METHOD FOR SEPARATING IRON FROM AN ORGANIC PHASE CONTAINING URANIUM AND METHOD FOR EXTRACTING URANIUM FROM AN AQUEOUS SOLUTION OF MINERAL ACID CONTAINING URANIUM AND IRON
20180187290 · 2018-07-05
Inventors
Cpc classification
C22B60/0282
CHEMISTRY; METALLURGY
International classification
Abstract
The application relates to a method for separating iron from an initial liquid organic phase containing uranium and iron, wherein the initial liquid organic phase is contacted with an aqueous solution referred to as aqueous de-ironing solution, whereby the iron passes into the aqueous solution to form a final liquid aqueous phase, and uranium remains in the initial liquid organic phase to form a final liquid organic phase referred to as de-ironed organic phase. The method is characterised in that the aqueous de-ironing solution contains an inorganic acid and uranium, and does not contain iron. The application also relates to a method for extracting uranium from an aqueous solution of an inorganic acid containing uranium and iron.
Claims
1. Method for separating iron from an initial liquid organic phase containing uranium and iron, wherein the initial liquid organic phase is contacted with an aqueous solution referred to as aqueous de-ironing solution, whereby the iron passes into the aqueous solution to form a final liquid aqueous phase, and uranium remains in the initial liquid organic phase to form a final liquid organic phase referred to as de-ironed organic phase; said method being characterised in that the aqueous de-ironing solution contains an inorganic acid and uranium, and does not contain iron.
2. Method according to 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 an organic diluent, non-reactive and non-miscible with water.
3. Method according to claim 2, wherein the organic extraction system comprises an extractant selected from organophosphorous compounds and mixtures thereof.
4. Method according to claim 3, wherein the organic extraction system comprises an extractant selected from acid organophosphorous compounds such as dialkylphosphoric acids, bifunctional organophosphorous compounds, neutral phosphine oxides such as trialkylphosphine oxides, and mixtures thereof.
5. Method according to claim 4, wherein the extraction system comprises the mixture of an acid organophosphorous compound and of a neutral phosphine oxide.
6. Method according to claim 2, wherein, the extractant system comprises as extractant a compound which corresponds to the following general formula (I): ##STR00005## wherein: m is a whole number equal to 0, 1 or 2; R.sup.1 and R.sup.2, identical or different, are a hydrocarbon group, saturated or unsaturated, linear or branched, comprising from 6 to 12 carbon atoms; R.sup.3 is: 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 monocyclic hydrocarbon group, saturated or unsaturated, comprising from 3 to 8 carbon atoms and optionally one or more heteroatoms; or a monocyclic aryl or heteroaryl group; or instead R.sup.1 and R.sup.3 together form a (CH.sub.2).sub.n group wherein n is a whole number ranging from 1 to 4; R.sup.4 is a hydrocarbon group, saturated or unsaturated, linear or branched, comprising from 2 to 8 carbon atoms, or a monocyclic aromatic group; whereas R.sup.5 is a hydrogen atom or a hydrocarbon group, saturated or unsaturated, linear or branched, comprising from 1 to 12 carbon atoms.
7. Method according to claim 6, wherein the compound of formula (I) corresponds to the following specific formula (I-a): ##STR00006## wherein: m, R.sup.4 and R.sup.5 are as defined in claim 6; R.sup.2 is a hydrocarbon group, saturated or unsaturated, linear or branched, comprising from 6 to 12 carbon atoms; whereas R.sup.3 is: 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 monocyclic hydrocarbon group, saturated or unsaturated, comprising from 3 to 8 carbon atoms and optionally one or more heteroatoms; or a monocyclic aryl or heteroaryl group.
8. Method according to claim 6, wherein the compound of formula (I) corresponds to the specific formula (I-b): ##STR00007## wherein m, n, R.sup.4 and R.sup.5 are such as defined in claim 6.
9. Method according to claim 1, wherein 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. Method according to claim 1, wherein the inorganic acid of the aqueous de-ironing solution is selected from sulphuric acid, nitric acid, hydrochloric acid, phosphoric acid, and mixtures thereof.
11. Method according to claim 10, wherein the inorganic acid of the aqueous de-ironing solution is sulphuric acid.
12. Method according to claim 1, wherein the quantity of uranium provided by the aqueous de-ironing solution is such that the concentration of uranium in the organic phase is at least equal to 50%, preferably at least equal to 60%, further preferably at least equal to 70%, of the concentration of uranium corresponding to saturation of the organic phase with uranium.
13. Method according to claim 1, wherein 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.
14. Method according to claim 1, wherein, during the contacting the initial organic phase is mixed with the aqueous de-ironing solution then said mixture is decanted, wherein the contacting is carried out in a battery of 1 to 5 mixers-decanters, counter-current supplied with the initial organic phase and with the aqueous de-ironing solution.
15. Method according to claim 1, wherein the final aqueous phase contains more than 90% of the weight of iron contained in the initial organic phase, and less than 1% of the weight of uranium contained in the initial organic phase, and the de-ironed organic phase contains at least 90% of the weight of uranium contained in the initial organic phase, and less than 10% of the weight of iron contained in the initial organic phase.
16. Method 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) the first aqueous solution of inorganic acid is contacted with a first liquid organic phase; whereby are obtained, on the one hand, a second liquid organic phase containing a majority by weight of the quantity of uranium contained in the first aqueous solution of inorganic acid, and a minority by weight of the quantity of iron contained in the first aqueous solution of inorganic acid and, on the other hand, a second desuraniated aqueous phase containing the inorganic acid, a minority by weight of the quantity of uranium contained in the aqueous solution of inorganic acid, and a majority by weight of the quantity of iron contained in the aqueous solution of inorganic acid; b) the iron is separated from the second liquid organic phase containing uranium and iron, by contacting the second liquid organic phase with a third aqueous solution referred to as aqueous de-ironing solution, whereby the iron passes into the aqueous de-ironing solution to form a final liquid aqueous phase, and uranium remains in the second liquid organic phase to form a final liquid organic phase referred to as de-ironed organic phase; said method being characterised in that the aqueous de-ironing solution contains an inorganic acid and uranium, and does not contain iron.
17. Method according to claim 16, wherein the inorganic acid of the first aqueous solution of inorganic acid of step a) is a solution of phosphoric acid, sulphuric acid or nitric acid.
18. Method according to claim 16, wherein 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.
19. Method according to claim 16, wherein the first aqueous solution of inorganic acid is an aqueous uranium bearing solution of phosphoric acid, such as industrial phosphoric acid, coming from the lixiviation, attack, of a natural phosphate ore, generally based on apatite, by sulphuric acid, or an aqueous uranium bearing solution of sulphuric acid or nitric acid coming from the lixiviation, attack, of a non-phosphate uranium bearing ore, for example non-apatite based, respectively by sulphuric acid or nitric acid.
20. Method according to claim 16, 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 quantity of uranium contained in the first aqueous solution of inorganic acid (starting solution), and from 0.1 to 50% by weight of the quantity of iron contained in the first aqueous solution of inorganic acid; and the second desuraniated aqueous phase obtained contains the inorganic acid, from 0 to 10% by weight of the quantity of uranium, and from 50 to 99.9%, for example from 80% to 90% by weight of the quantity of iron contained in the first aqueous solution of inorganic acid (starting solution).
21. Method according to claim 16, 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 from 0 to 100 mg/L of uranium and from 0.1 to 6 g/L of iron.
22. Method according to claim 16, which further comprises a step c) wherein the iron-removed organic phase obtained in step b) is contacted with an aqueous solution of a complexing base; whereby are obtained, 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. Method according to claim 22, which further comprises a step d) wherein the organic phase free of uranium, further containing the complexing base obtained in step c), is contacted with the aqueous phase coming from step b) and neutralised, whereby are obtained, on the one hand, an organic phase consisting of the organic solvent which is sent back to step a) and, on the other hand, an aqueous phase.
24. Method according to claim 22, which further comprises a step e) wherein the aqueous phase loaded with uranium obtained in step c), is contacted with a base such as sodium hydroxide, whereby an uranate precipitate, such as sodium uranate precipitate, which is separated, and an aqueous solution which is sent to step c) after addition of a complexing base, are obtained.
25. Method according to 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 sulphuric acid, and the aqueous solution obtained containing an inorganic acid and uranium is sent to step b) after having optionally adjusted the concentration of inorganic acid.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0173]
[0174] It should be noted that all the indications given in
[0175]
[0176] On the Y-axis is given the de-ironing (iron removal) yield of the solvent (in %) and on the X-axis is given the time (in min.).
[0177]
DETAILED DESCRIPTION OF PARTICULAR EMBODIMENTS
[0178] The detailed description that is made relates to one embodiment of the method according to the invention, for extracting uranium from an aqueous solution of mineral acid, containing uranium and iron, in which the aqueous solution of mineral acid is an aqueous solution of phosphoric acid containing uranium and iron.
[0179] It is clearly obvious that, subject to some minor adaptations within the reach of the man skilled in the art, the method described hereafter may easily be implemented with aqueous solutions of other mineral acids such as sulphuric acid or nitric acid, containing uranium and iron.
[0180] The aqueous solution of phosphoric acid containing uranium and iron which is treated by the method according to the invention, referred to as starting aqueous solution of phosphoric acid (1), generally has a concentration expressed in P.sub.2O.sub.5 from 26% to 32% by weight, preferably from 28% to 32% by weight, for example from 28% to 30% by weight expressed in P.sub.2O.sub.5.
[0181] The aqueous solution of phosphoric acid treated by the method according to the invention generally contains from 0.05 to 1 g/L of uranium, notably from 0.08 to 0.4 g/L of uranium (expressed in [U]).
[0182] The uranium in this aqueous solution is generally in solution in the form of U(VI) and U(IV), the latter having to be the subject of a prior step of oxidation into U(VI).
[0183] The aqueous solution of phosphoric acid treated by the method according to the invention generally contains from 0.1 to 10 g/L of iron, notably from 1 to 6 g/L of iron.
[0184] This aqueous solution is generally an aqueous solution, known as attack solution, obtained during the attack of phosphate ores by sulphuric acid.
[0185] Before being treated by the method according to the invention, the phosphoric acid solution containing uranium and iron may undergo one or more pre-treatment steps (2), notably a step of flash cooling, then a Solid/Liquid separation step, then a step of oxidation for example by hydrogen peroxide.
[0186] The cooling step makes it possible for example to cool the attack solution, which is hot.
[0187] The Solid/Liquid separation step makes it possible to separate the gypsum in super saturation in the solution.
[0188] The oxidation step, for example by hydrogen peroxide or by another oxidant such as NaClO.sub.3, makes it possible to oxidise uranium in the form of U (IV) into uranium in the form of U (VI).
[0189] According to the invention, in the first step or step a) also called extraction step (3), of the method according to the invention, the aqueous solution of phosphoric acid (1) is placed in contact with an organic extraction solvent (4) comprising a single extractant or instead a synergistic mixture of extractants, diluted in an organic diluent, non-reactive and non-miscible with water.
[0190] Synergistic mixture of extractants is taken to mean that this mixture has extractive properties higher than or even much higher than the extractive properties obtained by the simple addition of the extractive properties of each of the extractants which constitute the mixture of extractants.
[0191] Examples of such extractants, and of such synergistic mixtures of extractants, are known to the man skilled in the art in this technical field and are given for example in documents [1] to [4] and documents FR-A-2 442 796, FR-A-2 459 205, FR-A-2 494 258, and EP-A1-053 054 cited above, to the description of which reference may be made in this respect.
[0192] Preferred extractants used alone are Di.sub.2EHPA, preferably at a concentration of 0.5 M.
[0193] Other preferred extractants used alone are the bifunctional extractants of document [4] described above, such as DEHCNPB, preferably at a concentration of 0.1 M to 0.5 M.
[0194] Synergistic mixtures of extractants may consist for example of a neutral phosphine oxide and of an acid-organophosphorous compound, in particular a mixture of a dialkylphosphoric acid and of a trialkylphosphine oxide.
[0195] Preferably, the acid-organophosphorous compound of the mixture, such as a dialkylphosphoric acid, is selected from bis 2-ethylhexyl phosphoric acid (Di.sub.2EHPA), bis dibutoxy 1,3 propyl 2 phosphoric acid (BIDIBOPP) and bis dihexyloxy 1,3 propyl 2 phosphoric acid (BIDIHOPP); and the neutral phosphine oxide is selected from trioctylphosphine oxide (TOPO) and di-n-hexyl octyl methoxy phosphine oxide (DinHMOPO).
[0196] Preferred extractant mixtures of this type are the following: [0197] TOPO/Di.sub.2EHPA; [0198] TOPO/BIDIBOPP; [0199] TOPO/BIDIHOPP; [0200] DinHMOPO/Di.sub.2EHPA; [0201] DinHMOPO/BIDIBOPP; [0202] DinHMOPO/BIDIHOPP.
[0203] A particularly preferred synergistic extractant mixture is a mixture of D.sub.2EHPA and TOPO, preferably a mixture of 0.5 M D.sub.2EHPA and 0.125 M TOPO.
[0204] Another synergistic mixture of extractants is a mixture of D.sub.2EHPA and TBP, preferably a mixture of 0.2 M D.sub.2EHPA and 0.2 M TBP: this is the mixture used in the DAPEX method.
[0205] The organic diluent, non-miscible and non-reactive with water, is generally selected from liquid hydrocarbons.
[0206] These liquid hydrocarbons may be selected from aromatic hydrocarbons such as benzene, aliphatic hydrocarbons such as n-heptane and n-octane, and mixtures thereof. A mixture of hydrocarbons that is suitable as diluent according to the invention is kerosene.
[0207] Aliphatic kerosenes, such as the products available under the denomination ShellSol, may thus be suitable for use in the organic diluent.
[0208] Other mixtures of hydrocarbons that are suitable as diluent according to the invention are the products available under the denomination SANE such as SANE IP 185.
[0209] This extraction step may be carried out in static mode or in dynamic mode.
[0210] This extraction step may be carried out in any suitable extraction apparatus, for example in one or more mixers-decanters, and/or in one or more agitated or pulsed columns.
[0211] The man skilled in the art may easily determine the number of suitable theoretical stages that the extraction apparatus has to comprise to carry out the extraction.
[0212] Generally, this extraction step is carried out with a battery of mixers-decanters in dynamic counter-current operation, that is to say with the organic phase and the aqueous phase circulating in counter-current to each other from the first, respectively the last, of the mixers-decanters, up to the final respectively first, of the mixers-decanters.
[0213] The number of mixers-decanters may range from 1 to 10, notably from 1 to 5.
[0214] Preferably, 5 mixers-decanters, in other words 5 mixing-decanting stages are implemented.
[0215] The supply with organic phase may then take place for example in stage 1, whereas the supply with aqueous phase takes place for example in stage 5.
[0216] The overall O/A ratio for all of the battery of mixers-decanters, all of the stages, is generally 1/6 i.e. 0.1667, to 1/8 i.e. 0.1250, depending on the initial concentration of uranium in the starting solution of phosphoric acid.
[0217] It should be recalled that O/A designates the ratio of the flow rate of organic phase to the flow rate of aqueous phase.
[0218] This step of the method is generally carried out at a temperature from 10 C. to 60 C., notably 10 C. to 50 C. It may be carried out at room temperature, for example 20 C. to 25 C., but it is preferably carried out at a temperature from 30 C. to 35 C., which makes it possible to obtain a relatively rapid kinetic for extracting uranium.
[0219] The mixing time per mixer is generally from 0.5 to 5 minutes, preferably 2 minutes, when the mixing is carried out within the preferred range of temperatures indicated above.
[0220] The dwell time in the decanters, per stage, is generally from 2 to 10 minutes, preferably 5 minutes, when the mixing is carried out within the preferred range of temperatures indicated above.
[0221] The yield for extracting uranium during this step is generally greater than or equal to 95%, preferably greater than or equal to 97%, further preferably greater than or equal to 98%.
[0222] Uranium leakage is generally less than or equal to 10 mg/L, preferably less than or equal to 5 mg/L, further preferably less than or equal to 3 mg/L.
[0223] At the end of this extraction step (3), are obtained, on the one hand, an organic phase (5) which contains from 90 to 100% by weight, for example 95% by weight, of the quantity of uranium contained in the aqueous solution of phosphoric acid (starting solution), and from 0.1 to 10% by weight of iron contained in the aqueous solution of phosphoric acid; and, on the other hand, a desuraniated (uranium-removed) 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).
[0224] The organic phase (5) obtained at the end of step a) of extraction (3) thus generally contains from 0.5 to 10 g/L of uranium and from 0.1 to 10 g/L of iron whereas the desuraniated (uranium-removed) aqueous phase (6) obtained at the end of step a) thus generally contains from 0 to 100 mg/L of uranium and from 0.1 to 6 g/L of iron.
[0225] The uranium-removed aqueous phase (6) may be optionally subjected to one or more post-treatments (7) selected for example from a coalescence treatment and a treatment with activated carbon in order notably to eliminate organic matters (coming from scavenging of the organic phase in the aqueous phase), and the phosphoric acid thereby recovered, which has a concentration expressed in P.sub.2O.sub.5 from 26% to 32% by weight, preferably from 28% to 32% by weight, for example from 28% to 30% by weight, analogous to the starting phosphoric acid, may next be used for example in fertiliser production plants.
[0226] The organic phase (5) obtained at the end of step a) (3), or extraction step, generally has a high Fe/U ratio of the order of 0.1 to 1, notably 0.5.
[0227] Next, during a step b), or de-ironing step (step of iron removal) of the solvent (8) according to the invention, the organic phase (5) obtained in step a) is placed in contact with an aqueous de-ironing solution (9).
[0228] According to the invention, the aqueous de-ironing solution (9) contains an inorganic acid and uranium, and does not contain iron.
[0229] The inorganic acid of the aqueous de-ironing solution (9) may be selected from sulphuric acid, nitric acid, hydrochloric acid, phosphoric acid, and mixtures thereof.
[0230] The preferred inorganic acid of the aqueous de-ironing solution is sulphuric acid.
[0231] Advantageously, the concentration of inorganic acid of the aqueous de-ironing solution such as sulphuric acid is from 1 to 1.5 M.
[0232] The concentration of uranium of the aqueous de-ironing solution is preferably from 35 to 40 g/L, for example 40 g/L.
[0233] Indeed, at constant acidity the initial concentration of uranium constitutes a key parameter on the yields of selective de-ironing of the solvent.
[0234] The technical-economic optimum seems to be comprised in the aforementioned range of 35 to 40 g/L of uranium initially contained in the aqueous influent for an elimination of iron of the order of 90% in one contact.
[0235] Exhaustion (depletion) tests of the aqueous phase have also shown the absence of salting out of iron on the solvent and efficient uranium exhaustion generally in three successive contacts with contact times less than 5 minutes.
[0236] It has also been shown that the concept of selective de-ironing of the solvent by chemical displacement was valid whatever the acid, i.e. sulphuric, nitric, hydrochloric, or phosphoric.
[0237] This step of the method is generally carried out at a temperature from 10 C. to 50 C.
[0238] It may be carried out at room temperature, for example 20 C. to 25 C., but it is preferably carried out at a temperature from 40 C. to 45 C.
[0239] Indeed, the experimental results show a notable influence of the temperature on this step with a substantial gain in the mixing time necessary to attain the required performance.
[0240] As an example, the suitable contact time at 40 C. seems to be comprised between 5 and 10 minutes instead of the 30 minutes necessary at 20 C.
[0241] This step of de-ironing (iron removal step) (8) may be implemented in any suitable contacting apparatus, and be carried out in static mode or in dynamic mode.
[0242] Generally this step de-ironing (iron removal step) (8) is carried out with a battery of mixers-decanters in dynamic counter-current operation.
[0243] The number of mixers-decanters may range from 1 to 5.
[0244] Preferably, 3 mixers-decanters, in other words 3 mixing-decanting stages are implemented.
[0245] The supply with organic phase (5) takes place in stage 1, whereas the supply with aqueous phase (9) takes place in stage 3 which is also called super-stage.
[0246] The overall O/A ratio for all of the battery of mixers-decanters, all of the stages, is generally from 1/5 to 5/1.
[0247] A preferred overall O/A ratio is 1/1.
[0248] The contact time is generally of the order of 10 minutes for stage 3, that is to say for the aqueous supply stage, and 3 minutes for the two other stages.
[0249] The dwell time in the decanter is generally 5 minutes at the most.
[0250] In step b) (8) are obtained, on the one hand, an aqueous phase (10) containing from 50% to 90% of the iron contained in the organic phase (5) obtained in step a) and, on the other hand, a de-ironed (iron removed) 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. De-ironed, Iron-removed, from which iron has been removed, free of iron, not containing iron are generally taken to mean that this organic phase (11) contains less than 10 mg/L of iron, for example 5 mg/L of iron, or even 0 mg/L of iron.
[0251] The organic phase (11) obtained at the end of the de-ironing step (iron removal step) b) (8) thus generally contains from 0.5 to 60 g/L of uranium and from 0 to 10 mg/L of iron, whereas the desuraniated (uranium-removed) aqueous phase (10) obtained at the end of step b) thus contains generally from 0 to 1 g/L of uranium and from 0 to 2 g/L of iron. This aqueous phase (10) is an acid phase containing the inorganic acid described above.
[0252] The method according to the invention further generally comprises a step c), also called back extraction of uranium (12), in which the organic phase, de-ironed and loaded with uranium (11), obtained at the end of step b) of de-ironing of the solvent is contacted with an aqueous solution of a complexing base (13).
[0253] The complexing base may be selected from alkali metal carbonates, such as sodium carbonate, alkaline-earth metal carbonates, and ammonium carbonates.
[0254] The concentration of complexing base such as sodium carbonate of the aqueous solution is generally from 1 to 2 M, for example 1.5 M.
[0255] This step of back extraction (12) may be carried out in static mode or in dynamic mode. It may be carried out in any suitable extraction apparatus.
[0256] This step of back extraction (12) is generally carried out with a battery of mixers-decanters in dynamic counter-current operation.
[0257] The number of mixers-decanters may range from 1 to 5.
[0258] Preferably, 3 mixers-decanters, in other words 3 mixing-decanting stages are implemented.
[0259] The supply with organic phase (11) may take place, for example, in stage 1, whereas the supply with aqueous phase (13) may take place, for example, in stage 3.
[0260] The overall O/A ratio for all of the battery of mixers-decanters, all of the stages, is generally from 1/2 to 2/1, depending on the initial concentration of uranium in the starting organic phase.
[0261] A preferred overall O/A ratio is 1/1.
[0262] This step of back extraction of uranium (12) of the method is generally carried out at a temperature from 10 C. to 50 C.
[0263] It may be carried out at room temperature, for example 20 C. to 25 C., and a satisfactory separation of phases is obtained even at 25 C., but an increase in the operating temperature makes it possible to improve the performance.
[0264] The step of back extraction of uranium (12) is thereby carried out preferably at a temperature from 40 C. to 45 C., which makes it possible to obtain a relatively rapid kinetic of back extraction of uranium.
[0265] The mixing time is generally from 1 to 10 minutes, preferably 5 minutes, when the mixing is carried out within the preferred range of temperatures indicated above.
[0266] At the end of this step of back extraction of uranium (12) are obtained, on the one hand, an aqueous phase loaded with uranium (14) and, on the other hand, an organic phase (15) constituted by the organic solvent, free of uranium.
[0267] The aqueous phase loaded with uranium (14) generally contains from 5 to 80 g/L of uranium and from 0 to 100 mg/L of iron and the organic phase free of uranium (15) generally contains from 0 to 100 mg/L of uranium and from 0 to 10 mg/L of iron.
[0268] The method according to the invention further generally comprises a step d), referred to as step of acidification of the solvent (16), in which the organic phase free of uranium (15), further containing the complexing base coming from step c) (12)in other words the desuraniated (uranium-removed) solvent coming from the step of back extraction of uranium (12)is contacted with the aqueous phase (10) coming from step b), that is to say the step of de-ironing of the solvent (8). The acid concentration could optionally be adjusted if necessary.
[0269] This step of acidification of the solvent (16) may be carried out in static mode or in dynamic mode.
[0270] This step of acidification (16) may be carried out in any suitable contacting apparatus.
[0271] This step of acidification (16) is generally carried out with one mixer-decanter or a battery of mixers-decanters, for example from 1 to 8 mixers-decanters in dynamic counter-current operation.
[0272] Preferably, a single mixer-decanter, in other words a single mixing-decanting stage is implemented.
[0273] The overall O/A ratio for the single mixer-decanter, or for all of the battery of mixers-decanters, all of the stages, is generally from 1/5 to 5/1.
[0274] A preferred overall O/A ratio is 1/1.
[0275] This step of acidification (16) of the method according to the invention is generally carried out at a temperature from 10 C. to 50 C.
[0276] It may be carried out at room temperature, for example 20 C. to 25 C., but an increase in the operating temperature makes it possible to improve the performance.
[0277] The step of acidification (16) is thereby carried out preferably at a temperature from 40 C. to 45 C.
[0278] The mixing time is generally from 1 to 10 minutes per stage, preferably 5 minutes, when the mixing is carried out within the preferred range of temperatures indicated above.
[0279] At the end of this step of acidification of the solvent (16), are obtained, on the one hand, an organic phase (4) constituted by the organic solvent regenerated in acid form which is sent to step a) of extraction (3) and, on the other hand, an aqueous phase (17).
[0280] This aqueous phase (17) contains iron, for example at a level from 0 to 2 g/L, and the inorganic acid that was contained in the aqueous de-ironing solution implemented during the step of iron removal b) at a concentration of 1 to 1.5 M.
[0281] This aqueous phase (17) may be beneficiated. Thus, if the inorganic acid is sulphuric acid, this aqueous phase (17) may be recycled to a step of phosphate ore lixiviation (18).
[0282] The aqueous phase loaded with uranium (14) obtained at the end of the step of back extraction of uranium is generally treated in a step e), referred to as step of precipitation of uranate (19), in the course of which this aqueous phase loaded with uranium (14) is contacted with a base (20) such as sodium hydroxide whereby a uranate precipitate such as a sodium uranate precipitate is obtained, which is separated, and an aqueous solution free of uranium (21) is obtained which is sent back to step c) of back extraction of uranium (12) after a complexing base such as sodium carbonate has been added thereto.
[0283] The uranium contained in the aqueous phase loaded with uranium obtained at the end of the step of back extraction of uranium (12) may be in various forms.
[0284] If the complexing base is an alkali or alkaline-earth metal carbonate, such as sodium carbonate, then the uranium is in the form of uranyl tricarbonate of alkali or alkaline-earth metal, such as sodium uranyl tricarbonate.
[0285] The uranium is thus made to precipitate by addition of a base (20) such as sodium hydroxide, to the aqueous phase (14), for example at a temperature of 80 C. for a duration of 1 hour.
[0286] An uranate precipitate is thereby obtained, for example a sodium diuranate precipitate (SDU) or sodium uranate precipitate, if sodium hydroxide was used for the precipitation.
[0287] This uranate precipitate is separated by any suitable solid-liquid separation method, for example by filtration.
[0288] All or part (22) of this uranate precipitate, such as sodium uranate obtained in the step e) of precipitation (19), may be dissolved, during a step referred to as re-dissolution of the uranate (23), in an inorganic acid (24) such as sulphuric acid, at a pH for example of 3 to 3.5.
[0289] The inorganic acid (24) used for the dissolution may be selected from the same acids as those already mentioned for the aqueous de-ironing (iron removal) solution, namely, sulphuric acid, nitric acid, hydrochloric acid, phosphoric acid, and mixtures thereof.
[0290] The preferred inorganic acid is sulphuric acid.
[0291] Following the dissolution of the uranate, a dissolution aqueous solution is thereby obtained containing an inorganic acid such as sulphuric acid, and uranium in the form of uranyl sulphate.
[0292] All or part of this dissolution aqueous solution (25) may be sent to step b) (8) to serve as aqueous de-ironing solution (9) after an optional adjustment of the acid concentration to obtain the desired acid concentration for the uranium bearing acid aqueous de-ironing solution (9).
[0293] Thus, an input of inorganic acid (26), such as sulphuric acid, could be made on the pipe carrying the dissolution aqueous solution (25).
[0294] As has been specified above, the concentration of inorganic acid of the aqueous de-ironing solution (9) such as sulphuric acid is in fact advantageously from 1 to 1.5 M, and the concentration of uranium of the aqueous de-ironing solution is advantageously from 35 to 40 g/L, for example 40 g/L.
[0295] All or part (27) of the uranate precipitate may be placed in vessels such as drums during a step referred to as uranate drumming (28).
[0296] All or part (29) of the dissolution aqueous solution of the uranate may optionally be sent to an optional step of precipitation (30) by hydrogen peroxide (31), generally carried out at room temperature, at the end of which a precipitate of uranium peroxide UO.sub.4 (32) is obtained, which may be optionally separated by any suitable solid-liquid separation method, for example by filtration.
[0297] The precipitate of uranium peroxide may then be placed in vessels such as drums during a step referred to as UO.sub.4 drumming (33).
[0298] In total, the method according to the invention implements for example twelve mixing-decanting stages.
[0299] The invention will now be described with reference to the following examples, given for indicative purposes and non-limiting.
EXAMPLES
Example 1
[0300] In this example, the influence is shown of the initial concentration of uranium in the de-ironing solution used in the method according to the invention for separating iron and from a liquid organic phase.
[0301] In order to study the influence of the initial concentration of uranium in the aqueous de-ironing solution, laboratory-scale tests were carried out in separating funnels in the following conditions: [0302] Aqueous iron removal solution (Aqueous phase A): 3 M H.sub.2SO.sub.4 containing uranium at a variable concentration; [0303] Initial organic phase (Organic phase O), solvent loaded with uranium and with iron: Synergistic mixture of 0.5 M D.sub.2EHPA and 0.125 M TOPO in the diluent Isane IP185, loaded with uranium [U]=1200 mg/L and with iron [Fe]=526 mg/L; [0304] Ratio of O/A phases=1/1. [0305] Room temperature (22 C.). [0306] Variable contact time.
[0307] The kinetics of back extraction of uranium and iron from the solvent are determined by analytical monitoring of the concentrations in the aqueous phase after contact with the solvent.
[0308] The results of these tests are presented in Table I below.
TABLE-US-00001 TABLE I Kinetic monitoring of the concentrations of uranium and iron after contact of the loaded solvent with a 3M H.sub.2S0.sub.4 solution containing uranium at a variable concentration (O/A = 1/1, room temperature). Aqueous phase Organic phase U.sub.initial Time U Fe U Fe Solvent iron (g/L) (min) (mg/L) (mg/L) (mg/L) (mg/L) removal 0 0 0 0 1,200 526 0.0% 5 1 27 1,199 499 5.2% 10 1 77 1,199 450 14.6% 15 1 108 1,199 418 20.6% 30 1 183 1,199 343 34.7% 45 1 200 1,199 326 38.1% 60 1 214 1,199 312 40.8% 50 0 4,7357 0 1,200 526 0.0% 5 6,138 140 42,420 386 26.7% 10 5,970 318 42,588 208 60.4% 15 5,681 400 42,877 126 76.1% 30 5,632 482 42,926 44 91.6% 45 5,517 480 43,041 46 91.2% 60 5,652 489 42,905 37 93.0% 60 0 57,387 0 1,200 526 0.0% 5 13,936 128 44,652 398 24.4% 10 13,303 307 45,285 219 58.4% 15 13,177 416 45,411 110 79.1% 30 12,914 472 45,673 54 89.7% 45 12,763 492 45,824 34 93.6% 60 13,074 491 45,513 35 93.4% 70 0 66,626 0 1,200 526 0.0% 5 20,713 142 47,113 385 26.9% 10 20,512 331 47,315 195 62.8% 15 20,137 411 47,689 115 78.2% 30 20,074 475 47,753 52 90.2% 45 19,958 478 47,868 48 90.9% 60 20,230 478 47,596 48 90.9% 100 0 95,757 0 1,200 526 0.0% 5 43,987 125 52,971 401 23.8% 10 43,346 330 53,611 197 62.6% 15 43,049 388 53,908 138 73.8% 30 42,722 457 54,235 69 86.9% 45 42,819 459 54,139 67 87.2% 60 43,330 457 53,627 69 86.9%
[0309] These experimental results show a marked increase in the yield of iron removal from the moment that the aqueous phase initially contains, in accordance with the method according to the invention, uranium in high concentrations.
[0310] Furthermore, the kinetic of elimination of iron seems to be of the order of 30 minutes, the time for which the yield of de-ironing of the solvent reaches a plateau above 90% in one contact, except for a pure sulphuric solution for which the kinetic seems to be slower.
Example 2
[0311] In order to complete the preceding data obtained in example 1, complementary, further laboratory-scale tests were carried out in separating funnels in the following conditions: [0312] Aqueous de-ironing solution (Aqueous phase A): 3 M H.sub.2SO.sub.4 containing uranium at a variable concentration; [0313] Initial organic phase (Organic phase O), solvent loaded with uranium and with iron: Synergistic mixture of 0.5 M Di.sub.2EHPA and 0.125 M TOPO in the diluent Isane IP185, loaded with uranium [U]=1093 mg/L and with 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); [0314] Ratio of O/A phases=1/1; [0315] Room temperature (22 C.).
[0316] The kinetics of back extraction of uranium and iron from the solvent are determined by analytical monitoring of the concentrations in the aqueous phase after contact with the solvent.
[0317] The results of these complementary, further tests are presented in Table II below.
TABLE-US-00002 TABLE II Kinetic monitoring of the concentrations of uranium and iron after contact of the loaded solvent with a 3M H.sub.2S0.sub.4 solution containing uranium at a variable concentration (O/A = 1/1, room temperature) during the complementary tests. Aqueous phase Organic phase U.sub.initial Time U Fe U Fe Solvent iron (g/L) (min) (mg/L) (mg/L) (mg/L) (mg/L) removal 10 0 9,965 0 1,093 437 0.0% 5 21 58 11,037 379 13.3% 15 21 126 11,037 311 28.9% 30 19 171 11,039 266 39.2% 120 21 249 11,037 188 57.0% 20 0 21,208 0 1,093 437 0.0% 5 103 87 22,198 351 19.8% 15 64 117 22,237 320 26.8% 30 69 245 22,233 192 56.1% 120 72 282 22,229 155 64.5% 30 0 31,912 0 1,093 437 0.0% 5 483 124 32,522 314 28.3% 15 350 259 32,654 178 59.2% 30 323 322 32,682 115 73.6% 120 345 368 32,660 69 84.2% 35 0 36,698 0 1,093 437 0.0% 120 1,284 375 36,507 63 85.6% 40 0 41,485 0 1,093 437 0.0% 5 2,842 180 39,736 257 41.2% 15 2,768 313 39,810 125 71.5% 30 2,553 383 40,025 54 87.6% 120 2,541 390 40,037 47 89.2%
[0318] The complementary tests of this example reveal a notable influence of the initial concentration of uranium in the de-ironing solution, notably for the low concentrations selected. Thus, the yield of iron removal (de-ironing yield) increases with the concentration of uranium while reducing the kinetic of iron removal.
[0319] Furthermore,
[0320] This figure shows, moreover, two distinct populations: [0321] when the concentration of uranium is comprised between 0 and 30 g/L, for which the yield of iron removal increases and the time to reach kinetic equilibrium decreases; [0322] when the concentration of uranium is comprised between 35 and 100 g/L, for which the curves are superimposed, not just from the thermodynamic viewpoint (de-ironing yield, yield of iron removal) but also from the kinetic viewpoint (plateau reached at the end of 30 minutes at room temperature); [0323] finally, the kinetic for extracting uranium seems for its part relatively rapid with an optimum comprised between 5 and 10 minutes at room temperature.
Example 3
[0324] In this example, tests are carried out in which the method according to the invention for separating iron from a liquid organic phase is implemented in a battery of 3 mixers-decanters (MD) in dynamic counter-current operation.
[0325] The conditions for these tests are the following: [0326] Aqueous de-ironing solution (Aqueous phase A): 3 M H.sub.2SO.sub.4 ([H+]=5.9 mol/L) containing 39.76 g/L of uranium, with a supply flow rate of 120 mL/h; [0327] Initial organic phase (Organic phase O), solvent loaded with uranium and iron: Synergistic mixture of 0.5 M D.sub.2EHPA and 0.125 M TOPO in the diluent Isane IP185, loaded with uranium [U]=994 mg/L and with iron [Fe]=307 mg/L, with a supply flow rate of 120 mL/h; [0328] Useful volume: 50 ml mixer and 200 ml decanter for stage 3; [0329] Useful volume: 30 ml mixer and 200 ml decanter for stages 1 and 2; [0330] Supply with organic phase in stage 1; [0331] Supply with aqueous phase in stage 3; [0332] Ratio of O/A phases=1/1; [0333] Temperature: 40 C. with double-walled mixers and decanters and a heat exchanger containing glycol as heat-transfer fluid.
[0334] At the end of 30 hours of operation, samples of the organic phases and of the aqueous phases are taken to quantify the concentration profiles on each of the 3 stages as well as the yield of iron removal (de-ironing yield) from the balance on the organic phases.
[0335] The results of these tests are presented in Table III below.
TABLE-US-00003 TABLE III Concentration profiles of uranium and iron in each MD stage. Stage 1 (*) Stage 2 Stage 3 (**) Influent Contact: 7.5 min Contact: 7.5 min Contact: 12.5 min Aqueous phase [U] (g/L) 39.76 0.68 21.82 33.00 [Fe] (mg/L) 0 328 116 22 Organic phase [U] (g/L) 0.994 22.13 30.90 38.94 [Fe] (mg/L) 307 114 32 5 Iron removal 62.9% 89.6% 98.2% Fe/U by weight ~31% 0.515% 0.104% 0.014% (*) Organic phase supply in stage 1 (**) Aqueous phase supply in stage 3
Example 4
[0336] In this example, solvents or extraction systems loaded with uranium are prepared by placing the attack liquors loaded with uranium in contact with solvents.
[0337] In a first step, a sulphuric attack liquor or solution, a phosphoric attack liquor or solution, and a nitric attack liquor or solution are prepared.
[0338] The phosphoric and sulphuric attack liquors are prepared from industrial liquors, juices.
[0339] Thus, the sulphuric attack liquor comes from an ore lixiviation liquor, juice doped with vanadium and with zirconium (see Table IV).
TABLE-US-00004 TABLE IV Composition and characterisation of the sulphuric attack liquor Element Concentration (mg/L) Experimental data U 4,430.0 Specific gravity (20 C.) 1.102 Fe 8,187.9 [H*] (M) 0.06 Mo 471.7 E.sub.h (mV) (Ref. Ag/AgCl) 505 V 1,179.1 Zr 3,085.6
[0340] The phosphoric attack liquor comes from an American industrial phosphoric acid SIMPLOT diluted twice and doped with uranium (see Table V).
TABLE-US-00005 TABLE V Composition and characterisation of the phosphoric attack liquor Element Concentration (mg/L) Experimental data U 1,239.1 Specific gravity (20 C.) 1.158 Fe 2,802.4 [H*] (M) 0.96 Mo 4.7 E.sub.h (mV) (Ref. Ag/AgCl) 490 V 262.9 Zr 15.1
[0341] The nitric attack liquor was, for its part, prepared from nitric acid, uranyl nitrate and iron sulphate (III) (see Table VI).
TABLE-US-00006 TABLE VI Composition and characterisation of the nitric attack liquor Element Concentration (mg/L) Experimental data U 4,698.5 Specific gravity (20 C.) 1.163 Fe 4,500.8 [H*] (M) 0.20 E.sub.h (mV) (Ref. Ag/AgCl) 695
[0342] The chemical analysis of the solutions shows that the sulphuric solution is highly loaded with impurities, notably iron, vanadium and zirconium.
[0343] On the other hand, the phosphoric and nitric solutions are only loaded with iron. Furthermore, the redox potential of the solutions thereby prepared shows that iron is mainly in ferric form (the redox potential of the solution being inherent to the pair iron(II)/iron(III)).
[0344] It should be recalled that the partition coefficient of iron(III) is higher than that of iron(II) on organophosphorous solvents.
[0345] In a second step, the solvents are prepared.
[0346] These solvents comprise an organic organophosphorous extractant or a mixture of organic organophosphorous extractant(s), diluted in an organic diluent, non-reactive and non-miscible with water, namely an aliphatic kerosene (ISANE IP 185).
[0347] The following extractants were chosen: [0348] D.sub.2EHPA (di-2-ethylhexylphosphoric acid) supplied by the Lanxess company. [0349] TOPO (trioctyl phosphine oxide) supplied by the Cytec company. [0350] TBP (tributyl phosphate). [0351] DEHCNPB (Butyl 1-(Diethylhexyl Carbamoyl) Nonyl Phosphonate).
[0352] With these extractants and the diluent ISANE IP 185, the following 5 solvents were prepared:
[0353] 0.5 M D.sub.2EHPA in ISANE.
[0354] 0.5 M D.sub.2EHPA+0.125 M TOPO (solvent of the Oak Ridge method) in ISANE.
[0355] 0.2 M D.sub.2EHPA+0.2 M TBP (solvent of the DAPEX method) in ISANE.
[0356] 0.1 M or 0.5 M DEHCNPB in ISANE.
[0357] In a third step, the solvents described above are contacted with the attack liquors prepared beforehand during the first step. The placing in contact is carried out for 30 minutes at room temperature (25 C.) with an O/A phase volume ratio of 1/1, the volume of the aqueous phase A and the organic phase each being 100 ml.
[0358] The various contacts tests carried out during this third step are described in table VII.
TABLE-US-00007 TABLE VII Description of the tests selected for this study Experiment Solvent Attack liquor A D.sub.2EHPA 0.5M + TOPO 0.125M Sulphuric B D.sub.2EHPA 0.5M C DEHCNPB 0.5M D DEHCNPB 0.1M E D.sub.2EHPA 0.2M + TBP 0.2M F DEHCNPB 0.5M Phosphoric G DEHCNPB 0.1M H D.sub.2EHPA 0.2M + TBP 0.2M L D.sub.2EHPA 0.5M + TOPO 0.125M I D.sub.2EHPA 0.5M + TOPO 0.125M Nitric J DEHCNPB 0.5M K D.sub.2EHPA 0.5M M D.sub.2EHPA 0.2M + TBP 0.2M
[0359] An analysis of the loaded solvents at the end of these first contacts was conducted with monitoring of the concentrations of uranium, iron, molybdenum, vanadium and zirconium (see Tables VIII to X).
[0360] It should be noted that problems of analytical reproducibility (mineralisation of the solvent and associated acquisition) did not make it possible to determine the concentration of zirconium in the loaded solvents. The trends will thus be drawn up on the basis of monitoring in aqueous phase for this element if need be.
TABLE-US-00008 TABLE VIII Composition of the solvents loaded from the sulphuric attack liquor Test A B C D E Solvent D.sub.2EHPA 0.5M D.sub.2EHPA 0.5M DEHCNPB 0.5M DEHCNPB 0.1M D.sub.2EHPA 0.2M TOPO 0.125M TBP 0.2M Specific gravity (20 C.) 0.812 0.804 0.825 0.779 0.792 [U] (mg/L) 3,032.8 2,665.0 2,482.4 3,781.3 3,235.3 [Fe] (mg/L) 1,177.4 1,234.2 1,122.0 246.9 407.9 [Mo] (mg/L) 289.3 218.4 253.3 177.6 295.4 [V] (mg/L) 203.8 162.4 344.9 30.4 137.8 [Zr] (mg/L)
[0361] The loaded solvents derived from the contacts with the sulphuric solution are globally loaded at 3 g/L of uranium, between 0.5 and 1 g/L of iron, 200 mg/L of molybdenum and vanadium.
[0362] It may be noted that the observed extraction performances between the systems 0.5 M DEHNCPB and 0.5 M D.sub.2EHPA are similar in the studied sulphuric medium.
[0363] Furthermore, it would seem that a reduction in the concentration of DEHCNPB leads to better uranium/impurities selectivity.
TABLE-US-00009 TABLE IX Composition of the solvents loaded from the phosphoric attack liquor Test F G H L Solvent DEHCNPB 0.5M DEHCNPB 0.1M D.sub.2EHPA 0.2M D.sub.2EHPA 0.5M TBP 0.2M TOPO 0.125M Specific gravity (20 C.) 0.822 0.776 0.787 0.804 [U] (mg/L) 938.7 951.4 780.7 918.4 [Fe] (mg/L) 1,537.1 274.7 61.4 699.7 [Mo] (mg/L) 3.5 2.4 <1 2.7 [V] (mg/L) 132.3 30.3 1.5 16.9 [Zr] (mg/L)
[0364] The loaded solvents derived from the contacts with the phosphoric solution are globally loaded with 1 g/L of uranium with variable concentrations of impurities, notably for iron and vanadium.
[0365] Molybdenum, for its part, is very little loaded in all of the 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.
[0366] Thus, the mixture D.sub.2EHPA/TBP seems to be the system the most selective to extraction in our conditions since the concentrations of iron, molybdenum and vanadium are very low.
[0367] Furthermore, a gain in selectivity is also obtained when the concentration of DEHCNPB is reduced.
TABLE-US-00010 TABLE X Composition of the solvents loaded from the nitric attack liquor Test I J K M Solvent D.sub.2EHPA 0.5M DEHCNPB 0.5M D.sub.2EHPA 0.5M D.sub.2EHPA 0.2M TOPO 0.125M TBP 0.2M Specific gravity (20 C.) 0.814 0.827 0.805 0.793 [U] (mg/L) 3,545.8 3,344.4 3,640.2 3,556.6 [Fe] (mg/L) 3,231.6 3,374.2 3,115.4 1,498.8
[0368] The solvents derived from the contacts with the nitric solution are globally loaded with 3 g/L of uranium and iron, apart from the system D.sub.2EHPA/TBP for which the concentration of iron is two times lower.
[0369] Furthermore, similar performances between the molecules D.sub.2EHPA and DEHCNPB are observed and it is noted that TOPO no longer here plays the role of synergy agent in a nitric matrix.
Example 5
[0370] In this example, aqueous solutions are prepared, referred to as aqueous de-ironing solutions, intended to be contacted with the loaded solvents prepared in example 4 with the aim of separating iron from these loaded organic solvents.
[0371] Two aqueous solutions are prepared (see Table XI): namely a 1.5 M solution of pure sulphuric acid (which does not comply with the aqueous de-ironing solution used in the method of the invention) which constitutes the reference aqueous solution, and a 1.5 M sulphuric acid solution containing uranium at a level of 40 g/L (in accordance with the aqueous de-ironing solution used in the method of the invention) which constitutes the aqueous solution under study.
[0372] The tests carried out with the reference solution (pure acid) will be identified by the number 1 following the letter designating the loaded solvent contacted with the aqueous solution, whereas the tests carried out with the solution in accordance with the method according to the invention will be identified by the number 2 following the letter designating the loaded solvent contacted with the aqueous solution.
TABLE-US-00011 TABLE XI Composition of the aqueous reagents used for the scrubbing of impurities from the loaded solvents Solution Specific gravity (20 C.) [H.sub.2SO.sub.4] (M) [U] (mg/L) Reference 1.093 1.57 <1 Study 1.146 1.54 40,454
Example 6
[0373] In this example, purification tests are carried out on loaded solvents prepared in example 4 from the sulphuric attack liquor (Table VIII, tests A to E), by means of the aqueous solution in accordance with that used in the method according to the invention and of the comparative solution prepared in example 5.
[0374] The conditions for these tests are the following: [0375] Use of dedicated separating funnels and mechanical stirrers. [0376] Duration: 30 minutes. [0377] Room temperature (25 C.). [0378] Volume ratio of the O/A phases of 1/1 (80 ml for each of the phases).
[0379] At the end of the contacts between the loaded solvents and the 1.5 M solution of sulphuric acid containing or not uranium, analyses are conducted on the aqueous phases (cf. tables XII and XIV) and the organic phases (cf. tables XIII and XV) after filtration with monitoring of uranium, and iron, molybdenum, vanadium and zirconium impurities.
[0380] As a reminder, the analytical uncertainty is comprised between 5 and 10% depending on the considered element.
TABLE-US-00012 TABLE XII Analyses of the aqueous phases after contact of the loaded solvents with a pure 1.5M sulphuric acid solution Test A1 B1 C1 D1 E1 Specific 1.093 1.093 1.092 1.091 1.091 gravity (20 C.) [U].sub.aq (mg/L) 2.0 70.0 <1 1.3 182.2 [Fe].sub.aq (mg/L) 170.5 31.7 55.7 185.5 86.2 [Mo].sub.aq (mg/L) 1.6 2.2 <1 10.6 20.7 [V].sub.aq (mg/L) 192.4 158.5 203.1 32.7 141.8 [Zr].sub.aq (mg/L) 67.8 5.1 <1 4.6 159.3
TABLE-US-00013 TABLE XIII Analyses of the organic phases after contact of the loaded solvents with a 1.5M sulphuric acid solution Test A1 B1 C1 D1 E1 Specific 0.811 0.804 0.825 0.779 0.792 gravity (20 C.) [U].sub.orga (mg/L) 3,167.8 2,713.3 2,659.8 3,804.4 3,169.6 [Fe].sub.orga (mg/L) 1,013.8 1,196.5 957.0 54.5 343.4 [Mo].sub.orga (mg/L) 287.9 219.2 251.6 167.3 264.1 [V].sub.orga (mg/L) 13.0 8.8 146.9 1.2 1.3 [Zr].sub.orga (mg/L)
[0381] As a reminder, the calculated material balance holds globally for all of the analysed elements to 5%.
[0382] The results of the tests carried out with an aqueous solution constituted by pure sulphuric acid which are set out in Tables XII and XIII show that a washing with pure 1.5 M sulphuric acid makes it possible: [0383] to limit the loss in uranium except for tests B and E for which the concentration of uranium in the aqueous phase is greater than 50 mg/L; [0384] to ensure good scrubbing of the solvent of vanadium, apart from test C; which complies with the literature data; [0385] to eliminate only a small proportion of the iron contained in the loaded solvents.
[0386] Washing tests are then carried out on loaded solvents, with a sulphuric solution of same acidity (1.5 M) but containing uranium, that is to say a solution in accordance with that used in the method according to the invention.
[0387] The results of these tests are set out in Tables XIV and XV.
TABLE-US-00014 TABLE XIV Analyses of the aqueous phases after contact of the loaded solvents with a 1.5M sulphuric acid solution containing uranium Test A2 B2 C2 D2 E2 Specific gravity (20 C.) 1.115 1,121 1.110 1.135 1.143 [U].sub.aq (mg/L) 8,552.1 14,685.1 2,064.6 30,304.5 28,575.0 [Fe].sub.aq (mg/L) 1,181.9 854.2 1,024.5 278.1 418.3 [Mo].sub.aq (mg/L) 27.9 10.6 26.6 128.3 147.4 [V].sub.aq (mg/L) 199.6 164.8 316.9 28.4 137.2 [Zr].sub.aq (mg/L) 399.2 265.7 542.8 535.7 480.1
TABLE-US-00015 TABLE XV Analyses of the organic phases after contact of the loaded solvents with a 1.5M sulphuric acid solution containing uranium Test A2 B2 C2 D2 E2 Specific gravity (20 C.) 0.845 0.830 0.866 0.787 0.803 [U].sub.orga (mg/L) 34,302.8 29,109.8 44,881.3 12,197.7 14,374.5 [Fe].sub.orga (mg/L) 65.1 356.9 116.0 8.7 48.2 [Mo].sub.orga (mg/L) 253.5 215.0 226.9 59.0 161.4 [V].sub.orga (mg/L) 8.4 2.2 <1 1.3 1.3 [Zr].sub.orga (mg/L)
[0388] As a reminder, once again, the calculated material balance holds globally for all of the elements analysed to 5%.
[0389] The results of the tests show that a washing with pure 1.5 M sulphuric acid containing uranium, in accordance with the method of the invention, makes it possible: [0390] to scrub in a limited manner molybdenum but with yields greater than those observed with a solution of sulphuric acid free of uranium; [0391] to ensure quasi-quantitative scrubbing of the solvent of vanadium, including for test C (unlike the solution of sulphuric acid free of uranium); [0392] to eliminate quasi-quantitatively the iron contained in the loaded solvent for all of the tests; [0393] to improve the elimination of zirconium if based uniquely on the analyses of the aqueous phases after contact.
Example 7
[0394] In this example, purification tests are carried out on the loaded solvents prepared in example 4 from the phosphoric attack liquor (Table IX, tests F to H and L), by means of the aqueous solution in accordance with that used in the method according to the invention and of the comparative solution prepared in example 5.
[0395] The conditions of these tests are the following: [0396] Use of dedicated separating funnels and mechanical stirrers. [0397] Duration: 30 minutes. [0398] Room temperature (25 C.). [0399] Volume ratio of the O/A phases of 1/1 (80 ml for each of the phases).
[0400] At the end of the contacts between the loaded solvents and the 1.5 M sulphuric acid solution containing or not uranium, analyses are carried out on the aqueous phases (cf. tables XVI and XVIII) and on the organic phases (cf. tables XVII and XIX) after filtration with monitoring on uranium and iron, molybdenum, vanadium and zirconium impurities.
[0401] As a reminder, the analytical uncertainty is comprised between 5 and 10% depending on the considered element.
TABLE-US-00016 TABLE XVI Analyses of the aqueous phases after contact of the loaded solvents with a pure 1.5M sulphuric acid solution Test F1 G1 H1 L1 Specific gravity (20 C.) 1.087 1.091 1.089 1.093 [U].sub.aq (mg/L) <1 1.9 13.1 1.9 [Fe].sub.aq (mg/L) 75.0 93.8 4.7 56.8 [Mo].sub.aq (mg/L) <1 <1 <1 <1 [V].sub.aq (mg/L) 67.4 28.4 1.5 15.3 [Zr].sub.aq (mg/L) <1 <1 <1 <1
TABLE-US-00017 TABLE XVII Analyses of the organic phases after contact of the loaded solvents with a pure 1.5M sulphuric acid solution Test F1 G1 H1 L1 Specific gravity (20 C.) 0.821 0.775 0.787 0.806 [U].sub.orga (mg/L) 939.2 951.7 785.4 905.1 [Fe].sub.orga (mg/L) 1,494.2 185.2 55.1 689.9 [Mo].sub.orga (mg/L) 3.4 2.5 <1 2.6 [V].sub.orga (mg/L) 66.8 3.3 <1 1.3 [Zr].sub.orga (mg/L)
[0402] As a reminder, the calculated material balance holds globally for all of the elements analysed to 5%.
[0403] The results of the tests carried out with an aqueous solution constituted by pure sulphuric acid which are set out in Tables XVI and XVII show that a washing with pure 1.5 M sulphuric acid makes it possible: [0404] to limit the loss in uranium except for test H for which the concentration of uranium in the aqueous phase is greater than 10 mg/L; [0405] to ensure quasi-quantitative scrubbing of the solvent of vanadium, apart from test F; [0406] to eliminate only a small proportion of iron contained in all the loaded solvents studied.
[0407] Washing tests are then carried out of the loaded solvents, with a sulphuric solution of same acidity (1.5 M) but containing uranium, that is to say a solution in accordance with that used in the method according to the invention.
[0408] The results of these tests are set out in Tables XVIII and XIX.
TABLE-US-00018 TABLE XVIII Analyses of the aqueous phases after contact of the loaded solvents with a 1.5M sulphuric acid solution containing uranium Test F2 G2 H2 L2 Specific 1.110 1.135 1.130 1.110 gravity (20 C.) [U].sub.aq (mg/L) 888.8 27,467.0 25,199.0 6,682.2 [Fe].sub.aq (mg/L) 1,430.0 252.0 44.1 653.8 [Mo].sub.aq (mg/L) <1 <1 <1 <1 [V].sub.aq (mg/L) 129.8 25.0 <1 12.2 [Zr].sub.aq (mg/L) 2.6 2.2 <1 <1
TABLE-US-00019 TABLE XIX Analyses of the organic phases after contact of the loaded solvents with a 1.5M sulphuric acid solution containing uranium Test F2 G2 H2 L2 Specific 0.864 0.788 0.803 0.842 gravity (20 C.) [U].sub.orga (mg/L) 42,240.1 13,285.7 15,602.3 34,566.6 [Fe].sub.orga (mg/L) 56.2 15.0 17.7 18.5 [Mo].sub.orga 4.8 1.0 <1 2.5 (mg/L) [V].sub.orga (mg/L) <1 <1 <1 2.5 [Zr].sub.orga (mg/L)
[0409] As a reminder, once again, the calculated material balance holds globally for all of the elements analysed to 5%.
[0410] The results of the tests show that a washing with pure 1.5 M sulphuric acid containing uranium, in accordance with the method of the invention, makes it possible: [0411] to ensure quasi-quantitative scrubbing of the solvent of vanadium; [0412] to eliminate quasi-quantitatively iron from all the loaded solvents studied.
Example 8
[0413] In this example, purification tests are carried out of the loaded solvents prepared in example 4 from the nitric attack liquor (Table X, tests I to K and M), by means of the aqueous solution in accordance with that used in the method according to the invention and of the comparative solution prepared in example 5.
[0414] The conditions for these tests are the following: [0415] Use of dedicated separating funnels and mechanical stirrers. [0416] Duration: 30 minutes. [0417] Room temperature (25 C.). [0418] Volume ratio of the O/A phases of 1/1 (80 ml for each of the phases).
[0419] At the end of the contacts between the loaded solvents and the 1.5 M sulphuric acid solution containing or not uranium, analyses are conducted on the aqueous phases (cf. tables XX and XXII) and the organic phases (cf. tables XXI and XXIII) after filtration with monitoring of uranium and iron as main impurity.
[0420] As a reminder, the analytical uncertainty is comprised between 5 and 10% depending on the considered element.
TABLE-US-00020 TABLE XX Analyses of the aqueous phases after contact of the loaded solvents with a pure 1.5M sulphuric acid solution Test I1 J1 K1 M1 Specific gravity (20 C.) 1.093 1.088 1.089 1.095 [U].sub.aq (mg/L) 2.5 <1 291.9 146.7 [Fe].sub.aq (mg/L) 589.1 256.8 369.2 734.7
TABLE-US-00021 TABLE XXI Analyses of the organic phases after contact of the loaded solvents with a pure 1.5M sulphuric acid solution Test I1 J1 K1 M1 Specific gravity (20 C.) 0.813 0.827 0.803 0.791 [U].sub.orga (mg/L) 3,579.6 3,384.9 3,422.4 3,383.1 [Fe].sub.orga (mg/L) 2,658.5 3,059.9 2,762.3 739.6
[0421] As a reminder, the calculated material balance holds globally for all of the elements analysed to 5%.
[0422] The results of the tests carried out with an aqueous solution constituted by pure sulphuric acid which are set out in Tables XX and XXI show that a washing with pure 1.5 M sulphuric acid makes it possible: [0423] to limit the loss in uranium except for tests K and M for which the concentration of uranium in the aqueous phase is greater than 100 mg/L; [0424] to only eliminate a very small proportion of iron contained in the loaded solvents, apart from test M.
[0425] Washing tests are next carried out on the loaded solvents with a sulphuric solution of same acidity (1.5 M) but containing uranium, that is to say a solution in accordance with that used in the method according to the invention.
[0426] The results of these tests are set out in Tables XXII and XXIII.
TABLE-US-00022 TABLE XXII Analyses of the aqueous phases after contact of the loaded solvents with a 1.5M sulphuric acid solution containing uranium Test I2 J2 K2 M2 Specific 1.113 1.113 1.123 1.135 gravity (20 C.) [U].sub.aq (mg/L) 6,499.9 617.7 14,599.0 26,672.5 [Fe].sub.aq (mg/L) 2,916.1 3,238.8 2369.5 1,418.8
TABLE-US-00023 TABLE XXIII Analyses of the organic phases after contact of the loaded solvents with a 1.5M sulphuric acid solution containing uranium Test I2 J2 K2 M2 Specific 0.847 0.867 0.829 0.806 gravity (20 C.) [U].sub.orga (mg/L) 35,133.6 41,284.8 29,509.9 16,929.2 [Fe].sub.orga (mg/L) 155.8 124.8 457.6 23.4
[0427] As a reminder, again, the calculated material balance holds globally for all of the elements analysed, to 5%.
[0428] The results of the tests show that a washing with pure 1.5 M sulphuric acid containing uranium, in accordance with the method of the invention, makes it possible to eliminate quasi-quantitatively in one contact the iron contained in the loaded solvents for all of the tests with very good yields for tests I, J, and M.
Conclusions from Examples 6, 7, and 8
[0429] The yields of iron removal are represented in
[0430] The change in these yields (
[0431] Indeed, the yields of iron removal obtained in one contact are generally less than 20% in the case of the reference aqueous solution (pure solution of sulphuric acid), apart from tests D and M with yields of iron removal of the order of 80 and 50% respectively.
[0432] The yields of iron removal obtained in one contact are 90% in the case of the uranium bearing solution of sulphuric acid, apart from tests B and H for which the yield is of the order of 70%.
[0433] These results clearly show that the method according to the invention, which uses an aqueous de-ironing (iron removal) solution containing uranium, may be implemented with success with all the loaded solvents, whether said solvents contain pure organophosphorous extractants or as synergistic mixtures and whatever the matrix of the attack liquor having made it possible to obtain these loaded solvents.