Enhanced Wettability and Transport Control of Ultrafiltration and Reverse Osmosis Membranes with Grafted Polyelectrolytes

Kai Gao, Logan T. Kearney, Ruocun Wang, John A. Howarter

Research output: Contribution to journalArticlepeer-review

22 Scopus citations

Abstract

End-functionalized poly(acrylic acid) (PAA-silane) was synthesized with reversible addition-fragmentation chain-transfer (RAFT) polymerization and attached to both polysulfone ultrafiltration (UF) and polyamide reverse osmosis (RO) membranes through a nonimpairing, one-step grafting to approach in order to improve membrane surface wettability with minimal impact on membrane transport performance. After PAA grafting, composition and morphology changes on the membrane surface were characterized with Fourier transform infrared spectroscopy (FTIR) and atomic force microscopy (AFM). Static contact angle on PAA grafted membranes exhibited an increase in surface hydrophilicity and hence a potential enhancement in antifouling performance. The native contact angle on the polysulfone membrane systems was 86° and was reduced to 24° after modification, while the polyamide film contact angle decreased from 58° to 25°. The PAA layer endowed the porous UF membrane with dynamic control over the permeability and selectivity through the manipulation of the solution pH. The UF membrane with a 35 nm average pore size displayed a 115% increase in flux when the contact solution was changed from pH 11 to pH 3. This effect was diminished to 70% and 32% as the average pore size decreased to 20 and 10 nm, respectively. Modified RO membranes displayed no reduction in membrane performance indicating that the underlying materials were unaffected by the modification environment or added polymer. Model polyamide and polysulfone surfaces were reacted with the PAA-silane inside a quartz crystal microbalance (QCM) to help inform the deposition behavior for the respective membrane chemistries.

Original languageEnglish
Pages (from-to)24839-24847
Number of pages9
JournalACS Applied Materials and Interfaces
Volume7
Issue number44
DOIs
StatePublished - Nov 11 2015
Externally publishedYes

Keywords

  • membrane
  • polyelectrolyte
  • quartz crystal microbalance (QCM)
  • stimuli-responsive
  • surface modification

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