Regenerable magnetic carbonized Calotropis gigantea fiber for hydrophobic-driven fast removal of perfluoroalkyl pollutants

Using Calotropis gigantea fiber (CGF) as the bio-template, the magnetic carbonized fiber (MC-CGF) was successfully prepared by anchoring Fe3O4 onto CGF surface via pyrolysis, and well characterized by means of instrumental analysis. Subsequently, MC-CGF was used as the adsorbent to remove perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) from water. The adsorption equilibrium of PFOA and PFOS on MC-CGF could be achieved within 1 h and 2 h, with maximum adsorption capacity of ~ 200 mg/g for them at pH 3.0. Coexisting ions (Na+, Mg2+, Fe3+) promoted the adsorption efficiency of MC-CGF to PFOA/PFOS, in particular for multivalent metal cations. During the adsorption process, hydrophobic interaction was principally involved, and was considered to be the driving force for fast removal of perfluoroalkyl pollutants. Such a hydrophobic-driven interaction was further evidenced using other perfluoroalkyl pollutants with different C–F chain length and functional groups as the models. Finally, MC-CGF was easily regenerated and recycled many times, demonstrating its potential for removing perfluoroalkyl pollutants from water in the future.