Sonocatalytic Degradation of Tetracycline with Cu-Doped TiO2 Nanoparticles as the Catalyst: Optimization, Kinetics, and Mechanism

Dearth of effective treatment technologies to remove antibiotics in water and wastewater necessitates innovative methods to tackle the problem of such recalcitrant pollutants. In this study, Cu-doped TiO2 (Cu/TiO2) nanoparticles synthesized by sol–gel process were employed as sonocatalyst for the degradation of tetracycline (TTC) in a multi-frequency hexagonal reactor. The synthesized particles were characterized by X-Ray diffraction (XRD) spectroscopy, transmission electron Microscope (TEM), Fourier-transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and UV–Vis diffused reflectance spectroscopy (UV-DRS). The effect of ultrasonic frequency (20, 50, and 80 kHz), catalyst dosage (0.5, 0.75, and 1 g L−1), and pH (4, 7, and 10) on the TTC degradation and mineralization was studied. Response surface methodology using a Box-Behnken Design (RSM-BBD) of experiments was used to evaluate the combined effects of these variables. Maximum sonocatalytic degradation efficiency of 92.52 ± 1.38% and mineralization efficiency of 63.77 ± 4.26% were achieved at the optimized conditions of US frequency 50 kHz, pH 8.1, and 0.71 g L−1 Cu/TiO2 dosage. Degradation of TTC followed pseudo-first-order kinetics for the sonocatalytic process. The better removal of TTC with doped Cu/TiO2 nanoparticles is speculated with improved utilization of cavitation phenomenon with solid catalyst and sonoluminescence phenomenon with doped catalyst having better photoactivity.