Ca2+, Fe3+ co-crosslinked tannic acid-bridged sodium alginate gel membrane for organic solvent nanofiltration

It is necessary to prepare a nanofiltration membrane with high permeation flux that can be used in the field of organic solvents. Gel membranes have a high solvent permeation flux, but their chained macromolecular structure is often unstable. In this study, tannic acid-bridged sodium alginate (TAx-Ca/FeSA) organic solvent nanofiltration (OSN) membranes were prepared by the phase transition method using aqueous Ca2+ and Fe3+ solutions as cross-linking agents. TA can interact with SA through hydrogen bonding hydrophobic bonding and other interactions to form an interpenetrating three-dimensional network structure. Compared with Ca/FeSA membrane, the average pore size of TA0.125-Ca/FeSA membrane was reduced from 1.03 nm to 0.74 nm, and the porosity was increased from 47.62 to 59.2 %. In addition, the TA0.125-Ca/FeSA membrane has the characteristics of a negative charge, super hydrophilicity, and high mechanical properties, exhibits a high permeation flux of 48.97 L·m−2·h−1·bar−1 with a rejection of 96.25 % for Congo red ethanol solution, has excellent solvent resistance, stain resistance, and self-cleaning ability. The TA0.125-Ca/FeSA membrane was demonstrated to have great potential for application in the fields of purification and solvent recovery.