Rational design of sustainable thin-film composite membranes: Computational and experimental investigation of deep eutectic solvents as a green alternative to hexane for enhanced desalination performance

The development of sustainable and high-performance membranes is critical for addressing global water treatment challenges while adhering to the principles of green chemistry. This study introduces a novel approach for fabricating thin-film composite (TFC) membranes by replacing hexane with deep eutectic solvents (DES) as the organic phase in interfacial polymerization. A DES composed of DL-menthol and lauric acid was identified as the most promising alternative through computational screening, which demonstrated its superior solubility, higher capacity and significantly stronger interaction energy for DES-TMC (−19.8 kcal/mol) compared to hexane-TMC (−6.4 kcal/mol). Comparative performance evaluations demonstrated that DES-based membranes outperformed their hexane-based counterparts, achieving NaCl rejection of up to 84 % and superior dye rejection, even at lower monomer concentrations. Mass and solvent intensity analysis further highlighted the environmental benefits of DES, with reductions of 23 % and 26 % as compared to hexane, highlighting its resource efficiency. Membrane characterization revealed that DES facilitated the formation of highly cross-linked, hydrophilic and selective polyamide layer due to its slower monomer diffusion and enhanced control over polymerization dynamics. Despite these advances, challenges such as scalability and long-term stability warrant further investigation. This study establishes DES as a transformative, sustainable alternative for TFC membrane fabrication, advancing the field toward environmentally benign water treatment technologies while enhancing performance efficiency. The dual benefits of superior functionality and reduced environmental footprint make this work a significant contribution to the ongoing pursuit of sustainable membrane science and technology.