Process for the recovery of uranium contained in an impure phosphoric acid

Claim 1

In a continuous process for the recovery of uranium (VI) contained in an impure phosphoric acid comprising: (a) a first cycle comprising (i) extracting an impure phosphoric acid with an organic phase which extracts uranium (VI) without extracting substantial amounts of uranium (IV), followed by separating the phases; (ii) extracting the resultant organic phase charged with uranium (VI) with an aqueous solution containing an oxidizing-reducing agent in the reduced state, said oxidizing-reducing agent being a reducing agent for uranium (VI) to uranium (IV) in said aqueous solution and comprising iron (II) ions, said aqueous solution being a solution of phosphoric acid and the phosphoric acid concentration of said aqueous solution being between about 18% and about 70% by weight of P 2 O 5 , followed by separating the phases; (iii) recycling the resultant organic phase depleted of uranium to the extracting of the impure phosphoric acid; and (iv) treating the resultant aqueous solution charged with uranium (IV), to oxidize the uranium (IV) to uranium (VI) and to convert the oxidizing-reducing agent to its oxidized state; and (b) a second cycle comprising (i) extracting the oxidized aqueous solution resulting from the first cycle with an organic phase which extracts uranium (VI), followed by separating the phases; (ii) washing the resultant organic phase charged with uranium (VI) with a phosphoric acid solution free of iron, the concentration of the phosphoric acid in the washing solution being close to that of the aqueous extracting solution employed in step (ii) of the first cycle, followed by separating the resultant purified organic phase, treating said purified organic phase with an aqueous solution containing carbonate and ammonium ions to precipitate the uranium in said solution in the form of ammonium uranyl tricarbonate, separating the depleted organic phase from the aqueous suspension and recovering the uranium from said aqueous suspension in the form of ammonium uranyl tricarbonate; and (iii) regenerating and then recycling the resultant organic phase depleted of uranium to the second cycle extracting step; the improvement comprising: (i) carrying out step (iv) of the first cycle by treating the aqueous solution charged with uranium (IV) resulting from the extracting step (ii) of the first cycle in its entirety in the anodic compartment of an electrolytic cell under direct current voltage; (ii) carrying out step (i) of the second cycle by treating the oxidized aqueous phase issuing from and anodic compartment with the organic extracting phase of the second cycle; (iii) treating the resultant aqueous phase depleted of uranium in its entirety in the cathodic compartment of said electrolytic separation cell under direct current voltage, to afford an aqueous phase containing the oxidizing-reducing agent in the reduced state; and (iv) recycling the resultant aqueous phase to the back extracting step of the first cycle; whereby the aqueous solution is circulated in a closed loop between the first and second cycles, in the form of a third cycle.