Fabrication of Hydrophobic Cellulose Aerogels from Renewable Biomass Coir Fibers for Oil Spillage Clean-Up

Hydrophobic cellulose aerogels with high porosities (~ 97.5%) were successfully prepared from renewable biomass coir fibers for use as absorbents for oil separation from oil-water mixtures. The preparation routes included delignification, dissolution and coagulation of cellulose pulp, and freeze drying. Delignification was performed via an alkalization process, and the pulp was dissolved in an aqueous NaOH-urea solution. The cellulose aerogel had ultralow density (ρ = 0.047 g cm⁻³) and excellent elastic properties. Due to the large number of hydroxyl groups on the cellulose surface, the cellulose aerogel was hydrophilic. It absorbed 22 times its original weight in water and 18 times in oil. To make it hydrophobic, the hydroxyl groups were exchanged with trialkylsilyl groups via silylation. The process significantly improved the hydrophobicity of the cellulose aerogel without influencing its physical properties. Although the oil absorption capacity decreased, the selectivity of the hydrophobic aerogel for separation of oil from a water-oil mixture was greatly enhanced and water was repelled completely. Moreover, the aerogel could be squeezed to force out the absorbed oil and recycled. Therefore, it has great potential for use in oil-spill recovery because it is prepared from low-cost and environmentally-friendly biomass.