Green preparation of silk nanofiber membranes from natural silkworms for effective dye/salt fractionation

While membranes are widely used in sustainable separations, they are mostly made from petroleum-based polymers and toxic solvents, which are not only harmful to the environment, but also pose a major risk to the safety and health of people. Aiming to enhance the sustainability of fabricating membranes, a biobased silk nanofiber (SNF) membrane is uniquely developed from natural silkworms using green solvents and pressure-assisted deposition method for dye/salt fractionation. One key feature is the replacement of traditional toxic solvents used for SNF extraction to a green solvent, deep eutectic solvent (DES) which is utilized and recycled for SNF preparation. The use of DES can effectively weaken the bonding to disintegrate the silk fibers into microfibrils without destroying the inherent properties of silk fibers. Various SNF loadings were explored to investigate the self-assembling of SNF and optimize the separation performance. The optimized SNF membrane exhibits a high separation factor of 110.7 and remarkable stability in continuously separating NaCl and rose bengal for 100 h. As compared to the conventional membranes for dye/salt fractionation, the newly developed biobased SNF membrane significantly reduces the environmental hazard by incorporating renewable polymers and green solvents, offering a promising pathway towards the establishment of a sustainable membrane industry.