LU81850A1 - PROCESS FOR REDUCING RE-EXTRACTION OF THE URANIUM FROM AN ORGANIC EXTRACTANT - Google Patents

Description

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Patent application November 5, 1979 Designation of the Inventor 0 The undersigned Mon? Je U r. Charles München attorneys in br.e.vet.sa Luxem bourg ..................................... ................ Il.a..3 ...... baul.evard .... P.ri..n.ce .-. H..c .rj: i .............................................. .................................................. ..................

acting as depositor - agent of the depositor - 0 J a société ...... anonyme known as: ...... METAmJ_RGI_E HOPP.Ë.EN.:. 0VERPELT, 8, rue fionta.gne ... .du ..... Parc .., ..... BxuxeJJ.es .., ....... Be] .. gi, .gue .... and the limited company known as SOCIETE DE P. RAY.ONjlßjGr Lo.r.lJ.TIIog.z ..?. Belgi Jul_________; (J) of the invention concerning: "Reductive re-extraction process of uranium from an organic .. 6. ^. £ l.éX.t.é.nt1 ', designated as inventor (s): 1 ) First and last name My sie u rAchille DE S ÇHE P PE R? Berken] aan 8, _____

Address ................................... 21.5.1 ...... Li ... c ..b..ta.ax..t .., ...... ß..elgiq.ue ........................ .................................................. ..........................

2. Surname and first names ............................................. .................................................. .................................................. .................................................. ...................................

Address ................................................. .................................................. .................................................. .................................................. ...............................................

3. Surname and first names ............................................. .................................................. .................................................. .................................................. .................................

~ Address ................................................ .................................................. .................................................. .................................................. ...............................

He affirms the sincerity of the aforementioned indications and declares to assume full responsibility for them.

............. k u x em b o y r g / | e ...... 9 .... n g y e m b r e 19 79 {slgnaturel A 68026_ (') Name, first names, firm, address.

> 2 \ Μλμ λγλλ rt rrt r nnpnpca ait i dnnnpnnt i U *! j a.mss \ i \ \ î DESCRIPTIVE MEMORY filed in support of an INVENTION PATENT application b in the Grand Duchy of Luxembourg on behalf of the Société anonyme known as METALLURGIE HOBOKEN JDVERPELT and the Société anonyme known as

i; SOCIETY OF PRAYON

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Π "for:" Reductive re-extraction process of ;; 1Turanium from an organic extractant. "J

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The present invention relates to a process t for reductive re-extraction of uranium from an extractant comprising a dialkylphosphoric acid and a trialkylphosphine oxide dissolved in an organic solvent immiscible with water, using a solution aqueous phosphoric acid containing ferrous ions, comprising the following stages: j, (a) the organic extractant is brought into contact ♦ with the aqueous phosphoric acid solution, a fraction of this aqueous solution being already recycled solution charged with uranium, thereby producing an organic phase depleted in uranium and an aqueous phase | phosphoric acid enriched in uranium and ferric ions and depleted in ferrous ions, (b) the organic phase depleted in uranium is separated from the uranium aqueous phase, (c) a fraction of the uranium aqueous phase resulting from step (b) towards; „- step (a), and (d) the content of ferrous ions in the fraction which is recycled is adjusted.

Such a process is described in American patent t 3-737-513. In this known process, the content of ferrous ions in the fraction which is recycled is adjusted, by subjecting this fraction to an electrolytic reduction so as to transform the ferric ions contained therein into ferrous ions.

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However, the incorporation of an electrolytic operation in a liquid-liquid extraction process using volatile and flammable organic liquids, poses very serious safety problems, the slightest spark coming into contact with organic vapor can cause a disaster. .

the object of the present invention is to provide a method as defined above, which avoids these security problems.

To this end, according to the invention, the content of ferrous ions in the fraction that is recycled is adjusted, by treating the aqueous phase resulting from step (b) with metallic iron.

It should be noted that it is already known from American patent 3,711,591 to adjust the ferrous ion content of a phosphoric acid solution containing ferric ions either by subjecting this solution to an electrolytic reduction, or by treating this solution with metallic iron, and subsequently use the solution thus obtained for the reductive re-extraction of uranium from an extractant comprising a dialkylphosphoric acid and a trialkylphosphine oxide dissolved in an organic solvent immiscible with water . However, in this known process it is simply a question of preparing a starting solution, this process not providing, unlike the processes of the present invention and of American patent 17 ° 3-737.51 ^ / _ 5 - above , no regeneration of ferrous ions during the re-extraction process and therefore having the serious drawback of requiring the re-extraction to be carried out under an inert atmosphere (see "Recovery of uranium; from væt -process phosphoric acid by solvent extraction "i by FJ Hurst, paper to be presented at the AIME Annus1

Meeting, Las Vegas, Nevada, Rebruary 22-26, 1976, pre-print number 76-B-66, page 8, item 6).

i · i; In the process of the invention, it is particularly advantageous to use the solution, the content of; ferrous ions must be adjusted, intermittently in i - ’contact with a mass of iron having a large specific surface, such as iron in the form of pellets or! granules, to continuously measure the electro-chemical potential of the solution and to act the measured potential on the duration of contact between the mass of iron and the solution.

Other details and particularities of the invention will emerge from the description of an embodiment of the: method of the invention, given below by way of example / non-limiting and with reference to the attached drawings / / · / // - 4 -

In these drawings: FIG. 1 represents the diagram of an installation for carrying out the method of the present invention, this installation essentially comprising a battery of three mixer-settlers identical as s; - Figure 2 shows a plan view of one of these mixer-settlers; - And Figure 3 shows a perspective view of the outlet of one of these mixer-settlers, the outer walls of the device having been partially omitted for the sake of clarity.

In the various figures, the same elements are designated by the same reference numbers.

Uranium must be re-extracted from an organic extractant consisting of a solution of 0.5 M di- (2-ethylhexyl) phosphoric acid (D2EHPA) and 0.075 M trioctylphosphine oxide (TOPO) in an inert aliphatic diluent ("ESCAID-1'10" from the company Esso Chemical Cy).

This extractant, which contains 235 mg / l of i +, has been used to extract uranium phosphoric acid produced by sulfuric acid leaching from uranium phosphate rock.

The re-extraction is carried out with an aqueous solution of phosphoric acid at 30 ° C. of P2O3 containing 12 g / l ^ /: - 5 - • i ji of Fe2 +. This solution is prepared by passing phosphoric acid, produced by sulfuric acid leaching from uranium phosphate rocks and from which uranium t has not been extracted, at 50 ° C. through a bed of pellets of iron.

The? E2 + content of the solution having passed this bed is checked by potentiometric control, and this solution is passed through the bed again when its Fe Fe + content is less than 12 g / l.

i; The re-extraction is carried out in three stages using for this purpose three identical mixer-settlers 1, 2 and 5. Each mixer-settler comprises in a way j:; known per se, a mixing compartment 4 provided with a stirrer 3 with a pumping effect, a settling compartment 6. μ [> and an outlet compartment 7 for phase evacuation

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|| separated. It can be seen in FIG. 1 that the extractant from the desuran tree 8, the flow of which is represented by a continuous line I, enters the installation through the compartment. £.

mixture 4 of the mixer-settler 1 and leaves the installation r through the outlet compartment 7 of the mixer-settler 3, while the re-extraction solution 9, the flow of which is represented by a broken line, enters; | the installation through the mixing compartment 4 of the mixer-decanter 3 and leaves the installation through the compartment of! outlet 7 of the mixer-settler 1. The deuranite extractant 8. is introduced into the installation at a dehit of 200 l / hour I and at a temperature of 35 ° C, and the re-extraction solution! /

I tion 9, at a flow rate of 4.8 l / hour and at a temperature of 50 ° C

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Each outlet compartment 7 comprises in a manner known per se a gutter 10 for the evacuation of the organic phase 8 (see arrows 0) and a siphoning chamber 11, provided with a siphon 12, for the evacuation of the aqueous phase 9 (see arrows A).

Since the organic phase: aqueous phase ratio is 200: 4.8 and the aqueous phase must be maintained as a continuous phase during the re-extraction, only a minor part of the arriving aqueous phase 9 is removed, - below the gutter 10, in the siphoning chamber 11, by the siphon 12 and the rest is recycled to the mixing compartment 4 of the same mixer-settler (see arrow AR), as was already done in the processes of prior art mentioned above. In the case of the present invention, this recycling takes place via a pipe 13 connecting the siphoning chamber 11 with the mixing compartment 4, and by the pumping effect exerted by the agitator 5. The pipe 13 is provided with a valve 14 for adjusting the flow rate of the recycled current. This flow rate is adjusted so as to obtain an organic phase: aqueous phase ratio of 1: 2 in the mixing compartment 4, which means that the flow rate through line 13 is about 30 times higher than the flow rate at through the siphon 12.

In the recycling line 13 there is a cell 15 for continuously measuring the potential of the recycled aqueous phase 9. As soon as this cell 15 measures one. / ß - 7 - j potential too high, eg 450 mY, indicating a content! i too low in Pe2 + from the recycled phase, the cell commands! a device known in itself and not shown which makes diving! a basket 16, filled with iron pellets 17, in the siphoning chamber 11. The Pe2 + content of the recycled phase will now increase until cell 15 will measure 'i a too low potential, eg 250 mY, indicating a content .i] too high in]? E2 +, and will release by means of the device J. above-mentioned basket 16 of the siphoning chamber 11. One h / thus obtains, by particularly simple and economical means, at all times and in each compartment i. of mixture 4 an appropriate content of Pe2 +, the potential of the U6 + / U4 + couple being 400 mV.

It should be noted that the reaction between the iron pellets 17 and the aqueous phase 9 in the siphoning chamber 11 produces, not only Pe ^ + ions, but also j (also hydrogen. One might have expected that this hydrogen liberates in mass from the aqueous phase in the siphoning chamber 11 and is thus lost. However, we note ". that almost all of this hydrogen is entrained in the form of very fine bubbles by the current of recycling to the mixing compartment 4, where it is used in part to reduce U ° + and ie3 + ions and in part to constitute a

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protective atmosphere covering delaying the aspiration of oxygen from the air by agitated liquids. This constitutes an additional and unexpected advantage of the process of in //

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A temperature ranging from 45 to 55 ° C is maintained in the three mixer-settlers. For this purpose, each of the recycling pipes 13 is surrounded by a heating element 18, for example with steam. This temperature of around 50 ° C is ideal, because the distribution coefficient of 44 + between the aqueous phase and the organic phase is then high and the reaction between the aqueous phase and the metallic iron is rapid.

. The pellets 17 are punching waste carbon steel. They have an average diameter of around 5 mm and an average thickness of around 2 mm.

The deuranized extractant leaving the installation at a flow rate of 200 l / h via the outlet compartment 7 of the mixer-settler 3 has a U content of 0.01 g / l. This extractant can be re-used to extract uranium from phosphoric acid produced by leaching with sulfuric acid from uranium phosphate rocks.

The uranium-containing aqueous phase leaving the installation at a flow rate of 4.8 l / h via the outlet compartment 7 of the mixer-settler 1 has a U content (ü4 +) of 9.37 g / l and an iron content ( Pe2 + + Pe3 +) of 22.5 g / 1. Uranium can be recovered from this aqueous phase by a well-known process, which consists in oxidizing the u4 + to Tj5 +, in extracting the U ^ + with an extractant consisting of a solution of D2EHPA and TOPO in an aliphatic diluent inert and to re-extract the U ^ + with an aqueous solution of (1 * 24) 2 CO * r /

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Claims (3)

1. A process for the reductive extraction of uranium i I from an extractant comprising a dialkylph.osphoriq.ue acid and a trialkylphosphine oxide dissolved in an organic solvent immiscible with water, using a solution A aqueous phosphoric acid containing ferrous ions,:! t comprising the following stages: i; (a) the organic extractant is brought into contact i with the aqueous phosphoric acid solution; a fraction of this aqueous solution being i of the recycled solution already loaded with uranium, thereby producing an organic phase depleted in uranium and an aqueous phase of phosphoric acid enriched in uranium and I in ferric ions and depleted in ferrous ions, I (b) the organic phase depleted in uranium is separated from the uranium-bearing aqueous phase, (c) a fraction of the uranium-bearing aqueous phase resulting from stage (b) is recycled to: * stage (a), and i (d) adjusting the content of ferrous ions in the fraction i which is recycled, i | characterized in that the content of ferrous ions of the fraction which is recycled is adjusted, by treating the aqueous phase j, resulting from step (b) with metallic iron., / / U P f 1 REVERDI CAHOES ' 2. Method according to claim 1, characterized in that the content of ferrous ions in the fraction which is recycled is adjusted by bringing the aqueous phase resulting from step (b) intermittently into contact with a mass of iron having a large specific surface, by continuously measuring the electrochemical potential of the fraction recycled in (c) and by making the measured potential act on the contact time between the mass of iron and the aqueous phase * resulting from step (b) . 3. Method according to claim 1 or 2, characterized in that one operates at a temperature ranging from 45 to 55 ° C. Drawings: -J -......., ..... -M ... .... Γ-Τίν - :: -: 1 ....... j ........ r SL ------:. / ........ I-. 5 tryr> MrrrJ * l ♦