Highly compressible and hydrophobic aerogel from microfibrillated cellulose for efficient oil/water separation

Microfibrillated cellulose aerogel (MFCA) has gained increasing attention due to its eco-friendliness, low-cost production, and tunable surface chemistry. However, the utilization of MFCA in treating oil pollution is limited by poor selectivity in oil/water separation, weak mechanical properties and suboptimal adsorption capacities. In the present work, a highly compressible and hydrophobic aerogel was developed from microfibrillated cellulose via a combined silane acid hydrolysis and freeze-drying process. The influence of methyltrimethoxysilane (MTMS) incorporation on the structure, hydrophobicity, oil-water separation and mechanical properties of MFCA was systematically explored. The successfully prepared aerogel displayed a disordered lamellar matrix with enhanced pore uniformity. Increasing the MTMS dosage from 10 mmol/g (MFC) to 50 mmol/g (MFC) led to a significant enhancement in the water contact angle, from 121.12° to 133.50°, while it resulted in a decrease in adsorption capacity from 94.68 g/g to 51.91 g/g. Notably, at an optimal MTMS dosage of 30 mmol/g, the modified aerogel simultaneously exhibited exceptional hydrophobicity and high lipophilicity, with an adsorption capacity of 94.68 g/g for n-heptane. Furthermore, the compression recovery properties of the MFCA were investigated. The results showed that as the MTMS concentration increased from 10 mmol/g (MFC) to 50 mmol/g (MFC) , the adsorption capacity recovery performance of the modified MFCA increased from 20.04 % to 37.60 % after 30 cycles. More importantly, it retained 54.53 % of its initial capacity after 30 cycles of reuse. This work highlights the potential of aerogel in oil/water separation, offering a scalable and eco-friendly solution to address environmental challenges.