Synthesis of carbon-coated magnetic nanocomposite (Fe3O4@C) and its application for sulfonamide antibiotics removal from water

The occurrence of antibiotics in the environment has recently raised serious concerns regarding their potential threat to human health and aquatic ecosystem. A new magnetic nanocomposite, Fe₃O₄@C (Fe₃O₄ coated with carbon), was synthesized, characterized, and then applied to remove five commonly-used sulfonamides (SAs) from water. Due to its combinational merits of the outer functionalized carbon shell and the inner magnetite core, Fe₃O₄@C exhibited a high adsorption affinity for selected SAs and a fast magnetic separability. The adsorption kinetics of SAs on Fe₃O₄@C could be expressed by the pseudo second-order model. The adsorption isotherms were fitted well with the Dual-mode model, revealing that the adsorption process consisted of an initial partitioning stage and a subsequent hole-filling stage. Solution pH exerted a strong impact on the adsorption process with the maximum removal efficiencies (74% to 96%) obtained at pH 4.8 for all selected SAs. Electrostatic force and hydrogen bonding were two major driving forces for adsorption, and electron-donor-acceptor interactions may also make a certain contribution. Because the synthesized Fe₃O₄@C showed comprehensive advantages of high adsorptivity, fast magnetic separability, and prominent reusability, it has potential applications in water treatment.