A facile sol–gel synthesis of chitosan–boehmite film with excellent acid resistance and adsorption performance for Pb(II)

Abstract

A chitosan–boehmite (CS–boehmite) film with excellent acid resistance for effective Pb(II) removal was successfully synthesized via a facile sol–gel method. The composite, corresponding boehmite and CS films were characterized by XRD, ATR-FT-IR, TG, SEM and XPS. The static adsorption experiment showed that their adsorption well matched the pseudo-second order model on chemisorption adsorption, and the modified Langmuir model on homogenously surface for monolayer adsorption. Especially, the composite film with cross-linking mass ratio of 1:1 did not dissolve after shaking in an acidic solution of pH=2.0 for 1h due to formation of the monodentate C(O−Al)2 ligand, while the boehmite and CS films dissolved 24wt% and 100wt%, respectively. The maximum adsorption capacity of the composite film is 33.00mg/g from the modified Langmuir model which is much higher than 19.57mg/g of the boehmite film and 17.48mg/g of the CS film, respectively, and these values are highly close to their calculated values from the pseudo-second order model and also from the experiment values. Furthermore, the composite film shows strong capability of resisting disturbance for the coexisting cations (Na+, Mg2+, K+ and Ca2+); its adsorption mechanisms involve electrostatic attraction, complexation to form PbOH and the chemical precipitation of Pb3(CO3)2(OH)2.