Process for stripping uranium from an alkyl pyrophosphoric acid

Claim 2

A process for stripping uranium from a pregnant organic extractant comprising an extractant having a high affinity for tetravalent uranium dissolved in a substantially water-immiscible organic diluent, said organic extractant containing tetravalent uranium, comprising stripping said organic extractant with a stripping solution comprising an aqueous solution of an alkali metal or ammonium oxalate to strip tetravalent uranium from said organic extractant into said stripping solution, and separating said organic extractant from said stripping solution containing stripped tetravalent uranium.

Claim 3

The process of claim 1 in which said extractant is an alkyl pyrophosphoric acid which is a reaction product of phosphoric oxide and an alcohol containing 4 to 20 carbon atoms.

Claim 4

The process of claim 2 wherein said alcohol contains 6 to 12 carbon atoms.

Claim 5

The process of claim 2 in which said organic extractant contains about 10 to 100 g/l of said alkyl pyrophosphoric acid.

Claim 6

The process of claim 1 in which said stripping solution is an aqueous ammonium oxalate solution.

Claim 7

The process of claim 1 in which said stripping solution has a pH of above about 5.

Claim 8

The process of claim 6 in which said pH is about 5 to 5.5.

Claim 9

A process for stripping uranium from an organic extractant comprising an alkyl pyrophosphoric acid dissolved in an essentially water-immiscible organic diluent, said organic extractant containing tetravalent uranium and ferric iron, stripping said organic extractant with an oxalic acid stripping solution to strip ferric iron from said organic extractant into said oxalic acid stripping solution, and stripping said organic extractant with an alkali metal or ammonium oxalate stripping solution to strip tetravalent uranium from said organic extractant into said oxalate stripping solution.

Claim 10

A process for stripping uranium from an organic extractant comprising an alkyl pyrophosphoric acid dissolved in an essentially water-immiscible organic diluent, said organic extractant containing tetravalent uranium and ferric iron, stripping said organic extractant with an oxalic acid stripping solution to strip ferric iron from said organic extractant into said oxalic acid stripping solution, and stripping said organic extractant with an alkali metal or ammonium oxalate stripping solution to strip tetravalent uranium from said organic extractant into said oxalate stripping solution.

Claim 11

The process of claim 8 in which said alkyl pyrophosphoric acid is a reaction product of phosphoric oxide and an alcohol containing 4 to 20 carbon atoms.

Claim 12

The process of claim 9 in which said alcohol contains 6 to 12 carbon atoms.

Claim 13

The process of claim 8 in which said organic extractant contains about 10 to 100 g/l of said alkyl pyrophosphoric acid.

Claim 14

The process of claim 8 in which said oxalate stripping solution is an aqueous ammonium oxalate solution.

Claim 15

The process of claim 8 in which the pH of said oxalic acid stripping solution is about 1.5 to 2.

Claim 16

The process of claim 8 in which the pH of said oxalate stripping solution is about 5 to 5.5.

Claim 17

A process for recovering uranium from wet-process phosphoric acid comprising contacting wet-process phosphoric acid containing tetravalent uranium with an organic extractant to extract said tetravalent uranium from said wet-process phosphoric acid, said organic extractant comprising an alkyl pyrophosphoric acid dissolved in an essentially water-immiscible organic diluent, separating said organic extractant containing said tetravalent uranium from said wet-process phosphoric acid, contacting said pregnant organic extractant with a first stripping solution comprising an aqueous solution of oxalic acid to strip iron from said pregnant organic extractant into said first stripping solution, contacting said pregnant organic extractant with a second stripping solution comprising an aqueous solution of an alkali metal or ammonium oxalate to strip uranium from said pregnant organic extractant into said stripping solution, and recycling barren organic extractant for contacting with fresh wet-process phosphoric acid.

Claim 18

A process for recovering uranium from wet-process phosphoric acid comprising contacting wet-process phosphoric acid containing tetravalent uranium with an organic extractant to extract said tetravalent uranium from said wet-process phosphoric acid, said organic extractant comprising an alkyl pyrophosphoric acid dissolved in an essentially water-immiscible organic diluent, separating said organic extractant containing said tetravalent uranium from said wet-process phosphoric acid, contacting said pregnant organic extractant with a first stripping solution comprising an aqueous solution of oxalic acid to strip iron from said pregnant organic extractant into said first stripping solution, contacting said pregnant organic extractant with a second stripping solution comprising an aqueous solution of an alkali metal or ammonium oxalate to strip uranium from said pregnant organic extractant into said stripping solution, and recycling barren organic extractant for contacting with fresh wet-process phosphoric acid.

Claim 19

The process of claim 15 in which a portion of said recycled barren organic extractant is treated to separate diluent from the remainder of said organic extractant, fresh alkyl pyrophosphoric acid is added to said separated diluent to form fresh organic extractant, and said fresh organic extractant is added to said recycled barren organic extractant.

Claim 20

The process of claim 16 in which said diluent is separated by distillation.

Claim 21

The process of claim 15 in which said recycled barren organic extractant is reacidulated with a mineral acid.

Claim 22

The process of claim 15 in which said stripped uranium is precipitated in said oxalate stripping solution, said precipitate is separated from said stripping solution, and said stripping solution is recycled for contact with pregnant organic extractant.

Claim 23

The process of claim 19 in said said precipitated uranium is dried to form a final UO 3 product.

Claim 24

A process for recovering uranium from wet-process phosphoric acid comprising contacting wet-process phosphoric acid containing tetravalent uranium with an organic extractant to extract said tetravalent uranium from said wet-process phosphoric acid, said organic extractant comprising an alkyl pyrophosphoric acid dissolved in an essentially water-immiscible organic diluent, contacting said pregnant organic extractant with a stripping solution comprising an aqueous solution of an alkali metal or ammonium oxalate to strip uranium from said pregnant organic extractant into said stripping solution, separating said organic extractant containing said alkyl pyrophosphoric acid from said stripping solution containing said stripped uranium, recycling barren organic extractant for contacting with fresh wet-process phosphoric acid, treating a portion of said recycled barren organic extractant to separate diluent from the remainder of said organic extractant, adding fresh alkyl pyrophosphoric acid to said separated diluent to form fresh organic extractant, adding said fresh organic extractant to said recycled barren organic extractant, separating said uranium from said stripping solution by precipitation, and recycling said stripping solution for contacting with fresh organic extractant.

Claim 25

A process for recovering uranium from wet-process phosphoric acid comprising contacting wet-process phosphoric acid containing tetravalent uranium with an organic extractant to extract said tetravalent uranium from said wet-process phosphoric acid, said organic extractant comprising an alkyl pyrophosphoric acid dissolved in an essentially water-immiscible organic diluent, contacting said pregnant organic extractant with a stripping solution comprising an aqueous solution of an alkali metal or ammonium oxalate to strip uranium from said pregnant organic extractant into said stripping solution, separating said organic extractant containing said alkyl pyrophosphoric acid from said stripping solution containing said stripped uranium, recycling barren organic extractant for contacting with fresh wet-process phosphoric acid, treating a portion of said recycled barren organic extractant to separate diluent from the remainder of said organic extractant, adding fresh alkyl pyrophosphoric acid to said separated diluent to form fresh organic extractant, adding said fresh organic extractant to said recycled barren organic extractant, separating said uranium from said stripping solution by precipitation, and recycling said stripping solution for contacting with fresh organic extractant.

Claim 26

The process of claim 21 in which said pregnant organic extractant is stripped with an oxalic acid stripping solution to strip ferric iron from said organic extractant.

Claim 27

The process of claim 21 in which said precipitated uranium is dried to form a final UO 3 product.