Three-Phase Distribution Analysis for Complexation in Anion Exchangers

THREE-PHASE DISTRIBUTION ANALYSIS FOR COMPLEXATION IN ANION EXCHANGERS 

For Eq. (26) only ftee metal ion is assumed to enter the cation exchanger phase. This assumption is acceptable only when Donnan invasion of negatively charged species is sufficiently low. VC th the two distribution ratios made available from a common equilibrating solution their ratio is examined to provide the following alternate path to species identification  

Employment of the Donnan relationship in the presence of the supporting electrolyte, B+A , used to proAdde a constant ionic strength, leads to the derivation of the above equation and those that follow  

Ni(II)-NaSCN-NaC104 (1=1.0) experimental plot -------theoretical slope. 

An example of the use of this approach is shown [12] for the nickel-thiocyanate, Dowex-50W-X4, and Dowex 1-X4 system (Fig. 7). In the lowest SCN concentration range, the slope is -1 and NiSCN is identified in the middle SCN concentration range the slope increases from negative to positive and finally with further increase of SCN concentration it reaches +4 to signal the predominance of the fully coordinated Ni(SCN)g complex in the anion-exchanger phase. The absorption spectrum of this last complex is shown in Fig. 8. It has not yet been observed in concen- 

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