Insights into the photocatalytic behavior of carbon-rich shungite-based WO3/TiO2 catalysts for enhanced dye and pharmaceutical degradation

Abstract Carbon-rich shungite-based WO3/TiO2 catalysts were synthesized by a solvothermal method. The morphological, structural, optical and physical features of the catalysts were characterized by XPS, FTIR, Raman spectroscopy, SEM and UV–Vis diffuse-reflectance spectroscopy (DRS). The photocatalytic performance of the catalysts was investigated for the degradation of Orange II dye and pharmaceuticals under UV-A irradiation. SEM images show that the shungite surface is completely covered with WO3/TiO2 particles. Raman and XPS analyses demonstrate that the carbon-rich shungite is well-incorporated with the WO3 and TiO2. UV–Vis DRS indicates enhanced visible-light absorption and a lowered band gap (2.83 eV) for the catalysts. The degradation degree of Orange II increases with increasing shungite ratio, which is ascribed to a combined effect of adsorption and photocatalysis, and the improved light absorption and easy transfer of photogenerated holes and electrons across the interface of W/Ti. Mechanism studies indicate that the π–π conjugation between a dye molecule and the aromatic bonds of carbon materials are more dominant rather than columbic interactions, and that •is the main species in Orange II degradation. However, the Orange II degradation efficiency is lowered in drinking water due to the photo-generated hole (h+)-scavenging effects by organic matter and salts and their competing adsorption with the target pollutant in the active sites on the catalyst surface. This work provides a possible use of the carbon-rich shungite as a natural carbon resource for the fabrication of carbon-based photocatalysts.