Magnetic Porous Polymers Prepared via High Internal Phase Emulsions for Efficient Removal of Pb²⁺ and Cd²⁺

Magnetic porous polymers (MPPs) were successfully fabricated by a facile strategy of the high internal phase emulsions (HIPEs) technique. The microstructure, chemical composition, and magnetic properties of the MPPs were characterized. Impregnated with poly(styrene-divinylbenzene), stabilized by the amine-functionalized Fe₃O₄ nanoparticles (Fe₃O₄-NH₂), the as-prepared MPPs with rich pore hierarchy were employed to removal Pb²⁺ and Cd²⁺ from aqueous solution. The MPPs display outstanding removal capacities toward Pb²⁺ (257 mg/g) and Cd²⁺ (129 mg/g) within 15 min, and the encapsulated Fe₃O₄-NH₂ nanoparticles endow the MPPs with the ability of magnetic separation (30.15 emu/g). Additionally, the results indicate that the adsorptions of Pb²⁺ and Cd²⁺ are strongly dependent on pH and ionic strength, demonstrating that the interactions of Pb²⁺ and Cd²⁺ were mainly dominated by outer-sphere surface complexation and electrostatic attraction. The adsorption process is revealed by thermodynamic parameters to be spontaneous and endothermic. Further study demonstrates that the adsorption is involved in ion-exchange and cation-π interactions (between heavy metals and aromatic ring) on the surface of MPPs. Thus, feasible preparation of the MPPs with high adsorption capacities, excellent regeneration, and easy separation properties opens a new expectation in the potential application for engineering.