• carbon;
  • chromium;
  • core/shell materials;
  • magnetic materials;
  • microporous materials;
  • microporous carbon


Magnetic hollow structures with microporous shell and highly dispersed active cores (Fe/Fe3C nanoparticles) are rationally designed and fabricated by solution-phase switchable transport of active iron species combined with a solid-state thermolysis technique, thus allowing selective encapsulation of functional Fe/Fe3C nanoparticles in the interior cavity. These engineered functional materials show high loading (≈54 wt%) of Fe, excellent chromium removal capability (100 mg g−1), fast adsorption rate (8766 mL mg−1 h−1), and easy magnetic separation property (63.25 emu g−1). During the adsorption process, the internal highly dispersed Fe/Fe3C nanoparticles supply a driving force for facilitating CrVI diffusion inward, thus improving the adsorption rate and the adsorption capacity. At the same time, the external microporous carbon shell can also efficiently trap guest CrVI ions and protect Fe/Fe3C nanoparticles from corrosion and subsequent leaching problems.