Surfactant Removal from Mesoporous ‎Silica Shell of Core-Shell Magnetic ‎Microspheres by Modified Supercritical ‎CO2‎

   In this paper, a kind of core–shell magnetic mesoporous microspheres of Fe3O4@SiO2@meso-SiO2 with high surface areawas prepared, where magnetic Fe3O4 nanospheres were used as the inner core, tetraethyl orthosilicate (TEOS) as silica source, and cetyltrimethylamonium bromide (CTAB) as pore forming agent. Methanol-enhanced supercritical CO2 extraction has been attempted on structurally order mesoporous shell to remove the cationic template of CTAB and the effects of operating conditions i.e. pressure and temperature on the extraction efficiency were investigated. The influence of the methanol-enhanced supercritical CO2 on the structural properties of magnetic mesoporous silica nanocomposites was examined in detail by means of FE-SEM, FTIR, XRD, N2 adsorption/desorption and VSM. The obtained results reflected that the methanol-enhanced supercritical CO2 extraction had well preserved the structural stability of Fe3O4@SiO2@meso-SiO2 with high surface area ca.569 m2/g. The strong magnetization value (60 emu/ g) of the core–shell particles suggests their suitability for magnetic separation in a short time.