Reactive and basic dyes removal by sorption onto chitosan derivatives.

In this study, the removal of a reactive (Remazol Yellow Gelb 3RS) and a basic (Basic Yellow 37) dye from aqueous solutions was investigated using cross-linked chitosan derivatives as sorbents (either powder or beads), which have been grafted with carboxyl and amide groups. The sorption behavior of the materials was examined through equilibrium, kinetic and pH-edges experiments. The reuse of sorbents was affirmed by sequential sorption-desorption cycles. Three isotherms (Langmuir, Freundlich, and Langmuir-Freundlich) were used to fit the equilibrium data, while the pseudo-second order equation for the kinetic data. Chitosan powder presented higher sorption capacity than beads. Chitosan grafted with amide groups was found superior sorbent for reactive dye at pH 2 (Q(max)=1211 mg/g), while chitosan grafted with carboxyl groups for basic dye at pH 10 (Q(max)=595 mg/g). For both cases the optimum contact time was 4 h using 1 g/L sorbent. The characterization of sorbents was achieved by scanning electron microscopy, particle size analysis and FTIR spectroscopy.