Effects of different parameters on the synthesis of silica aerogel microspheres in supercritical CO 2 and their potential use as an adsorbent

Synthesis of metal oxide microspheres in supercritical carbon dioxide (SCO 2 ) is very attractive for a wide range of applications such as catalysis, controlled release, and separation science due to their identical properties. The aim of this study is the synthesis of silica microspheres (SM) in SCO 2 by sol–gel method. The effects of temperature, pressure, flow rate, time, co-solvent and its ratio on the synthesis of silica microspheres in SCO 2 were investigated. The synthesized microspheres were characterized by several techniques including field emission scanning electron microscopy (FE-SEM), Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), dynamic light scattering (DLS), and surface area analysis. The results indicated that the optimum condition for the synthesis of SM was determined at 150 bar, 80 °C, and 2.5 mL min −1 of SCO 2 flow rate. The usability of SM as an adsorbent for the removal of dyes and heavy metals from aqueous solutions was also examined. Kinetic and isotherm studies for the adsorption of Pb(II) ions and Acid Blue 260 (AB260) onto SM were carried out.