Thermo-responsive adsorption-desorption of perfluoroorganics from water using PNIPAm hydrogels and pore functionalized membranes

Anthony Saad, Rollie Mills, Hongyi Wan, M. Abdul Mottaleb, Lindell Ormsbee, Dibakar Bhattacharyya

Research output: Contribution to journalArticlepeer-review

26 Scopus citations

Abstract

Perfluorochemicals (PFCs) are emerging contaminants in various water sources. Responsive polymers provide a new avenue for PFC adsorption/desorption from water. Poly-N-isopropylacrylamide's (PNIPAm's) temperature-responsive behavior and hydrophilic/hydrophobic transition is leveraged for reversible adsorption and desorption of PFCs. Adsorption of PFOA (perfluoro-octanoic acid) onto PNIPAm hydrogels yielded Freundlich distribution coefficients (Kd) of 0.073 L/g at 35 °C (above LCST) and 0.026 L/g at 22 °C. Kinetic studies yielded second order rate constants (k2) of 0.012 g/mg/h for adsorption and 12.6 g/mg/h for desorption, with initial rates of 28 mg/g/h and 41 mg/g/h, respectively. Interaction parameters of PNIPAm's functional groups in its different conformational states, as well as the hydrophobic fluorinated carbon tails and hydrophilic head groups of PFOA are used to describe relative adsorption. Polyvinylidene difluoride (PVDF) provides a robust membrane structure for the commercial viability of polymeric adsorbents. Temperature swing adsorption of PFOA using PNIPAm functionalized PVDF membrane pores showed consistent adsorption and desorption capacity over 5 cycles. PFOA desorption percentage of 60% was obtained in pure water at temperatures below PNIPAm's lower critical solution temperature (LCST) while 13% desorption was obtained at temperatures above the LCST, thus showing the importance of the LCST on desorption performance.

Original languageEnglish
Article number117821
JournalJournal of Membrane Science
Volume599
DOIs
StatePublished - Apr 1 2020

Bibliographical note

Funding Information:
This research is supported by the NIH-NIEHS-SRC (Award number: P42ES007380 ) and the NSF KY EPSCoR grant (Grant no: 1355438 ). LC-MS analysis was supported by UK-CARES through Grant P30 ES026529 . Its contents are solely the responsibility of the authors and do not necessarily represent the official views of the NIEHS.

Funding Information:
This research is supported by the NIH-NIEHS-SRC (Award number: P42ES007380) and the NSF KY EPSCoR grant (Grant no: 1355438). LC-MS analysis was supported by UK-CARES through Grant P30 ES026529. Its contents are solely the responsibility of the authors and do not necessarily represent the official views of the NIEHS.

Publisher Copyright:
© 2020 Elsevier B.V.

Keywords

  • Adsorption
  • Hydrogel
  • PFOA
  • PFOS
  • PNIPAm
  • Water detoxification

ASJC Scopus subject areas

  • Biochemistry
  • Materials Science (all)
  • Physical and Theoretical Chemistry
  • Filtration and Separation

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