Structural and separation evaluation of polysulfone-based loose NF membrane modified with itaconic acid-choline chloride deep eutectic solvent as additive

Abstract

In this research, a type of deep eutectic solvent (DES) based on itaconic acid-choline chloride (IA-CC) was used as an efficient additive to modify the structure of the polysulfone-based membrane. Structural investigation of the as-obtained loose nanofiltration (LNF) membrane was performed through various analyses. The results showed that the use of a very low amount of IA-CC DES in the structure of the polysulfone (PSF) membrane caused the formation of finger-like pores in the structure and increased the porosity. Consequently, a significant increase in the water flux was obtained compared to the membrane synthesized with polyvinylpyrrolidone (PVP) as a common pore former (from 18.22 to 257.14 LMH). The rejection for anionic and cationic dyes as well as the binary mixtures of dyes was evaluated. The rejection of divalent Mg and Ca ions was 16.5% and 15.0%, respectively, while that of monovalent sodium ions was less than 3%. Based on the best of our knowledge, the highest water flux at low pressure (2 bar) despite the high rejection for dyes among all the NF membranes has been reported in this work. Moreover, the antifouling properties of DES-modified membrane against bovine serum albumin (BSA) showed a slight increase in the antifouling index.