Photocatalytic Degradation Performance of Fluorine and Nitrogen Co‐doped TiO₂/AC Composites over Printing and Dyeing Wastewater under Visible‐Light Irradiation

Abstract

Printing and dyeing wastewater is one of the difficult wastewater to treat because of its complex composition, difficult degradation, high color and high concentration of organic matter. At present, photocatalysis, a chemical treatment method, is playing an increasingly important role in the field of printing and dyeing wastewater treatment. To improve the photocatalytic degradation efficiency of TiO2 on printing and dyeing wastewater, F−N‐TiO2/AC composite photocatalysts were prepared by loading titanium dioxide (TiO2) particles onto activated carbon (AC) using an impregnation‐hydrothermal method and co‐doping with fluorine and nitrogen. The characterization results showed that the TiO2 particles were loaded onto the surface and pores of AC, which increased the specific surface area of the composite and the average particle size of the TiO2 particles was reduced by the co‐doping of fluorine and nitrogen. Using methyl orange solution to simulate dye wastewater, the highest degradation efficiency (100 %) of methyl orange was achieved via F−N‐TiO2/AC composite photocatalysts when the F/TiO2 molar ratio was 0.3 and N/TiO2 molar ratio was 0.5. The rate of adsorption reaction for methyl orange by F−N‐TiO2/AC followed the pseudo second‐order kinetic. The effects of the catalyst dosage, environmental pH and interferences in water on the degradation efficiency of the F−N‐TiO2/AC composite photocatalyst were then investigated. The photocatalytic degradation of methyl orange is well fitted by a first‐order kinetic model and the degradation rate is 0.09616 min−1, which is about 6 times higher than that of TiO2/AC composites. Meanwhile, the F−N‐TiO2/AC composite photocatalyst had good recycling performance and the degradation efficiency toward methyl orange was still >80 % after five times of repeated use.