GB764067A - Improvements in electrolytic processes - Google Patents

Abstract

764,067. Electrodialysis. PERMUTIT CO., Ltd. March 25, 1954 [April 7, 1953], No. 9420/53. Class 41. In a process of electrodialysis in a multicompartment cell having an anode compartment and a cathode compartment and at least five intermediate compartments between the two electrode compartments, the compartments being separated from one another by alternate cation and anion exchange diaphragms, an anion exchange diaphragm being next to the anode and a cation exchange diaphragm next to the cathode, one solution is passed continuously in one direction through every alternate intermediate compartment and a second different solution is passed in the opposite direction through the remainder of the intermediate compartments, while a direct current is continuously passed through all the compartments in series. The solutions in the electrode compartments may be continuously changed. The liquid leaving one set of intermediate compartments may be passed through one of the electrode compartments. A solution having lower electrode potentials than the electrolyte being treated and having a reaction at the cathode which is the reverse of the reaction at the anode may be continuously circulated between the two electrode compartments, as described in Specification 764,068. An illustrated embodiment shows a cell comprising five intermediate compartments 1, 2, 3, 4 and 5 between an anode compartment 6 containing an anode 10 and a cathode compartment 7 containing a cathode 11. These compartments are separated from one another by anion exchange diaphragms 8 and cation exchange diaphragms 9. A solution from which a dissolved electrolyte is to be removed is fed to compartment 1 and flows thence to compartment 3 and then to compartment 5. At the same time a solution to receive the electrolyte removed from the first solution is passed through compartment 4 and then through compartment 2. The diaphragms may be made With peripheral projections to hold them apart and cooperating holes formed in the projections so that the solutions may flow through the conduits thus formed and enter and leave the compartments through passages connecting the holes with the compartments. The two end diaphragms are shielded on the sides nearest to the electrodes by further diaphragms 12 of ordinary macroporous material, e.g. porous ceramic material, whereby the products of electrolysis produced at the electrodes are hindered from diffusing towards and attacking the ionexchange diaphragms. The liquid leaving compartment 5 may be passed through compartment 6 or alternatively the liquid leaving compartment 2 may be passed through compartment 7.