SEPARATION OF CUPRIC AND FERRIC IONS WITH A CATION-EXCHANGE MEMBRANE IN THE PRESENCE OF COMPLEXING AGENTS

The separation of cupric and ferric ions in chloride solution has been studied with a cation-exchange membrane in a batch dialyzer. Citric acid, oxalic acid, malonic acid, succinic acid, ethylenedinitrilotetraacetic acid, and glycine have been employed as complexing agents used in the feed phase in order to increase the separation effect. The experimental results show that citric acid, compared to the others, is an effective complexing agent to increase the separation coefficient, T(Fe)Cu, from 0.5 to 50. The separation behavior depends on the pH of the co solution, the stoichiometric ratios of complexing agents to metal ions, and the kinds of complexing agents, but is independent of counterion concentration in the stripping phase. The integral interdiffusion coefficients of cupric and ferric ions in Selemion CMV have also been evaluated and found to be D(Fe-Na)BAR > D(Cu-Na)BAR at concentrations ranging from 0.0015 to 0.0085 M. In the absence of complexing agents, T(Fe)Cu falls in the neighborhood of the D(Cu-Na)BAR/D(Fe-Na)BAR value when the pH is less than 2.0.