Patent GB-831206-A (GB)
Title: Improvements relating to ion-exchange processes and apparatus
Inventor: ARDEN THOMAS VICTOR
IPC: C22B60/02
Filed: 1956-12-04
Abstract: <PICT:0831206/III/1> <PICT:0831206/III/2> <PICT:0831206/III/3> The absorption of an ion, such as a complex uranium anion, from solution on ion exchange material and subsequent elution therefrom is conducted by passing the solution in series through a number of absorption vessels in each of which in turn eluted exchanger is formed into a bed and transferring each of these beds in turn via a washing-tank to one of a number of elution vessels to form a bed through which the eluant passes in series, the passage of solution and eluant through successive absorption and elution vessels being such that each successive bed through which the liquid flows has greater available exchange capacity than the preceding bed. By operating in this way, the eluate containing the desired ion is more concentrated than that obtained by the standard use of three vessels in each of which both absorption and elution take place, and since backwashing may be avoided, the beds may be deeper.  As illustrated in Fig. 4, two sets of absorption vessels 1, 2, 3 and 11, 22, 31 are employed in conjunction with a washing vessel 7 and eluting vessels 4, 5, 6.  When bed A in vessel 1 becomes fully loaded, the bed is removed as a slurry to the washing vessel 7, freshly eluted material G, from vessel 4 is transferred to vessel 1 and the washed material is transferred to vessel 4.  During the time that vessel 1 is empty, the pregnant liquor passes successively through beds B and C, and when the bed G is transferred to vessel 1, the latter is added at the end of the series; similarly the eluant flows successively through beds H, I and A in vessels 5, 6 and 4 when the latter vessel is refilled.  This phase of operation is shown in Fig. 5.  The absorption in vessels 11, 21 and 31 is staggered in relation to that in vessels 1, 2 and 3 so that by the time bed A is fully loaded and B is half loaded, bed D is three quarters loaded.  The next stage of operation involves transferring bed D to washing vessel 7, bed H to absorption vessel 11 and bed D from washing vessel 7 to elution vessel 5, the flow of liquids through the vessels being changed in accordance with the invention to that shown in Fig. 6.  The next bed to be eluted is B, which after washing takes the place of bed I.  The cycle is completed when each bed has been loaded and eluted once.  If desired, washing vessel 7 may be used as a stock tank for fully loaded material and a vessel provided as a stock tank for eluted material; the elution cycle can thus be made independent of the absorption cycle.  If desired a chemical cleaning process can be inserted into each cycle of operations or at regular intervals. The process may be applied to the treatment of uranium solutions obtained by extracting low grade ores with acid in the presence of oxidizing agents and clarifying the slurry by settling and decantation and/or filtering; anion exchange material is then used and the eluant solution may be aqueous ammonium nitrate; the uranium may be precipitated from the eluate as oxide.