Multifunctional Fe3O4@nSiO2@mSiO2–Fe core–shell microspheres for highly efficient removal of 1,1,1-trichloro-2,2-bis(4-chlorophenyl)ethane (DDT) from aqueous media

• A novel multifunctional Fe3O4@nSiO2@mSiO2–Fe core–shell nanomaterial was prepared.
• Fe3O4@nSiO2@mSiO2–Fe exhibits high adsorptive ability and catalytic activity.
• The adsorption rate of DDT can reach ca. 0.1 μg mg−1 min−1 over these materials.
• Over 96% DDT can be adsorbed in 1 h, and completely degraded at 350 °C by these materials.
• The core–shell materials have strong superparamagnetism, and can be easily separated.

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 the removal 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 °C 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.

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