FR3038326A1 - METHOD OF SEPARATING IRON FROM AN URANIUM-CONTAINING ORGANIC PHASE AND METHOD OF EXTRACTING URANIUM FROM AN AQUEOUS SOLUTION OF MINERAL ACID CONTAINING URANIUM AND IRON - Google Patents

Abstract

The invention relates to a process for separating iron from an initial liquid organic phase containing uranium, and iron, in which the initial liquid organic phase is brought into contact with an aqueous solution called an aqueous de-ironing solution. whereby the iron passes into the aqueous solution to form a final aqueous liquid phase, and the uranium remains in the initial liquid organic phase to form a final liquid organic phase called de-ironed organic phase; said method being characterized in that the aqueous deferrisation solution contains an inorganic acid and uranium. The invention further relates to a process for extracting uranium from an aqueous solution of an inorganic acid containing uranium and iron.

Description

METHOD OF SEPARATING IRON FROM AN URANIUM-CONTAINING ORGANIC PHASE AND METHOD OF EXTRACTING URANIUM FROM AQUEOUS SOLUTION OF MINERAL ACID CONTAINING URANIUM AND IRON

DESCRIPTION

TECHNICAL FIELD The invention relates to a process for separating iron from a liquid organic phase containing uranium and iron.

More specifically, the invention relates to a method for separating iron from a liquid organic phase containing uranium and iron. The invention applies to the separation of iron from a liquid organic uranium phase, containing an organic extraction system comprising an organic extractant diluted in an organic diluent.

This organic phase can be in particular an organic phase resulting from the extraction of uranium by a solvent from an aqueous inorganic uranium uraniferous acid solution, such as phosphoric acid, nitric acid or sulfuric acid. The invention therefore also relates to a process for extracting uranium from an aqueous solution of mineral acid, containing uranium and iron.

This aqueous solution of mineral acid may be either an aqueous uraniferous solution of phosphoric acid, such as industrial phosphoric acid, resulting from the leaching, etching, of a natural phosphate ore, generally based on apatite with sulfuric acid, an aqueous uraniferous acid solution of sulfuric acid or nitric acid resulting from the leaching, attacking a non-phosphate, for example non-apatitic uranium ore, with sulfuric acid or nitric acid. The invention therefore finds its application in the treatment of natural phosphates to enhance the uranium contained in these phosphates, but also in the treatment of uranium ores subjected to attack, leaching, by sulfuric acid or nitric acid in order to to valorize the uranium present in these ores.

STATE OF THE PRIOR ART

If we focus first of all on the valorization of uranium contained in phosphates, we must first of all recall that to meet the growing demand for uranium, particularly for nuclear reactors, it has become today interesting to value the uranium contained in so-called "unconventional" sources such as phosphates. Uranium is present at very low levels, usually 50 to 200 ppm in phosphates. Some phosphate deposits may contain significant amounts of uranium and thus become potentially exploitable uranium deposits.

The valorization of uranium from phosphates primarily concerns the valorization of the uranium contained in industrial phosphoric acid, called "wet" phosphoric acid, which constitutes, with phosphate fertilizers, the main production from phosphates. This "wet" phosphoric acid is the acid obtained by etching natural phosphated ores with concentrated sulfuric acid, followed by a solid-liquid separation treatment to separate the phosphoric acid from the gypsum precipitated during the attack.

More precisely, after the attack with sulfuric acid, a solution of phosphoric acid is obtained, which title for example between 26% and 32% by weight in P2O5 in the case of a process known as the "Dihydrate" process. which is the process generally implemented in current production facilities.

This solution of phosphoric acid contains in addition to uranium, already mentioned, notable impurities in the forefront of which iron, but also silica, vanadium, molybdenum, and zirconium.

In order to recover the uranium from these aqueous solutions of phosphoric acid, extraction of the uranium is carried out by an organic solvent comprising an organic extractant in an organic diluent and thus a uranium-containing organic phase is obtained.

However, this uraniferous organic phase also contains the impurities listed above, and mainly iron which is extremely troublesome and does not make it possible to obtain, during the next de-extraction step, uranium having the required purity in order to of its subsequent use.

Indeed, significant amounts of iron are extracted despite a separation factor between uranium and high iron (ie: FSu / Fe close to 200), which can lead to the formation of precipitates during the removal of uranium. in carbonate medium. By way of example, the iron precipitates in the form of ferric hydroxide during the uranium stripping step, which requires additional filtration operations and poses problems as to the conduct of the process.

Co-extraction of impurities such as iron and phosphates is penalizing because it makes it difficult to meet the ASTM specifications for uranium concentrates.

The valorization of the uranium contained in phosphates, and more particularly in the aqueous solutions of phosphoric acid resulting from the attack by sulfuric acid of phosphate ores, has been the subject of numerous studies.

Document FR-A-2,596,383 [1] and EP-A1-0 239 501 [2] generally describe a process for extracting uranium present in phosphoric acid solutions, especially in phosphoric acid solutions obtained from iron-containing phosphate ores.

The process of these documents uses new extracting molecules or more exactly a new synergistic mixture, implemented in a single uranium extraction-extraction cycle, which increases the uranium partition coefficient, and comprises a step selective deferrisation of the solvent by an acid upstream of the uranium removal step.

This acid may be chosen from oxalic acid, a mixture of phosphoric and sulfuric acid, and de-ironized phosphoric acid.

This acid prevents the phenomena of precipitation of ferric hydroxides during the extraction of uranium.

Thus, more particularly, the documents FR-A-2,596,383 [1] and EP-A1-0 239 501 [2] describe a process for separating iron from a uranium-containing organic solution in which an iron system is used. extractants consisting of a neutral phosphine oxide and an acidic organophosphorus compound.

The new extracting molecules used in the processes of documents FR-A-2,596,383 [1] and EP-A1-0 239 501 [2] are in particular those described in documents FR-A-2442 796, FR-A-2. 459,205, FR-A-2,494,258, and EP-A1-0 053 054.

Although promising, this process has some major disadvantages: the new extractant synergistic mixture used increases the partition coefficients of uranium and iron compared to conventional solvents, but the selectivity uranium / iron is less good; operating expenses are higher, irrespective of the acid selected for the selective de-ironing of the solvent, in particular because of losses in industrial phosphoric acid, of the impact on recycling, if any, at the ore leaching stage , and losses of reagent.

More precisely, if de-ironed industrial phosphoric acid is used, then it is necessary to add mixer-settler stages to de-iron the acid; if a mixture of phosphoric acid and sulfuric acid is used, this has an impact on the leaching stage of the ore, and contamination of the industrial phosphoric acid occurs; and if oxalic acid is used, the cost of this reagent is important, and the efficiency of the regeneration of the reagent is insufficient.

One way of improving the extraction of uranium from an aqueous solution of phosphoric acid is to replace the synergistic mixture D12EHPA / TOPO by combining the two functions "cationic exchanger" and "solvating extractant" within a alone and even composed.

A bifunctional extractant has the advantage of having to manage only one compound instead of two.

The document FR-A1-2,604,919 [3] relates to a bifunctional compound comprising a phosphine oxide function and a phosphoric or thiophosphoric function, these two functions being connected to each other by a suitable spacer group, such as a ether group, thioether, polyether or polythioether.

This type of compound has two disadvantages. Indeed, the tests that were carried out with one of these compounds showed that, if this compound is solubilized in n-dodecane, a third phase is formed during the extraction of uranium, while it is solubilized in chloroform, it also forms a third phase but during the removal of uranium. However, the appearance of a third phase is totally unacceptable for a process intended to be implemented on an industrial scale. Moreover, the presence within the spacer group of a P-O or P-S bond, which is readily hydrolyzable, renders these compounds extremely sensitive to hydrolysis.

It can be considered that, in this document, the organic phase produced at the end of the extraction contains iron, and no deferrisation process of this phase is proposed.

The document WO-A1-2013 / 167516 [4] relates to bifunctional compounds which are free from the various disadvantages presented by the bifunctional compounds proposed in documents [2] to [3] mentioned above and, in particular, from the need to to reduce uranium (VI) to uranium (IV) beforehand, the formation of a third phase and the risk of hydrolysis.

The bifunctional compounds of this document correspond to the general formula (I) below: in which:

m represents an integer equal to 0.1 or 2; R1 and R2, which may be identical or different, represent a hydrocarbon group, saturated or unsaturated, linear or branched, comprising from 6 to 12 carbon atoms; R3 represents: - a hydrogen atom; a hydrocarbon group, saturated or unsaturated, linear or branched, comprising from 1 to 12 carbon atoms and optionally one or more heteroatoms; a hydrocarbon group, saturated or unsaturated, monocyclic, comprising from 3 to 8 carbon atoms and optionally one or more heteroatoms; or - a monocyclic aryl or heteroaryl group; or R2 and R3 together form a group - (Chhjn-) wherein n is an integer from 1 to 4; R4 represents a hydrogen atom, a hydrocarbon group, saturated or unsaturated, linear or branched, comprising from 2 to 8 carbon atoms, or a monocyclic aromatic group, while R5 represents a hydrogen atom or a linear or branched, saturated or unsaturated hydrocarbon group comprising from 1 to 12 carbon atoms.

It can be considered that, in this document, the organic phase produced at the end of the extraction contains iron, and no deferrisation process of this phase is proposed.

Although these new extracting molecules make it possible to dispense with a synergistic mixture of extractants and that they are more efficient in terms of uranium extraction, they are not sufficiently selective to allow the elimination of the de-ironing step of the solvent in a process for upgrading the uranium contained in phosphate-bearing uranium ores.

If one is interested now in the valorization of the uranium contained in the uranium nonphosphated ores, one begins by carrying out an attack, lixiviation, with sulfuric acid or nitric acid of these ores by means of which one obtains a uraniferous aqueous solution of sulfuric acid or nitric acid.

This uraniferous aqueous solution of sulfuric acid or nitric acid contains, in addition to uranium, significant impurities which were present in the ore, chiefly iron, but also silica, vanadium, molybdenum, and zirconium. .

In order to recover the uranium from these aqueous solutions of sulfuric acid or nitric acid, the uranium is extracted with an organic solvent comprising an organic extractant in an organic diluent and an organic phase is thus obtained. uranium.

However, this uraniferous organic phase, just like the organic phase resulting from an aqueous uraniferous solution of phosphoric acid, also contains the impurities listed above, and mainly iron which is extremely troublesome and does not make it possible to obtain, when the next step of desetching uranium with the required purity for later use.

Many processes were developed in the 1950s-1960s to recover quantitatively and selectively uranium from sulfuric liquors.

The so-called DAPEX process, which is based on the mixture of D12EHPA / TBP extractants, can thus be cited. The main constraint of this process is its sensitivity to Fe (III) ions.

This has led to the replacement of this process in industrial plants by the so-called AMEX process described in Merritt, RC: "The Extractive Metallurgy of Uranium", Colorado School of Mining Research Institute (1971) [5], which is based on a mixture of a tertiary amine, for example a tri-octyl / dodecyl amine insoluble in water, and tridecanol acting as a phase modifier This mixture is very selective towards iron.

It can be considered that, in this document, the organic phase produced at the end of the extraction contains iron, and no deferrisation process of this phase is proposed.

There is therefore, in the light of the foregoing, a need for an iron separation process (i.e., a de-ironing process) from a liquid organic phase containing uranium and iron ( for example a liquid organic phase comprising an organic extractant and an organic diluent) which does not have the disadvantages and disadvantages of the prior art de-ironing process mentioned above, in particular in documents [1] and [2] and which solves the problems of this process.

In particular, there is a need for such a process, which ensures a selective separation of the iron, while avoiding the loss of uranium or the phenomena of impurity precipitation impediments for the conduct of the process observed during the implementation of the processes. of the prior art.

There is also a need for a process for extracting uranium from an aqueous solution of an inorganic acid containing uranium and iron, comprising a step of de-ironing an organic phase resulting from the treatment of said aqueous solution, which does not have the drawbacks of the uranium extraction processes of the prior art, and which provides a solution to the problems posed by the uranium extraction processes of the prior art.

There is still a need for such a process which is simple and which therefore has a limited number of unit operations, which is reliable, robust, and economical, which uses reagents easily and widely available in particular, and which makes it possible to reduce costs. .

STATEMENT OF THE INVENTION

This and other objects are achieved, in accordance with the invention, by a process for separating iron from an initial liquid organic phase containing uranium and iron, in which the initial liquid organic phase with an aqueous solution called aqueous deferrisation solution, whereby the iron passes into the aqueous solution to form a final liquid aqueous phase, and the uranium remains in the initial liquid organic phase to form a so-called final liquid organic phase de-ironed organic phase; said method being characterized in that the aqueous deferrisation solution contains an inorganic acid and uranium.

The method of separating iron according to the invention, also called de-ironing process, is fundamentally different from the iron separation processes of the prior art and in particular from the process described in documents FR-A-2 596 383 [1], and EP-A-239 501 [2], in that it uses a specific aqueous deferrisation solution which contains an inorganic acid and uranium and not only an inorganic acid.

This specific aqueous ironing solution makes it possible, surprisingly, to selectively remove iron from the organic phase loaded with uranium and iron.

Indeed, it occurs during the contacting of the organic phase with the aqueous iron removal solution according to the invention a chemical shift of iron by the uranium to the aqueous phase, which thus ensures a selective deferrisation of the phase organic loaded with uranium and iron.

In documents FR-A-2 596 383 [1] and EP-A-239 501 [2], an acid selected from oxalic acid, a mixture of phosphoric and sulfuric acid, is used during the de-ironing step. or sulfuric acid déferrisé, without any addition of uranium, thus in addition to the disadvantages mentioned above related to the use of these acids, a selective removal of iron due to the chemical shift of iron by uranium can practically not be obtained.

It has been shown (see examples), surprisingly, that the de-ironing efficiency of an organic phase obtained with an aqueous solution of inorganic acid according to the invention loaded with uranium, was much higher respectively than the de-ironing efficiency. obtained with an aqueous solution of inorganic acid containing no uranium.

The concept according to the invention of purification, deferrization by chemical shift applies to all kinds of organic phases, for example to all organic phases containing organophosphorus extractants.

The de-ironing process according to the invention overcomes the disadvantages listed above, due to the implementation during the de-ironing step of an acid selected from oxalic acid, mixtures of phosphoric acid and sulfuric acid, or phosphoric acid de-ironed. For example, there is no loss of industrial phosphoric acid in the process according to the invention.

The method according to the invention uses only common inorganic reagents which are for example already present, inter alia, on the sites of production of phosphoric acid, which can significantly reduce the operating costs of the process.

The process according to the invention limits the number of unit operations and eliminates the impinging impurities in an original manner by saturation of the solvent with the recoverable materials, namely uranium.

There is no limitation on the initial organic phase, and the method according to the invention can be successfully applied to the treatment of any organic phase whatever the nature and provenance.

1U

The method according to the invention may especially apply to the treatment of an initial liquid organic phase which comprises an organic extraction system comprising an organic extruder or a mixture of organic extractant (s), diluted in a diluent organic non-reactive and immiscible with water.

It has been shown (see Examples) that the de-ironing process according to the invention can be successfully implemented for the treatment of any organic phase of this type regardless of the nature of the organic extraction system.

In particular (see Examples), it has been shown that the de-ironing process according to the invention can be successfully implemented both with an organic extraction system comprising a single organic extruder and with an organic extraction system. comprising a mixture of organic extruder (s) synergistic, and whatever the nature of the extraders or.

The organic extraction system may be chosen in particular from all the extradion systems described in documents [1] to [4] and the documents FR-A-2442 796, FR-A-2 459 205, FR-A- 2 494 258, and EP-A1-0 053 054, cited above, to the description of which reference is expressly made in this regard.

The organic extradion system may in particular comprise an extruder chosen from organophosphorus compounds and their mixtures. Here again, the de-ironing process according to the invention can be successfully implemented with all these organophosphorus extractants, used alone or as a mixture.

Advantageously, the extraction system may comprise an extruder chosen from acidic organophosphorus compounds such as dialkylphosphoric acids, bifunctional organophosphorus compounds, neutral phosphine oxides such as trialkylphosphine oxides, and mixtures thereof.

In one embodiment, the extraction system may comprise mixing an acidic organophosphorus compound and a phosphine neutral oxide.

Advantageously, the acidic organophosphorus compound may be chosen from di (2-ethylhexyl) phosphoric acid (D12EHPA), bis (1,3-dibutoxy, 2-propyl) phosphoric acid (BIDIBOPP) and bis (l) acid. 3-dihexyloxy, 2-propyl) phosphoric acid (BIDIHOPP); and the phosphine neutral oxide is selected from trioctylphosphine oxide (TOPO), and di-n-hexyl octyl methoxy phosphine oxide (DinHMOPO).

In particular, the extractant system may be chosen from the following extractant mixtures: a mixture of TOPO and D12EHPA; a mixture of TOPO and BIDIBOPP; a mixture of TOPO and BIDIHOPP; a mixture of DinHMOPO and D12EHPA; a mixture of DinHMOPO and BIDIBOPP; a mixture of DinHMOPO and BIDIHOPP.

In another embodiment, the extraction system may comprise a mixture of a trialkylphosphoric acid and a trialkyl phosphate, such as TBP.

In yet another embodiment, the extraction system may comprise as an extractant a compound which corresponds to the following general formula (I):

m represents an integer equal to 0.1 or 2; R1 and R2, which may be identical or different, represent a hydrocarbon group, saturated or unsaturated, linear or branched, comprising from 6 to 12 carbon atoms; r3 represents: - a hydrogen atom; a hydrocarbon group, saturated or unsaturated, linear or branched, comprising from 1 to 12 carbon atoms and optionally one or more heteroatoms; a hydrocarbon group, saturated or unsaturated, monocyclic, comprising from 3 to 8 carbon atoms and optionally one or more heteroatoms; or - a monocyclic aryl or heteroaryl group; or R2 and R3 together form a - (CH2) n- group wherein n is an integer from 1 to 4; R4 represents a hydrocarbon group, saturated or unsaturated, linear or branched, comprising from 2 to 8 carbon atoms, or a monocyclic aromatic group; while R5 represents a hydrogen atom or a hydrocarbon group, saturated or unsaturated, linear or branched, comprising from 1 to 12 carbon atoms.

Depending on the meaning of R 2 and R 3, the compound of formula (I) can meet: * either the following specific formula (I-a): in which:

m, R1, R4 and R5 are as previously defined; R2 represents a hydrocarbon group, saturated or unsaturated, linear or branched, comprising from 6 to 12 carbon atoms; while R3 represents: - a hydrogen atom; a hydrocarbon group, saturated or unsaturated, linear or branched, comprising from 1 to 12 carbon atoms and optionally one or more heteroatoms; a hydrocarbon group, saturated or unsaturated, monocyclic comprising from 3 to 8 carbon atoms and optionally one or more heteroatoms; or - a monocyclic aryl or heteroaryl group; * the following special formula (1-b):

wherein m, n, R 1, R 4 and R 5 are as previously defined.

According to the invention, the term "hydrocarbon group, saturated or unsaturated, linear or branched, comprising from 6 to 12 carbon atoms", any alkyl, alkenyl or alkynyl group, straight or branched chain, which comprises 6, 7 , 8, 9, 10, 11 or 12 carbon atoms.

In a similar manner, the term "linear or branched, saturated or unsaturated hydrocarbon group comprising from 2 to 8 carbon atoms" means any linear or branched chain alkyl, alkenyl or alkynyl group which comprises 2, 3, 4 , 5, 6, 7 or 8 carbon atoms.

Furthermore, the term "saturated or unsaturated hydrocarbon group, linear or branched, comprising from 1 to 12 carbon atoms and optionally one or more heteroatoms", any group consisting of a hydrocarbon chain, linear or branched, which comprises 1 , 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 or 12 carbon atoms, the chain of which may be saturated or, on the contrary, have one or more double or triple bonds and whose chain may be interrupted by one or more heteroatoms or substituted by one or more heteroatoms or by one or more substituents comprising a heteroatom. In this respect, it is specified that the term "heteroatom" means any atom other than carbon and hydrogen, this atom typically being a nitrogen, oxygen or sulfur atom.

Furthermore, the term "hydrocarbon group, saturated or unsaturated, monocyclic, comprising from 3 to 8 carbon atoms and optionally one or more heteroatoms", any cyclic hydrocarbon group which comprises only one ring and whose cycle comprises 3 , 4, 5, 6, 7 or 8 carbon atoms. This ring can be saturated or, on the contrary, comprise one or more double or triple bonds, and can comprise one or more heteroatoms or be substituted by one or more heteroatoms or by one or more substituents comprising a heteroatom, this or these heteroatoms being typically N, O or S. Thus, this group can in particular be a cycloalkyl, cycloalkenyl or cycloalkynyl group (for example a cyclopropane, cyclopentane, cyclohexane, cyclopropenyl, cyclopentenyl or cyclohexenyl group), a saturated heterocyclic group (for example, a tetrahydrofuryl group). , tetrahydrothiophenyl, pyrrolidinyl or piperidinyl), an unsaturated but nonaromatic heterocyclic group (eg, pyrrolinyl or pyridinyl), an aromatic group or a heteroaromatic group. In this respect, it is specified that the term "aromatic group" means any group whose cycle satisfies Hückel's aromaticity rule and therefore has a number of delocalized π electrons equal to An + 2 (for example, a phenyl or benzyl group), while the term "heteroaromatic group" is intended to mean any aromatic group such as has just been defined but whose ring comprises one or more heteroatoms, this or these heteroatoms being typically chosen from the following groups: nitrogen, oxygen and sulfur (for example, a furanyl, thiophenyl or pyrrolyl group).

Finally, the group - (wherein n is an integer from 1 to 4 may be methylene, ethylene, propylene or butylene.

In the particular formula (I-a) above, R 1 and R 2, which may be the same or different, advantageously represent a linear or branched alkyl group comprising from 6 to 12 carbon atoms.

More preferably, it is preferred that R 1 and R 2 are identical to each other and that they both represent a branched alkyl group comprising from 8 to 10 carbon atoms, the 2-ethylhexyl group being very particularly preferred.

On the other hand, in the particular formula (I-a) above: - m is, preferably, equal to 0; R3 advantageously represents a hydrogen atom, a linear or branched alkyl group comprising from 1 to 12 carbon atoms, or a monocyclic aryl group, preferably phenyl or ortho-, meta- or para-tolyl; while - R5 preferably represents a hydrogen atom.

More preferably, it is preferred that R3 is hydrogen, methyl, n-octyl or phenyl.

Finally, in the particular formula (Ia) above, R4 preferably represents a linear or branched alkyl group comprising from 2 to 8 carbon atoms and, more preferably, from 2 to 4 carbon atoms such as an ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl or tert-butyl group, the ethyl and n-butyl groups being very particularly preferred.

Compounds of particular formula (Ia) above which have these characteristics are in particular: - ethyl 1- (/ V, / V-diethylhexylcarbamoyl) benzylphosphonate, which corresponds to the particular formula (la) above in which m is 0, R1 and R2 are both 2-ethylhexyl, R3 is phenyl, R4 is ethyl, and R5 is hydrogen; ethyl 1 - (/ V, / V-diethylhexylcarbamoyl) ethylphosphonate, which corresponds to the above particular formula (Ia) in which m is equal to 0, R1 and R2 both represent a 2-ethyl- hexyl, R3 is methyl, R4 is ethyl, and R5 is hydrogen; ethyl 1- (N, N-diethylhexylcarbamoyl) nonylphosphonate, which corresponds to the above particular formula (la) in which m is equal to 0, R 1 and R 2 both represent a 2-ethyl- hexyl, R3 is n-octyl, R4 is ethyl, and R5 is hydrogen; - Butyl-1 - (/ V, / V-diethylhexylcarbamoyl) nonylphosphonate, which corresponds to the particular formula (la) above in which m is equal to 0, R1 and R2 both represent a 2-ethyl-hexyl group R3 is n-octyl, R4 is n-butyl, and R5 is hydrogen; and butyl 1- (N, N-dioctylcarbamoyl) nonylphosphonate, which corresponds to the above particular formula (Ia) in which m is 0, R1, R2 and R3 all represent a n-group; octyl, R4 is n-butyl while R5 is hydrogen.

Of these compounds, ethyl 1- (N, N-diethylhexylcarbamoyl) nonylphosphonate and especially butyl 1- (N, N-diethylhexylcarbamoyl) nonylphosphonate (DEHCNPB) are particularly preferred.

In the particular family (1-b) above, R 1 advantageously represents a linear or branched alkyl group comprising from 6 to 12 carbon atoms.

Moreover, in this particular formula: m is, preferably, equal to 0; R4 preferably represents a linear or branched alkyl group comprising from 2 to 8 carbon atoms and, more preferably, from 2 to 4 carbon atoms, while - R5 represents, preferably, a hydrogen atom.

A compound of particular formula (Ib) above having these characteristics is especially ethyl (N-dodecylpyrrolidone) -1-phosphonate which corresponds to the particular formula (Ib) in which R 1 represents an n-dodecyl group, R2 and R3 together form an ethylene group (-CH2-CH2-), R4 represents an ethyl group while R5 represents a hydrogen atom.

The compounds of formula (I), (Ia), and (Ib), and the particular compounds mentioned above are described in document WO-A1-2013 / 167516 [11], to the description of which is made in this regard expressly reference.

In a particularly preferred manner, the extractant system is chosen from D 2 EHPA, for example at a concentration of 0.5 M; a mixture of D12EHPA, preferably at a concentration of 0.5M, and TOPO, preferably at a concentration of 0.125M; a mixture of D12EHPA, preferably at a concentration of 0.2 M, and TBP, preferably at a concentration of 0.2 M; and 1- (Diethylhexylcarbamoyl) butyl nonylphosphonate (DEHCNPB) at a concentration of 0.1M or 0.5M.

It has thus been shown (see examples) that the process according to the invention can be successfully implemented with an organic phase resulting from the extraction of uranium by a first organic phase, or a solvent phase from a uraniferous inorganic inorganic acid aqueous solution, such as phosphoric acid, nitric acid or sulfuric acid. It has also been shown (see examples) that the process according to the invention could be successfully implemented irrespective of the origin of this aqueous uraniferous inorganic acid solution.

Thus, this aqueous uraniferous inorganic acid solution may be both an aqueous uraniferous solution of phosphoric acid, such as industrial phosphoric acid, resulting from the leaching, etching, of a natural phosphate ore, generally based on apatite, with sulfuric acid, that an aqueous solution uraniferous sulfuric acid or nitric acid resulting from the leaching, attacking a non-phosphate, for example non-apatitic uranium ore, respectively by the acid sulfuric acid or nitric acid. Generally, the initial organic phase contains from 0.5 to 10 g / L of uranium; and 0.1 to 10 g / L iron.

Advantageously, the inorganic acid of the aqueous de-ironing solution is chosen from sulfuric acid, nitric acid, hydrochloric acid, phosphoric acid, and mixtures thereof. The preferred inorganic acid of the aqueous iron removal solution is sulfuric acid.

Indeed, it is particularly advantageous to use sulfuric acid which is widely available at phosphoric acid production sites because large quantities of sulfuric acid are consumed during the leaching of phosphate ores.

Advantageously, the concentration of inorganic acid of the aqueous de-ironing solution is from 0.1 M to 18 M, preferably from 1 to 1.5 M.

Advantageously, the quantity of uranium supplied by the aqueous deferrisation solution is such that the concentration of uranium in the organic phase is at least 50%, preferably at least 60%, more preferably at least equal to 70% of the uranium concentration corresponding to the uranium saturation of the organic phase.

Advantageously, the concentration of uranium, expressed in [U] of the aqueous de-ironing solution, is from 0.10 to 800 g / l, preferably from 30 to 50 g / l, for example 40 g / l. bringing it into contact, the initial organic phase is mixed with the aqueous de-ironing solution and then said mixture is decanted.

After the mixture has been decanted, a final aqueous liquid phase containing the iron contained in the initial organic phase is obtained on the one hand, and a final organic phase, known as the defrosted phase containing uranium, on the other hand. was contained in the initial organic phase and not containing iron.

A definition of the terms "not containing iron" is given below.

Advantageously, the contacting is carried out in a battery of 1 to 5 settling mixers, for example 3 mixer-settlers, fed with countercurrent in the initial organic phase and in aqueous de-ironing solution.

Advantageously, the contacting can be carried out at a temperature of 0 ° C. to 70 ° C. within the flash temperature of the organic diluent, preferably at a temperature of 40 ° C. to 45 ° C.

Advantageously, the ratio of the flow rate of the initial organic phase to the flow rate of the aqueous de-ironing solution O / A is 1/5 to 5/1, for example 1/1.

Advantageously, the final aqueous phase contains more than 90% of the mass of the iron contained in the initial organic phase, and less than 1% of the mass of uranium contained in the initial organic phase, and the de-ironized organic phase contains at least 90 % of the mass of uranium contained in the initial organic phase, and less than 10% of the mass of iron contained in the initial organic phase.

Thanks to the process according to the invention, a selective elimination of iron is obtained which can be greater than 90% in a contact. The weight ratio Fe / U in the de-ironized organic phase is generally less than 0.15%, which is in accordance with ASTM specifications. The invention furthermore relates to a process for extracting uranium from a first aqueous solution of an inorganic acid containing uranium and iron, in which at least the following successive steps are carried out a) contacting the first aqueous inorganic acid solution with a first liquid organic phase; whereby a second liquid organic phase containing a majority of the quantity of uranium contained in the first aqueous solution of inorganic acid and a minority in mass of the amount of iron contained in the first aqueous solution is obtained on the one hand. of inorganic acid, and secondly a second aqueous phase containing the inorganic acid, a minority in mass of the amount of uranium contained in the aqueous solution of inorganic acid and a majority in mass of the amount of iron contained in the aqueous solution of inorganic acid; b) separating the iron from the second liquid organic phase containing uranium and iron, bringing the second liquid organic phase into contact with a third aqueous solution called aqueous iron removal solution, whereby the iron passes into the an aqueous deferrisation solution for forming a final aqueous liquid phase, and the uranium remains in the second organic liquid phase to form a final liquid organic phase called de-ironed organic phase; said method being characterized in that the aqueous deferrisation solution contains an inorganic acid and uranium.

In this process for extracting uranium and iron from an aqueous solution of an inorganic acid, step b) is carried out by the de-ironing process according to the invention as it has been discussed above, and the entire description of the iron removal process provided above fully applies to step b). The second liquid organic phase treated during step b) corresponds to the second liquid organic phase of step a) treated by the iron removal process according to the invention. The third aqueous solution, called an aqueous de-ironing solution, corresponds to the aqueous de-ironing solution used in the de-ironing process according to the invention and has been described in detail above.

It will be further understood that the first liquid organic phase is different from the second organic phase in that it contains neither uranium nor iron and is therefore exclusively composed of organic compounds. For example, this first organic phase may consist of an organic extraction system comprising an organic extractant or a mixture of organic extractant (s) diluted in an organic non-reactive diluent and immiscible with water. Such an organic extraction system has already been described in detail above.

In step a), the second organic phase obtained contains at least 90% by weight, for example from 95 to 100% by weight, of the quantity of uranium contained in the first aqueous inorganic acid solution (starting solution ), and from 0.1 to 50% by weight of the amount of iron contained in the first aqueous solution of inorganic acid; and the second aqueous desuranium phase obtained contains the inorganic acid, from 0 to 10% by weight of the amount of uranium, and from 50 to 99.9%, for example from 80 to 90% by weight of the amount of iron. contained in the first aqueous solution of inorganic acid (starting solution). Generally, the second organic phase obtained at the end of step a) contains from 0.5 to 10 g / l of uranium, and from 0.1 to 10 g / l of iron, and the second aqueous phase obtained at the end of step a) contains from 0 to 100 mg / l of uranium, and from 0.1 to 6 g / l of iron.

The process according to the invention is fundamentally different from the processes of the prior art, in that the de-ironing step b) is carried out with a specific aqueous deferrisation solution which contains an inorganic acid and uranium.

In other words, the de-ironing step b) is carried out by implementing the de-ironing method according to the invention as described above, and therefore has all the advantages inherent to this de-ironing process.

This aqueous de-ironing solution surprisingly makes it possible to selectively remove iron from the second organic phase, or solvent phase loaded with uranium, and iron.

Indeed, it occurs during the contacting of the organic phase or solvent phase obtained in step a) with the aqueous iron removal solution according to the invention a chemical shift of iron by uranium to the aqueous phase. which thus ensures a selective deferrisation of the organic phase, loaded with uranium and iron.

The implementation of the aqueous solution according to the invention in the deferrisation step b) which thus makes it possible to obtain a selective elimination of iron, has never been described in the prior art.

Thus, in documents FR-A-2 596 383 [1] and EP-A-239 501 [2], an acid selected from oxalic acid, a mixture of phosphoric acid, is used during the de-ironing step. and sulfuric acid or sulfuric acid déferrisé, without any addition of uranium, thus in addition to the disadvantages mentioned above related to the use of these acids, a selective elimination of iron, due to the chemical shift of iron by uranium can not be obtained.

The process according to the invention, in particular because of the implementation of the specific solution mentioned above during the de-ironing step, does not have the disadvantages, defects, limitations and disadvantages of the processes of the prior art and solves the problems of the processes of the prior art.

In particular, there is, for example, no loss of industrial phosphoric acid in the process according to the invention.

The method according to the invention especially during the de-ironing step uses only inorganic reagents that are already present on the phosphoric acid production sites.

For example, it is particularly advantageous to use sulfuric acid which is widely available at phosphoric acid production sites because large quantities of sulfuric acid are consumed during the leaching of phosphate ores.

In summary, the process according to the invention, while being more economical, allows, among other things, a selective removal of iron by chemical displacement while avoiding the loss of uranium and the iron precipitation phenomena which hinder the conduct of the process. The process according to the invention limits the number of unit operations and eliminates the impinging impurities by saturation of the solvent with the recoverable materials, namely uranium.

Advantageously, the inorganic acid of the first aqueous inorganic acid solution of step a) is a solution of phosphoric acid, sulfuric acid or nitric acid.

Advantageously, the first aqueous solution of inorganic acid of step a) contains from 0.1 to 10 g / l of iron, and from 0.05 to 10 g / l of uranium.

It has been shown (see Examples) that the process according to the invention can be successfully implemented with a wide variety of aqueous solutions of inorganic acid irrespective of their origin, ie for example an aqueous uraniferous solution. phosphoric acid, such as industrial phosphoric acid, resulting from the leaching, etching, of a natural phosphate ore, generally based on apatite, with sulfuric acid, or an aqueous uraniferous solution of sulfuric acid or nitric acid, resulting from the leaching, etching of a non-phosphated uranium ore, for example non-apatitic, by respectively sulfuric acid or nitric acid as previously described.

Advantageously, step a) is carried out at a temperature of 30 ° C to 35 ° C, in a battery of 5 mixer-decanters supplied with countercurrent in the organic phase and in the aqueous phase, and with a ratio of the flow rate of the organic phase at the flow rate of the aqueous phase O / A of 1/6 to 1/8, for example 1/7.

The method according to the invention may further comprise a step c) in which the de-ironed organic phase obtained in step b) is brought into contact with an aqueous solution of a complexing base; whereby one obtains on the one hand an aqueous phase loaded with uranium and on the other hand an organic phase free of uranium, and further containing the complexing base.

Advantageously, the complexing base is an alkali metal or alkaline earth metal carbonate such as sodium carbonate.

The process according to the invention may also comprise a step d) in which the uranium-free organic phase, additionally containing the complexing base obtained in step c), is brought into contact with the aqueous phase resulting from the step b) and neutralized, whereby one obtains firstly an organic phase consisting of the organic solvent which is returned in step a) and secondly an aqueous phase.

The process according to the invention may furthermore comprise a step e) in which the uranium-loaded aqueous phase obtained in step c) is brought into contact with a base such as sodium hydroxide, whereby a precipitate is obtained. uranate, such as sodium uranate, which is separated, and an aqueous solution which is sent in step c) after addition of a complexing base.

Advantageously, all or part of the uranate precipitate, such as sodium uranate, obtained in step e), is dissolved in an inorganic acid such as sulfuric acid, and the resulting aqueous solution containing an acid inorganic and uranium is sent to step b) after possibly adjusting the concentration of inorganic acid. The invention will be better understood on reading the following detailed description of an embodiment of the process according to the invention for extracting uranium from an aqueous solution of mineral acid containing uranium, iron and possibly one or more other impurities.

This description is given for illustrative and not limiting and is made with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a block diagram of the method according to the invention.

It should be noted that all the indications given in Figure 1 without exception, for example concerning the reagents used, concentrations, temperatures, etc. are only an example and in no way constitute a limitation.

Figure 2 is a graph which shows the kinetic profiles of the selective de-ironing efficiency of the solvent for different initial concentrations of uranium: namely 0 g / L (curve A), 10 g / L (curve B), 20 g / L ( curve C), 30 g / L (curve D), 35 g / L (curve E), 40 g / L (curve F), 50 g / L (curve G), 60 g / L (curve H), 70 g / L (curve I), 100 g / L (curve J), in the aqueous phase during the complementary tests of Example 2.

On the ordinate is carried the de-ironing efficiency of the solvent (in%) and on the abscissa the time is taken (in min.).

Figure 3 is a graph which gives the deferrisation efficiency (or removal of Fe in%) of the loaded solvents A, B, C, D, E, F, G, H, L, I, J, K, and M prepared. in Example 4, in contact with either 1.5 M pure sulfuric acid (for each test A, B, C, D, E, F, G, H, L, I, J, K, and M: left bar), or with 1.5 M sulfuric acid containing uranium (for each test: right bar).

DETAILED PRESENTATION OF PARTICULAR EMBODIMENTS

The detailed description which is made relates to an embodiment of the process according to the invention, of extracting uranium from an aqueous solution of mineral acid, containing uranium and iron, in which the solution aqueous mineral acid is an aqueous solution of phosphoric acid containing uranium and iron.

It is obvious that, with minor adaptations within the reach of those skilled in the art, the method described in the following can easily be implemented with aqueous solutions of other mineral acids such as sulfuric acid or nitric acid, containing uranium and iron.

The aqueous solution of phosphoric acid containing uranium and iron which is treated by the process according to the invention, the so-called aqueous phosphoric acid "starting" solution (1), generally has a concentration expressed as P2O5 of 26. % to 32% by weight, for example from 28% to 30% by weight, expressed as P2O5.

The aqueous solution of phosphoric acid treated by the process according to the invention generally contains from 0.05 to 1 g / l of uranium, in particular from 0.08 to 0.4 g / l of uranium (expressed in [U] ). The uranium in this aqueous solution is generally in solution in the form of U (VI) and U (1 V), the latter to be the subject of a preliminary oxidation stage in U (VI).

The aqueous solution of phosphoric acid treated by the process according to the invention generally contains from 0.1 to 10 g / l of iron, in particular from 1 to 6 g / l of iron.

This aqueous solution is generally an aqueous solution, called etching solution, obtained during the attack of phosphate ores with sulfuric acid.

Before being treated by the process according to the invention, the phosphoric acid solution containing uranium and iron may undergo one or more pretreatment steps (2), in particular a flash cooling step, then a step of solid / liquid separation, then an oxidation step for example with hydrogen peroxide. The cooling step allows for example to cool the attack solution, which is hot. The solid / liquid separation step makes it possible to separate the gypsum into supersaturation in the solution. The oxidation step, for example with hydrogen peroxide or with another oxidant such as NaCIC> 3, makes it possible to oxidize uranium in the form of U (IV) in uranium in the form of U (VI).

According to the invention, in the first step or step a), also called the extraction step (3), of the process according to the invention, the aqueous solution of phosphoric acid (1) is brought into contact with a solvent of organic extraction (4) comprising a single extractant or a synergistic extractant mixture, diluted in an organic immiscible diluent and non-reactive with water.

By synergistic extractant mixture, it is meant that this mixture has extractive properties greater than or substantially greater than the extractive properties obtained by the simple addition of the extractive properties of each of the extractants that constitute the extractant mixture.

Examples of such extractants and such synergistic extractant mixtures are known to those skilled in this field of the art and are given for example in documents [1] to [4] and documents FR-A- 2442 796, FR-A-2,459,205, FR-A-2,494,258 and EP-A1-0,053,054 cited above to the description of which we can in this regard refer.

Preferred sole extractants used are D2EHPA, preferably at a concentration of 0.5 M. Other preferred sole extractants used are the bifunctional extractants of [4] described above as DEHCNPB, preferably at a concentration of 0. , 1 M to 0.5 M.

The synergistic extractant mixtures may consist, for example, of a neutral phosphine oxide and an acidic organophosphorus compound, in particular a mixture of a dialkylphosphoric acid and a trialkylphosphine oxide.

Preferably, the acidic organophosphorus compound of the mixture, such as a dialkylphosphoric acid, is chosen from bis (2-ethylhexyl) phosphoric acid (DITHEPA), 1,3-dibutoxypropylphosphoric acid (BIDIBOPP) and acid. 1,3-dihexyloxypropylphosphoric acid (BIDIHOPP); and the neutral phosphine oxide is selected from trioctylphosphine oxide (TOPO) and di-n-hexyl octyl methoxy phosphine oxide (DinHMOPO).

Preferred extractant mixtures of this type are: TOPO / D12EHPA; TOPO / BIDIBOPP; TOPO / BIDIHOPP;

DinHMOPO / Di2EHPA;

DinHMOPO / BIDIBOPP;

DinHMOPO / BIDIHOPP.

A particularly preferred synergistic extractant mixture is a mixture of D2EHPA and TOPO, preferably a mixture of 0.5M D2EHPA and 0.125M TOPO.

Another synergistic extractant mixture is a mixture of D2EHPA and TBP, preferably a mixture of 0.2 M D2EHPA and 0.2 M TBP: this is the mixture used in the "DAPEX" process.

The immiscible organic diluent which is not reactive with water is generally chosen from liquid hydrocarbons.

These liquid hydrocarbons may be chosen from aromatic hydrocarbons such as benzene, aliphatic hydrocarbons such as n-heptane and n-octane, and mixtures thereof. A hydrocarbon mixture which is suitable as a diluent according to the invention is kerosene.

Aliphatic kerosenes, such as the products available under the name ShellSol®, may thus be suitable for use in the organic diluent. Other hydrocarbon mixtures which are suitable as diluent according to the invention are the products available under the name ISANE® such as ISANE® IP 185.

This extraction step can be performed in static mode or in dynamic mode.

This extraction step can be carried out in any suitable extraction apparatus, for example in one or more settling mixers, and / or in one or more agitated or pulsed columns. Those skilled in the art can easily determine the number of appropriate theoretical stages that must be included in the extraction apparatus to perform the extraction. Generally, this extraction step is carried out with a battery of mixer-settlers operating in dynamic against the current, that is to say with the organic phase and the aqueous phase flowing against the current one of the other since the first, respectively last, mixers-decanters, until the last, respectively first mixer-settlers.

The number of mixer-settlers can range from 1 to 10, in particular from 1 to 5.

Preferably, 5 mixer-settlers, in other words 5 stages of mixing-decantation are used. The organic phase feed can then take place for example in stage 1, while the aqueous phase feed takes place for example in stage 5.

The overall O / A ratio for the entire mixer-settler battery, all the stages, is generally 1/6, ie 0.1667, at 1/8 or 0.1250, depending on the initial concentration of the mixture. uranium in the starting phosphoric acid solution.

Remember that O / A designates the ratio of the flow rate of the organic phase to the flow rate of the aqueous phase.

This process step is generally carried out at a temperature of 10 ° C to 60 ° C, especially 10 ° C to 50 ° C. It can be carried out at room temperature, for example 20 ° C to 25 ° C, but it is preferably carried out at a temperature of 30 ° C to 35 ° C, which makes it possible to obtain a kinetic of extraction of l relatively fast uranium.

The mixing time per mixer is generally 0.5 to 5 minutes, preferably 2 minutes, when operating within the preferred temperature range indicated above.

The residence time in the decanters, per stage, is generally 2 to 10 minutes, preferably 5 minutes, when operating in the preferred temperature range indicated above.

The extraction efficiency of the uranium during this step is generally greater than or equal to 95%, preferably greater than or equal to 97%, more preferably greater than or equal to 98%.

The leakage of uranium is generally less than or equal to 10 mg / l, preferably less than or equal to 5 mg / l, more preferably less than or equal to 3 mg / l. At the end of this extraction step (3), an organic phase (5) is thus obtained on the one hand, which contains from 90 to 100% by weight, for example 95% by weight, of the amount of uranium contained in the aqueous solution of phosphoric acid (starting solution), and from 0.1 to 10% by weight of the iron contained in the aqueous solution of phosphoric acid; and on the other hand a deurane aqueous phase (6) which contains phosphoric acid, from 0 to 10% by weight of the uranium, and from 80% to 99.9% by weight of the iron contained in the aqueous solution of phosphoric acid (starting solution).

The organic phase (5) obtained at the end of the extraction step (a) (3) therefore generally contains from 0.5 to 10 g / l. uranium and 0.1 to 10 g / L. of iron while the aqueous phase deurane (6) obtained at the end of step a) generally contains from 0 to 100 mg / l. uranium and 0.1 to 6 g / L. of iron.

The deurane aqueous phase (6) may optionally be subjected to one or more post-treatments (7) chosen, for example, from a coalescence treatment and an activated carbon treatment in order, in particular, to eliminate organic matter (resulting from a training of the organic phase in the aqueous phase), and the phosphoric acid thus recovered, which has a concentration expressed as P2O5 of 26% to 32% by weight, for example from 28% to 30% by weight, similar to phosphoric acid starting point, can then be used for example in fertilizer production workshops.

The organic phase (5) obtained at the end of step a) (3), or extraction step, generally has a significant Fe / U ratio of the order of 0.1 to 1, in particular of 0, 5.

Then, during a step b), or de-ironing step of the solvent (8) according to the invention, the organic phase (5) obtained in step a) is brought into contact with an aqueous iron removal solution (9). .

According to the invention, the aqueous iron removal solution (9) contains an inorganic acid and uranium. The inorganic acid of the aqueous de-ironing solution (9) may be chosen from sulfuric acid, nitric acid, hydrochloric acid, phosphoric acid, and mixtures thereof. The preferred inorganic acid of the aqueous iron removal solution is sulfuric acid.

Advantageously, the concentration of inorganic acid of the aqueous iron removal solution such as sulfuric acid is from 1 to 1.5 M.

The uranium concentration of the aqueous de-ironing solution is preferably 35 to 40 g / l, for example 40 g / l.

Indeed, at constant acidity the initial concentration of uranium is a key parameter on the yields of selective deferrisation of the solvent. The technico-economic optimum appears to be within the aforementioned range of 35 to 40 g / L of uranium initially contained in the influent aqueous for an elimination of iron of the order of 90% in a contact.

The tests for depletion of the aqueous phase also showed the absence of iron release on the solvent and effective uranium depletion generally in three successive contacts with contact times of less than 5 minutes.

It has also been shown that the concept of selective deferrisation of the solvent by chemical displacement was valid irrespective of sulfuric, nitric, hydrochloric or phosphoric acid.

This process step is generally carried out at a temperature of 10 ° C to 50 ° C.

It can be carried out at room temperature, for example 20 ° C to 25 ° C, but is preferably carried out at a temperature of 40 ° C to 45 ° C.

Indeed, the experimental results show a notable influence of the temperature on this step with a substantial gain on the mixing time necessary to reach the required performances. For example, the adequate contact time at 40 ° C seems to be between 5 and 10 minutes instead of 30 minutes required at 20 ° C.

This deferrisation step (8) can be implemented in any suitable contacting apparatus, and be performed in static mode or in dynamic mode. Generally this de-ironing step (8) is carried out with a battery of mixer-settlers operating in counter-current dynamics.

The number of mixer-settlers can range from 1 to 5.

Preferably, 3 mixer-settlers, in other words 3 stages of mixing-decantation are implemented. The organic phase feed (5) takes place in stage 1, while the aqueous phase feed (9) takes place in stage 3 which is also called "super stage".

The overall O / A ratio for the entire battery of mixer-settlers, all stages, is generally 1/5 to 5/1.

A preferred overall O / A ratio is 1/1.

The contact time is generally of the order of 10 minutes for stage 3, that is to say for the stage of the aqueous feed, and 3 minutes for the other two stages.

The residence time in the decanter is generally 5 minutes maximum.

In step b) (8), an aqueous phase (10) containing from 50% to 90% of the iron contained in the organic phase (5) obtained in step a) is obtained on the one hand and on the other hand a de-ironized organic phase (11) containing at least 85% by weight of the uranium contained in the organic phase (5) obtained in step a) and not containing iron, free of iron. By "de-ironed", "iron-free", "iron-free", it is generally meant that this organic phase (11) contains less than 10 mg / L of iron, for example 5 mg / L of iron.

The organic phase (11) obtained at the end of the iron removal stage b) (8) therefore generally contains from 0.5 to 60 g / l. uranium and from 0 to 10 mg / L. of iron, while the deurane aqueous phase (10) obtained at the end of step b) therefore generally contains from 0 to 1 g / L. uranium and 0 to 2 g / L. of iron. This aqueous phase (10) is an acid phase containing the inorganic acid described above.

The method according to the invention also generally comprises a step c), also called the uranium extraction step (12), in which the de-ironed and uranium-laden organic phase (11) obtained at the end of the step b) de-ironing the solvent is brought into contact with an aqueous solution of a complexing base (13).

The complexing base may be selected from alkali metal carbonates, such as sodium carbonate, alkaline earth metal carbonates, and ammonium carbonates.

The concentration of complexing base such as sodium carbonate of the aqueous solution is generally 1 to 2 M, for example 1.5 M.

This de-extraction step (12) can be performed in static mode or in dynamic mode. It can be carried out in any suitable extraction apparatus.

This de-extraction step (12) is generally carried out with a battery of mixer-settlers operating in counter-current dynamics.

The number of mixer-settlers can range from 1 to 5.

Preferably, 3 mixer-settlers, in other words 3 stages of mixing-decantation are implemented. The organic phase feed (11) can take place, for example, in stage 1, while the aqueous phase feed (13) can take place, for example, in stage 3.

The overall O / A ratio for the entire battery of mixer-settlers, all the stages, is generally 1/2 to 2/1, depending on the initial concentration of the uranium in the starting organic phase. .

A preferred overall O / A ratio is 1/1.

This process (20) of uranium extraction (12) is generally carried out at a temperature of 10 ° C to 50 ° C.

It can be carried out at room temperature, for example 20 ° C to 25 ° C, and a satisfactory phase separation is achieved even at 25 ° C, but an increase in the operating temperature can improve performance. The uranium (12) de-extraction step is thus preferably carried out at a temperature of 40 ° C. to 45 ° C., which makes it possible to obtain relatively rapid uranium extraction kinetics.

The mixing time is generally from 1 to 10 minutes, preferably 5 minutes, when operating within the preferred temperature range indicated above. At the end of this step of extracting uranium (12), an aqueous phase loaded with uranium (14) and an organic phase (15) consisting of the organic solvent are obtained on the one hand, free of uranium.

The aqueous phase loaded with uranium (14) generally contains from 5 to 80 g / l. uranium and from 0 to 100 mg / L. of iron and the uranium-free organic phase (15) generally contains from 0 to 100 mg / L. uranium and from 0 to 10 mg / L. of iron.

The method according to the invention furthermore comprises, in general, a step d), called the acidification step of the solvent (16), in which the uranium-free organic phase (15), furthermore containing the complexing base derived from step c) (12) -in other words the de-uranium solvent from the uranium extraction step (12) -is contacted with the aqueous phase (10) from step b) , that is to say the de-ironing step of the solvent (8). The acid titre could possibly be adjusted if necessary.

This acidification stage of the solvent (16) can be carried out in static mode or in dynamic mode.

This acidification step (16) can be carried out in any suitable contacting apparatus.

This acidification step (16) is generally carried out with a mixer-settler or a battery of mixer-settlers, for example from 1 to 8 mixer-settlers operating in dynamic against the current.

Preferably, a single mixer-settler, in other words a single mixing-decantation stage is implemented.

The overall O / A ratio for the single mixer-decanter, or for the entire mixer-decanter battery, all stages, is generally 1/5 to 5/1.

A preferred overall O / A ratio is 1/1.

This acidification step (16) of the process according to the invention is generally carried out at a temperature of 10 ° C. to 50 ° C.

It can be performed at room temperature, for example 20 ° C to 25 ° C, but an increase in the operating temperature can improve performance. The acidification step (16) is thus preferably carried out at a temperature of 40 ° C to 45 ° C.

The mixing time is generally 1 to 10 minutes per stage, preferably 5 minutes, when operating in the preferred temperature range indicated above. At the end of this step of acidifying the solvent (16), an organic phase (4) consisting of the organic solvent regenerated in acid form which is sent to the extraction step a) is obtained on the one hand ( 3) and on the other hand an aqueous phase (17).

This aqueous phase (17) contains iron, for example at a rate of 0 to 2 g / L, and the inorganic acid which was contained in the aqueous ironing solution used during the iron removal stage b) at a rate of concentration from 1 to 1.5 M.

This aqueous phase (17) can be valorized. Thus, if the inorganic acid is sulfuric acid, this aqueous phase (17) can be recycled to a leach stage of phosphate ore (18).

The aqueous phase loaded with uranium (14) obtained at the end of the uranium de-extraction step is generally treated in a step e), called the uranate precipitation step (19) during which this aqueous phase charged with uranium (14) is brought into contact with a base (20) such as sodium hydroxide whereby a precipitate of uranate such as sodium uranate which is separated, and an aqueous solution free of uranium are obtained. (21) which is returned to step (c) of uranium (12) de-extraction after adding a complexing base such as sodium carbonate. The uranium contained in the aqueous phase loaded with uranium obtained at the end of the uranium stripping step (12) can be in various forms.

If the complexing base is an alkali or alkaline earth metal carbonate, such as sodium carbonate, then the uranium is in the form of alkali or alkaline earth metal uranyl tricarbonate, such as sodium uranyl tricarbonate.

The uranium is thus precipitated by adding a base (20) such as sodium hydroxide to the aqueous phase (14), for example at a temperature of 80 ° C. for a period of 1 hour.

A precipitate of uranate, for example sodium diuranate ("SDU") or sodium uranate, is thus obtained if sodium hydroxide has been used for the precipitation.

This uranate precipitate is separated by any suitable solid-liquid separation process, for example by filtration.

All or part (22) of this uranate precipitate, such as sodium uranate obtained in the precipitation step e) (19), can be dissolved during a so-called redissolution step of the uranate (23), in an inorganic acid (24) such as sulfuric acid, at a pH of, for example, 3 to 3.5. The inorganic acid (24) used for the dissolution can be chosen from the same acids as those already mentioned for the aqueous de-ironing solution, namely, sulfuric acid, nitric acid, hydrochloric acid, acid phosphoric acid, and mixtures thereof. The preferred inorganic acid is sulfuric acid.

Following the dissolution of the uranate, an aqueous solution of dissolution containing an inorganic acid such as sulfuric acid and uranium in the form of uranyl sulphate is thus obtained.

All or part of this aqueous dissolution solution (25) can be sent in step b) to serve as an aqueous deferrisation solution (9) after a possible adjustment of the acid concentration to obtain the desired acid concentration for the acidic, uranized aqueous solution of ironing (9).

Thus, an addition of inorganic acid (26), such as sulfuric acid, may be carried out on the pipe conveying the aqueous solution of dissolution (25).

As already mentioned above, the concentration of the inorganic acid of the aqueous iron removal solution (9) such as sulfuric acid is advantageously 1 to 1.5 M, and the uranium concentration of the The aqueous de-ironing solution is advantageously from 35 to 40 g / l, for example 40 g / l.

All or part (27) of the uranate precipitate can be placed in containers such as drums during a so-called "firing" stage of the uranate (28).

All or part (29) of the aqueous dissolution solution of uranate can optionally be sent to an optional precipitation step (30) with hydrogen peroxide (31), generally carried out at room temperature, at the end of from which there is obtained a UO4 uranium peroxide precipitate (32) which can be optionally separated everywhere adequate solid-liquid separation process, for example by filtration.

The precipitate of uranium peroxide can then be placed in containers such as drums during a so-called "flaring" stage of ΓΙΙΟ4 (33).

In total, the process according to the invention uses, for example twelve mixing-settling stages. The invention will now be described with reference to the following examples, given by way of illustration and not limitation. EXAMPLES.

Example 1

In this example, it shows the influence of the initial concentration of uranium in the iron removal solution used in the method according to the invention for separating iron and from a liquid organic phase.

In order to study the influence of the initial concentration of uranium in the aqueous iron removal solution, tests at the laboratory scale were carried out in a separating funnel under the following conditions:

Aqueous de-ironing solution (aqueous phase A): 3 MH 2 SO 4 containing uranium at a variable concentration;

Initial organic phase (organic phase O), solvent loaded with uranium and iron: Synergistic mixture of 0.5 M D2EHPA and 0.125 M TOPO in Isane® diluent IP185, loaded with uranium [U] = 1200 mg / L and iron [Fe] = 526 mg / L;

O / A phase ratio = 1/1.

Ambient temperature (22 ° C).

Variable contact time.

The kinetics of uranium and iron de-extraction of the solvent are determined by the analytical monitoring of the concentrations in the aqueous phase after contact with the solvent.

The results of these tests are shown in Table I below.

Table I: Kinetic monitoring of uranium and iron concentrations after contact of the solvent loaded with a solution of 3 MH 2 SO 4 containing uranium at a variable concentration (O / A = 1/1, room temperature).

These experimental results show a clear increase in the deferrisation efficiency as soon as the aqueous phase initially contains, in accordance with the process according to the invention, uranium in high concentrations.

Moreover, the kinetics of elimination of iron seems to be of the order of 30 minutes, during which time the de-ironing performance of the solvent reaches a plateau greater than 90% in one contact, except for a pure sulfuric solution for which the kinetics seems to be slower.

Example 2

In order to supplement the previous data obtained in Example 1, additional tests at the laboratory scale were carried out in a separating funnel under the following conditions:

Aqueous de-ironing solution (aqueous phase A): 3 MH 2 SO 4 containing uranium at a variable concentration;

Initial organic phase (organic phase O), Solvent loaded with uranium and iron: Synergistic mixture of 0.5 M DI2EHPA and 0.125 M TOPO in Isane® diluent IP185, loaded with uranium [U] = 1093 mg / L and in iron [Fe] = 437 mg / L (The composition of the solvent is thus slightly different from the composition of the solvent in the tests of Example 1 where [U] = 1.2 g / L and [Fe] = 526 mg / L);

O / A phase ratio = 1/1;

Ambient temperature (22 ° C).

The kinetics of uranium and iron de-extraction of the solvent are determined by the analytical monitoring of the concentrations in the aqueous phase after contact with the solvent.

The results of these additional tests are shown in Table II below.

Table II: Kinetic monitoring of the concentrations of uranium and iron after contact of the solvent loaded with a solution of 3 MH 2 SO 4 containing uranium at a variable concentration (O / A = 1/1, ambient temperature) during the complementary tests .

The additional tests of this example reveal a significant influence of the initial concentration of uranium in the de-ironing solution, especially for the selected low concentrations. Thus, the de-ironing efficiency increases with the uranium concentration while reducing the de-ironing kinetics.

On the other hand, Figure 2 shows the kinetic profiles of the selective deferrization efficiency of the solvent for different initial uranium concentrations (ie 0 g / L, 10 g / L, 20 g / L, 30 g / L, 35 g / L 40 g / L, 50 g / L, 60 g / L, 70 g / L, 100 g / L) in the aqueous phase during the further tests of Example 2.

This figure also shows two distinct populations: when the uranium concentration is between 0 and 30 g / L for which the deferrisation efficiency increases and the kinetic equilibrium equilibrium decreases; when the uranium concentration is between 35 and 100 g / L for which the curves are superimposed, both from a thermodynamic point of view (deferrisation efficiency) and from a kinetic point of view (plateau reached after 30 minutes at room temperature, finally, the kinetics of extraction of uranium seems relatively fast with an optimum of between 5 and 10 minutes at room temperature.

Example 3

In this example, tests are carried out in which the process according to the invention for separating iron and from a liquid organic phase is carried out in a battery of 3 mixer-settlers (MD) operating in a counter-dynamic mode. current.

The conditions of these tests are as follows:

Aqueous de-ironing solution (aqueous phase A): H2SO4 3 Μ ([H +] = 5.9 mol / L) containing 39.76 g / L of uranium, with a feed rate of 120 ml / h;

Initial organic phase (organic phase O), solvent loaded with uranium and iron: Synergistic mixture of 0.5 M D2EHPA and 0.125 M TOPO in Isane® diluent IP185, loaded with uranium [U] = 994 mg / L and iron [Fe] = 307 mg / L, with a feed rate of 120 mL / h;

Useful volume: 50 ml mixer and 200 ml decanter for stage 3;

Useful volume: mixer of 30 ml and decanter of 200 ml for stages 1 and 2;

Organic phase feed in stage 1;

Water phase feed in stage 3;

O / A phase ratio = 1/1;

Temperature: 40 ° C with double jacketed mixers and settlers and a heat exchanger containing glycol as heat transfer fluid. After 30 hours of operation, samples of the organic phases and the aqueous phases are made to quantify the concentration profiles on each of the 3 stages and the deferrisation yield from the balance on the organic phases.

The results of these tests are presented in Table III below.

Table III: Profiles of Uranium and Iron Concentrations in Each MD Stage.

Example 4

In this example, uranium-loaded solvents or extraction systems are prepared by contacting etching liquids charged with uranium with solvents.

In a first step, an attack liquor or sulfuric solution, an attack liquor or phosphoric solution, and an attack liquor or nitric solution are prepared.

Phosphoric and sulfuric acid liquors are prepared from industrial juices.

Thus, the sulfuric acid etching liquor comes from a vanadium and zirconium ore leach juice (see Table IV).

Table IV: Composition and characterization of sulfuric attack liquor

The phosphoric attack liquor comes from a US industrial phosphoric acid SIMPLOT diluted in two and doped with uranium (see Table V).

Table V: Composition and Characterization of the Phosphoric Etching Liquor

The nitric attack liquor was, in turn, prepared from nitric acid, uranyl nitrate and iron (III) sulphate (see Table VI).

Table VI: Composition and characterization of the nitric attack liquor

The chemical analysis of the solutions shows that the sulfuric solution is very loaded with impurities, in particular iron, vanadium and zirconium.

On the contrary, phosphoric and nitric solutions are only loaded with iron. Moreover, the redox potential of the solutions thus prepared shows that the iron is predominantly in ferric form (the redox potential of the solution being inherent to the iron (11) / iron (111) pair).

Recall that the partition coefficient of iron (III) is higher than that of iron (II) on organophosphorus solvents

In a second step, the solvents are prepared.

These solvents comprise an organophosphorus organic extractant or a mixture of organophosphorus organic extractant (s), diluted in a non-reactive and immiscible organic diluent with water, namely an aliphatic kerosene (ISANE® IP 185).

The following extractants were chosen: D2EHPA (di-2-ethylhexylphosphoric acid) supplied by Lanxess. TOPO (trioctyl phosphine oxide) supplied by Cytec. - TBP (tributyl phosphate). - DEHCNPB (1- (diethylhexylcarbamoyl) butyl nonylphosphonate).

With these extractants and the ISANE® IP 185 diluent, the following solvents were prepared: 0.5M D2EHPA in ISANE®. D2EHPA 0.5M + TOPO 0.125M (Oak Ridge process solvent) in ISANE D2EHPA 0.2M + 0.2M TBP (DAPEX process solvent) in 0.1M or 0M ISANE.DEHCNPB, 5 M in ISANE.

In a third step, the solvents described above are brought into contact with the attack liquors previously prepared during the first step. The contacting is carried out for 30 minutes at room temperature (25 ° C.) with a phase volume ratio O / A of 1/1, the volume of the aqueous phase A and of the organic phase being each of 100 ml. .

The various contacting tests carried out during this third step are described in Table VII.

Table VII: Description of the selected trials for this study

An analysis of the solvents charged after these first contacts was made with a monitoring of the concentrations of uranium, iron, molybdenum, vanadium and zirconium (see Tables VIII to X). It should be noted that problems of analytical reproducibility (mineralization of the solvent and associated acquisition) did not make it possible to determine the concentration of zirconium on the charged solvents. Trends will therefore be based on the water phase monitoring for this element where appropriate.

Table VIII: Composition of solvents charged from sulfuric attack liquor

The charged solvents resulting from contacting with the sulfuric solution are generally charged to 3 g / l of uranium, between 0.5 and 1 g / l of iron, 200 mg / l of molybdenum and vanadium.

It is noted that the extraction performances observed between 0.5M DEHNCPB and 0.5M D2EHPA systems are similar in the sulfuric medium studied.

Moreover, it seems that a decrease in the concentration of DEHCNPB leads to a better selectivity of uranium / impurities.

TABLE IX Composition of the Solvents Charged with the Phosphoric Etching Liquor

The charged solvents resulting from contacting with the phosphoric solution are generally charged to 1 g / L of uranium with variable impurity contents, especially for iron and vanadium.

Molybdenum, meanwhile, has very little charge on all solvents; this being linked to the very low initial concentration of molybdenum in the phosphoric liquor and / or to the highly complexing nature of this matrix,

Thus, the D2EHPA / TBP mixture seems to be the most selective system for extraction under our conditions since the concentrations of iron, molybdenum and vanadium are very low.

Moreover, a selectivity gain is also obtained when the concentration of DEHCNPB decreases.

Table X: Composition of solvents charged from nitric attack liquor

The solvents resulting from the contact with the nitric solution are globally charged with 3 g / L of uranium and iron, except for the D2EHPA / TBP system for which the iron concentration is twice as low.

Moreover, there is a similar performance between the molecules D2EHPA and DEHCNPB and it is found that the TOPO no longer plays the role of synergist in a nitric matrix.

Example 5

In this example, aqueous solutions, so-called aqueous de-ironing solutions intended to be put in contact with the charged solvents prepared in Example 4, are prepared for the purpose of separating the iron from these charged organic solvents.

Two aqueous solutions are prepared (see Table XI): namely a solution of 1.5 M pure sulfuric acid (which is not in accordance with the aqueous deferrisation solution used in the process of the invention) which constitutes the reference aqueous solution, and a solution of 1.5 M sulfuric acid containing uranium at a rate of 40 g / L (in accordance with the aqueous deferrisation solution used in the process of the invention) which constitutes the aqueous solution of study.

The tests carried out with the reference solution (pure acid) will be identified by the number 1 following the letter designating the charged solvent brought into contact with the aqueous solution, whereas the tests carried out with the solution according to the process according to the invention will be identified. by the number 2 following the letter designating the charged solvent brought into contact with the aqueous solution.

Table XI: Composition of the aqueous reagents used for the impurity purification of the charged solvents

Example 6

In this example, purification tests of the charged solvents prepared in Example 4 are carried out from the sulfuric acid liquor (Table VIII, Tests A to E), using the aqueous solution in accordance with that used in the present invention. process according to the invention and the comparative solution prepared in Example 5.

The conditions of these tests are as follows: - Use of a separating funnel and dedicated mechanical stirrers. - Duration: 30 minutes. - Ambient temperature (25 ° C). - Phase volume ratio O / A of 1/1 (80 ml for each of the phases). After the contacts between the charged solvents and the 1.5 M sulfuric acid solution containing or without uranium, analyzes are carried out on the aqueous phases (see Tables XII and XIV) and the organic phases. (see Tables XIII and XV) after filtration with a follow-up on the uranium and impurities iron, molybdenum, vanadium and zirconium.

As a reminder, the analytical uncertainty is between 5 and 10% depending on the element under consideration.

Table XII: Analyzes of the aqueous phases after contact of the solvents charged with a

pure 1.5 M sulfuric acid solution

Table XIII: Analyzes of the organic phases after contact of the solvents charged with a

1.5 M sulfuric acid solution

As a reminder, the material balance calculated is generally checked for all elements analyzed to within 5%.

The results of the tests carried out with an aqueous solution constituted by pure sulfuric acid which are exposed in Tables XII and XIII show that a washing with 1.5 M pure sulfuric acid makes it possible: to limit the loss of uranium except for tests B and E for which the concentration of uranium in the aqueous phase is greater than 50 mg / L; ensure good purification of the vanadium solvent, except for test C; which is in accordance with the data of the literature; to remove only a small proportion of the iron contained in the charged solvents.

The solvents were then washed with a sulfuric acid solution of the same acidity (1.5 M) but containing uranium, that is to say a solution corresponding to that used in the process according to the invention. invention.

The results of these tests are shown in Tables XIV and XV.

Table XIV: Analyzes of the aqueous phases after contact of the solvents charged with a solution of sulfuric acid to 1.5 M containing uranium

Table XV: Analyzes of the organic phases after contact of the solvents charged with a solution of sulfuric acid to 1.5 M containing uranium

For the record, again, the material balance calculated is generally checked for all elements analyzed to 5%.

The results of the tests show that washing with 1.5 M pure sulfuric acid containing uranium, in accordance with the process of the invention, makes it possible: to purify the molybdenum in a limited manner but with yields greater than those observed with sulfuric acid solution free of uranium; to ensure an almost quantitative purification of vanadium solvent, including for test C (unlike the solution of sulfuric acid free of uranium); to eliminate almost quantitatively the iron contained in the loaded solvent for all the tests; to improve the elimination of zirconium based solely on analyzes of the aqueous phases after contact.

Example 7

In this example, purification tests of the charged solvents prepared in Example 4 are carried out from the phosphoric acid liquor (Table IX, tests F to H and L), by means of the aqueous solution corresponding to that used. in the process according to the invention and the comparative solution prepared in Example 5.

The conditions of these tests are as follows: - Use of a separating funnel and dedicated mechanical stirrers. - Duration: 30 minutes. - Ambient temperature (25 ° C). - Phase volume ratio O / A of 1/1 (80 ml for each of the phases). At the end of the contacts between the charged solvents and the 1.5 M sulfuric acid solution containing or not containing uranium, analyzes are carried out on the aqueous phases (see Tables XVI and XVIII) and the organic phases. (see Tables XVII and XIX) after filtration with a follow-up on the uranium and impurities iron, molybdenum, vanadium and zirconium.

As a reminder, the analytical uncertainty is between 5 and 10% depending on the element under consideration.

Table XVI: Analyzes of the aqueous phases after contact of the solvents charged with a

pure 1.5 M sulfuric acid solution

Table XVII: Analyzes of the organic phases after contact of the solvents charged with a pure solution of 1.5 M sulfuric acid

For the record, the calculated material balance is globally verified for all elements analyzed at 5% near.

The results of the tests carried out with an aqueous solution constituted by pure sulfuric acid which are exposed in Tables XVI and XVII show that a washing with 1.5 M pure sulfuric acid makes it possible: to limit the loss of uranium except for test H for which the concentration of uranium in the aqueous phase is greater than 10 mg / L; to ensure an almost quantitative purification of the solvent in vanadium, except for test F; to eliminate only a small proportion of the iron contained in all the charged solvents studied.

The solvents were then washed with a sulfuric acid solution of the same acidity (1.5 M) but containing uranium, that is to say a solution corresponding to that used in the process according to the invention. invention.

The results of these tests are presented in Tables XVIII and XIX.

Table XVIII: Analyzes of the aqueous phases after contact of the solvents charged with a solution of sulfuric acid to 1.5 M containing uranium

Table XIX: Analyzes of the organic phases after contact of the solvents charged with a 1.5 M sulfuric acid solution containing uranium

For the record, again, the material balance calculated is generally checked for all elements analyzed to 5%.

The results of the tests show that a washing with pure sulfuric acid 1.5 M containing uranium, according to the method of the invention, makes it possible: to ensure quasi-quantitative purification of the vanadium solvent; to virtually eliminate iron from all the charged solvents studied.

Example 8.

In this example, purification tests of the charged solvents prepared in Example 4 are carried out starting from the nitric attack liquor (Table X, tests I to K and M), by means of the aqueous solution corresponding to that used. in the process according to the invention and the comparative solution prepared in Example 5.

The conditions of these tests are as follows:

Use of separating funnels and dedicated mechanical stirrers.

Duration: 30 minutes.

Ambient temperature (25 ° C).

O / A phase volume ratio of 1/1 (80 ml for each phase). At the end of the contacts between the charged solvents and the 1.5 M sulfuric acid solution containing or not containing uranium, analyzes are carried out on the aqueous phases (see Tables XX and XXII) and the organic phases. (see Tables XXI and XXIII) after filtration with a follow-up on uranium and iron as the main impurity.

As a reminder, the analytical uncertainty is between 5 and 10% depending on the element under consideration.

Table XX: Analyzes of the aqueous phases after contact of the solvents charged with a

pure 1.5 M sulfuric acid solution

Table XXI: Analyzes of the organic phases after contact of the solvents charged with a

pure 1.5 M sulfuric acid solution

As a reminder, the material balance calculated is generally checked for all elements analyzed to within 5%.

The results of the tests carried out with an aqueous solution constituted by pure sulfuric acid which are exposed in Tables XX and XXI show that a washing with 1.5 M pure sulfuric acid makes it possible: to limit the uranium loss except for tests K and M for which the concentration of uranium in the aqueous phase is greater than 100 mg / L; to eliminate only a very small proportion of the iron contained in the loaded solvents, except for the test M.

The solvents were then washed with a sulfuric acid solution of the same acidity (1.5 M) but containing uranium, that is to say a solution corresponding to that used in the process according to the invention. invention.

The results of these tests are given in Tables XXII and XXIII.

TABLE XXII: Analyzes of the aqueous phases after contact of the solvents charged with a 1.5 M sulfuric acid solution containing uranium

Table XXIII: Analyzes of the organic phases after contact of the solvents charged with a 1.5 M sulfuric acid solution containing uranium

For the record, again, the material balance calculated is generally checked for all elements analyzed to 5%.

The results of the tests show that washing with 1.5 M pure sulfuric acid containing uranium, in accordance with the process of the invention, makes it possible to virtually eliminate, in one contact, the iron contained in the charged solvents. for all tests with very good yields for tests I, J, and M.

Conclusion of examples 6, 7, and 8.

The deferrisation yields are shown in FIG. 3 for all the tests of Examples 6, 7 and 8 as a function of the aqueous iron removal solutions used, namely the solution of 1.5 M pure sulfuric acid (which does not is not in accordance with the aqueous deferrisation solution used in the process of the invention) which constitutes the reference aqueous solution, and the solution of 1.5 M sulfuric acid containing uranium at the rate of 40 g / L which is in accordance with the aqueous deferrisation solution used in the process of the invention). The evolution of these yields (FIG. 3) clearly shows a significant gain when the washing of the loaded solvent is carried out in the presence of uranium for all the tests.

Indeed, the de-ironing yields obtained in a contact are generally less than 20% in the case of the reference aqueous solution (pure solution of sulfuric acid), except for the D and M tests with deferrisation efficiencies of the order of 80 and 50% respectively.

The deferrisation yields obtained in one contact are 90% in the case of the uraniferous sulfuric acid solution, except for tests B and H for which the yield is of the order of 70%.

These results clearly show that the process according to the invention, which uses an aqueous deferrisation solution containing uranium, can be successfully used with all of the charged solvents, whether these solvents contain pure or mixed organophosphorus extractants. synergistic and regardless of the matrix of the attack liquor which made it possible to obtain these charged solvents.

Claims (25)

1. A process for separating iron from an initial liquid organic phase containing uranium and iron, in which the initial liquid organic phase is brought into contact with an aqueous solution called aqueous ironing solution, whereby the iron passes into the aqueous solution to form a final aqueous liquid phase, and the uranium remains in the initial liquid organic phase to form a final liquid organic phase called de-ironed organic phase; said method being characterized in that the aqueous deferrisation solution contains an inorganic acid and uranium. 2. The method of claim 1, wherein the initial liquid organic phase comprises an organic extraction system comprising an organic extractant or a mixture of organic extractant (s), diluted in a non-reactive and immiscible organic diluent. with water. 3. The method of claim 2, wherein the organic extraction system comprises an extractant selected from organophosphorus compounds and mixtures thereof. 4. The method of claim 3, wherein the extraction system comprises an extractant selected from acidic organophosphorus compounds, bifunctional organophosphorus compounds, neutral phosphine oxides such as trialkylphosphine oxides, and mixtures thereof. The process of claim 4, wherein the extraction system comprises mixing an acidic organophosphorus compound and a phosphine neutral oxide. 6. Process according to any one of the preceding claims, in which the extraction system comprises an extractant which corresponds to the general formula (I) below: m represents an integer equal to 0.1 or 2; R1 and R2, which may be identical or different, represent a hydrocarbon group, saturated or unsaturated, linear or branched, comprising from 6 to 12 carbon atoms; r3 represents: - a hydrogen atom; a hydrocarbon group, saturated or unsaturated, linear or branched, comprising from 1 to 12 carbon atoms and optionally one or more heteroatoms; a hydrocarbon group, saturated or unsaturated, monocyclic, comprising from 3 to 8 carbon atoms and optionally one or more heteroatoms; or - a monocyclic aryl or heteroaryl group; or R2 and R3 together form a - (CH2) n- group wherein n is an integer from 1 to 4; R4 represents a hydrocarbon group, saturated or unsaturated, linear or branched, comprising from 2 to 8 carbon atoms, or a monocyclic aromatic group; while R5 represents a hydrogen atom or a hydrocarbon group, saturated or unsaturated, linear or branched, comprising from 1 to 12 carbon atoms. 7. Process according to claim 6, in which the extractant of formula (I) corresponds to the following particular formula (I-a): in which: m, R1, R4 and R5 are as defined in claim 6; R2 represents a hydrocarbon group, saturated or unsaturated, linear or branched, comprising from 6 to 12 carbon atoms; while r3 represents: - a hydrogen atom; a hydrocarbon group, saturated or unsaturated, linear or branched, comprising from 1 to 12 carbon atoms and optionally one or more heteroatoms; a hydrocarbon group, saturated or unsaturated, monocyclic comprising from 3 to 8 carbon atoms and optionally one or more heteroatoms; or - a monocyclic aryl or heteroaryl group. The process according to claim 6, wherein the extractant of formula (I) has the particular formula (I-b): wherein m, n, R 1, R 4 and R 5 are as defined in claim 6. 9. Process according to any one of the preceding claims, in which the initial organic phase contains from 0.5 g / l to 10 g / l of uranium and from 0.1 to 10 g / l of iron. 10. Process according to any one of the preceding claims, in which the inorganic acid of the aqueous de-ironing solution is chosen from sulfuric acid, nitric acid, hydrochloric acid and phosphoric acid, and mixtures thereof. . 11. The process according to claim 10, wherein the inorganic acid of the aqueous iron removal solution is sulfuric acid. 12. Process according to any one of the preceding claims, in which the quantity of uranium provided by the aqueous deferrisation solution is such that the concentration of uranium in the organic phase is at least 50%, preferably at least equal to at 60%, more preferably at least 70%, of the uranium concentration corresponding to the uranium saturation of the organic phase. 13. Process according to any one of the preceding claims, in which the concentration of uranium, expressed in [U], of the aqueous de-ironing solution is 0.10 to 800 g / l, preferably 30 to 50 g / l. for example 40 g / L. 14. Process according to any one of the preceding claims, in which, during the contacting, the initial organic phase is mixed with the aqueous de-ironing solution and then said mixture is decanted; preferably the contacting is carried out in a battery of 1 to 5 settling mixers, for example 3 mixer-decanters, fed in countercurrent flow in the initial organic phase and in aqueous de-ironing solution. 15. The process as claimed in any one of the preceding claims, in which the final aqueous phase contains more than 90% of the mass of iron contained in the initial organic phase, and less than 1% of the mass of uranium contained in the initial organic phase, and the déferrisée organic phase contains at least 90% of the mass of uranium contained in the initial organic phase, and less than 10% of the mass of iron contained in the initial organic phase. 16. A process for extracting uranium from a first aqueous solution of an inorganic acid containing uranium and iron, wherein at least the following successive steps are carried out: a) contacting the first aqueous solution of inorganic acid with a first organic liquid phase; whereby a second liquid organic phase containing a majority in mass of the quantity of uranium contained in the first aqueous solution of inorganic acid is obtained on the one hand, and a minority in mass of the quantity of iron contained in the first solution aqueous solution of inorganic acid, and secondly a second dewatered aqueous phase containing the inorganic acid, a minority in mass of the amount of uranium contained in the aqueous solution of inorganic acid, and a majority in mass of the amount iron contained in the aqueous solution of inorganic acid; b) separating the iron from the second liquid organic phase containing uranium and iron, bringing the second liquid organic phase into contact with a third aqueous solution called aqueous iron removal solution, whereby the iron passes into the an aqueous deferrisation solution for forming a final aqueous liquid phase, and the uranium remains in the second organic liquid phase to form a final liquid organic phase called de-ironed organic phase; said method being characterized in that the aqueous deferrisation solution contains an inorganic acid and uranium. The process according to claim 16, wherein the inorganic acid of the first aqueous inorganic acid solution of step a) is a solution of phosphoric acid, sulfuric acid or nitric acid. The method of any one of claims 16 and 17, wherein the first aqueous inorganic acid solution of step a) contains from 0.1 to 10 g / L iron, and from 0.05 to 10 g / L of uranium. 19. Process according to any one of claims 16 to 18, in which the first aqueous solution of inorganic acid is a uraniferous aqueous solution of phosphoric acid, such as industrial phosphoric acid, resulting from the leaching, etching, of a natural phosphate ore, generally based on apatite, with sulfuric acid, a uraniferous aqueous solution of sulfuric acid or nitric acid resulting from the leaching, of a non-phosphate-treated uranium ore, by nonapatitic example, by sulfuric acid or nitric acid respectively. 20. Process according to any one of claims 16 to 19, wherein, in step a), the second organic phase obtained contains at least 90% by weight, for example from 95 to 100% by weight, of the amount. uranium contained in the first aqueous solution of inorganic acid (starting solution), and from 0.1 to 50% by weight of the amount of iron contained in the first aqueous solution of inorganic acid; and the second aqueous desuranium phase obtained contains the inorganic acid, from 0 to 10% by weight of the amount of uranium, and from 50 to 99.9%, for example from 80% to 90% by weight of the amount of iron contained in the first aqueous solution of inorganic acid (starting solution). 21. A process according to any one of claims 16 to 20, wherein the second organic phase obtained at the end of step a) contains from 0.5 to 10 g / l of uranium and from 0.1 to 10 g / L of iron, and the second aqueous phase obtained at the end of step a) contains 0 to 100 mg / L of uranium and 0.1 to 6 g / L of iron. 22. A method according to any one of claims 16 to 21, which further comprises a step c) wherein the de-ironed organic phase obtained in step b) is brought into contact with an aqueous solution of a complexing base; whereby one obtains on the one hand an aqueous phase loaded with uranium and on the other hand an organic phase free of uranium, and further containing said complexing base. 23. The method of claim 22, which further comprises a step d) wherein the uranium-free organic phase, further containing the complexing base obtained in step c), is brought into contact with the resulting aqueous phase. of step b) and neutralized, whereby one obtains firstly an organic phase consisting of the organic solvent which is returned in step a) and secondly an aqueous phase. 24. A process according to any one of claims 22 to 23 which further comprises a step e) in which the aqueous phase loaded with uranium obtained in step c) is brought into contact with a base such as sodium hydroxide. whereby a precipitate of uranate, such as sodium uranate, which is separated, and an aqueous solution which is sent to step c) after addition of a complexing base are obtained. 25. The process as claimed in claim 24, wherein all or part of the uranate precipitate, such as sodium uranate, obtained in step e) is dissolved in an inorganic acid such as sulfuric acid, and the resulting aqueous solution containing an inorganic acid and uranium is sent to step b) after possibly adjusting the inorganic acid concentration.