Issue 0, 1978

Stability of metal uncharged ligand complexes in ion exchangers. Part 3.—Complex ion selectivity and stepwise stability constants

Abstract

A new method is presented for obtaining the stepwise stability constants of ion-exchanged metal–uncharged ligand complexes: it is based upon the measurement of the effect of increasing ligand concentration on complex-ion selectivity and provides a more sensitive means of characterizing adsorbed complexes than the usual method, relying on the measurement of ligand numbers in the exchanger.

In special cases where a more favourable coordination of the first ligand in the ion exchanger (as compared with the bulk solution) is accompanied by a less favourable coordination of the second ligand, a maximum occurs in the complex ion selectivity coefficient. This maximum occurs at a critical ligand concentration which equals the reciprocal of the average stability constant [graphic omitted] of the complex in solution. The maximum selectivity coefficient of the complex ion depends mainly on the ratio of stepwise stability constants in solution, K1/K2, and its upper limit equals the ratio of stepwise constants, K1/K2 in the exchanger and the solution.

The method is illustrated by the case of the silver–thiourea complex in a macroreticular sulphonic acid resin in which the stability constant for the one-complex exceeds the value in solution by more than four orders of magnitude.

Article information

Article type
Paper

J. Chem. Soc., Faraday Trans. 1, 1978,74, 2470-2480

Stability of metal uncharged ligand complexes in ion exchangers. Part 3.—Complex ion selectivity and stepwise stability constants

A. Maes and A. Cremers, J. Chem. Soc., Faraday Trans. 1, 1978, 74, 2470 DOI: 10.1039/F19787402470

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