Organic solvent nanofiltration (OSN) membranes made from plasma grafting of polyethylene glycol on cross-linked polyimide ultrafiltration substrates

A novel organic solvent resistant nanofiltration (OSN) membrane was developed via plasma grafting of a high-density polyethylene glycol (PEG) on a cross-linked polyimide (cPI) ultrafiltration (UF) substrate in this work. The argon plasma treatment successfully formed an ultrathin dense layer on the substrate surface and directly converted the UF membrane to a nanofiltration (NF) membrane. The PEG-modified composite membrane has an isopropanol (IPA) permeance of 5.91 Lm(-2) h(-1) bar(-1) at 10 bar because of its relatively high polarity. Comparing to the cPI membrane, the PEG-modified membrane shows a significant increase in rejection of Rose Bengal (a molecular weight of 1017.64 g mol(-1)) from 70.10% to 99.64% in IPA. The newly developed OSN membranes also demonstrate good stability in various solvents for 400-h tests, especially in IPA and 1-butanol. To our best knowledge, this is the first endeavor of utilizing PEG to directly develop OSN membranes by means of plasma grafting. The work aims to provide useful insights to design environmentally friendly and high-performance composite OSN membranes by the PEG immobilization via the cold plasma treatment.