Magnetically recoverable carbon-coated iron carbide with arsenic adsorptive removal properties

Abstract: Magnetic particles, generally nanostructured and magnetite-based, have been studied extensively to remove drinking water contaminants. Compositions beyond Fe₃O₄ could address long-standing issues of magnetic recoverability and materials integrity in drinking waters. Herein carbon-coated iron carbide (Fe₃C@C) were studied for the first time for their stability, magnetic characteristics, magnetic separability, and arsenic adsorptive properties. Experimental results show that (i) Fe₃C@C with a 9-nm thick graphitic shell is chemically stable in simulated drinking water; (ii) is ferromagnetic with small magnetic remanence and a magnetic saturation that is ~ 2 × greater than Fe₃O₄; (iii) can be separated from water magnetically under continuous-flow conditions with greater than 99% recovery; and (iv) has a surface area-normalized adsorption capacity for arsenic (6.75 µg/m²) of the same order of magnitude as that of Fe₃O₄ (9.62 µg/m²). Fe₃C@C can be a viable alternative to Fe₃O₄ with further development, for the magnetic removal of arsenic and other contaminants from drinking water sources. Graphic abstract: A comparative look at the chemical stability, adsorptive prowess, and magnetic capturability of nanostructured carbon-coated iron carbide for arsenic removal from simulated drinking water. [Figure not available: see fulltext.].