Patent GB-694223-A (GB)
Title: Apparatus for modifying the chemical composition of substances by ion transfer
IPC: C08F214/18
Filed: 1951-07-12
Abstract: 694,223. Electro-dialysis. KOLLSMAN, P. July 12, 1951 [July 21, 1950], No. 16533/51. Class 41. In apparatus for the ion-enrichment and deionization of liquids under the influence of an electric current, comprising a plurality of liquid spaces separated from one another by membrane walls of two types, one type of membrane being permeable to ions of one sign and passageresistant to ions of the opposite sign, the other type being permeable to ions of the opposite sign only, the two types of membrane walls alternating in sequence, and electrodes being provided in certain liquid spaces, the intermediate liquid spaces lying between the electrode containing spaces, which are alternately concentration compartments and de-ionization compartments, are free from electrodes and passages are provided for conducting liquid to be de-ionized through the de-ionization compartments and for removing liquid from the concentration compartments, flow-restricting means being provided in the concentration compartments for the purpose of reducing the volume withdrawn from these compartments per time unit to less than the liquid admitted to the de-ionization compartments. The apparatus may be used for the treatment of water or for the production of chemical compositions from other compositions, as for example, the production of potassium bromide and hydrogen chloride from potassium chloride and hydrogen bromide in the presence of water. As shown, a tank 11 is divided into cells by diaphragms 12, 13 arranged alternately, the diaphragms 12 being anion-permeable and the diaphragms 13 being cation-permeable. Terminal cells 14, 15 contain electrodes 17, 16, respectively, the electrode 17 being connected to the positive pole and the electrode 16 to the negative pole of a source of current 20. The liquid to be treated is supplied to cells 19 through a duct 24 and inlet ports 23, and is discharged through outlet ports 25 and a duct 26. The alternate concentration cells 18 receive liquid through a duct 28 and ports 27, the liquid being discharged through restricted ports 29 leading to a discharge duct 30. When an electric potential is applied to the electrodes, the liquid flowing upwardly through the cells 19 is deprived of its ions which pass through the diaphragms (the anions towards the anode 17 and the cations towards the cathode 16) and are conveyed away by the liquid flowing downwardly through the cells 18. The flow of the liquid through the cells 18 is at a volumetric rate which is only a fraction of that through the cells 19, so that the liquid leaving the cells 18 is more concentrated than that receiving treatment in the cells 19. Liquid may enter the terminal compartments 14, 15 in either direction. In a modification which may be used, for example, for the treatment of sea water, the ducts 26, 28 are replaced by a single duct 36, Fig. 3, and the duct 24 is provided with a pump 35. The duct 36 is connected by ports 25 to the de-ionization cells 19 and to the terminal cells 14, 15, and by ports 27 provided with valves 37 to the concentration cells 18, which have reduced discharge ports 29. The cells 18 may have vent ducts 39 for release of gas. This apparatus may be used with the valves 37 closed or open ; in the former case the liquid in the cells 18 being obtained solely through the diaphragms. The spaces between the diaphragms are preferably less than the thickness of the diaphragm, for example spacings of 1 or 2 mm. are suitable in the case of diaphragms of 3 mm. thickness.