Patent GB-622724-A (GB)
Title: Electrolytic process and apparatus
IPC: B01D59/42
Filed: 1942-09-14
Abstract: 622,724. Electrolytic separation of substances. LONDON, H., and APPLETON, E. V. Sept. 14, 1942, No. 12965. [Class 41] In the electrolytic separation of components of a solution whose ions are of different mobility, e.g. isotopes, a hydrodynamic flow is set up to compensate the ionic flow by supplying a " leading solution " in the neighbourhood of the appropriate electrode, the supply being in excess of that required for compensation and the excess overflowing continuously through a constant level device; a boundary is thus set up between the " leading solution " and the solution to be treated and its position is automatically maintained constant. The " leading solution " is preferably of lower specific gravity than the solution to be treated and for the separation of cations may be a solution of an acid or salt having the same anion as the solution to be treated and a cation of greater mobility than either of those to be separated. In the treatment of uranyl chloride solution the " leading solution " may be a solution of hydrogen chloride. In the treatment of uranyl nitrate solution the " leading solution " may contain lithium nitrate. In the apparatus shown in Fig. 1, the cell comprises a narrow U-tube 1, whose bore is of the order of 1 mm., having wider vertical extensions 2, 3. The tube 3 is connected by a siphon to the electrolyte reservoir 4 which is also connected by a siphon to an overflow 5 containing the anode 6. The solution to be treated is supplied to the reservoir 4 by a pipe 7 provided with a cock. The cathode 12 is mounted in one limb of a U-tube 11 having an overflow 14, the "leading solution" being supplied to the other limb by pipe 8 and passing to a tube 9, where it is heated by resistance 10 to remove dissolved gases, and thence to tube 2. The upper part of the tube 9 serves as a reflux condenser. A boundary between the two liquids forms at 15 and rises slightly on the passage of current. A small amount of acid may be supplied in the neighbourhood of the cathode by a pipe 13 having an adjustable cock. The faster ion or isotope accumulates in the neighbourhood of the boundary 15. In treating an aqueous solution of uranyl perchlorate, an increase of about 40 per cent in the concentration of U 234  corresponding to an increase of about 30 per cent in the concentration of U  235  was obtained. The base of the U-tube.1 may be of wider bore and packed with inert material such as fine glass powder. Fig. 2 shows an arrangement instead of the tube 2 in which the separation tube 1 expands to a somewhat wider portion 16 which in turn expands into a wider portion 17, a rod 18 being mounted so as to leave a narrow annular passage in the portion 16, thereby minimizing circulation due to thermal effects. In the arrangement shown in Fig. 3, the reservoir 19 to which the " leading solution " is supplied is connected to the cathode-containing reservoir 21 by an inverted U-tube 20 containing agar-agar or similar gelatinous colloid. The reservoirs 19, 21 are provided with overflows 14, 14a respectively for leading solution and acid. " Leading solution " passes from the reservoir 19 to the separation tube via a tube 9 as in Fig. 1.