Kinetics and mechanism of chelating reaction between chitosan derivatives with Ca(II)

Abstract

Chitosan derivatives, such as chitosan alpha-ketoglutaric acid (KCTS) and hydroxamated chitosan alpha-ketoglutaric acid (HKCTS), are prepared and their coordination behavior toward Ca(II) was studied. The adsorption isotherms were correlated by dc/dt = −kcⁿ at 20°C, 30°C, 40°C, 50°C, and 60°C. By linear correlation, the shapes of the isotherm curves were similar to the kinetic function of 1/c = kt and the rate equation was dc/dt = −kc ²; the activation energies were 13.31 and 14.76 kJ mol⁻¹ for KCTS and HKCTS, respectively. The overall rate of Ca(II) adsorption is likely to be controlled by the chemical process. The coordination mechanism of chitosan derivatives with Ca(II) was studied by infrared and X-ray photoelectron spectroscopy. The results indicated that –NH– of KCTS was coordinated. Nitrogen of amino, oxygens of hydroxamic acid, and carbonyl in HKCTS coordinated with Ca(II).

Keywords:

• Chitosan derivatives
• Adsorption
• Chelating reaction

Acknowledgments

This work was supported by research grants from the National Science Foundation of China (Project No. 20576142), the Postdoctoral research fund of China (No. 20090461026), and the education subject of Hunan province of China (No. 10C0178).