Cellulose hollow fibers for organic resistant nanofiltration

Cellulose is the most abundant biopolymer, but it is difficult to process due to its low solubility in most of the solvents. In this work, we demonstrate the preparation, of self-standing and defect-free cellulose hollow fiber membranes made by a sustainable process for filtration in organic solvent medium. The hollow fibers were made by the simple spinning technique using ionic liquids as a solvent. The spun solutions were prepared with three different ionic liquids, having imidazolium-based cations and acetate or phosphates as anions. We used X-ray diffraction to evaluate the influence of the different ionic liquids on the crystallinity of the cellulose and the membrane solvent stability. We used cryo-scanning electron microscopy to investigate the porous structure of the hydrated membranes, distinguishing it from that of the dry membranes. The hollow fiber membrane performance was studied using dyes in water and ethanol solutions. The rejection of Congo Red (696 g mol⁻¹) was higher than 90% in ethanol and even closer to 100% in water. The best results were obtained by using 1-ethyl-3-methyimidazolium diethyl phosphate and 1,3-dimethylimidazolium dimethyl phosphate. Our results indicate that by using greener process is possible to obtain solvent resistant cellulose hollow fibers.