Cross-linked chitosan/beta-cyclodextrin composite for selective removal of methyl orange: Adsorption performance and mechanism

A complex chitosan/beta-cyclodextrin polymer was synthesized by bridging with maleoyl chains followed by cross-linking with glutaraldehyde. The adsorption performance of the synthetic polymer was investigated for selective removal of methyl orange (MO) from aqueous solution. The kinetic behavior was well fitted by the pseudo-second order model, while the adsorption process at equilibrium followed the Langmuir isotherm model. The thermodynamic parameters suggested that the adsorption was exothermic and spontaneous. Under optimal adsorption conditions, the capacity for MO reached 392 mg/g with the dosage of 10 mg/50 mL. Based on the analysis from FTIR, H-1 NMR, TGA and zeta potential, the adsorption mechanism could be explained by the synergistic effect of electrostatic attraction of amino groups from chitosan and host-guest interaction from beta-cyclodextrin. This adsorbent also demonstrated high selectivity towards MO due to the unique structure of crosslinked chitosan/beta-cyclodextrin polymer that are complementary to that of MO molecule.