Electrodialysis treatment accompanied by metal substitution reaction was studied in order to separate calcium, cobalt, magnesium and strontium ions from a solution of their ethylenediaminetetraacetic acid (EDTA) complex. The electrodialysis stack consisted of three units of three cells containing the Feed, Reaction, and Strip compartments. The Feed solution, the Reaction solution, and the Strip solution, each of which flowed from the corresponding compartment, contained CuCl
2, EDTA-metal complex, and NaCl solution, respectively. When the voltage was applied to the electrodialyzer, Cu
2+ proceeded from the Feed compartment to the Reaction compartment and acted as the substitute for the metal elements in the EDTA complexes. The resulting free metal ions moved to the Strip compartment and were separated. When the pH of the initial reaction solution was greater than 10, the solution pH changed significantly to acidic during electrodialysis. The behavior of pH changes in the reaction compartment was explained by a mathematical model that considered the equilibrium of the solution, the material balance of the chemical species, and electroneutrality in the solution.
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