Preparation and characterization of quaternary chitosan salt: adsorption equilibrium of chromium(VI) ion

Quaternary chitosan salt (QCS) was synthesized with the aid of a substituent containing a quaternary ammonium group, glycidyl trimethyl ammonium chloride. The polymer was characterized by IR, H-1 NMR, TGA and amount of quaternary ammonium groups. The studies on Cr(IV) ion adsorption equilibrium were conducted taking into account contact time, pH and amount of cross-linked QCS. The kinetic adsorption mechanism of the Cr(VI) ion was best described by the pseudo-second-order equation with a rate constant of 1.0 x 10(-3) mg/g min. The Langmuir isotherm model was employed in order to adjust adsorption data, and the capacity was shown to depend on pH. The adsorption capacity for Cr(VI) at pH 9.0 was 30.2 mg/g (0.58 mmol/g), while at pH 4.5 the capacity was 68.3 mg/g (1.31 mmol/g). Cr(VI) ions can be eluted from cross-linked QCS by treatment with a 1 mol/l solution of NaCl/NaOH showing an efficiency of more than 95%. (C) 2004 Elsevier B.V. All rights reserved.