Photo catalytic degradation of Alizarin red S using ZnS and cadmium doped ZnS nanoparticles under unfiltered sunlight

Abstract

Zinc sulphide (ZnS) and cadmium doped ZnS (Cd-ZnS) nanoparticles were prepared by co-precipitation method and characterized by UV–Visible spectroscopy, X-ray diffraction (XRD) studies, Transmission electron microscopy (TEM) and Scanning electron microscopy (SEM). The optical band gaps of the synthesized materials were calculated from UV–Visible absorption spectra using Tauc plots. The band gap of ZnS was decreased from 3.4eV to 2.44eV due to substitution of Cd2+ ions in ZnS lattice at 0.5M cadmium content. This variation in the optical bandgap effectively monitored degradation of the dye. Photo catalytic degradation of Alizarin red S (ARS) by the nanoparticles showed that the cadmium doped ZnS acted as a potential photo catalyst under unfiltered natural sunlight of irradiation 300W/m2. The ARS dye was degraded about 50% and 96.7% in the presence of ZnS and Cd-ZnS (Cd 0.5M) nanoparticles respectively in 120min. Furthermore the effect of various parameters, i.e., photocatalyst concentration, dye concentration, and pH of the solution on the percentage of degradation was also studied. Degradation followed first order kinetics.