A mixed matrix polyimide ultrafiltration membrane for efficient removal of bentazon from water

In this research, choline chloride/malonic acid (ChCl-MA) deep eutectic solvent (DES) supported onto silica (SiO2) nanoparticles were incorporated into polyimide (PI) membrane precursor solution to develop novel composite mixed matrix membranes via phase inversion to improve their hydrophilicity, porosity, mean pore size, surface roughness, and water flux. The hydrophilicity and surface texture of the modified membranes were improved due to the incorporation of ChCl-MA@SiO2. The optimal ChCl-MA@SiO2 loading at 2 wt% on PI displayed a pure water flux of 238 L/m2h, which is 8-times and 2-times higher than the pristine PI and SiO2(2 wt %)@PI membranes, respectively. The mixed matrix membrane with 2 wt% ChCl-MA@SiO2 loading exhibited a remarkable improvement of 89% over that of pristine PI (8-times) and SiO2 (2 wt%)@PI membranes (2-times) from 40 mg/l aqueous feed at neutral pH by the vacuum filtration method. At pH 2, 92 % of removal efficiency for bentazon that was decreased to 82% at pH 10. Such a remarkable membrane performance of the ChClMA@SiO2 at the pH conditions are attributed to the involvement of functional groups (N+Cl-, COOH and OH) in DES fragment via the cooperative hydrogen bonding and electrostatic interactions with bentazon in the feed solution.

Automated summary

This research developed novel composite mixed matrix membranes by incorporating choline chloride/malonic acid (ChCl-MA) deep eutectic solvent (DES) supported onto silica (SiO2) nanoparticles into polyimide (PI) membrane precursor solution. The membranes showed improved hydrophilicity, surface texture, water flux, and removal efficiency for bentazon, attributed to the functional groups in DES fragment and their interactions with bentazon in the feed solution.