Synthesis and characterization of crosslinked membranes based on sodium alginate/polyvinyl alcohol/graphene oxide for ultrafiltration applications

Novel sodium alginate/polyvinyl alcohol/graphene oxide (SA/PVA/GO) nanocomposite ultrafiltration membranes were successfully synthesized via the phase inversion process. Their application in ultrafiltration requires crosslinking. The resulting hydrophilic membranes were in situ crosslinked using glutaraldehyde as a covalent crosslinker and calcium chloride as an ionic crosslinker. The synthesized membranes were characterized using differential scanning calorimetry, X-ray diffraction, water contact angle, scanning electron microscopy and Fourier-transform infrared spectroscopy. Performance tests showed that the sodium alginate membranes have a high affinity for bovine serum albumin and can remove 87% at an optimum transmembrane pressure of 2 bar. The presence of GO improved the cobalt and copper rejection, reaching around 23% (Co) and 34% (Cu) at 2 bar. The prepared membrane showed a higher affinity for Cu2+ than for Co2+ due to the size effect. The permeability of the membranes was improved by increasing the PVA concentration up to 3 wt.%. The use of graphene oxide increased the hydrophilic property of the membrane, which yielded a significantly higher flux than the unmodified membrane. The as-prepared membrane with 3 wt.% SA, 9 wt.% PVA, and 0.3 wt.% GO percentages was chosen as the best membrane and was found to have the optimal performance.