Facile preparation of a nano-imprinted polymer on magnetite nanoparticles for the rapid separation of lead ions from aqueous solution

A novel nanostructured magnetic ion-imprinted polymer (IIP) was synthesized for the selective adsorption of Pb(II) from aqueous solution. The IIP was prepared on functional Fe3O4@SiO2 core/shell nanoparticles as a support. Monomer units in the polymer featured the typical bidentate ligand itaconic acid. We used ethylene glycol dimethacrylate and 2,2-azoisobisbutyronitrile as a cross-linker and an initiator, respectively. Monomers with different acid–base properties and different proportions of cross-linker were investigated to obtain high-performance adsorbents. Our results showed that the IIP prepared from itaconic acid had a high adsorption capacity owing to the strong binding between the monomer and Pb(II) template ion. The IIPs were characterized using Fourier transform infrared spectroscopy, Brunauer–Emmett–Teller surface area analysis, thermogravimetric analysis, and transmission electron microscopy. We confirmed the formation of a nano-imprinted shell layer on the surface of Fe3O4@SiO2. The adsorption rate was fast, conforming to a pseudo-second-order kinetic and Langmuir adsorption model; the adsorption mechanism was deemed to be chemisorption as a single molecular layer. The maximum adsorption capacity of the IIP (51.2 mg g−1) was approximately three times as large as that of the non-imprinted polymer (17.9 mg g−1). The selectivity factors for Pb(II) in mixed solutions of Pb(II)/Co(II), Pb(II)/Cu(II), and Pb(II)/Zn(II) were 45.6, 6.45, and 8.3, respectively. Pb-IIP exhibited a high selectivity towards Pb(II), which enabled the enrichment of Pb(II) in aqueous solution.