Iranian Journal of

Background and Objective: Most of the dyes used in the textile industries can be toxic and carcinogenic. One of the suitable technologies to remove them is advanced oxidation processes. The main purpose of this study was to investigate the positive effect of adding oxidant Na₂S₂O₈ to the photocatalytic process using TiO₂ nano-particles immobilized on concrete and UV radiation for removal of Direct Blue71 dye. Materials and Methods: Concrete was covered by 40 g/m² of TiO₂ nanoparticles using SSP method. After selecting suitable oxidant concentration and optimum pH, initial dye concentration, UV irradiation intensity, and time, the efficiency and rate of dye removal and breaking amounts of benzene rings and COD variation were investigated in two systems of UV/TiO₂ and UV/TiO₂/Na₂S₂O₈. Results: In UV/TiO₂ system, 50.48 percent dye removal was observed at initial dye concentration of 100 ppm, pH 9, and 90 Watt UV lamp after 55 minutes and for UV/TiO₂/Na₂S₂O₈ system, initial dye concentration of 200 ppm, pH 6.9, and 0.24 g/L oxidant under the same abovementioned conditions resulted in 88.65 percent dye removal. Conclusion: Oxidant addition increased the dye removal efficiency and decreased total time for complete decolorization indicating the positive effect of oxidant on photocatalytic process in dye removal.