Solvent-free engineering of Fe0/Fe3C nanoparticles encased in nitrogen-doped carbon nanoshell materials for highly efficient removal of uranyl ions from acidic solution

Abstract In this work, nitrogen-doped carbon nanoshell structure with the encased Fe0/Fe3C nanoparticles (Fe@NC) was synthesized with a solvent-free method via direct carbonizing the ground mixture of dicyandiamide and ferric chloride hexahydrate. The morphology, structure, and surface properties of as-synthesized Fe@NC were characterized systematically, and the removal performance of Fe@NC towards U(VI) was studied in detail. The results manifested that the Fe@NC possessed large surface area (127.0 m2/g) with mesoporosity and the encapsulated Fe0/Fe3C nanoparticles were concentrated at the tip of N-doped carbon nanotubes. Moreover, the Fe@NC hybrid material exhibited the maximum removal capacities of 0.85 and 0.44 mg/m2 at pH 4.5 and 1.5, respectively. The mechanism of U(VI) removal by the Fe@NC was attributed to the synergistic effects of adsorption via nitrogen/oxygen-containing groups and redox reaction between Fe0/Fe2+ and U(VI).