Reductive stripping process for the recovery of uranium from wet-process phosphoric acid

Abstract

A reductive stripping flow sheet for recovery of uranium from wet-process phosphoric acid is described. Uranium is stripped from a uranium-loaded organic phase by a redox reaction converting the uranyl to uranous ion. The uranous ion is reoxidized to the uranyl oxidation state to form an aqueous feed solution highly concentrated in uranium. Processing of this feed through a second solvent extraction cycle requires far less stripping reagent as compared to a flow sheet which does not include the reductive stripping reaction.

What is claimed is: 
     
       1. A process for the recovery of uranium from a wet-process phosphoric acid solution derived from the acidulation of uraniferous phosphate ores which comprises contacting said solution with an organic extractant consisting essentially of di(2-ethylhexyl)phosphoric acid and trioctylphosphine oxide dissolved in an organic diluent, reductively stripping the extractant of uranium with a strip solution in which ferrous ion is used to reduce uranyl ions in the extractant to uranous ions in the strip solution, disengaging the strip solution from the organic phase, contacting said strip solution with an oxidizing reagent which converts quadrivalent uranium to hexavalent form, and then passing the resultant solution through a second liquid-liquid solvent extraction cycle where the uranium is stripped from the organic phase with an aqueous solution of ammonium carbonate to produce a product consisting essentially of ammonium uranyl carbonate. 
     
     
       2. The process according to claim 1 in which the reductive strip solution contains from 5 to 20 grams per liter of ferrous ion dissolved in a 5 to 7-molar solution of phosphoric acid. 
     
     
       3. The process according to claim 1 in which the ammonium uranyl tricarbonate product is converted to an oxide of uranium. .Iadd. 4. Process for obtaining uranium values from a synergistic extractant comprising a dialkylphosphoric acid and a trialkylphosphine oxide dissolved in a water-immiscible organic solvent which comprises stripping the extractant with a 5- to 7-molar aqueous phosphoric acid solution having dissolved therein a divalent iron salt. .Iaddend..Iadd. 5. The process according to claim 4 wherein the aqueous phase is oxidized after uranium stripping. .Iaddend. .Iadd. 6. Process according to claim 4 wherein said phosphoric acid solution contains dissolved therein from 5 to 20 grams of divalent iron per liter of solution. .Iaddend. .Iadd. 7. A process for the recovery of uranium from a wet-process phosphoric acid solution derived from the acidulation of uraniferous phosphate ores which comprises contacting said solution with an organic extractant consisting essentially of di(2-ethylhexyl)phosphoric acid and trioctylphosphine oxide dissolved in an organic diluent, reductively stripping the extractant of uranium with a strip solution in which ferrous ion is used to reduce uranyl ions in the extractant to uranous ions in the strip solution, and disengaging the strip solution from the organic phase. .Iaddend..Iadd. 8. Process for obtaining uranium values from an extractant comprising di-(2-ethylhexyl)phosphoric acid and a trioctylphosphine oxide dissolved in a water-immiscible organic solvent which comprises stripping the extractant with an aqueous phosphoric acid solution containing from about 40 to 85 percent by weight H 3  PO 4  having dissolved therein a divalent iron salt. .Iaddend.