Visible and solar photodegradation of textile wastewater by multiple doped TiO2/Zn nanostructured thin films in fixed bed photoreactor mode

Azo dyes degradation in aqueous solution as an actual sample of textile wastewater was studied by the photocatalytic process using Zn, N and S, and Zn, N and S tri-doped TiO2 thin films. Thin films were synthesized by a sol-gel method, successfully. Spectroscopy and chemical oxygen demand techniques were used to assess the progress and efficiency of the reaction. UV Vis results demonstrated that at natural pH 5.8 of the sample solution, maximum decomposition of 87-99% of azo dyes in 4 h has happened under visible irradiation with a primary concentration of 25 mg/l. According to COD results, after 4 h, a decreasing of the COD values from the azo dyes of solution significantly was obtained in the same condition. Besides, our results demonstrated, which nanostructure of TiO2/Zn-urea thin films with the highest efficiency decomposition, are recycled and permanent, showing a good potential of this technique in practical application. The immobilized TiO2 on the glass balls were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDS), diffuse reflectance spectroscopy (DRS), CHNS analysis and atomic absorption spectroscopy (AAS).