Friction coefficients and properties of polyelectrolyte membranes

Abstract

Transport through a polyelectrolyte membrane in aqueous binary electrolyte solutions is described by six constants, either six permeabilities Lik (with i, k = 1, 2, 3, including i = k) or friction coefficients fik (with i, k = 1, 2, 3, 4; i ≠ k). In a porous, selective membrane the friction of the co‐ion with the polymer matrix can be neglected, whereas the molecular friction coefficient of small ions and solvent approaches its free solution value. The required experimental information reduces to three independent measurements, for which electro‐osmosis, conductivity and co‐ion diffusion may be taken. A check on the fik values thus calculated is provided by expressing the ratio of electric transference numbers in friction quantities and comparing with experiment. The proposed device does not involve concentration averages; it is shown to be compatible with experimental data.

Electroosmosis in Ion-Exchange Membranes

“…In view of this constancy Eq. [11] can be written for two electrolytes M1 and M2 as --(C1/C3)]M2 [12] and from this, as pointed out by Dorst and Staverman (58),-tw for M2 may be inferred, provided all the required data for M1 and the values of C1 and Ca for M2 are known. Since C2 = 0 for the membrane phase, the nature of the anion should have little effect on the ratio (XI3) M1 + / (XI3) M2 +.…”