Adsorption of reactive red 136 onto chitosan/montmorillonite intercalated composite from aqueous solution

Chitosan/montmorillonite intercalated composite (CTS/MMT) was used as an effective adsorbent for removal of reactive red 136 (RR136). 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 shown that the most effective parameter is initial concentration of dye. The optimal adsorption conditions were found in pH 3, initial concentration of dye 240 mg/L, temperature 20 degrees C, adsorbent dosage 0.4 g/L and contact time 135 min. Under the optimal condition, the removal percentages and adsorption capacity were 74.7% and 445.38 mg/g, respectively. The adsorption behaviors showed that the adsorption isotherms and kinetics were in best agreement with the Toth isotherm and Brouers-Weron-Sotolongo model, respectively. Applicability of mechanistic models exhibited that film diffusion and infra-particle diffusion were involved in the current adsorption processes and infra-particle diffusion was not the only rate-controlling step. CTS/MMT before and after adsorption were characterized through FT-IR, XRD and SEM. The results indicated that the RR136 adsorption process was not only surface adsorption but intercalation, and -OH, -CONH2 , -NH2, and Si-O group of CTS/MMT were involved in the adsorption process. Moreover, the desorption and regeneration experiments revealed CTS/MMT showed excellent adsorption performance even after 15 adsorption-desorption cycles.