A high lignin-content, ultralight, and hydrophobic aerogel for oil-water separation: preparation and characterization

This work was aimed to beneficiate biomass waste (lignin) to prepare a low-cost, ultralight, and high absorbent lignin-based aerogel via a facile and environmentally-friendly method that entailed blending of modified lignin with amine (LA) under high shear with polyvinyl alcohol (PVA) solution and followed by a freeze-drying process. Methyltriethoxy silicon (MTMS) was used as a silanization agent to improve the hydrophobicity of LA-PVA aerogel via chemical vapor deposition (CVD) reaction. The chemical and physical properties of the aerogel were then investigated using several characterization techniques such as Fourier transform infrared (FTIR) spectroscopy, elemental analysis, proton nuclear magnetic resonance (HNMR) spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and thermogravimetric analysis. The hydrophobicity of the aerogels was satisfactory due to the formation of polysiloxane on the surface. The absorption capacity of oil and the organic solvent was varied between 2 and 12 times. The recycling experiments showed that after ten consecutive cycles, the separation efficiency was still above 90%, indicating a high recoverability. This was in addition to its other unique properties such as low density (0.1150 g/cm3), high porosity (88%), and satisfactory hydrophobicity (143°). Therefore, and based on the exceptional properties of the aerogel in terms of its reusability, oil/water separation efficiency, and mechanical properties render them ideal materials for application in oily wastewater treatment.