized to Ce (IV) and Fe (III) was gradually reduced to Fe (II) after the reaction, which indicates that Fe and Ce ions with different valences coexisted in dynamic equilibrium. The amount of oxygen vacancies in FeCeO_x significantly decreased after the reaction, which indicates that oxygen vacancy participated in the ultrasonic process. Singlet oxygen ¹O₂ was the primary reactive species in the degradation process, and the hydroxyl radicals OH and superoxide radical anion O₂^- also participated in the reaction. FeCeO_x had excellent chemical stability with negligible leaching ions in the ultrasonic process.