Preparation and characterization of a series of porous anion-exchanger chelating fibers and their adsorption behavior with respect to removal of cadmium(ii)

Abstract

The aim of the present study was to investigate a series of porous anion-exchanger chelating fibers (PP-g-AA-Am), prepared using polypropylene (PP) for the removal of Cd(II) in non-salt systems and in high-salt complex systems. FTIR, BET, FESEM, and XPS spectra indicated that AA was grafted onto the surface of PP fibers and, subsequently, amino functional groups and amide bonds were introduced by the amide reaction. A batch experimental study indicated that the adsorption of Cd(II) could be well-fitted with the pseudo-second-order kinetic model and the Freundlich isotherm. Thermodynamic studies indicated that the adsorption reaction was a spontaneous and endothermic process. Because of the electrostatic interactions and coordination bonds between Cd(II) and PP-g-AA-Am fibers, the resulting adsorption capacities are as follows: PP-g-AA-EDA (125.34 mg g⁻¹), PP-g-AA-DETA (116.15 mg g⁻¹), PP-g-AA-TETA (93.02 mg g⁻¹) and PP-g-AA-TEPA (81.01 mg g⁻¹). The presence of high-salt NaCl solution, as well as CaCl₂, KCl and MgCl₂, did not significantly affect the Cd(II) adsorption process, whereas strongly acidic or strongly alkaline conditions were unfavorable. In addition, the reusability of the obtained fibers, without a significant deterioration in performance, was demonstrated with at least five repeated cycles.