Removal of Cu(II) ions from aqueous solutions using N-carboxymethyl chitosan.

N-carboxymethyl chitosan (NCMC) was synthesized by reacting chitosan with chloroacetic acid in water under triethylamine (Et(3)N) as catalyst. The chemical structures of NCMC were characterized by Fourier transform infrared (FT-IR) and hydrogen-1 nuclear magnetic resonance ((1)H-NMR) spectroscopy and confirmed that carboxymethylation occurred on the amino groups. Samples of NCMC were used for removal of Cu(II) from aqueous solution. The effects of degree of substitution of NCMC, initial pH value and adsorption kinetics on the adsorption were studied. Adsorption experiments showed that NCMC has a high adsorption speed and high adsorption capacity for remove Cu(II) from aqueous solution. The adsorption kinetics data were best fitted with the pseudo-second-order model. The experimental equilibrium data of Cu(II) on the NCMC were both fitted to the Langmuir model and Freundlich model, which revealed that the maximum capacity for monolayer saturation was 147.93 mg/g.