Enhanced stability and permeability of graphene oxide nanocomposite membranes via glycine and diglycine cross-linking

Abstract Surface coating of graphene oxide (GO) on membrane surfaces often suffers from low stability, with the GO layer prone to swelling and detachment during filtration. Cross-linking with environmentally friendly amino acids is expected to enhance the interfacial interaction between GO nanosheets and membrane surface via van der Waals interactions. This study introduces glycine (Gly) and diglycine (diGly) as cross-linking agents to improve the stability and performance of GO nanocomposite membranes. Field emission scanning electron microscopy (FESEM) images revealed that amino acid-crosslinked GO formed a thick pile structure on the membrane surface. The chemical bonding between GO and glycine derivatives was confirmed by Fourier transform infrared (FTIR) and X-ray diffraction (XRD) analyses. Stability test via continuously running water across the membrane surface in a crossflow filtration cell showed that cross-linking with glycine derivatives reduces the tendency of GO detachment from the self-fabricated polyethersulfone (PES) membrane surface. Ultrafiltration tests demonstrated that water permeability of nanocomposite membranes increased in the order of diGly-GO (14.70 LMH bar −1 ) > Gly-GO (8.66 LMH bar −1 ) > GO (4.57 LMH bar −1 ), without compromising bovine serum albumin (BSA) rejection efficiency (82–84 %). However, the reduction of hydroxyl groups in Gly-GO and diGly-GO nanocomposite membranes made them more susceptible to BSA fouling. Consequently, the pristine GO nanocomposite membrane exhibited the lowest flux declination rate and the highest flux recovery rate among the membranes. Overall, the results indicate that cross-linking GO nanosheets with glycine derivatives enhances membrane permeability and stability by improving the stacking of GO nanosheets.