Hydrophobic Eutectic Solvent-Engineered Membranes for Highly Permeable, Selective, and Antifouling Pharmaceutical Removal from Municipal Wastewater

Persistent pharmaceutical pollutants present a critical challenge for water remediation, often forcing a trade-off between permeability, selectivity, and fouling resistance. This study resolves this trilemma through the molecular-level integration of hydrophobic deep eutectic solvents (HDES) into ultrafiltration membranes, establishing a filler-free platform for advanced separations. The optimized polyethersulfone matrix, tailored with 5 wt.% tetrabutylammonium bromide:octanoic acid, achieved a sixfold increase in pure-water flux (7.3 L m⁻² h⁻¹) while maintaining 95% tetracycline and 86% diclofenac rejection. The membrane performance was also validated with authentic municipal wastewater from Abu Dhabi, where the membrane removed >86% of bulk organics and pharmaceuticals, surpassing EU Directive 2024/3019 requirements. Exceptional stability was also demonstrated with an 89% flux recovery ratio. Moreover, integrated density functional theory calculations and molecular dynamics simulations revealed that HDES nanodomains electronically “soften” the polymer matrix (reducing chemical hardness to 1.604 eV) to lower water transport barriers while simultaneously doubling pollutant binding energies via cooperative hydrogen bonding and cation-π interactions. This scalable, low-energy approach (≈0.12–0.16 kWh m⁻³) offers a robust, regulation-ready solution for next-generation environmental materials.