Dual-Functional Nanofiltration and Adsorptive Membranes for PFAS and Organics Separation from Water

Francisco Léniz-Pizarro, Ronald J. Vogler, Phillip Sandman, Natalie Harris, Lindell E. Ormsbee, Chunqing Liu, Dibakar Bhattacharyya

Research output: Contribution to journalArticlepeer-review

10 Scopus citations

Abstract

Challenges associated with water separation technologies for per- and polyfluoroalkyl substances (PFASs) require efficient and sustainable processes supported by a proper understanding of the separation mechanisms. The solute rejections by nanofiltration (NF) at pH values near the membrane isoelectric point were compared to the size- and mass-transfer-dependent modeled rejection rates of these compounds in an ionized state. We find that the low pKa value of perfluorooctanoic acid (PFOA) relates to enhanced solute exclusions by minimizing the presence and partitioning of the protonated organic compound into the membrane domain. The effects of Donnan exclusion are moderate, and co-ion transport also contributes to the PFAS rejection rates. An additional support barrier with thermo-responsive (quantified by water permeance variation) adsorption/desorption properties allows for enhanced separations of PFAS. This was possible by successfully synthesizing an NF layer on top of a poly-N-isopropylacrylamide (PNIPAm) pore-functionalized microfiltration support structure. The support layer adsorbs organics (178 mg PFOA adsorbed/m2 membrane at an equilibrium concentration of 70 mg/L), and the simultaneous exclusion from the NF layer allows separations of PFOA and the smaller sized heptafluorobutyric acid from solutions containing 70 μg/L of these compounds at a high water flux of 100 L/m2-h at 7 bar.

Original languageEnglish
Pages (from-to)863-872
Number of pages10
JournalACS ES and T Water
Volume2
Issue number5
DOIs
StatePublished - May 13 2022

Bibliographical note

Publisher Copyright:
© 2022 American Chemical Society.

Keywords

  • PFAS
  • organic anions
  • responsive materials
  • water treatment

ASJC Scopus subject areas

  • Water Science and Technology
  • Chemical Engineering (miscellaneous)
  • Chemistry (miscellaneous)
  • Environmental Chemistry

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