Sonocatalytic removal of naproxen by synthesized zinc oxide nanoparticles on montmorillonite

•Sonocatalytic degradation of naproxen in the presence of ZnO/MMT nanocomposite.•Characterization of nanocatalyst by XRD, SEM and TEM techniques.•Investigating the effect of operational parameters on sonocatalytic degradation of naproxen.•Identifying the intermediates formed during sonocatalysis using GC–MS analysis. ZnO/MMT nanocomposite as sonocatalyst was prepared by immobilizing synthesized ZnO on the montmorillonite surface. The characteristics of as-prepared nanocomposite were studied by scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM) and X-ray diffraction (XRD) techniques. The synthesized samples were used as a catalyst for sonocatalytic degradation of naproxen. ZnO/MMT catalyst in the presence of ultrasound irradiation was more effective compared to pure ZnO nanoparticles and MMT particles in the sonocatalysis of naproxen. The effect of different operational parameters on the sonocatalytic degradation of naproxen including initial drug concentration, sonocatalyst dosage, solution pH, ultrasonic power and the presence of organic and inorganic scavengers were evaluated. It was found that the presence of the scavengers suppressed the sonocatalytic degradation efficiency. The reusability of the nanocomposite was examined in several consecutive runs, and the degradation efficiency decreased only 2% after 5 repeated runs. The main intermediates of naproxen degradation were determined by gas chromatography–mass spectrometry (GC–Mass).