M. Kawaguchi et al., MEMBRANE-POTENTIALS IN CHARGED MEMBRANES SEPARATING SOLUTIONS OF WEAKELECTROLYTES, Journal of the Chemical Society. Faraday transactions, 93(7), 1997, pp. 1351-1356
Citations number
43
Categorie Soggetti
Chemistry Physical","Physics, Atomic, Molecular & Chemical
The transport of weak electrolyte ions through a charged membrane has
been studied. The membrane potential across cation- and anion-exchange
membranes was measured for acetic acid and glycine methyl ester hydro
chloride aqueous solutions. Membrane potentials were correlated to a t
ransport theory using the Donnan equilibrium and the Nernst-Planck equ
ation of ion flux by introducing the dissociation constant of a weak e
lectrolyte in aqueous solution. The anion-to-cation mobility ratios in
the membrane were determined via a non-linear regression method. In t
he case of acetic acid solutions in an anion-exchange membrane, the ra
tios were about 0.0001-0.001 times larger than those in water. On the
other hand, they were about 10000 times larger than in water if a cati
on-exchange membrane was employed. Therefore, the ion mobilities of we
ak electrolytes are significantly affected by groups of fixed charge i
n the membrane. In the case of glycine methyl ester hydrochloride, the
mobility ratio was the same as in water, which means that it behaves
as a strong electrolyte. It is suggested that the transport phenomena
of weak electrolyte ions in a charged membrane can be explained by the
above-described transport theory.