Lightweight and highly hydrophobic silica aerogels dried in ambient pressure for an efficient oil/organic solvent adsorption

Abstract

Silica aerogels are ultra-porous materials with three-dimensional cage-like morphology that makes these materials ideal for separation applications. However, their hydrophilic behavior and shrinkage of the porous network during drying makes them impractical for such applications. Therefore, conducting a proper modification strategy is crucial both in imparting a hydrophobic behavior to aerogels and in preserving the porous network during drying. This study evaluated the performance of silica aerogels silylated with mono (TMCS), tri (MTMS, MTES), or organofunctional silanes (MEMO, GLYMO) as potential adsorbing materials for oil pollution remediation. Silica aerogels were prepared by the sol-gel method under ambient conditions and were characterized by conducting Si-NMR, BET, TGA, and contact angle measurements. Among the samples, silica aerogels modified with TMCS and MTMS exhibited good hydrophobicity (θ > 140°), well-constructed solid network with mesoporous structure, high porosity (94%, 89%), and low density (0.13 g/cm3 and 0.24 g/cm3). These samples also can selectively separate oil or organic solvents from water and the adsorption capacity can reach 12.5 g/g and 8.7 g/g for S-TMCS and S-MTMS, respectively. They displayed enduring adsorption property for organic solvents after 7 cycles, which shows that silica aerogels modified with TMCS and MTMS can be promising candidates for oil/organic solvent clean up practices.