Developments of cyclodextrin-coated Fe3O4@Fe0 nanoparticles to both efficiently activate persulfates and rapidly access hydrophobic PAHs in water

We report new activated persulfate systems with cyclodextrin (CD)-coated Fe3O4@Fe0 nanoparticles (Fe3O4@Fe0-CD) that are characterized by both highly activating persulfates and rapidly accessing hydrophobic PAHs. Fe3O4@Fe0-β-CD displays chain-like structure of core–shell Fe3O4@Fe0 nanoparticles coated with a CD layer (about 5.9 nm). CD coating stabilizes the polycrystalline structure of Fe3O4@Fe0 nanoparticles and accelerates mass transfer of PAHs in water, thereby making Fe3O4@Fe0-β-CD intrinsically stable and reactive. Fe3O4@Fe0-β-CD/PS, featured by high yields of highly reactive Fe(IV), had about 30-fold rate constants of naphthalene (Nap) in water as much as Fe3O4@Fe0/PS. Fe3O4@Fe0-β-CD/PS completely removed Nap in water during 13 of total 18 supplementations of Nap and/or PS, whereas Fe3O4@Fe0/PS completely removed Nap only at the first supplementation of Nap. Likewise, Fe3O4@Fe0-β-CD/PS completely removed Nap in simulated groundwater, and degraded four PAHs in soils by >63%. This study may provide a technical basis for the developments of new PS activators to remove recalcitrant hydrophobic contaminants in water and soils.