Chitosan flakes and chitosan–GLA beads for adsorption of p-nitrophenol in aqueous solution

A batch adsorption system was applied to study the adsorption of p-nitrophenol onto chitosan flakes and a cross-linked chitosan beads. The cross-linked chitosan beads were prepared using glutaraldehyde (GLA), a cross-linking agent, to enhance the chemical resistance and mechanical strength of chitosan beads. Adsorption experiments were carried out as function of pH, agitation period, agitation rate and different concentration of p-nitrophenol. Langmuir and Freundlich adsorption models were applied to describe the isotherms and isotherm constants. Equilibrium data agrees very well to the Freundlich model giving adsorption capacity of 0.63 mg g−1 for chitosan flakes and 2.48 mg g−1 for chitosan–GLA beads. The kinetic experimental data properly correlated with the second-order kinetic model with a rate constant of 3.82 × 10−1 g mg−1 min−1 and 3.34 × 10−1 g mg−1 min−1 for chitosan flakes and chitosan–GLA beads, respectively. Results showed that chitosan flakes and chitosan–GLA beads are favourable adsorbents.