Patent GB-736276-A (GB)
Title: Continuous method for concentrating ions in solutions
Inventor: MCILHENNY WILLIAM FRANKLIN
IPC: B01J47/10
Filed: 1953-11-25
Abstract: <PICT:0736276/III/1> Ions are concentrated by feeding (at 21) a dilute aqueous solution containing the ions to be concentrated into a column (1) into which a granular ion exchange material is fed so that said material descends the column counter to an up-flow of the liquid, withdrawing said material from the solution (e.g. through a star-valve 5) and passing it by means of a stream of carrier introduced at jet 6 into an upper section of a second column 2 which is partially filled with an up-flowing stream of an aqueous regenerating solution (entering at 11) comprising an ionizable solute which reacts with the ion exchanger to replace the ions to be concentrated, in sufficient concentration to form a solution containing the replaced ions in greater concentration than the starting solution, said regenerating solution being more dense than the carrier liquid and less dense than the ion exchanger, so that the two liquid streams meet at an interfacial zone between outlets 12 and 13 for said streams, and the ion exchanger descends through the liquid layers into the regeneration zone, from which it is returned (via star-valve 8) to column 1 by means of a carrier liquid (introduced at jet 9), the upper surface of the ion exchanger being maintained at least as high as said interface, by controlling the rates of feed and withdrawal of material to the column.  The numerals in brackets relate to the illustrated embodiment which is described with particular reference to the concentration of magnesium ions found in seawater, e.g. as chloride, nitrate or sulphate which may be concentrated and crystallized.  It is preferred in this case to use a resin sulphonate as cation exchanger and a regenerating solution of 10 per cent aqueous sodium chloride: higher concentrations, up to the use of a saturated solution, are advantageous.  Anion exchangers may alternatively be used to concentrate an anion, and exchangers having preferential absorption for a specific ion may be used to concentrate said ion.  Sodium, potassium, lithium, calcium and strontium are mentioned.  Two pairs of columns may be used to concentrate an anion and cation in the same solution.  In this case the outlet 22 of the first column of one pair is connected to the inlet (as 21) of the first column of the second pair, one pair of columns is used to concentrate each type of ion, and concentrated cation and anion-containing solutions respectively emerge from the outlets 12. By this means demineralized water is obtained, inter alia, from the outlet of the first column of the second pair.  This is described in detail with respect to a solution of sodium chloride.  The process may be performed at any temperature between the boiling point and freezing point of the solutions treated: in an example 60 DEG  to 80 DEG  C. was used. Constructional and other details may include the use of perforated headers connected to 21 and 22 in column 1 to feed and collect the liquid at a number of points throughout the cross-sectional area of the column; the use of a beam of light from lamp 14 to activator cell 15 whereby the rate of flow of one or more materials through column 2 may be controlled, the beam being subject to interruption by the loose mass of exchanger in the upper part of the column; several pairs of electrodes 16 and 17 whereby the level of the interface may be determined by conductivity and corresponding adjustments made (automatically if desired); alternatively, a solid float or a series of refractometers may be used; the use of perforated plates 19 having one or more downcomers 20 to retard the rate of descent of the exchanger; feeding a second stream of water into a star-valve or similar device parallel to the rotor shaft to prevent binding or locking; the use of a vacuum in a space above the liquids in column 2 to remove air particles which may be on the ion exchanger.  The height of column 1 should be such that half or more of the magnesium ions are absorbed during passage therethrough, and column 2 should be of such height (e.g. 12 feet in the case of seawater) as to allow replacement of nearly all the magnesium ions. Examples are given of suitable ion exchange materials for the various specific applications.