Multi-cell electrodialysis appts. - esp. for organic acid recovery from salt

摘要

Appts. for recovering an acid from its salt comprises electrodialysis cells, each of which has four adjacent chambers sepd. by cationic and anionic exchange membranes, the novelty being that; (i) the cells are stacked in a row; (ii) only the chambers (I, IV) of the two outer cells of the stack have an anode or cathode electrode; and (iii) the outer chambers (I, IV) of the other cells are sped. from the outer chambers of adjacent cells by liq.-tight high conductivity plates. Acid is recovered using the appts. by (a) passing an acid through the anode side outer chambers (I) and an alkali through the cathode side outer chambers (IV); (b) supplying an organic salt to the cathode side inner chamber (III) and water to the anode side inner chamber (II); and (c) withdrawing the conc. acid product from the anode side inner chamber (II) and residual products from the cathode-side inner chamber (III). USE/ADVANTAGE - The appts. is used esp. for recovering organic acids such as citric acid from their salts. The process does not involve proton addn. from an inorganic acid (thus avoiding inorganic salt formation), allows high throughputs and does not require a large number of expensive electrodes.