Polyimide ultrafiltration membrane embedded with reline-functionalized nanosilica for the remediation of pharmaceuticals in water

This study introduces the use of choline chloride-urea (ChCl-U) deep eutectic solvent (DES) in polyimide (PI) ultrafiltration (UF) membranes to enhance the filtration removal of aqueous pharmaceuticals such as ibuprofen and paracetamol. The DES is immobilized over silica nanofiller particles by impregnation, and the composite ChCl-U@SiO2 is embedded at different loadings in the preparation of the PI UF membrane case solutions. The effects of ChCl-U@SiO2 loading on the resulting surface roughness, porosity, average pore size, hydrophilicity, and mechanical properties of the membranes were evaluated and correlated with the UF performance. The modified membrane was assessed using dead-end vacuum filtration experiments to measure the water permeate flux, solution permeate flux, and removal efficiency for 50 ppm paracetamol and 50 ppm ibuprofen from synthetic aqueous mixtures. The results showed that a 2 wt% ChCl-U@SiO2 nanofiller loading was necessary to produce membranes with the optimal aforementioned performance characteristics. The ChCl-U@SiO2 (2 wt%) PI UF membrane showed a significant increase in the water flux (250 L/m2 h) compared to the pristine membrane (30 L/m2 h), due to the enhancement of the hydrophilic character of the membrane. The large water flux was accompanied by an outstanding removal efficiency of up to 99.9% for paracetamol, exceeding that of the bare PI membrane (15%) by ~ 6 folds. The rejection removal of ibuprofen (87%) was roughly 7.9 times greater than that for the pristine membrane. This study provided substantial insights for the potential application of DES as a green modifier in the membrane-based removal of pharmaceutical pollutants from water.