## Abstract

Starting with the Stefan-Maxwell equations, general expressions for the ionic flux rates for binary exchange in ion-exchange resins have been developed. These equations have been shown to reduce to the Nernst-Planck equations exactly only as the concentration of either exchanging ion approaches unity. Furthermore, the single-ion diffusion coefficients used In the Nernst-Planck equations are shown to be certain combinations of the Stefan-Maxwell Interaction coefficients. Most importantly, these combinations of the Stefan-Maxwell interaction coefficients are shown to reduce to the tracer diffusion coefficient of each exchanging ion, measured in ion-exchange resin completely in the competing ion form. As these limiting tracer Ion diffusion coefficients may be very different from the usual pure self-diffusion coefficients, this result may explain existing anomalies resulting from the use of the Nernst-Planck equations to describe diffusion in ion-exchange resins and related ion-exchange systems.

Original language | English (US) |
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Pages (from-to) | 360-365 |

Number of pages | 6 |

Journal | Industrial and Engineering Chemistry Fundamentals |

Volume | 21 |

Issue number | 4 |

DOIs | |

State | Published - Nov 1 1982 |

## ASJC Scopus subject areas

- Engineering(all)