Removal of naphthalene from aqueous solutions by phosphorus doped-titanium dioxide coated on silica phosphoric acid under visible light

In this research, titanium dioxide-phosphorus (TiO2-P) immobilized on silica phosphoric acid (SPA) was prepared by a simple modified sol-gel method with SPA as a precursor instead of phosphoric acid. TiO2-P thin film photocatalyst immobilized on SPA as a novel high-efficiency photocatalyst was investigated to remove naphthalene as a toxic compound from wastewater. The novel resulting photocatalyst were characterized by energy-dispersive X-ray (EDX) and X-ray diffraction pattern revealed nano-photocatalyst TiO2-P with the average size of 15-20 nm. EDX analysis showed the presence of phosphorus elements in the crystalline structure of TiO2 and diffuse reflectance spectroscopy showed the energy bandgap narrowing and transfer of photocatalytic activity of TiO2-P to the visible region. The excellent photocatalytic activity of TiO2-P/SPA compared with TiO2-N,S as thin films coated on glass microspheres. The results showed that the optimal pH, time, concentration, and efficiency removal of naphthalene for TiO2-P were 5, 50 min, 25 mg/L, and 92.12% and TiO2-N,S catalyst were 5, 60 min, 25 mg/L, and 88.47%, respectively (P < 0.05). The removal of chemical oxygen demand in pH 5 for TiO2-N,S was obtained 79.26% and for TiO2-P was obtained 81.64%. In this research, the ability to use immobilized TiO2-P in SPA can be used as a new, effective and practical method in the treatment of water and industrial wastewater containing naphthalene in the presence of visible light.