Organic solvent resistant poly(ether-ether-ketone) nanofiltration membranes

In this work a poly(ether ether ketone) (PEEK) membrane is presented for its suitability for organic solvent nanofiltration (OSN) applications using polar aprotic solvents, such as DMF and THF, high temperatures, and basic/acidic conditions. Four grades of PEEK polymer were tested and it was verified that different grades produced membranes with different performances; the post-phase inversion drying process of membrane fabrication was shown to be crucial in obtaining separation performance in the nanofiltration range. The degree of sulphonation (DS) was also important and was controlled to be in the range of 3.7-6.7 wt%. The tightest membrane, produced from VESTAKEEP (R) 4000P and obtained after drying at 20 degrees C from water, presented a permeance of 0.22 L h(-1) m(-2) bar(-1) and molecular weight cutoff (MWCO) of 400 g mol(-1) in THF, and a permeance of 0.07 L h(-1) m(-2) bar(-1) and a MWCO of around 470 g mol(-1) in DMF. To the best of our knowledge this is the first report on a non-sulphonated and non-modified PEEK membrane capable of separations in the nanofiltration range and resistant to DMF and THE and to basic and acidic aqueous solutions. (C) 2015 Elsevier B.V. All rights reserved.