Novel Core–Shell Structured Mn–Fe/MnO2 Magnetic Nanoparticles for Enhanced Pb(II) Removal from Aqueous Solution

Lead (Pb) is a priority pollutant, and the demand is growing for its cost-effective removal from water. A nanomaterial with Mn(II)-bearing Fe 3 O 4 (Mn–Fe) as magnetic core and MnO 2 as shell was synthesized, giving a specific surface area of 113.3 m 2 /g, particle size of 90–130 nm, cubic spinel magnetic phase, and saturation magnetization of 35.1 emu/g. It exhibited a strong propensity for adsorbing Pb(II), with a maximal adsorption capacity of 261.1 mg/g at pH 5.0. The process was rapid and pH dependent, but only slightly affected by ionic strength and coexisting cations, indicating the formation of the inner-sphere complexes. Used nanomaterial could be easily separated from solution by a magnet and readily regenerated with HCl. Its Pb(II) adsorption efficiency remained at about 80% of the original after the fourth regeneration. Thus, it has the potential for use as an effective adsorbent to remove Pb(II) from water.