Modeling the effect of charge density in the active layers of reverse osmosis and nanofiltration membranes on the rejection of arsenic(III) and potassium iodide

Orlando Coronell, Baoxia Mi, Benito Jose Marinas, David G Cahill

Research output: Contribution to journalArticle


We used an extended solution-diffusion model that incorporates Donnan electrostatic exclusion of ions and unhindered advection due to imperfections, and measurements of charge density in the polyamide active layers of reverse osmosis (RO) and nanofiltration (NF) membranes, to predict the rejection of a strong electrolyte (i.e., potassium iodide) and a weak acid (i.e., arsenious acid) as a function of the pH of the feed aqueous solution. Predictions of solute rejection were in agreement with experimental data indicating that (i) the extended solution-diffusion model taking into account Donnan exclusion and unhindered advection due to imperfections satisfactorily describes the effect of pH on solute rejection by RO/NF membranes and (ii) measurement of charge density in active layers provides a valuable characterization of RO/NF membranes. Our results and analysis also indicate that independent ions, and not ion pairs, dominate the permeation of salts.

Original languageEnglish (US)
Pages (from-to)420-428
Number of pages9
JournalEnvironmental Science and Technology
Issue number1
StatePublished - Jan 2 2013


ASJC Scopus subject areas

  • Chemistry(all)
  • Environmental Chemistry

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