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.
