Effect of supercritical CO2 drying variables and gel composition on the textural properties of cellulose aerogels

Cellulose aerogels are interesting platforms for biomedical and drug delivery applications, due to their biocompatibility, biodegradability, water absorption capacity, and good textural properties. Supercritical CO₂ drying has been proven as an efficient technology for obtaining aerogels and preserving the porous structure. In this work, the effect of relevant process variables (CO₂ density, depressurization rate, and intermediate depressurization mode) and gel composition on the textural properties of cellulose aerogels is studied. Experiments are performed in batch-mode, and aerogel monoliths are characterized in terms of apparent density, porosity, specific surface area, and crystalline morphology. Water uptake in different buffer solutions is also evaluated. The use of thiourea in the gel formation leads to lower porosity. On the other hand, higher porosity and surface area are obtained when depressurization is slow and the system is only partially depressurized between drying cycles. Aerogels showed a good and fast water uptake capacity, regardless of the pH (200–500 %).