Application of response surface methodology for the optimization of hexavalent chromium removal using a new low-cost adsorbent

The adsorption capacity of a novel adsorbent (Ageratum conyzoide leaf powder) was investigated for Cr(VI) removal from aqueous solution. Experiments were designed with the Box�Behnken model of the response surface methodology (RSM). Preliminary experiments were conducted to obtain the optimum range of process variables used for the Box�Behnken model. Three independent variables (pH, initial concentration, and adsorbent mass) were examined. The results show that Cr(VI) removal was more favorable at pH 2. Increase in pH above 2 resulted in negative Cr(VI) removal. Cr(VI) removal increased when adsorbent mass was increased, but decreased with increase in initial concentration. Cr(VI) removal of 92 was obtained at pH 2 and adsorbent mass of 0.3 g. Experiments were successfully optimized by RSM. Kinetics study correlated with the pseudo-second-order kinetic model, whereas equilibrium study was best described by the Langmuir isotherm model with maximum adsorption capacity of 437 mg/g. Thermodynamic parameters indicate a spontaneous, exothermic, and physiosorption process. © 2015 Balaban Desalination Publications. All rights reserved.