Adsorption of reactive dyes onto chitosan/montmorillonite intercalated composite: multi-response optimization, kinetic, isotherm and thermodynamic study

Chitosan/montmorillonite intercalated composite (CTS/MMT) was used as an effective adsorbent for removal of reactive dyes, i.e. Reactive Black 5 (RB5), Reactive Red 136 (RR136), Reactive Yellow 145 (RY145) and Reactive Blue 222 (RB222). Taguchi method attached grey relational analysis was applied to determine the optimal adsorption conditions, including pH, initial concentration of dye, temperature, adsorbent dosage and contact time, for achieving simultaneous maximization of removal percentage and adsorption capacity. The percentage contribution of each adsorption condition was determined in the analysis of variance and showed that the most effective parameter in removal of RB5, RY145 and RB222 is the dye solution pH, whereas the initial concentration was the determining factor for optimum efficiency for the dye RR136. Under respective optimal condition, the removal percentages and adsorption capacity of four reactive dyes onto CTS/MMT were both found in the following order: RR136 > RY145 > RB5 > RB222. The maximum removal percentages of 78.8 and 49.5%, and the adsorption capacity of 315.20 and 123.75 mg/g were obtained for RR136 and RB222, respectively. The adsorption behaviors showed that the adsorption kinetics and isotherms were in best agreement with Avrami fractionary order model and the Toth isotherm, respectively.