Ultrasound-assisted degradation of organic dyes over magnetic CoFe2O4@ZnS core-shell nanocomposite.

Magnetic CoFe2O4@ZnS core-shell nanocomposite was successfully synthesized via one-step hydrothermal decomposition of zinc(II) diethanoldithiocarbamate complex over CoFe2O4 nanoparticles at low temperature of 200°C. The obtained nanocomposite was characterized by X-ray diffraction, Fourier-transform infrared spectroscopy, UV-Vis spectroscopy, field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, magnetic measurements, and Brunauere-Emmette-Teller. The results confirmed the formation of CoFe2O4@ZnS nanocomposite with the average crystallite size of 18nm. The band gap of 3.4eV was obtained using UV-vis absorption of CoFe2O4@ZnS nanocomposite, which made it a suitable candidate for sono-/photo catalytic processes. This nanocomposite was applied as a novel sonocatalyst for the degradation of organic pollutants under ultrasound irradiation. The results showed complete degradation of methylene blue (MB) (25mg/L) within 70min in the presence of CoFe2O4@ZnS nanocomposite and H2O2 (4mM). The trapping experiments indicated that OH radicals are the main active species in dye degradation. In addition, sonocatalytic activity of the CoFe2O4@ZnS nanocomposite was higher than those of pure ZnS and CoFe2O4, showing that the combining ZnS with magnetic CoFe2O4 could be an excellent choice to improve its sonocatalytic activity. The nanocomposite could be magnetically separated and reused without any observable change in its structure and performance even after five consecutive runs.