Fabrication of elastic SiO2 aerogels with prominent mechanical strength and stability reinforced by SiO2 nanofibers and polyurethane for oil adsorption

The separation of oil from wastewater and materials for oil absorption are highly demanded in the modern industrialization. For these purposes, silica aerogels with high hydrophobicity and surface aera and low density are promising candidates for oil absorption, but limited by the poor mechanical strength and structure stability during the usage. In this study, we presented a novel compressive silica aerogel by silica nanofiber (SNF) reinforcement and subsequent hydrophobic polyurethane strengthening via moisture curing (PSAG). The obtained PSAG exhibits unique core/shell fibrous reinforcement and prominent crosslinked network structure. The porous PSAG has a porosity of 81.06 % and density of 0.43 g cm−3 at solid content of 20 %. The hydrophobic PSAG shows an impressive sorption capacity towards CH2Cl2 (11.2 g g−1), THF (5.5 g g−1) and acetone (3.8 g g−1), being able to separate 100 % of oils from an immiscible oil–water mixture. The PSAG shows exceptional resistance to acidic and alkaline conditions and has high flexibility and desirable reusability in repeatedly oil adsorption. Most importantly, the mechanical strength of SAG can be improved to 0.27 MPa of PSAG at prepolymer solid content of 20 %, and no cracking or deformation were observed after 50 cycles. Additionally, the PSAG shows impressive thermal insulation and flame retardancy performance in the air, which should have potential application as insulator for the solar evaporation for the purification of wastewater. This work provides new understanding and insight for further design and optimization of polyurethane-based reinforced aerogels.