Porous cellulose facilitated by ionic liquid [BMIM]Cl: fabrication, characterization, and modification

Porous celluloses (PCs) were successfully prepared by a simple process of freezing the cellulose solution in ionic liquid, followed by solvent exchange and drying at normal temperature instead of the supercritical drying. PCs were composed of cellulose sheets of low crystallinity, as evidenced by SEM, XRD, TGA and FTIR, oriented into unidirectional structures when the cellulose concentration was low (1 %). When the cellulose concentration was high (4 %) the structure was twisted and randomly oriented. PCs had low apparent densities of 44–88 mg/cm³ and oil adsorption capacities ranging from 9.70 to 22.40 g/g (oil/PC) due to the ultralight porous structures. Oxidation of sodium periodate introduced dialdehyde groups into the porous structure. After the same reaction time, the aldehyde content of PC was much higher than the untreated cellulose counterpart. The resultant dialdehyde modified-PC had better urea adsorption than modified-viscose fiber. The high reactivity of PCs was related to the low crystallinity and porous structure.