Rational construction of CeO₂–ZrO₂@MoS₂ hybrid nanoflowers for enhanced sonophotocatalytic degradation of naproxen: Mechanisms and degradation pathways

This study proposed a novel heterogeneous sonophotocatalytic system to effectively treat pharmaceutical wastewater employing molybdenum disulfide (MoS₂) decorated ceria (CeO₂)-zirconia (ZrO₂) ternary hybrid nanoflowers (CZx/100 M). The generation of dominant oxidizing species, both radical and nonradical, was deeply scrutinized under ultrasound (US) irradiation coupled with visible-light by electron spin resonance spectroscopy analysis and scavenging experiments, for the first time. Interestingly, the pairing of US with visible-light illumination in a sonophotocatalytic degradation system resulted in 96% degradation efficiency of naproxen (NPX) within 40 min, which confirmed that excellent synergistic effect of sono- and photocatalytic mechanisms in the presence of 0.5 g/L sonophotocatalyst at pH 5.8. The sonophotocatalytic activity was also manifested at various reaction time, catalyst dose, solution pH, initial NPX concentrations, and US frequency and power and in the presence of various anions. The mechanism for the catalytic degradation of NPX is proposed in the US/Vis/CZx/100 M system, and transformation products formed during the process were identified by an ultra-high performance liquid chromatography-mass spectrometry technique.