Degradation of Micropollutants in Wastewater Using Photocatalytic TiO2@Ag-NPs Coatings Under Visible Irradiation

The contamination of aquatic ecosystems by the micropollutants in wastewater discharges is currently a critical issue. Therefore, the development of novel treatment processes and materials is essential to ensure the availability of safe water. The present study aims to develop a photocatalytic material composed of silver nanoparticles (Ag-NPs)-doped TiO2 supported on a Pyrex® plate (TiO2@Ag-NPs) exhibiting catalytic activity under visible irradiation (λ > 400 nm). The effects of Ag-NPs doping on the TiO2 matrix, the resistance of the coating at the catalyst/substrate interface, and the photocatalytic degradation efficiency of the photocatalyst for a micropollutant (diuron) of the pesticide family were studied. The photocatalyst was characterised using X-ray diffraction, scanning electron microscopy, ultraviolet–visible spectrophotometry, and scratch tests. The solution concentrations were monitored using high-performance liquid chromatography and total organic carbon analyses. A 32% diuron removal was achieved using photocatalytic TiO2@Ag-NPs under visible irradiation, whereas undoped TiO2 showed no activity. Furthermore, the effects of the nanoparticle growth mode on the photocatalytic activity of TiO2@Ag-NPs were explored. The presence of a TiO2 sublayer ensured the adhesion of the coating and promoted the dispersion of nanoparticles within the matrix. It ensured chemical continuity (TiO2@Ag-NPs/Pyrex®), reduced the bandgap, and decreased electron–hole pair recombination.