The survey of Phothocatalytic degradation of naphthalene by TiO2 doped with Nitrogen-Sulfur and Phosphor under visible light

Naphthalene is one of the toxic and dangerous polycyclic aromatic hydrocarbons (PAHs) for human and the environment, and it is necessary to remove it from the environment. The aim of this research is to investigate the phothocatalytic degradation of naphthalene from aqueous environments using two nanocatalysts TiO2-N, S/SiO2 and TiO2-P/SPA under visible light in the presence of Oxygen.  
Material and This research was done in year 2019.  In this research, two phothocatalysts TiO2-N, S/SiO2 and TiO2-P/SPA were synthesized by sol-gel method and they were used to remove Naphthalene from the aqueous environments under visible light and in the presence of Oxygen.  The Effect of various parameters including the initial concentrations of naphthalene, pH, contact time were investigated, and the structure of these nanoparticles was investigated using scanning electron microscopy (SEM), energy-dispersive ray (EDAX) image and UV-Vis differential reflectance spectroscopy (DRS) analysis.
SEM image showed the nanoparticle size of synthetic phothocatalysts to be 10 to 20 nm and, the thickness of the phothocatalyst thin layer TiO2-N, S and TiO2-P on the microspheres was 698.68 nm and 1.73 µm, respectively. DRS analysis indicated that the energy band gap of both phothocatalysts has become narrower than TiO2 and their phothocatalytic activity has been transferred to the visible light region. In the optimal conditions of Naphthalene removal, the values of pH, time, Naphthalene concentration, and removal efficiency were obtained for TiO2-N, S equal to 5, 50, 25, 94.23% and for TiO2-P equal to 5, 40, 25, 97.39%, respectively (Pv<0.05).
Discussion and These photocatalysts can be used as a new, effective and practical method in the treatment of water and wastewater from industrials containing Naphthalene under sunlight and visible light.