Removal of Cd2+ from aqueous solution with carbon modified aluminum-pillared montmorillonite

To clarify the effect and mechanism of pillared montmorillonite on Cd2+ adsorption in aqueous solution, carbon modified alumina-pillared montmorillonite has been prepared by incorporating hydroxyl–aluminum cations into the lamellar spaces of montmorillonite via ion-exchanging together with polyvinyl alcohol (PVA), followed by calcining in N2 atmosphere. The pillared montmorillonites were characterized by XRD, FT-IR, TG–DTA and sorption isotherms. Uptake of Cd2+ from aqueous solution was analyzed by means of atomic absorption spectroscopy. The experimental results indicated that the pillared montmorillonites show better properties on both Cd2+ adsorption and desorption than the unpillared, which made them the promising recycling Cd2+ adsorbents. Moreover, adjusting the pH value of the solution could control the adsorbed amount of Cd2+. The adsorption process fitted the second-order kinetics well, and the two isotherm equations due to Freundlich and Langmuir showed good fits with the experimental data.