Energetic and Entropic Factors of Interphase Ion Exchange

Selectivity of sorption of organic ions by crosslinked polyelectrolytes in competition with small ions, in particular with metal ions, should be considered on the basis of the analysis of thermodynamic relationships of ion exchange. 

Within the framework of the proposed model, the ion exchange equilibrium between the solution and CP ion exchanger can be described by the equation  

Equation (3.1) does not take into account the electric work because equivalent ion exchange is considered. Therefore 

Taking into account the interdependence between chemical potentials and component activity jij = p + RT In a, Eqs. (3.1) and (3.2) yield a well known ion exchange equation 

Here Yi and y2 are the activity coefficients of ions in solution, y, and y2 are the coefficients of resin activity, cx and c2 are ion concentrations in solution, ntj and m2 are fixed ion concentrations (exchange or weight concentrations) and Ks is the concentration constant of ion exchange, the selectivity constant. 

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