pH-Swing membrane adsorption of perfluoroalkyl substances: Anion-exchange brushes and role of water chemistry

Hongyi Wan, Fumohan Fang, Ke Shi, Zhiyuan Yi, Linfeng Lei, Siyao Li, Rollie Mills, Dibakar Bhattacharyya, Zhi Xu

Research output: Contribution to journalArticlepeer-review

10 Scopus citations

Abstract

The pH-swing membrane adsorption, aiming for effective removal, high membrane permeability, and facile regeneration, was developed to remediate emerging perfluoroalkyl contaminants. Compared to the collapse transformation of deprotonated tertiary-amine brushes at neutral pH (pKb: ∼5.82), the quaternary-ammonium (QA) brushes endowed consistent membrane pore structure and higher isoelectric point (pHIEP: 11.2 versus 7.5), resulting in a suitable pH-swing adsorption/desorption range towards groundwater conditions. Such QA-grafted membranes (QA loading: 1.1 mmol/g) not only presented >90 % removal of perfluorooctanoic acid (PFOA) at a treatment capacity of 570 L per m2 of membrane area, but also enabled effective membrane regeneration that >97 % desorption was achieved at pH 12.5 and 5 % methanol. The remediation is driven by synergetic electrostatic and hydrophobic interactions, as demonstrated by (1) the zeta-potential dependent removal performance and (2) the greater maximum adsorption capacity towards the more hydrophobic perfluorooctane sulfonate than PFOA (Qm: 0.65 mmol/g and 0.44 mmol/g, respectively). Within three pH-swing adsorption/regeneration cycles, a total PFOA removal of 82.4 % was achieved with a treatment capacity of 2,930 L/m2. The impacts of ionic strength, ionic types, and natural organic matters were evaluated. Overall, the pH-swing strategy is an effective method with high permeability (165.6 L m−2h−1bar−1), stability, and tunable adsorption/regeneration processes.

Original languageEnglish
Article number124800
JournalSeparation and Purification Technology
Volume329
DOIs
StatePublished - Jan 15 2024

Bibliographical note

Publisher Copyright:
© 2023 Elsevier B.V.

Funding

This work was supported by the National Natural Science Foundation of China [22075076&22208097]. We highly appreciate the collaborations with the University of Kentucky NIEHS Superfund center. This work was supported by the National Natural Science Foundation of China [22075076&22208097]. We highly appreciate the collaborations with the University of Kentucky NIEHS Superfund center.

FundersFunder number
University of Kentucky NIEHS
National Natural Science Foundation of China (NSFC)22208097, 22075076

    Keywords

    • Adsorptive membrane
    • PFAS removal
    • Removal mechanism
    • Water matrix
    • pH-swing regeneration

    ASJC Scopus subject areas

    • Analytical Chemistry
    • Filtration and Separation

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