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Series Arrays of Ion‐Exchange Membranes: Concentration Profiles and Rectification of Electric Current
Author(s) -
Naparstek Avraham,
Roy Caplan S.,
KatzirKatchalsky Aharon
Publication year - 1973
Publication title -
israel journal of chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.908
H-Index - 54
eISSN - 1869-5868
pISSN - 0021-2148
DOI - 10.1002/ijch.197300027
Subject(s) - chemistry , electrodialysis , membrane , steady state (chemistry) , rectification , current (fluid) , series (stratigraphy) , non equilibrium thermodynamics , ion , ion exchange membranes , mechanics , analytical chemistry (journal) , ion exchange , thermodynamics , chemical physics , biophysics , chromatography , physics , biochemistry , paleontology , power (physics) , organic chemistry , biology
Using the nonequilibrium thermodynamic treatment of Kedem and Katchalsky a study has been made of series arrays of ion‐exchange membranes. A rule has been found which identifies certain classes of intermembrane concentrations which vary in the same way with respect to current under different steady‐state conditions. Among these is a set which is independent of the value of the steady‐state current. For the special case of series arrays containing alternately positive and negative fixed charges, with indefinitely large end reservoirs, it is shown that in the steady‐state the array may possess a set of desalinated intermembrane compartments, or a set of salinated intermembrane compartments, but never both simultaneously. This leads to the conclusion, which has been tested experimentally, that a large array of this kind may act as an efficient rectifier. The steady‐state concentration profile across a large array may be radically altered by changing a single membrane in the array, or even adding a single membrane at one end of the array. The approach to the steady‐state has been examined by means of a relaxation calculation, which leads to certain conclusions relating to optimization of flow‐rates in desalination by electrodialysis.