Fast and selective removal of Cr(VI) from aqueous solutions by a novel magnetic Cr(VI) ion-imprinted polymer

In the present study, a novel magnetic Cr(VI) ion-imprinted polymer (MGOIIP) was prepared by a sol-gel process for fast and selective adsorption of Cr(VI) anions from aqueous solutions. In the synthesis process, 4-vinyl pyridine (4-VP) and 2-hydroxyethyl methacrylate (HEMA) were used as functional monomer and co-monomer; ethylene glycol dimethacrylate (EGDMA) and N,N-azoisobisbutyronitrile (AIBN) were used as cross-linker and initiator, respectively; acetone was selected as solvent. Fe3O4@SiO2 nanoparticles were introduced for separating adsorbents from the aqueous solution conveniently, and graphene oxide (GO) could prevent Fe3O4@SiO2 particles from aggregating. Some different techniques including Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), SEM-energy dispersive spectroscopy (SEM-EDS), X-ray diffraction (XRD) and thermogravimetric analysis (TGA) were used to confirm the successful synthesis of ion-imprinted polymer on the surface of Fe3O4@SiO2/GO nanoparticles. The obtained magnetic ion-imprinted polymer has a high adsorption capacity (up to 311.95 mg/g) for Cr(VI) anions at an optimal pH of 2.0, and the adsorption equilibrium can be reached within 3 min. The adsorption process can be fitted well with Langmuir isotherm model and the pseudo-second-order kinetic model. Moreover, the results showed that MGOIIP has excellent selectivity and good regeneration ability. The prepared MGOIIP exhibited a satisfactory recovery for Cr(VI) anions in tap, river and lake water samples. (C) 2017 Elsevier B.V. All rights reserved.