Purification of textile wastewater by using coated Sr/S/N doped TiO2 nanolayers on glass orbs

Abstract

Simultaneous doping of TiO2 nanoparticles with three elements including Sr, S, and N is reported. The resulting material shows superior photocatalytic performance toward degradation of textile waste under visible and sunlight. The pure and doped TiO2 nanolayers were prepared by sol-gel method and were fixed on a bed of glass orbs. The immobilized TiO2 were characterized by a variety of techniques: X-ray diffraction (XRD), scanning electron microscopy (SEM), spectroscopy diffusion reflection (DRS), energy dispersive X-ray spectrometry (EDS) and elemental analysis (CHNS). The photocatalytic activity of the prepared fixed-bed materials toward degradation of the textile wastes was determined by using ultraviolet-visible spectroscopy (UV-Vis) and measurement of the chemical oxygen demand testing (COD). The best photocatalytic activity was observed with the use of Sr/S/N-TiO2 nano-layers. Afterwards, the experimental conditions were optimized by tuning reaction parameters, including amount of doped metal ion on photocatalyst structure, sample solution pH and photoreactor output flow rate. The results confirmed that at natural pH 5.9 of sample solution, maximum decomposition of 91-99% of azo dyes was obtained in 8 h under visible irradiation. Finally, the experiments were repeated under 1.5 AM sunlight with high volume of reactants in order to confirm the cost-effectiveness of the designed photocatalyst.