Tj. Chou et A. Tanioka, MEMBRANE-POTENTIAL ACROSS CHARGED MEMBRANES IN ORGANIC SOLUTIONS, JOURNAL OF PHYSICAL CHEMISTRY B, 102(37), 1998, pp. 7198-7202
The membrane potentials across cation- and anion-exchange membranes we
re measured for five LiBr-various-solvent systems. Water, dimethyl sul
foxide, ethylene glycol, methanol, and n-propanol were used as the sol
vents in this work. The experimental data were analyzed on the basis o
f the Donnan equilibrium and the Nernst-Planck equation of ion flux co
nsidering the effect of ion pairing of the electrolyte in the external
solution. The Fuoss formalism of ion pairing was adopted to estimate
the effective ion concentration in the external solutions, and the the
oretical predictions agreed well with the experimental data. The effec
tive membrane charge densities and the cation-to-anion mobility ratios
in the membrane were also determined in this work. The results showed
that the effective membrane charge density will vary with the kind of
solvent. We attempted to introduce the concept of ion pairing inside
the membrane to clarify this phenomenon.