Synthesis of a core-shell magnetic Fe₃O₄-NH₂@PmPD nanocomposite for efficient removal of Cr(VI) from aqueous media

The synthesis of reclaimable adsorbents with satisfactory adsorption performance and easy separation properties is necessary for environment-related applications. In this study, novel amine-functionalized magnetic Fe₃O₄ (Fe₃O₄-NH₂) nanoparticles coated with poly(m-phenylenediamine) (Fe₃O₄-NH₂@PmPDs) were synthesized successfully via oxidation polymerization. The as-prepared Fe₃O₄-NH₂@PmPDs with a well-defined core-shell structure were characterized, and their extraordinary Cr(vi) removal capability was investigated. Fe₃O₄-NH₂@PmPDs exhibit high adsorption capacity (508 mg g^-1) and fast adsorption rate towards Cr(vi). The abundant nitrogen-containing functional groups on the surface of Fe₃O₄-NH₂@PmPDs greatly contribute to the adsorption/reduction of Cr(vi). Moreover, the intraparticle diffusion model can be used to provide a good explanation of every stage of the process. The calculated thermodynamic parameters suggest that the adsorption of Cr(vi) onto Fe₃O₄-NH₂@PmPDs is endothermic and spontaneous. Fe₃O₄-NH₂@PmPDs can be easily separated, and the regenerated adsorbents still maintain high adsorption capacity. The results imply that Fe₃O₄-NH₂@PmPDs can be regarded as a suitable material for the treatment of Cr(vi) from contaminated water.