The polyaniline (PANI) doped with 8% CuCl2 was investigated as adsorbent for removal of the reactive azo dye by using batch adsorption process. Effects of the major independent variables (initial dye concentration, initial pH, and PANI mass) and their interactions during reactive azo dye adsorption were determined by response surface methodology (RSM) based on three-level Box-Behnken design (BBD). The results indicated that the adsorption efficiency of dye in aqueous solution was affected by all of the three factors studied. The PANI mass was the most significant variable affecting the reactive azo dye removal. Optimized values of initial dye concentration, initial pH and PANI mass for reactive azo dye sorption were found as 60 mg/L, 6, and 0.3006 g, respectively which correspond to 99.83% adsorption efficiency. (c) 2012 Elsevier B.V. All rights reserved.