Use of electrodialysis to remove acid, salt, and heavy metal mixtures from aqueous solutions

The effect of solution composition on the electrodialysis design parameters of overall current efficiency and apparent stack resistance for mixtures of acids, monovalent salts, and divalent metals is discussed, Current efficiency was observed to be dependent upon ion valence and independent of the nature of the ionic specie for the membrane system under investigation. Under many conditions, simple linear mixing rules fail to predict these design parameters, particularly for systems at low pH, or when the electrolyte concentration gradient across the membrane is large. However, under commercially desirable operating conditions of high current efficiency, linear mixing rules will predict system performance for mixed ion systems composed of ions of differing valences.