P-nitrophenol (PNP) is a toxic organic pollutant and it is difficult to remove from wastewater by means of conventional treatment processes. Therefore, effective and low cost alternative water treatment technologies are required. In the last years there has been a growing interest in advanced oxidation processes involving semiconductor mediated photocatalysis because the process mineralizes many toxic organic pollutants to carbon dioxide and water at ambient temperature under UV light.
The aim of this work is to synthetize ZnS photocatalyst starting from formerly ZnO prepared with different precursors such as zinc sulphate and zinc nitrate by means of precipitation method. ZnS was then obtained by sulfuration of ZnO particles. The sulfuration step was carried out at 450°C in presence of N2 gaseous stream containing H2S at 5 vol%. The prepared photocatalysts were characterized from chemical-physical point of view using different techniques (XRD, BET, UV-vis DRS, Raman).
The photocatalytic tests were carried out in a recirculating batch cylindrical photoreactor irradiated by a UV-LEDs strip (nominal power of 12W/m and wavelength emission peak at about 365 nm) surrounding the external surface of the reactor. The experimental results evidenced that the optimal sample is ZnS obtained from the sulphuration of ZnO synthetized by zinc sulphate. In particular, this sample was able to achieve about 51% PNP degradation after 240 min of UV light irradiation.