Isolation of hierarchical cellulose building blocks from natural flax fibers as a separation membrane barrier

Cellulose nanofibrils (CNF) is a natural nanomaterial composed of biomacromolecules that can be extracted from plants and has great potential applications in many fields due to its excellent regenerative, sustainable, and biodegradable properties. In this work, the flax CNF with hierarchical scales was obtained by using the flax fibers (FF) treated with different concentrations of alkaline solution, followed by the TEMPO-mediated ternary oxidation and mechanical treatment. Subsequently, the resultant CNF was implanted on the commercial filter paper as a surface barrier for oil/water preparation. The changes of cellulose crystal form and crystallinity caused by alkali treatment on FF were studied by Fourier transform infrared spectroscopy and X-ray diffraction. Morphological changes of FF before and after alkali treatment were observed. The morphology of obtained CNF was examined. Moreover, the transmittance of the prepared CNF suspension and films was also investigated by a UV spectroscopy. The prepared modified filter paper can effectively separate the oil/water mixture, which gives themselves promise as candidates in practical applications of oil/water separation.