Intrinsic p Kaof Nanofiltration Membrane Surfaces to Assess Fouling and Cleaning Behaviors Induced by Foulant-Membrane Electrostatic Interactions

Hojung Rho, Hojung Rho, Jaeweon Cho, Paul Westerhoff, Kangmin Chon

Research output: Contribution to journalArticle

Abstract

The fouling and cleaning behaviors of m-phenylenediamine (MPD), coumarin-3-carboxylic acid (CCA), and d-(+)-glucose (DG) on polyamide nanofiltration (NF) membrane surfaces were investigated with a focus on the two intrinsic equilibrium constants (pKa,intr.) of carboxylic and amine functional groups determined using potentiometric titration. The charged foulants (MPD and CCA) strongly influenced the pKa,intr. of the membrane surface after the fouling layer formed via electrostatic interactions (Virgin = 3.4 and 9.2; MPD-fouled = 4.1 and 8.1; CCA-fouled = 1.5 and 12.4). Moreover, the pKa,intr. of electrostatically fouled membranes substantially recovered when using cleaning agents that released electrostatic interactions (cleaned MPD-fouled = 3.5 and 9.0; cleaned CCA-fouled = 3.3 and 9.6). In contrast, the neutral foulant (DG) did not affect the pKa,intr. (DG-fouled = 3.5 and 9.2); however, the ζ-potential of DG-fouled membrane was closer to zero than the virgin membrane (Virgin = -28.1 mV and DG-fouled = -7.2 mV at pH 7). The pKa,intr. value accurately represented the electrostatic interactions between organic foulants and membrane surfaces. Potentiometric titration is a facile method of determining the pKa,intr. that gives an in-depth understanding of the electrostatic interactions at the membrane surface associated with the membrane fouling and cleaning mechanism.

Original languageEnglish (US)
Pages (from-to)7706-7714
Number of pages9
JournalEnvironmental Science and Technology
Volume54
Issue number12
DOIs
StatePublished - Jun 16 2020

ASJC Scopus subject areas

  • Chemistry(all)
  • Environmental Chemistry

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