Patent GB-783591-A (GB)
Title: Improvements relating to the recovery of uranium by ion-exchange
Inventor: ARDEN THOMAS VICTOR
IPC: B01J41/04
Filed: 1953-04-23
Abstract: <PICT:0783591/III/1> In the recovery of uranium by an anion-exchange resin in salt form from solutions containing both uranium and cobalti-cyanide, the resin employed is one which displays a substantially liner relation between the percentage of acid absorbed and the pH of a solution of hydrochloric acid when equilibrium has been attained. Such curves are shown in the drawing and whilst curves such as D, E and F are preferred, resins giving curves lying within the area bounded by the curves C and G are suitable.  The curves shown are obtained by bringing a given amount of the resin to be tested into contact with a series of solutions, each containing a different quantity of hydrochloric acid, and measuring the quantity of acid absorbed against the equilibrium pH.  The curves A to I, relate to resins containing, as groups attached to side chains, aniline, methylaniline ethanolamine, benzylamine, ethylamine, piperidine, diethylamine, dimethylamine and trimethylamine groups respectively.  The preferred resin, curve E, is a polystyrene bead resin containing ethylamine groups attached to side chains, prepared by treating chlormethylated cross-linked polystyrene beads with an excess of an aqueous solution of ethylamine and washing with acid to remove excess reagent or by removing the excess by distillation. Such resins, capable of absorbing and giving up cobalti-cyanide are preferably employed as in Specification 783,592 as a cobalti-cyanide trap through which the solutions to be treated are first passed before contact with another anionexchange resin mass, also in salt form, which absorbs the bulk of the uranium.  Such a cobalti-cyanide trap may be regenerated with caustic soda, sodium carbonate, ammonia or ammonium or potassium thiocyanate, preferably after the elution of any uranium in the trap by means of an acidified salt solution, for example an ammonium nitrate solution acidified with nitric acid. According to an example, a gold ore was treated with a cyanide solution as in conventional gold recovery and the gold containing solution was separated from the ore by filtration.  The residue was treated with sulphuric acid in the presence of pyrolusite to extract the uranium whereby after filtration a sulphuric acid solution containing uranium as uranyl sulphate, and cobalt as cobalti-cyanide, together with large amounts of other metallic sulphates was obtained. This solution was passed through an anion-exhange material in salt form to remove the uranium.  The resin used contained trimethylamine groups (curve I, and therefore outside the scope of the invention), and after absorption of uranium the resin was regenerated with acidified ammonium nitrate solution.  The quantity of uranium taken up decreased progressively with each cycle due to cobalti-cyanide take-up, which remained on the regenerated resin.  When the same initial solution was passed through a trap bed containing a resin having ethylamine groups before passage to the trimethylamine group-containing resin, the trap removed cobalti-cyanide and the reduction in efficiency of the trimethylamine containing resin ceased.  When cobalti-cyanide started to break through the trap bed, the trap resin was eluted to recover any uranium present and the cobalticyanide absorbed was thereafter removed with a 4 per cent caustic soda solution, after which the bed was treated with dilute sulphuric acid to return it to the salt form in which it was used. The treatment with sulphuric acid, although preferred, is not essential if the solution to be treated is acidic. Specification 626,882 also is referred to.