Evaluation of eco-friendly 1,3-dimethyl-2-imidazolidinone as an additive to enhance the desalination performance of polyamide membranes

The introduction of additives is a widely recognized and easily implementable strategy to regulate interfacial polymerization for preparing polyamide (PA) membranes in desalination applications. There is growing interest in minimizing potential health and environmental risks associated with conventional additives. In this study, we employed an environmentally friendly polar aprotic solvent, 1,3-dimethyl-2-imidazolidinone (DMI), as an aqueous-phase additive, to fabricate PA membranes with enhanced permeability and selectivity. Structural characterization and spectroscopic analysis consistently show that the resulting membranes are thin and dense, with ridge-and-valley features exhibiting a 37 % increase in surface roughness compared to the pristine membrane prepared without DMI. Solubility parameter calculations, physicochemical measurements, and molecular dynamics simulations reveal that DMI reduces the interfacial tension between the aqueous and organic phases, enlarges the miscible region, and facilitates amine monomer diffusion. With the addition of 3 wt% DMI, the resulting membranes achieved a water permeability of 3.73 L m −2  h −1 ·bar −1 , which is over 50 % higher than that of the control membrane, while maintaining a NaCl rejection of 98.36 % and excellent long-term operational stability. This study demonstrates the potential of DMI as a sustainable additive to enhance both performance and environmental compatibility in the fabrication of reverse osmosis membranes.