Synthesis of silica microspheres in supercritical carbon dioxide, its characterization and usebility as an adsorbent

Synthesis of silica microspheres in supercritical carbon dioxide (SCO2) medium is very attractive for a wide range of the applications such as catalysis, controlled drug release and separation science. In this research, silica microspheres were directly synthesized in SCO2 by using sol-gel method for the usability of them in this thesis. The effects of co-solvent type and its ratio, flow rate, temperature, pressure and operation time on the synthesis of silica microspheres in SCO2 were investigated. The results indicate that the optimum conditions for the synthesis of silica microspheres were determined as 150 bar, 80 oC and 2.5 mL min1 of CO2 flow rate. The synthesized microspheres were characterized by a several techniques including Scanning Electron Microscopy (SEM), Brunauer Emmett Teller (BET) surface area analysis, Fourier Transform Infrared Spectroscopy (FT-IR), X-ray diffraction (XRD) and Dynamic Light Scatterring (DLS). The surface charges of synthesized silica microspheres were also determined by zeta potential measurements. The usability of the synthesized silica microspheres as an adsorbent was investigated for the removal of Pb(II) and Cu(II) heavy metal ions and C.I. Acid Blue 260 (AM260) and C.I. Reactive Blue 19 (RM19) dyes from aqueous solutions.