Environmentally Friendly β-Cyclodextrin-Ionic Liquid Polyurethane-Modified Magnetic Sorbent for the Removal of PFOA, PFOS, and Cr(VI) from Water

Emerging contaminants such as perfluorinated compounds (PFCs) and heavy metals are of increasing concerns due to their detrimental effects on environment and human health. Their mixtures are often present at contaminated sites that pose a challenge in water remediation. Herein, we report a multifunctional magnetic sorbent (Fe3O4-CDI-IL MNPs) that was prepared by modifying the magnetic Fe3O4 nanoparticle with beta-cyclodextrin ionic liquid (beta-CD-IL) polyurethanes for the removal of perfluorooctanesulfonate (PFOS), perfluorooctanoic acid (PFOA), and Cr(VI) from aqueous solution. The successful grafting of the beta-CD-IL polymer on magnetic nanoparticles was confirmed by FTIR, zeta-potential, TGA, and VSM. The sorption behaviors of Fe3O4-CDI-IL MNPs were investigated in terms of sorption kinetics, isotherms, simultaneous removal capability, and reusability. The kinetic results showed that the sorption of PFOS, PFOA, and Cr(VI) reached equilibrium within 4, 6, and 3 h, respectively, and the pseudo-second-order kinetic model best described the kinetic data. The solution pH had more obvious effects on the sorption of PFOA and Cr(VI) than that of PFOS. The coupling of ionic liquid with the beta-CD polymer backbone could significantly enhance the removal efficiencies of both PFOS and PFOA. The sorption isotherms indicated that the heterogeneous sorption capacities of Fe3O4-CDI-IL MNPs were 13,200 and 2500 mu g/g for PFOS and PFOA, respectively, and the monolayer sorption capacity was 2600 mu g/g for Cr(VI) ions. The Cr(VI)-PFC binary sorption experiments exhibited a decrease in sorption capacities for PFCs, but the removal of Cr(VI) was unaffected with the introduction of PFCs as co-contaminants. The hydrophobic interactions and electrostatic attraction were mainly involved in the PFC sorption process, whereas the ion exchange and reduction was responsible for Cr(VI) sorption. In addition, Fe3O4-CDI-IL MNPs could be readily recovered with a permanent magnet, regenerated, and reused at least 10 times without any significant efficiency loss. This multifunctional sorbent thus shows potential in the removal of coexisting toxic contaminants from water or wastewater.