Non-polymeric solvents as membrane additives for tailoring membrane structure and performance

Abstract

Membranes are widely applied in water and wastewater treatment in the removal of a wide range of organic, inorganic, and biological pollutants. Despite their application, polyethersulfone (PES)‐based membranes are limited due to their hydrophobic nature; the inherent hydrophobicity restricts water transport, promotes membrane fouling, and reduces the effective removal of hydrophilic organic contaminants. This study systematically investigated the impact of hydrophilic additives (polyethylene glycol, glycerol and starch) on the structural properties, permeability, contaminant rejection, and antifouling and antimicrobial behavior of polyethersulfone (PES)‐based membranes. The additives produced distinct changes in membrane morphology, hydrophilicity, permeability, contaminant rejection, and fouling behaviour. Starch modification provided the highest rejection of ciprofloxacin (CIP), rhodamine B (RhB), and natural organic matter (NOM) (21.5%, 22.9%, and 67%, respectively), whereas glycerol provided the best antifouling performance (flux recovery ratio, FRR = 62.2%). PEG produced a highly porous membrane (94.95%) with a small estimated mean pore radius (2.2 nm), while the PEG/glycerol membrane exhibited the highest water permeability (1238 LMH). The ternary PEG/glycerol/starch formulation did not simultaneously improve membrane performance. Real water experiments further showed that NOM fouling affected contaminant rejection differently, with RhB rejection increasing whereas CIP rejection generally decreased after fouling. This study demonstrates that hydrophilic additive modification of PES membranes is an effective strategy for tuning membrane structure and performance, but the choice of additive and the decision to combine additives must be strategically aligned with the target application.