Browsing by Author "Turner, J. C. Robin"

Filter results by typing the first few letters
Now showing 1 - 2 of 2
  • No Thumbnail Available
    Item
    Coupled Fluxes in Electrochemistry Concentration Distributions near Electrodialysis Membranes
    (Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1978, 74 (09-12), 1978) Brady, John F.; Turner, J. C. Robin
    In electrodialysis the gradient of electrical potential leads to coupling of the flux equations for all the different ionic species. When these ions have the same (numerical) valency, their concentrations close to and within the electrodialysis membrane can be obtained from a closed-form solution, as can the potential. When they do not, a series solution is derived, which requires that all the ionic fluxes be known. If they are not available (e.g. from measurement) they must be guessed at the start of an iterative scheme. Concentration and potential profiles are discussed for cases with and without “water-splitting”, which is the production of sizeable fluxes of H+ and OH– ions even though the feed solution is effectively neutral. The concept of “limiting current density” is discussed, and is shown to lose much of its usefulness in the presence of water-splitting.
  • No Thumbnail Available
    Item
    Polarisation in electrodialysis. Rotating-disc studies
    (Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1978, 74 (09-12), 1978) Makai, Alexander J.; Turner, J. C. Robin
    Polarisation in an electrodialysis stack is difficult to examine because of the complex flow of the fluids through the stack. A rotating-disc apparatus has been built, for which the fluid mechanics are both well-known and convenient. Using anion-exchange membranes, the current against voltage plots at high voltages show considerable “water-splitting”, with large fluxes of H+ and OH– ions. The results correlate well with the treatments of Levich and of Cowan, and the enhancement of the anion fluxes by the water-splitting can be explained. Using cation-exchange membranes there is much less water-splitting, with anomalously high cation flux enhancement. Though these characteristics are desirable in practice, they are not explicable by the same approach as seems successful with anion membranes.