Fe3O4/cyclodextrin polymer nanocomposites for selective heavy metals removal from industrial wastewater

In this work, carboxymethyl-β-cyclodextrin (CM-β-CD) polymer modified Fe3O4 nanoparticles (CDpoly-MNPs) was synthesized for selective removal of Pb2+, Cd2+, Ni2+ ions from water. This magnetic adsorbent was characterized by TEM, FTIR, XPS and VSM. The adsorption of all studied metal ions onto CDpoly-MNPs was found to be dependent on pH, ionic strength, and temperature. Batch adsorption equilibrium was reached in 45 min and maximum uptakes for Pb2+, Cd2+ and Ni2+ in non-competitive adsorption mode were 64.5, 27.7 and 13.2 mg g−1, respectively at 25 °C. Adsorption data were fitted well to Langmuir isotherm and pseudo-second-order models for kinetic study. The polymer grafted on MNPs enhanced the adsorption capacity because of the complexing abilities of the multiple hydroxyl and carboxyl groups in polymer backbone with metal ions. In competitive adsorption experiments, CDpoly-MNPs could preferentially adsorb Pb2+ ions with an affinity order of Pb2+ ≫ Cd2+ > Ni2+ which can be explained by hard and soft acids and bases (HASB) theory. Furthermore, we explored the recyclability of CDpoly-MNPs.