H₂O₂-assisted sonophotocatalytic degradation of diclofenac using a visible light-active flower-like micron-sized TiO2 photocatalyst

The recovery of TiO₂nanoparticles after utilization is a major challenge that hinders the wide-scale implementation of photocatalytic technology in wastewater treatment. In this study, an easily recoverable flower-shaped micron-sized TiO₂(MST) photocatalyst was synthesized from nano-sized TiO₂seeds via a hydrothermal process. The synthesized MST photocatalyst displayed an average particle size of 1.577 μm with 2.7 eV bandgap energy and 100.18 m²/g surface area. The photocatalytic performance of the synthesized material was evaluated for the degradation of diclofenac (DCF) from aqueous solution under visible light. The degradation efficiency under visible light reached 52.87% in 120 min. When photocatalysis was coupled with ultrasonication (US), namely sonophotocatalysis, the DCF degradation efficiency increased to 62.61%. The highest DCF degradation efficiency (86.92%) was achieved under the optimized conditions of 30 kHz US frequency, 0.4 g/L of TiO₂loading, 10 ppm initial concentration of DCF, and 1.0 mM H₂O₂dosage. The synergy index of sonophotocatalysis was 1.25, indicating the synergistic effects of both sonocatalysis and photocatalysis on DCF degradation efficiency. The MST photocatalyst was easily recovered through centrifugation after reaction and reused for another two cycles of sonophotocatalysis. The photocatalyst was significantly stable under these process conditions, with only a 5.19% decrease in degradation after three consecutive cycles.