In this paper,the degradation of an azo dye Orange G (OG) on

In this paper,the degradation of an azo dye Orange G (OG) on nitrogen-doped TiO2 photocatalysts has been investigated under visible light and sunlight irradiation.Under visible light irradiation,the doped TiO2 nanocatalysts demonstrated higher activity than the commercial Dugussa P25 TiO2,allowing more efficient utilization of solar light,while under sunlight,P25 showed higher photocatalytic activity.According to the X-ray diffraction (XRD),X-ray photoelectron spectroscopy (XPS) and UV–vis spectra analyses,it was found that both the nanosized anatase structure and the appearance of new absorption band in the visible region caused by nitrogen doping were responsible for the significant enhancement of OG degradation under visible light.In addition,the photosensitized oxidation mechanism originated from OG itself was also considered contributing to the higher visible-light-induced degradation efficiency.The effect of the initial pH of the solution and the dosage of hydrogen peroxide under different light sources was also investigated.Under visible light and sunlight,the optimal solution pH was both 2.0,while the optimal dosage of H2O2 was 5.0 and 15.0 mmol/l,respectively.
Azodyes,which are characterized by the presence of one or more azo bonds ( N N ),are among the most notorious widespread environmental pollutants associated with textile,cosmetic,food colorants,printing,and pharmaceutical indus-tries.Because of their non-degradability,toxicity,potential mutagenicity and carcinogenicity,wastewaters originating from these dyes production or application industries pose a major threat to the surrounding ecosystems and human beings’ health.[1–3].Environmental concerns and the need of meeting the strin-gent international standards for rejecting wastewaters has made the development of novel and cost-effective processes for the purification of azo dyes effluents an issue of major technological importance.