Studying the Effect of Hydrophilic Deep Eutectic Solvents on the Membrane Performance and Antifouling Properties of Polysulfone

Abstract

Ultrafiltration (UF) has gained immense importance in the filtration of drinking water treatment. Various polymeric materials for UF have been proposed and Polysulfone (PSf) is one of them. PSfmembranes are hydrophobic in nature and hence are prone to organic fouling. In this study, deep eutectic solvent (DES) is used to tailor the morphology, separation performance (pure water flux, humic acid rejection), antifouling properties, relative flux reduction (RFR) and flux recovery ratio (FRR)) of the PSf membranes. Choline chloride-Urea based deep eutectic solvent (ChCl-Urea DES) has been used as an additive in the casting solution of the polymer with different loadings (0.1 wt.%, 0.25 wt.%, 0.5 wt.% and 1 wt.%). All membranes were prepared by phase inversion technique. The morphological characteristics i.e., surface roughness of membranes were investigated using Scanning Electron Microscopy (SEM) to obtain the cross- sectional images of the membranes. Water contact angle was measured to see the hydrophilicity/hydrophobicity of the modified membranes. The ultrafiltration experiments indicate that all the modified membranes showed high pure water flux than unfilled membrane while the rejection ratio didn’t change by adding ChCl-Urea DES. When the concentration of ChCl-Urea based DES was 0.5 wt%, the water flux of the membrane reached a maximum value of 353 l/m2/hr which was 37% more than neat PSf membrane and humic acid rejection up to 95% at 2 bar pressure. Moreover, membranes with ChCl-Urea based Deep Eutectic loading 0.5 wt%, showed superior antifouling properties with 87% FRR and reduced irreversible fouling up to 12%. Overall, this research shows that DES is a promising alternative as a pore forming additive for UF membrane formation with high performance.