Magnetically Responsive Core-Shell Fe₃O₄@C Adsorbents for Efficient Capture of Aromatic Sulfur and Nitrogen Compounds

Elimination of aromatic sulfur and nitrogen compounds via selective adsorption is an effective method for the purification of transportation fuels to meet the increasingly stringent environmental requirements. Since the adsorption processes proceed in liquid phases, separation and recycling of adsorbents should be greatly facilitated if they were endowed with magnetism. In the present study, magnetically responsive core-shell microspheres, Fe₃O₄@C, which comprise a magnetite core and a carbon shell with a thickness adjustable from 47 to 97 nm, were fabricated for the adsorption of aromatic sulfur and nitrogen compounds. The carbon shell derived from the carbonization of a resorcinol-formaldehyde polymer possesses abundant porosity with a hierarchical structure, which is highly active in the capture of aromatic sulfur and nitrogen compounds despite the absence of any active metal sites such as Cu(I) and Ag(I). Our results show that the Fe₃O₄@C adsorbents with BET surface areas ranging from 227 to 264 m² g^-1 are capable of removing thiophene (0.483 mmol g^-1), benzothiophene (0.476 mmol g^-1), indole (0.463 mmol g^-1), and quinolone (0.297 mmol g^-1) efficiently under ambient conditions. More importantly, the superparamagnetism allows the adsorbents to be separated conveniently from the adsorption system by the use of an external field. The regenerated adsorbents after six cycles still exhibit a good adsorption capacity comparable to that of the fresh one. The present magnetically responsive core-shell Fe₃O₄@C adsorbents with low cost, high efficiency, and convenient recycling make them highly promising in the purification of transportation fuels. (Figure Presented).