Vinyl-Methyl Substituted Silica Aerogel-Like Hybrids as Effective Oil/Organic Solvent Sorbents

Abstract

This work aimed to develop vinyl/methyl-decorated silica-based aerogel-like hybrids and evaluate their performance as novel oil/organic solvent adsorbents. Silica hybrids were prepared in two series by co-condensation of vinyltrimethoxysilane (VTMS) either with methyltrimethoxysilane (MTMS) (VM-series) or tetraethylorthosilicate (TEOS) (VT-series) followed by surface methylation with TMCS at ambient pressure. By gradual vinyl substitution, the changes in the physicochemical and morphological properties of the hybrids were monitored using complementary characterization techniques, such as FTIR, 29Si-NMR, SEM, N2 porosimetry, small angle neutron/X-ray scattering and contact angle measurements. The results confirmed the significant structural changes in VT-series with increasing VTMS content, whereas it had only a limited effect on the network formation in VM-series. In VT-series, the samples were predominantly mesoporous in nature, even up to a high VTMS content (75 mol%), resulting in large specific surface area values (792–1021 m2/g). However, in VM-series, the samples were mostly macroporous and emerged in sponge-like monolithic form after drying with very low densities (0.087–0.182 g/cm3) and high porosities (87.2–93.9%). The successful vinyl/methyl substitution also resulted in good hydrophobicity (up to 147°) in each series. Owing to its lightweight structure and hydrophobicity, the samples VT-100 and VM-50 had the highest sorption capacities (up to 11.63 g/g for VM-50 and 10.92 g/g for VT-100) for most organic pollutants and stable performance up to 10 cycles. The free-standing monolithic structure, well-developed porous network, enhanced hydrophobic behavior and superior adsorption performance make these materials excellent sorbents for oil spill remediation applications.