Water-soluble N-carboxymethylchitosan derivatives:Preparation,characteristics and its application

摘要

In this work,only N-substituted chitosan derivatives(water-soluble N-carboxymethylchitosan derivatives:N-CMC)with different degrees of substitution were obtained by reaction of a fully deacetylated chitosan(derived from deacetylation of chitosan using decrystallized method)with monochloroacetic acid at pH 8 and temperature of 90 °C.The structure of N-carboxymethylchitosan and chitosan was characterized by IR,~1H,~(13)C and ~1H-~(13)C NMR-HSQC spectra.In the IR spectrum of the N-carboxymethylchitosan,the appearance of peak at 1742 cm~(-1)was assigned for CO group of-NH-CH2-COOH of substituted chitosan.In the'H NMR spectra,the peaks at about 3.81÷4.06 ppm,assigned for-CH2-groups of-NH-CH2-and-N(CH2)2-,were the major feature,while in the ~1H-~(13)C NMR-HSQC spectra,signals of-CH2-confirmed the presence of these two different substituted-CH2-groups.The degree of substitution(DS)of N-monosubstitution(DS_(N-mono))decreased from 0.47 to 0.03 meanwhile that of N,N-disubstitution(DS_(N,N-di))increased from 0.52 to 0.96 since the mass ratio of chitosan/monochloroacetic acid changing from 1/1 to 1/4.The N-carboxymethylchitosan derivatives have been used for adsorption Cu(II)ion from aqueous solution.The results shown that the optimum conditions for adsorption Cu(II)ion in nitrate solution were pH 6.5,temperature of 30 °C,for 60-90 min and the substituted chitosan derivative having DS_(N-mono)of 0.16 and DS_(N,N-di)of 0.81 had maximum adsorption capacity of 192 mg Cu(II)per gram of N-CMC.