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α-Fe2O3 nanoparticle has been widely used in water purification because of its effective adsorption performance. However, aggregation and difficulty in separation limit its practical application. Herein, we presented a polyacrylonitrile (PAN) nanofiber mat decorated with α-Fe2O3 as adsorbent for effective removal of Pb 2+ from contaminated water, which can solve the above problems easily. The α-Fe2O3/PAN nanofiber mats were prepared via electrospinning followed by a facile hydrothermal method and characterized by SEM, HRTEM, FTIR and XRD. We demonstrated the formation mechanism of α-Fe2O3 anchored on PAN nanofiber surface consists of the adsorption of iron ions on the surface of PAN, and then the α-Fe2O3 nucleation and growth. The pH value of FeCl3 solution has a great impact on the formation process of α-Fe2O3/PAN nanofiber mat, which lead to the variation of morphology and the quantity of the coating coverage. When the pH value was 2.4, polyhedral particles were coated on PAN nanofibers uniformly and the optimized α-Fe2O3/PAN nanofiber mat was obtained. Controlled experiments were carried out to quantify the adsorption capacities of different samples and adsorption kinetics. The isotherm data from our experiments fitted well to the Langmuir model and the adsorption process can be described using the pseudo-second-model. Finally, the adsorption mechanism for Pb 2+ was investigated and the results revealed that ion exchange between proton of surface hydroxyl groups and Pb 2+ was accounted for the adsorption. Fig. 6 The effect of contact time on Pb 2+ adsorption capacity with different initial concentration (a), SEM image of α-Fe2O3/PAN (S2.4) after adsorption (b), the fitting results using pseudo first order (c), and pseudo second order (d) kinetic model.

Surface molecular imprinting in layer-by-layer (SMI-LbL) film is known as a facile and effective strategy to build imprinting sites that are more accessible to template molecules compared with molecular imprinting in polymers. Herein, we accomplished the formation of SMI-LbL film on electrospun nanofibers for the first time. The SMI-LbL nanofibers were prepared by a template-induced LbL process on the polyacrylonitrile (PAN) nanofiber substrates, followed by postinfiltrating and photo-cross-linking of photosensitive agent 4,4'-diazostilbene-2,2'-disulfonic acid disodium salt (DAS). The obtained nanofiber mat maintained the nanofibrous structure and showed rapid absorption and extraction of template molecules of meso-tetra(4-carboxyphenyl)-porphine (Por). The binding capacity of Por reached 2.1 mg/g when 3.5 bilayers were deposited on the nanofibers. After six cycles of extraction and reabsorption, the binding capacity of Por remained at 83%. Moreover, the absorption results of the targeted templated molecule of Por and the control molecule of Fast Green, which had a very similar chemical structure and charge status to Por, indicated the specific absorption for template molecule of Por. Thus, a surface molecular imprinted nanofiber mat with high selectivity of the templated molecule has been demonstrated.