Switchable Transport Strategy to Deposit Active Fe/Fe3C Cores into Hollow Microporous Carbons for Efficient Chromium Removal

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 (approximate to 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 Cr-VI 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 Cr-VI ions and protect Fe/Fe3C nanoparticles from corrosion and subsequent leaching problems.