| abstract |
Appts. for recovering an acid from its salt by electrodialysis has electrodialysis cells to which a p.d. can be applied, each with 4 adjacent compartments sepd. by cation exchange membranes and anion exchange membranes. The novel features are that the cells are arranged in a stack and connected in series; and adjacent cells are arranged inversely, so that they share one outer compartment (I) or (IV) and one electrode (+ or -). The outer compartments (I, IV) are sepd. from the inner compartments (II, III) by cation exchange membranes (K), whilst the 2 inner compartments are sepd. by an anion exchange membrane (A); or the outer compartment (I) on the anode side is sepd. from the adjacent inner compartment (II) by a cation exchange membrane and the other compartments (II, III, IV) are sepd. by anion exchange membranes. The electrodes consist of platinised Ti. An acid is supplied to (I), an aq. alkali soln. to (IV), an organic salt to (III) and water to (II), whilst the required conc. acid is discharged from (II) and residual prods. from (III). USE/ADVANTAGE - The appts. is esp. useful for recovering organic acids, e.g. citric, lactic, acetic, formic, butyric, succinic acid etc., from their salts without adding protons from an inorganic acid. |