Ultrasound aided sonocatalytic degradation of Rhodamine B with graphitic carbon nitride wrapped zinc sulphide nanocatalyst

The ultrasound aided catalytic degradation of a model pollutant, viz, Rhodamine B (RhB) dye, was carried out in presence of graphitic carbon nitride (g-C3N4) wrapped zinc sulphide (ZnS) composite nanocatalyst. The g-C3N4/ZnS composite was synthesized in-situ via hydrothermal route. To ascertain the chemical compositions and surface morphology of as synthesized product, different characterization tools, viz, X-ray photoelectron spectroscopy, X-ray diffraction, Fourier transformed infrared spectroscopy and Scanning electron microscopy were used. The results confirmed the successful synthesis of spherical shaped g-C3N4/ZnS composite having good crystallinity. The g-C3N4/ZnS nanocomposite exhibited excellent sonocatalytic activity with dye removal efficiency of 92%, while pristine ZnS showed only 64% removal of RhB. The best catalytic performances were obtained for catalyst dosage, ca. 0.2 g/L, and with solution pH, ca. 6.5. Any changes in solution pH from its neutral value (pH = 6.5) resulted in the inferior catalytic degradation performances. The obtained results lead to the conclusion that the synergistic effect between g-C3N4 and ZnS in the g-C3N4/ZnS nanocomposite played the crucial role, which promotes easy separation of hole-electron pairs and consequent transfer of electrons from ZnS to g-C3N4, leading to enhanced sonocatalytic performances.