Probing the charged nature and ion-exclusion mechanism of fluorine-enriched non-ionogenic polyamide derived thin film composite nanofiltration membranes. Issue 3 (20th May 2020)

• Record Type: Journal Article
• Authors: Pal, Avishek; Dey, T. K.; Bhattacharyya, Kaustava; Bindal, R. C.
• Is Part Of: Materials advances. Volume 1:Issue 3(2020)
• Page Start: 403
• Page End: 414
• Publication Date: 2020-05-20
• Subjects: 620.11
• DOI: 10.1039/d0ma00107d
• Languages: English
• ISSNs: 2633-5409

Abstract

Abstract : Thin film composite (TFC) nanofiltration (NF) membrane comprising a novel fluorine-enriched polyamide (FPA) as skin layer polymer has been developed by in situ interfacial polycondensation technique. Abstract : A thin film composite (TFC) nanofiltration (NF) membrane comprising a novel fluorine-enriched polyamide (FPA) as a skin layer polymer has been developed by in situ interfacial polycondensation between a cyclo-aliphatic diamine monomer, piperazine, and an acyclic fluorodiacyl chloride monomer, tetrafluorosuccinyl chloride. Instrumental investigations carried out by FTIR and XPS showed that the structure of FPA is devoid of intra- as well as inter-molecular H-bonds, which seems to be a rare finding in NF type membranes with decent performances. Stereoelectronic effects of the FPA structure, owing to the configurational mobility of polymer chains, electron-withdrawing ability of fluorine and lack of cohesive non-covalent type interactions, strongly influenced the surface morphology, topography and hydrophilicity of the TFC-NF membranes. The active skin layer of the membranes exhibited uniform charge-atmosphere in spite of not having any fixed charged groups in the polymer structure constituting it. Zeta potential measurement of the membranes revealed low values (−4.4 to −7 mV), indicating their low surface charge. However, a high Donnan-exclusion was observed towards a solute with multivalent anion (Na2 SO4, solute rejection: 87–93%) as opposed to that with monovalent anion (NaCl, solute rejection: 23–26%), with a solvent flux as high as 54 L m −2 h −1 at 15 bar transmembrane pressure. The current class of TFC-NF membranes with unique physicochemical attributes thus provides a promising scope for a variety of nanofiltration applications.