Preparation and characterization of C,N-codoped TiO₂ photocatalyst for the degradation of diclofenac from wastewater

Application of mesoporous C- and C,N-codoped TiO₂ in the removal of diclofenac from water was studied. The sol–gel method was used for the preparation of the photocatalysts. The physicochemical properties of studied materials were characterized by BET (Brunauer, Emmett and Teller), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy and X-ray diffraction (XRD) methods. XPS confirmed the incorporation of nitrogen and carbon atoms into TiO₂ lattice. The synthesized catalysts were effective in the removal of the studied pollutant from water and enabled reduction of the COD (chemical oxygen demand) value of the wastewater by at least 60%. The process of diclofenac photooxidation over the C,N-codoped and C-doped TiO₂ photocatalysts proceeded similarly and was followed by pseudo-first order kinetics. The increase in calcination temperature resulted in the rutile fraction (5%) slightly lowering the effectiveness of treatment. The results over pure anatase structures confirmed that anatase has usually a better photocatalytic activity than rutile. The best changes in the water quality were observed during the first 50 min of treatment, but mineralization of pollutant did not lead to complete.