Ag modified ZnS for photocatalytic water pollutants degradation: Influence of metal loading and preparation method

In this paper, the photocatalytic degradation of organic pollutants was investigated using Ag/ZnS nanoparticles at different noble metal loadings. The photocatalysts were prepared at room temperature by two different methods: photodeposition and chemical reduction. The obtained samples were characterized by Specific surface area measurement, X-ray photoelectron spectroscopy, X-ray Powder diffraction, ultraviolet-visible diffuse reflectance and Raman spectroscopy. The X-ray photoelectron spectroscopy spectra showed that Ag is present on ZnS surface as intermediate state between nanostructured Ag⁰ and Ag₂O. Moreover, the addition of silver caused a significant change of the absorption spectrum of bare ZnS, resulting in higher absorbance in the visible region, due to the Ag surface plasmon band. Methylene blue (MB) was used to evaluate the photocatalytic activity of the prepared samples. The best photocatalytic activity was observed using the sample at 0.1 wt% Ag loading prepared by chemical reduction method. In particular, the almost complete MB degradation was achieved using UV-LEDs as light sources and 6 g L^-1 of catalyst dosage. Finally, the optimized photocatalyst was also effective in the degradation of phenol in aqueous solution under UV irradiation.