H2O2-induced surface modification: A facile, effective and environmentally friendly pretreatment of chitosan for dyes removal

H2O2-induced modification of chitosan was developed to improve the adsorption of dyes onto chitosan. The modified chitosan showed a more ordered structure and a higher hydrophilic character without significantly change of functional group on surface, comparing with the untreated chitosan. By the analysis of the hydrophilic character, zeta potential and XPS of untreated and pretreated chitosan, it can be inferred that the enhancement of interaction between the dye and chitosan was attributed to the increase of free hydroxyl and amine groups on the chitosan surface due to the partial removal of amorphous components induced by H2O2. Thus, the H2O2-induced modification of chitosan should make it easily for amine groups on pretreated chitosan surface to get protonated in weak acidic solution and resulted in simultaneous enhancement of electrostatic interaction between the dye and chitosan molecule. The adsorption results indicated that the dye removal efficiency improved about 60% after the chitosan pretreated with 200 mM hydrogen peroxide for 2 h. In addition, the adsorption of other dyes and the regeneration studies demonstrated that the pretreated chitosan could be recovered and reused effectively for the adsorption of anionic dyes. These observations reveal that this pretreatment method of chitosan is much more facile, environmentally and interesting than previously reported and provide a paradigm for surface modification of adsorbents.