Glycerol-regulated blend membranes of polyether sulfone (PES) and sulfonated polyether sulfone (SPES) for the separation of dye and salt

Currently, in the field of dye wastewater treatment, loose nanofiltration membranes generally suffer from low flux and are prone to fouling. Moreover, compared to ultrafiltration membranes, they exhibit a certain retention rate for salts, which is not conducive to the efficient separation of dyes and salts. Therefore, there is an urgent need to develop membranes with high flux and high efficiency in separating dyes from salts. In this study, a phase-inversion-engineered blend membrane comprising polyether sulfone (PES) and sulfonated polyether sulfone (SPES) is reported, which forms a hydrophilic surface layer and compositionally graded substructure. Glycerol was used to modify the membrane, acting as both a lubricant and pore size regulator. By forming hydrogen bonds (intermolecular forces) with the polymer, it improved film formation properties and pore structure, enhanced hydrophilicity, and further increased water flux. Scanning electron microscopy, surface zeta potential, and fully automatic water contact angle test were used to characterize the surface and cross-sectional morphology, surface electronegativity, and hydrophilic of the loose nanofiltration membrane. The pure water flux of the membrane with a solid content of 35% and glycerol addition of 0.1 wt% increase from the original 65.31 L m −2 ·h −1 ·bar −1 to 104.16 L m −2 ·h −1 ·bar −1 . It achieves near-complete rejection (>96%) of multiple dyes including Congo red, Acid Blue 83, Coomassie Brilliant Blue G-250, and Rose Bengal, while maintaining ultralow salt rejection (Na 2 SO 4 : 16.86%; NaCl: 2.86%; MgSO 4 : 2.42%; MgCl 2 : 0.26%)—indicating effective size and charge-based selectivity. This work establishes a simple yet effective glycerol-mediated strategy for fabricating high-flux blend membranes with precise molecular discrimination, offering great potential for dye desalination and resource recovery in textile effluent treatment.