Removal of azo dyes from aqueous solutions using chitosan based composite hydrogels

Some cationic composite hydrogels based on chitosan (CS) and poly (N-2-aminoethyl acrylamide) (PAEA) covalently cross-linked with glutaraldehyde (GA) were tested as novel sorbents for two dis-azo dyes: Congo Red and Direct Blue 1. Three CS-based composite hydrogels having different molar ratios between the primary amine groups and the cross-linking agent (GA/NH2 = 5.3 and 12.5), the same total concentration of polycations (CPC = 2 wt%) and two molar ratios between polycations (PAEA:CS = 0.25 and 1.2) were used for this study. Pseudo-first order model, pseudo-second order model and the intraparticle diffusion model were used to analyze the experimental data in order to establish the mechanism of adsorption. The adsorption kinetics has been well described by the pseudo-second order model. The effect of temperature on the adsorption of both dyes has been also investigated.