Effect of the drying procedure on hybrid sono-aereogels for organic solvent remediation

Abstract

Hybrid organic–inorganic aerogels are highly hydrophobic porous solids that avoid the brittleness and moisture adsorption of the standard silica aerogels. Superhydrophobic porous materials have attracted great interest because of their ability for selective absorption of organic solvents while repelling water, as excellent candidates for remediation techniques. This work shows a comparative of three drying procedures of DEDMS/TEOS (diethoxydimethylsilane/tetraethylorthosilicate) gels, namely, by supercritical CO2, by supercritical ethanol, and dried at ambient conditions. Supercritical CO2 and ambient drying produced superhydrophobic aerogels (θ > 150°), while supercritical ethanol drying produces denser aerogels with smaller both porous volume and specific surface area. Regarding the absorption of organic liquids, swelling is observed in all cases. Hexane had faster diffusion that obeyed Fick's law (∝t0.5) whereas liquid polydimethylsiloxane exhibited slower non-Fickian diffusion process (∝tn, n 150°), el realizado en etanol supercrítico dio lugar a aerogeles de mayor densidad, con menor volumen poroso y superficie específica. En cuanto a la absorción de líquidos orgánicos, en todos los casos tiene lugar el hinchamiento de la red polimérica (swelling). El hexano presentó una difusión rápida, que obedece a la ley de Fick (∝t0,5), mientras que el polidimetilsiloxano líquido mostró un proceso de difusión más lento que no obedece la ley de Fick (∝tn, n < 0,5).

Keywords

• Sono-aerogel
• DEDMS-TEOS
• CO2 supercrítico
• Superhidrofóbico
• Ambigel
• Eliminación de solventes orgánicos