A novel hierarchical porous polyHIPE/Fe3O4 nanocomposite foam functionalized by 1-vinylimidazole for Fe2+ removal from aqueous solutions

Highly open porous poly(styrene-co-divinylbenzene) polyHIPE foam was successfully synthesized and then functionalized by different percentages of 1-vinylimidazole co-monomer. Fe3O4 nanoparticles were synthesized and incorporated in the functionalized polyHIPE foams to enhance Fe2+ removal efficiency from aqueous solutions. The co-monomer in the functionalized and functionalized/Fe3O4 nanocomposite foams is well-suited to enhance Fe2+ removal efficiency. The adsorption efficiency of the 1-vinylimidazole-functionalized polyHIPE foams increased with increasing 1-vinylimidazole percentage. The kinetic studies showed a pseudo-second-order adsorption kinetics at different co-monomer concentrations. The nanocomposite foam containing 10, 20, 30 wt% Fe3O4 removed 79.01, 84.03, and 72.56% of Fe2+ ions, respectively. The 1-vinylimidazole@PolyHIPE/20 wt% Fe3O4 nanocomposite with the highest Fe2+ removal capacity was selected for further adsorption studies. The Fe2+ removal efficiency by this nanocomposite foam was investigated at different pHs, adsorbent dosages, and initial Fe2+ concentrations using the response surface method (RSM) experimental design. In addition to aqueous solutions containing only Fe2+ ions, the Fe2+ removal efficiency was evaluated in the presence of Ni2+, Cr3+, Cr6+, Zn2+, and Pb2+ for comparison purposes. These competing metal ions in the solution decreased the Fe2+ removal efficiency from 84.03 to 77.20%. The adsorption isotherms were best fitted to the Langmuir equation, indicating the adsorption of a monolayer of Fe2+ ions on the polyHIPE walls.