Graphene oxide crosslinked chitosan composites for enhanced adsorption of cationic dye from aqueous solutions

Backgrounds: In this study, we combined chitosan (CS) – considered a green adsorbent, and graphene oxide (GO) – an excellent adsorbent, to synthesize CS/GO composites with different GO contents. These composites promised the synergic effect of two materials and broadening the adsorption ability for water treatment. Methods: The characteristic data proved the successful cross-linking between CS and GO where CS molecules might deposit on GO sheets via amide linkage and hydrogen bonding. The effects of operating conditions and co-existing ions on batch-mode adsorption performance of methylene blue (MB) on the composites were studied. Significant findings: The experimental results indicated that the combination of CS and GO could not only improve the surface area by reducing agglomeration of GO sheets but also enhance significantly the adsorption capacity of cationic dye on CS. The Langmuir adsorption capacity of MB reached 259.5 mg/g at a pH of 8 and 30 °C for CS/GO12 material. The effect of common matrix ions such as Na⁺, Ca²⁺, Fe³⁺, and NO₃⁻ was examined, suggesting that the adsorption of MB over the composite was dominated by electrostatic interaction and pore space occupation. The removal of MB by the composite still achieved over 75% after the fourth adsorption-regeneration cycle.