Multifunctional Fe3O4@nSiO2@mSiO2-Fe core-shell microspheres for highly efficient removal of DDTs from aqueous media----Technical Institute of Physics and Chemistry

A novel multifunctional microsphere with an iron oxide-improved mesoporous silica shell and a Fe₃O₄@SiO₂ core has been successfully prepared by a hydrothermal method and impregnation process. The resulting Fe₃O₄@nSiO₂@mSiO₂-Fe core-shell microspheres are utilized as a catalyst for removals of 1,1,1-trichloro-2,2-bis(4-chlorophenyl) ethane (DDT) and its derivatives, i.e., 1,1-dichloro-2,2-bis(4-chlorophenyl) ethane (DDD) and 1,1-dichloro-2,2-bis(4-chlorophenyl) ethylene (DDE). The results indicated that the iron oxide nanoparticles were well dispersed on the mesoporous silica shell of Fe₃O₄@nSiO₂@mSiO₂. DDT, DDD and DDE could be quickly and effectively removed from aqueous media in 60 min, and completely dechlorinated at 350 ^oC by Fe₃O₄@nSiO₂@mSiO₂-Fe. More importantly, the Fe₃O₄@nSiO₂@mSiO₂-Fe microspheres were superparamagnetic and could be separated and collected easily and rapidly using a magnet.

Journal of Colloid and Interface Science,2014

Schematic illustration of the synthetic procedure of Fe₃O₄@nSiO₂@mSiO₂-Fe core-shell microspheres.

XRD patterns of Fe₃O₄ (a), Fe₃O₄@nSiO₂ (b), Fe₃O₄@nSiO₂@mSiO₂ (c), Fe₃O₄@nSiO₂@mSiO₂-5%Fe (d), Fe₃O₄@nSiO₂@mSiO₂-10%Fe (e) and Fe₃O₄@nSiO₂@mSiO₂-15%Fe (f).

Representative TEM images of prepared magnetic microspheres: (a) Fe₃O₄@nSiO₂ (inset: TEM image at high magnification), (b) Fe₃O₄@nSiO₂@mSiO₂, (c) Fe₃O₄@nSiO₂@mSiO₂-5%Fe, (d) Fe₃O₄@nSiO₂@mSiO₂-10%Fe and (e) Fe₃O₄@nSiO₂@mSiO₂-15%Fe.

Photographs of a magnetic separation and redispersion process using Fe₃O₄@nSiO₂@mSiO₂-5%Fe microspheres.