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.