CdS-ZnS/ZTP NANOCOMPOSITE FOR PHOTOCATALYTIC DEGRADATION OF MALACHITE GREEN DYE UNDER ULTRAVIOLET AND VISIBLE LIGHT IRRADIATIONS

Abstract

Cadmium and zinc sulfide nanoparticles were synthesized by a direct precipitation method. The binary system CdS-ZnS nanocomposite was synthesized by impregnation method. Zirconium Titanium Phosphate (ZTP) was synthesized by a modified sol-gel method, whereas the CdS-ZnS/ZTP nanocomposite was synthesized by impregnation method by adding the assynthesized ZTP to a solution of cadmium(II) nitrate hexahydrate and zinc(II) nitrate hexahydrate. The photocatalysts were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR), scanning electron microscope-energy dispersive X-ray analysis (SEM-EDX), atomic absorption spectroscopy (AAS), and UV–Vis spectrophotometery to study the crystalline phases, functional groups, morphology, elemental analysis and band gap energies respectively. Photocatalytic degradation studies of malachite green using assynthesized photocatalysts were conducted under dark, UV as well as visible irradiations. The prepared CdS nanoparticles showed better photocatalytic activity than those of ZnS and ZTP under both visible and UV irradiations. The binary CdS-ZnS nanocomposite showed higher photocatalytic activity both under UV and visible irradiations as compared with the individual CdS and ZnS nanoparticles. This may be explained because of charge transfer and lower band gap energy of the binary sulfide nanoparticles. The highest photocatalytic degradation efficiency exhibited by CdS-ZnS/ZTP composite could be due to charge transfer, ion exchange property of ZTP and its lower band gap energy. The percentage degradation of MG dyes using different as-synthesized photocatalysts, ZTP, ZnS, CdS, CdS –ZnS and CdS-ZnS/ZTP at 180 min without irradiation were calculated as; 3.97%, 6.46%, 7.42%, 8.87% and 9.77% respectively. Whereas under UV and visible irradiations these values changed to 29.56%, 56.83%, 61.70%, 68.42%, 72.21% and 36.33%, 77.38%, 83.65%, 89.49%, 93.52%, respectively.