Statistical design of experiment as a tool for optimization of methylene blue sorption on CS/MCM-41/nano-γ alumina as a novel and environmentally friendly adsorbent: isotherm and kinetic studies

Chitosan/Mesoporous silica/Nano-γ alumina was synthesized and characterized by FTIR, XRD, FESEM, TGA and BET; also, it was applied as an efficient and eco-friendly adsorbent to investigate the adsorption properties of Methylene blue (MB) from the aqueous solution by following the optimization of influential parameters such as pH, contact time, adsorbent mass, and the initial concentration of MB by the central composite design (CCD) under a response surface methodology (RSM). Maximum removal efficiency at the optimum conditions (pH: 7.5, contact time: 45 min, adsorbent dosage: 0.088 mg, and the initial dye concentration: 15 mg/L) was achieved to be 90.23%. Analysis of variance and calculation of the correlation coefficient related to the predicted and experimental values of the removal percentage of MB proved the precision of the equation acquired by CCD. Subsequently, it was found that the adsorption isotherm was well fitted, and it was in a good agreement with the Langmuir isotherm model; the maximum adsorption efficiency (qmax) was found to be 80 mg/g. The study of the relation between time and the adsorption rate indicated that the adsorption of MB onto CS/MCM-41/Nano-alumina obeyed the pseudo-second-order. Besides, thermodynamic parameters calculated in this research, including ∆G°, ∆H°, and ∆S° revealed that the adsorption of MB on the adsorbent was spontaneous and endothermic. According to the results obtained in this research, CS/MCM-41/Nano-alumina could be regarded as an effective adsorbent for MB elimination from the aqueous solution.