Sulfur and nitrogen doped-titanium dioxide coated on glass microspheres as a high performance catalyst for removal of naphthalene (C10H8) from aqueous environments using photo oxidation in the presence of visible and sunlight

Naphthalene is a toxic aromatic compound whose presence in aqueous environments is very hazardous. In this research, naphthalene removal from wastewater using titanium dioxide–nitrogen– sulfur (TiO2–N–S) photocatalyst immobilized on glass microspheres was investigated. Additionally, the effect of visible and sunlight, radiation time, pH, and initial concentration of naphthalene on photocatalytic removal of naphthalene were studied. Scanning electron microscope images revealed nanoparticles with an average size between 10 and 15 nm, and X-ray diffraction pattern revealed nano-photocatalyst with an average size of 11 nm. Energy-dispersive X-ray showed the presence of two elements, that is, sulfur and nitrogen in the crystalline structure of TiO2 powder, and diffuse reflectance spectroscopy showed the energy bandgap narrowing and transfer of photocatalytic activity of TiO2–N–S to the visible region. Chemical kinetic equation of naphthalene removal was second-order kinetic. The maximum level of naphthalene removal in the presence of visible and sunlight was obtained at a concentration of 25 mg/L (94.29%) and 40 mg/L (93.24%), respectively. Therefore, the immobilized TiO2–N–S on glass microspheres can be used as a new, effective, and functional method in treating water and industrial wastewater containing naphthalene in the presence of visible and sunlight.