Improved Synthesis of Chitosan -Bearing boldbeta-Cyclodextrin and Its Adsorption Behavior towards Bisphenol A and 4-Nonylphenol

The synthesis of chitosan-bearing -cyclodextrin (CDC) has been improved by use of an alternative condensing agent, 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride (DMT-MM). CDC was obtained by the reaction of succinyl chitosan with a small amount of mono-6-amino-mono-6-deoxy--cyclodextrin (ACD) within a shorter reaction time. Under optimal conditions, the CD yields reached to 50%, which were almost the same as those in the reactions using 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide hydrochloride (EDC). The gelation time suggests that the crosslinking of chitosan and the immobilization of the ACD occur competitively. To test the potential of CDC for selective removal of pollutants, the adsorption of bisphenol A (BPA) and 4-nonylphenol (NP) from aqueous solution onto CDC was investigated. In the case of the equilibrium concentrations more than 10 mg/L, the amounts of both sorbents onto CDC were close to the estimated saturated value of the CDC (85 mg/g for BPA and 81 mg/g for NP).