Interstitial Compound Fe₃C‑Doped\nFe(0) Nanoparticles Embedded in Mesoporous Carbon Efficiently Boosting\nCr(VI) Removal

Abstract

The\nhigh reactivity of Fe(0) with Cr(VI) makes it the best choice\nfor Cr(VI) removal. Interstitial compound Fe₃C was produced\nduring the carbothermic reduction of mesoporous phenolic resin/ferric\nions to form Fe(0)/Fe₃C nanoparticles embedded in mesoporous\ncarbon (Fe(0)/Fe₃C@MesoC). Fe₃C accelerates\nthe electrochemical corrosion process of α-Fe(0) in solution,\nand the positive/negative equipotential interface that is formed by\niron–carbon (Fe–C) microelectrolysis of Fe(0)/Fe₃C@MesoC induces the capture of Cr(VI) anions and Cr(III) cations\nas a result of this process. Cr(VI) was completely reduced to Cr(III)\nby the Fe(0)/Fe₃C@MesoC catalyst with a high electron efficiency\n(40.5%) relative to nanosized zero-valent iron (1.9%) and Fe@MesoC\n(32.7%). Surface ferrous ions are the principal reactive species responsible\nfor Cr(VI) reduction (at least 64%); Fe(0)/Fe₃C and undetectable\nsurface ferrous ions account for a small part of Cr(VI) reduction\n(around 28%), and only 8% of Cr(VI) ions are reduced by active hydrogen\n(H*). The proposed structure of Fe(0)/Fe₃C@MesoC provides\nnew insight into iron–carbon material preparation and application\nin <i>in situ</i> chemical reduction.