Response surface statistical modeling for optimization of methylene blue adsorption from aqueous solution using chitosan/graphite composites: Isotherm and kinetics studies

The study aimed to create a chitosan/graphite composite (CGC) using the impregnation method to optimize its adsorptive efficiency for methylene blue dye from synthetic waste water. The composite adsorbent material was synthesized using a chitosan to expanded graphite ratio of 5% and acetic acid and glutaraldehyde. Expanded graphite was prepared by reacting it with H2SO4 and H2O2 for 90 minutes at room temperature. The specific surface area of graphite increased from 1193.75 m2/g to 1223.648 m2/g. The composite adsorbent material was synthesized using the impregnation method, with chitosan to expanded graphite ratio of 75:25. The CGC was characterized using FTIR, XRD, BET, SEM, and point of zero charge analysis. The adsorption of methylene blue dye onto CGC was optimized by response surface statistical experimental design method to achieve a removal efficiency of 98.61% at 5.24 initial concentration, pH of 9.98, and 95.43-minute contact time. The Langmuir isotherm best fitted the adsorption process, with an R2 value of 0.9974 and adsorption capacity of 98 mg/g. The kinetics of adsorption were best fitted to pseudo-second order with K value 0.0378. The composite was found to be the best alternative adsorbent for removing methylene blue dye from textile wastewater.