Synthesis and characterization of micrometer-sized silica aerogel nanoporous beads

Here we report the preparation of micrometer-sized highly nanoporous, relatively trasperant silica aerogel beads with high surface area as well as large pore volume with sizes ranging from 165 to 395 μm. The wet micrometer-sized silica hydrogel beads were prepared through hydrolysis and polycondensation of sodium silicate as a silica precursor. A hydrophobic micro-silica aerogel nanoporous bead was synthesized by simultaneous solvent exchange surface modification process of as synthesized micron sized silica hydrogel bead at an ambient pressure. Hydrophilic micron-sized silica aerogel beads with relatively more textural properties (surface area, pore volume and pore size) with its counterpart were obtained by heating the synthesized hydrophobic micro-silica aerogel beads at 395 °C for an hour. This study demonstrates a robust approach to high porous hydrophobic and hydrophilic micro-silica aerogel beads with a myriad of potential applications in various fileds such as catalysis, biomolecule immobilization, chromatographic separation, and CO2 absorption. This proposed synthesis, which exploits a low-cost silica source (water-glass), is suitable for large-scale industrial production of highly porous hydrophobic and hydrophilic micro-silica aerogel beads at an ambient pressure.

Graphical abstractTransparent micro-silica aerogel beads: a) Optical micrograph, scale bar = 2000 μm; b) scale bar = 1000 μm; c) optical micrograph of a single micro-silica aerogel bead, scale bar = 200 μm; d) surface optical micrograph (black and white) scale bar = 200 μm; and e) optical micrograph of a single micro-silica aerogel bead, scale bar = 200 μm.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► The study presents a facile route to synthesize micro-silica aerogel beads. ► High BET surface area (756 m2/g) and pore volume (3.9 cm3/g) were obtained. ► The transparent micro-silica aerogel beads with a spherical shape (165–395 μm) were obtained.