Colorants are largely used in most industries such as plastic, paper, cosmetics and textile. Presence of colorants in wastewaters can cause serious damages to the environments such as reducing dissolved oxygen, preventing of light penetration into the water, impaired photosynthesis and etc. One of the methods used in recent years for removing dyes from aqueous solutions are advanced oxidation processes. The main purpose of this research is the evaluation of photocatalytic process using TiO 2 catalyst as a suspension in aqueous solutions including textile dyes in presence of UV irradiation for removal of dyes. The textile dyes used for this research are acid blue 113 and acid red 88. In order to optimize the removal efficiency, four factors including solution pH, initial concentration of dye, catalyst dosage and irradiation time were investigated. The removal efficiency of dye was considered as the response of experiments. All of the experiments carried out in a pilot designed for this research using agitators to obtain a steady suspension of TiO 2 in dye solution under the irradiation of UV-C on the surface of solution produced with two mercury lamps of 30 W placed 30 cm above the solution’s surface. The Response Surface Methodology (RSM) was used to design experiments and modeling the results. Variance Analysis showed that all of the four studied parameters have significant effect on dye removal. The initial pH of solution and initial dye concentration for acid blue 113 and acid red 88 has the most effect in dye removal efficiency, respectively. The results showed that in optimal conditions, photocaltalytic process can remove 98.8% of acid blue 113 and 99% of acid red 88. Overall, it can be concluded that the photocatalytic degradation using TiO 2 catalyst suspension in dye solution under irradiaation of UV-C on the surface of solution, performed well for the removal of acid dyes from aqueous solutions. Key words : acid blue 113, acid red 88, advanced oxidation process, TiO 2 , UV irradiation, Response surface methodology.
