Cationic dye methylene blue (MB) was removed from aqueous solution by kapok fiber treated with sodium chlorite (NaClO2). During the treatment process of the adsorbent, response surface methodology (RSM) based on three-level three-factorial Box-Behnken design was used. The effects of three variables, such as NaClO2 content (0.3-1.2 g), acetic acid (HAc) content (0.1-1.9 mL) and reaction temperature (60-90 degrees C) on the adsorption capacity for MB (as response) were examined. The optimum treatment conditions (NaClO2 of 0.93g. HAc of 1.42 mL and reaction temperature of 90 degrees C) were determined by the results of statistical analysis, under which an adsorbent was prepared and used to remove MB from aqueous solution. The effects of contact time, pH on adsorption and adsorption mechanism were investigated. The predicted value of model (105.48 mg/g) was in excellent accordance with experimental value (110.13 mg/g). The adsorption process was rapid and obeyed pseudo-second-order kinetics. The adsorbent showed excellent reusability with 0.1 mol/L of hydrochloric acid solution as desorbing agent and could be used as a potential adsorbent for cationic dyes containing wastewater treatment. (C) 2012 Elsevier B.V. All rights reserved.