novel adsorbent called cetyltrimethylammonium bromide (CTAB)-modified TiO 2 nanoparticles were used for an efficient removal of anionic dyes (e.g. alizarin red S and indigo carmine) from water samples in single and binary batch systems. The influence of various factors such as initial pH, initial dye concentration and sorbent mass on the adsorption process was investigated. Statistical experimental design was utilized to optimize this adsorption process. A regression model was derived using a response surface methodology through performing the 416B model of hybrid central composite design. Model adequacy was checked by means of tests such as analysis of variance (ANOVA), a lack of fit test, and residuals distribution consideration. The proposed quadratic model resulted from the hybrid design approach fitted very well to the experimental data. The optimal conditions for dye removal were as follows: pH = 2, sorbent dose = 0.05 g, C AR (initial AR concentration) = 232.50 mg / L and C IC (initial IC concentration) = 298.3 mg / L. Moreover, the isotherms and kinetics of the adsorption process were also investigated.
