We report herein the synthesis of monodisperse cobalt ferrite (CoFe2O4) nanoparticles (NPs) via a surfactant-assisted high temperature thermal decomposition method and then their assembly on reduced graphene oxide (rGO) to yield CoFe2O4-rGO nanocomposites, which displayed outstanding sonocatalytic activity for the removal of organic dyes from aqueous solutions under ultrasonic irradiation. As-prepared CoFe2O4-rGO nanocomposites were characterized by using transmission electron microscopy (TEM), high-resolution scanning electron microscopy (HR-SEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), Micro-Raman spectroscopy, Vibrating sample magnetometer (VSM) and inductively couple plasma mass spectrometer (ICP-MS). To evaluate the sonocatalytic activity of the CoFe2O4-rGO nanocomposites, the sonocatalytic removal of several organic dyes (AO7, AR17, BR46 and BY28) was studied. The reaction conditions were optimized by studying the effects of various key operating parameters such as pH, catalyst dosage, H2O2 initial concentration, initial dye concentration, ultrasonic power and reaction time on the removal of AO7 dye. The maximum removal efficiency of 90.5% was achieved at pH 3 using 0.08gL-1 catalyst, 3mM H2O2 and 10mgL-1 AO7 dye under 350W ultrasonic power in 120min of reaction time span. Experimental results revealed that the kinetic of the removal process could be described using Langmuir-Hinshelwood (L-H) kinetic model. The trapping experiments showed that O2·- radicals constitute the major reactive oxygen species (ROS) in the AO7 dye removal process. The reusability of the nanocomposites revealed about 22% drop in the removal efficiency within five consecutive runs. A possible sonocatalytic mechanism for the removal of organic dyes was also proposed. The intermediate by-products of the dye formed in the removal process were characterized by using the GC-MS technique.

In this research, tungsten disulfide (WS2) nanosheets as sonocatalyst were synthesized through a sonochemical route. Characterization of as-synthesized sonocatalyst was carried out by X-ray diffraction (XRD), scanning electron microscopy (SEM), electron dispersive X-ray spectroscopy (EDX), Dot-mapping, high resolution transmission electron microscopy (HRTEM), Brunauer-Emmett-Teller (BET), Fourier transform infrared spectroscopy (FTIR), and ultraviolet-visible diffuse reflectance spectroscopy (UV-vis DRS) analysis. WS2 nanosheets were evaluated for their sonocatalytic performance in order to remove basic violet 10 (BV10) under ultrasonic irradiation. The removal efficiency was maximized (94.01%) via the use of 1 g L-1 catalyst and 10 mg L-1 BV10 at pH = 4.5 and an ultrasonic power of 400 W within a reaction time of 150 min. In addition to BV10, the sonocatalytic elimination for a number of organic dyes viz. direct blue 71, acid blue 92, methylene blue, basic orange 2 and basic red 46 was examined to demonstrate the performance of WS2 nanosheets under the ultrasonic irradiation. The experimentation of trapping was conducted using edetate disodium (EDTA-2Na), tert-butyl alcohol (t-BuOH), and benzoquinone (BQ). According to the results, all radicals participated in the sonocatalytic activity. OH played a more prominent role than h+ and O2-∙ in the process of BV10 separation. Following five repetitive runs, the nanocomposites revealed a reusability of circa 18% drop in the elimination efficiency. The main removal intermediates were recognized by GC-MS technique.