Permselectivity of Specific Ions through the Ion Exchange Membrane in Electrodialysis

Many attempts to prepare ion exchange membranes having permselectivity for specific ions and to find electrodialysis methods to achieve such a purpose have been made. In this chapter, studies on the modification of ion exchange membranes and electrodialysis methods to permeate specific ions through the membrane, mainly in electrodialysis, are explained. 

2 Permselectivity of Specific Ions through Ion Exchange Membranes in Electrodialysis 

The permselectivity between A ions and B ions (generally B = sodium or chloride ions), PBA, which is called the transport number of A relative to B ions, is defined as 

Since LM can be expressed by LAl — f/A)CRAl(d ,/dx) UAl is the mobility of A, ions in the membrane phase [cm2/(dis/cb ) s], CRAi the concentration of A( ions in the membrane phase during electrodialysis (eqcnr3) and (dE/dx) the electrical potential gradient in the membrane phase, Eq. (5.2) can be expressed as follows, 

The ion exchange equilibrium constant between A and B ions in the membrane, Kba, is expressed as, 

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