In this work, three types of N,F-codoped TiO2 nanoparticles (N,F-TiO2) were synthesized using modified sol-gel methods, and applied in degradation of acid red B (AR B); as a target pollutant in solution. The extents of the degradation of acid red B were investigated to compare the photocatalytic activities of prepared three photocatalysts. The results show that anatase N,F-TiO2 nanoparticles can be obtained using the three methods with significantly enhanced photocatalytic degradation extents. The degradation rate under visible light alone is very slow, and the N,F-TiO2(1) prepared by different adding sequence of nitrogen and fluorine sources, exhibits higher degradation effect. Also, crystallite sizes and dispersion of particles, adding sequence of nitrogen and fluorine sources, doped dose, and treatment temperature have significant effects on the photocatalytic activity. Moreover, more.OH radicals are generated under visible light, in the presence of N,F-TiO2(1) than those in the presence of N,F-TiO2(2) prepared by double sol method, and N,F-TiO2(3) prepared by direct method. Therefore, this work suggests that preparation of N,F-TiO2(1) nanoparticles using hydrofluoric acid as fluorine sources and ammonia water as nitrogen sources is promising, and N,F-TiO2(1) is a promising photocatalyst in applications dealing with treatment of dye wastewater using solar light. (C) 2016 Elsevier B.V. All rights reserved.