US20180187290A1 - 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 - Google Patents

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 Download PDF

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US20180187290A1
US20180187290A1 US15/738,441 US201615738441A US2018187290A1 US 20180187290 A1 US20180187290 A1 US 20180187290A1 US 201615738441 A US201615738441 A US 201615738441A US 2018187290 A1 US2018187290 A1 US 2018187290A1
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uranium
iron
aqueous
organic phase
solution
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Hamid Mokhtari
Bruno Courtaud
Frédéric Auger
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Orano Mining SA
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Areva Mines SA
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B60/00—Obtaining metals of atomic number 87 or higher, i.e. radioactive metals
    • C22B60/02—Obtaining thorium, uranium, or other actinides
    • C22B60/0204—Obtaining thorium, uranium, or other actinides obtaining uranium
    • C22B60/0217—Obtaining thorium, uranium, or other actinides obtaining uranium by wet processes
    • C22B60/0252—Obtaining thorium, uranium, or other actinides obtaining uranium by wet processes treatment or purification of solutions or of liquors or of slurries
    • C22B60/026—Obtaining thorium, uranium, or other actinides obtaining uranium by wet processes treatment or purification of solutions or of liquors or of slurries liquid-liquid extraction with or without dissolution in organic solvents
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B60/00—Obtaining metals of atomic number 87 or higher, i.e. radioactive metals
    • C22B60/02—Obtaining thorium, uranium, or other actinides
    • C22B60/0204—Obtaining thorium, uranium, or other actinides obtaining uranium
    • C22B60/0217—Obtaining thorium, uranium, or other actinides obtaining uranium by wet processes
    • C22B60/0252—Obtaining thorium, uranium, or other actinides obtaining uranium by wet processes treatment or purification of solutions or of liquors or of slurries
    • C22B60/0278—Obtaining thorium, uranium, or other actinides obtaining uranium by wet processes treatment or purification of solutions or of liquors or of slurries by chemical methods
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B60/00—Obtaining metals of atomic number 87 or higher, i.e. radioactive metals
    • C22B60/02—Obtaining thorium, uranium, or other actinides
    • C22B60/0204—Obtaining thorium, uranium, or other actinides obtaining uranium
    • C22B60/0217—Obtaining thorium, uranium, or other actinides obtaining uranium by wet processes
    • C22B60/0221—Obtaining thorium, uranium, or other actinides obtaining uranium by wet processes by leaching
    • C22B60/0226—Obtaining thorium, uranium, or other actinides obtaining uranium by wet processes by leaching using acidic solutions or liquors
    • C22B60/0243—Obtaining thorium, uranium, or other actinides obtaining uranium by wet processes by leaching using acidic solutions or liquors phosphorated ion as active agent
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B60/00—Obtaining metals of atomic number 87 or higher, i.e. radioactive metals
    • C22B60/02—Obtaining thorium, uranium, or other actinides
    • C22B60/0204—Obtaining thorium, uranium, or other actinides obtaining uranium
    • C22B60/0217—Obtaining thorium, uranium, or other actinides obtaining uranium by wet processes
    • C22B60/0252—Obtaining thorium, uranium, or other actinides obtaining uranium by wet processes treatment or purification of solutions or of liquors or of slurries
    • C22B60/0278—Obtaining thorium, uranium, or other actinides obtaining uranium by wet processes treatment or purification of solutions or of liquors or of slurries by chemical methods
    • C22B60/0282—Solutions containing P ions, e.g. treatment of solutions resulting from the leaching of phosphate ores or recovery of uranium from wet-process phosphoric acid

Definitions

  • the invention relates to a method for separating iron, from a liquid organic phase containing uranium and iron.
  • 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 uranium (uranium bearing, “uranifère”) liquid organic phase, containing an organic extraction system comprising an organic extractant diluted in an organic diluent.
  • uranium uranium bearing, “uranifère”
  • This organic phase may be notably an organic phase resulting from the extraction of uranium by a solvent from an aqueous uranium bearing solution of mineral, inorganic acid, such as phosphoric acid, nitric acid or sulphuric acid.
  • the invention thus further relates to a method for extracting uranium from an aqueous solution of mineral acid, containing uranium and iron.
  • This aqueous solution of mineral acid may equally well be an aqueous uranium bearing solution of phosphoric acid, such as industrial phosphoric acid, derived from the lixiviation, attack, of a natural phosphate ore, generally based on apatite, by sulphuric acid, as an aqueous uranium bearing solution of sulphuric acid or nitric acid derived from the lixiviation, attack, of a non-phosphate uranium bearing ore, for example non-apatite based, by sulphuric acid or nitric acid.
  • phosphoric acid such as industrial phosphoric acid, derived from the lixiviation, attack, of a natural phosphate ore, generally based on apatite, by sulphuric acid
  • an aqueous uranium bearing solution of sulphuric acid or nitric acid derived from the lixiviation, attack, of a non-phosphate uranium bearing
  • the invention thus finds application in the treatment of natural phosphates to beneficiate the uranium that these phosphates contain, but also in the treatment of uranium bearing ores subjected to an attack, lixiviation, by sulphuric acid or nitric acid in order to beneficiate the uranium present in these ores.
  • Uranium is in fact present at very low concentrations in phosphates, generally from 50 to 200 ppm. Certain phosphate deposits may contain non-negligible quantities of uranium and thus become potentially exploitable uranium deposits.
  • the beneficiation of uranium from phosphates firstly relates to the beneficiation of the uranium contained in industrial phosphoric acid, referred to as “wet process” phosphoric acid, which constitutes, with phosphate fertilizers, the main production from phosphates.
  • This “wet process” phosphoric acid is the acid obtained by attack of natural phosphate ores by concentrated sulphuric acid, followed by a solid-liquid separation treatment for separating the phosphoric acid from the gypsum that has precipitated during the attack.
  • This solution of phosphoric acid contains, apart from uranium, already cited, significant impurities at the forefront of which stands iron, but also silica, vanadium, molybdenum, and zirconium.
  • the extraction of uranium is carried out by an organic solvent comprising an organic extractant in an organic diluent and a uranium bearing organic phase is thereby obtained.
  • this uranium bearing organic phase also contains the impurities listed above, and mainly iron which is extremely bothersome and does not make it possible to obtain, during the following step of back extraction (“désextraction”), uranium having the required purity with a view to its later use.
  • iron precipitates in the form of iron hydroxide during the step of re-extraction (“réextraction”) of uranium, which requires additional filtration operations and poses problems with regard to carrying out the method.
  • the document FR-A-2 596 383 [1] and the document EP-A1-0 239 501 [2] describe in a general manner a method for extracting uranium present in solutions of phosphoric acid, notably in solutions of phosphoric acid obtained from phosphate ores containing iron.
  • the method of these documents uses novel extractant molecules or, more exactly, a novel synergistic mixture, implemented in a single cycle of extraction/re-extraction of uranium, which increases the partition coefficient of uranium, and comprises a step of selective de-ironing (iron removal, deferrization) of the solvent by an acid upstream of the step of back extraction of uranium.
  • This acid may be selected from oxalic acid, a mixture of phosphoric and sulphuric acid, and de-ironed (iron-removed, deferrization) phosphoric acid.
  • This acid prevents phenomena of precipitation of ferric hydroxides during the back extraction of uranium.
  • documents FR-A-2 596 383 [1] and EP-A1-0 239 501 [2] describe a method for separating iron from an organic uranium bearing solution in which a system of extractants constituted by a neutral phosphine oxide and an acid organophosphorous compound is used.
  • novel extractant molecules used in the methods of documents FR-A-2 596 383 [1] and EP-A1-0 239 501 [2] are notably those described in documents FR-A-2442 796, FR-A-2 459 205, FR-A-2 494 258, and EP-A1-053 054.
  • One means for improving the extraction of uranium from an aqueous solution of phosphoric acid consists in replacing the synergistic mixture Di 2 EHPA/TOPO by combining the two functions “cationic exchanger” and “solvating extractant” within a single and same compound.
  • a bifunctional extractant notably has the advantage of there being only a single compound instead of two to manage.
  • 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 linked to one another by an appropriate spacer group, such as an ether, thioether, polyether or polythioether group.
  • This type of compound has two drawbacks. Indeed, tests that have been carried out with one of these compounds have shown that, if this compound is solubilised in n-dodecane, a third phase is formed during the extraction of uranium, whereas, if it is solubilised in chloroform, a third phase is also formed but during the back extraction of uranium. Yet, the appearance of a third phase is totally unacceptable for a method intended to be implemented at an industrial scale. Furthermore, the presence within the spacer group of a P—O or P—S bond, which is easily hydrolysable, makes these compounds extremely sensitive to hydrolysis.
  • the organic phase produced at the end of the extraction contains iron, and no method for de-ironing of this phase is proposed.
  • the document WO-A1-2013/167516 [4] deals with bifunctional compounds that are free of the various drawbacks exhibited by the bifunctional compounds proposed in the aforesaid documents [2] to [3] and, in particular, of the necessity of reducing beforehand uranium(VI) into uranium(IV), of the formation of a third phase and of the risk of hydrolysis.
  • R 1 and R 2 are a hydrocarbon group, saturated or unsaturated, linear or branched, comprising from 6 to 12 carbon atoms;
  • R 3 is:
  • the organic phase produced at the end of the extraction contains iron, and no method for de-ironing of this phase is proposed.
  • the starting point is carrying out an attack, lixiviation, of these ores with sulphuric acid or nitric acid by means of which an aqueous uranium bearing solution of sulphuric acid or nitric acid is obtained.
  • This aqueous uranium bearing solution of sulphuric acid or nitric acid contains, apart from uranium, notable impurities that were present in the ore, at the forefront of which stands iron, but also silica, vanadium, molybdenum, and zirconium.
  • the extraction of uranium is carried out by an organic solvent comprising an organic extractant in an organic diluent and a uranium bearing organic phase is thereby obtained.
  • this uranium bearing organic phase just like the organic phase derived from an aqueous uranium bearing solution of phosphoric acid, also contains the impurities listed above, and mainly iron, and this is extremely bothersome and does not make it possible to obtain, during the following step of back extraction, uranium having the required purity in view of its later use.
  • the method referred to as the DAPEX method may thus be cited, which is based on the mixture of extractants Di 2 EHPA/TBP.
  • the main constraint of this method is its sensitivity to Fe(III) ions.
  • the organic phase produced at the end of the extraction contains iron, and no method for de-ironing of this phase is proposed.
  • a method for separating iron from an initial liquid organic phase containing uranium and iron in which the initial liquid organic phase is placed in contact with an aqueous solution referred to as aqueous de-ironing (iron removal, deferrization) 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 (iron-removed from which iron has been removed) organic phase; said method being characterised in that the aqueous de-ironing solution contains an inorganic acid and uranium, and does not contain iron.
  • aqueous de-ironing solution contains from 0 to 10 ppm of iron, preferably contains 0 ppm of iron (is free of iron).
  • the method for separating iron according to the invention also called de-ironing (iron removal method, deferrization method) fundamentally differs from the methods for separating iron of the prior art and notably from the method described in documents FR-A-2 596383 [1], and EP-A-239 501 [2], in that it uses a specific aqueous de-ironing solution which contains an inorganic acid and uranium and not uniquely an inorganic acid.
  • This specific aqueous de-ironing solution makes it possible, in a surprising manner, to eliminate, remove, selectively iron from the organic phase loaded with uranium and iron.
  • an acid is used that is selected from oxalic acid, a mixture of phosphoric and sulphuric acid or de-ironed sulphuric acid, without any addition of uranium, hence apart from the drawbacks mentioned above linked to the use of these acids, a selective elimination of iron due to the chemical displacement of iron by uranium can virtually not be obtained.
  • the method of de-ironing (iron removal) according to the invention overcomes the drawbacks listed above due to the implementation, during the de-ironing (iron removal) step, of an acid selected from oxalic acid, mixtures of phosphoric and sulphuric acid, or de-ironed phosphoric acid.
  • an acid selected from oxalic acid, mixtures of phosphoric and sulphuric acid, or de-ironed phosphoric acid.
  • the method according to the invention only uses common inorganic reagents which are for example already present, among others, on phosphoric acid production sites, which can notably reduce the operating costs of the method.
  • the method according to the invention limits the number of unitary operations and eliminates disadvantageous impurities in an original manner by saturation of the solvent with beneficiable materials, namely uranium.
  • the method according to the invention may notably apply to the treatment of an initial liquid organic phase which 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.
  • the de-ironing method according to the invention may be successfully implemented equally well with an organic extraction system comprising a single organic extractant as with an organic extraction system comprising a synergistic mixture of organic extractant(s), and whatever the nature of the extractant(s).
  • the organic extraction system may notably be selected from all the extraction systems described in documents [1] to [4] and documents FR-A-2442 796, FR-A-2 459 205, FR-A-2 494 258, and EP-A1-053 054, cited above, to the description of which reference is explicitly made in this respect and of which the passages relative to the extraction systems are consequently expressly included herein.
  • the organic extraction system may notably comprise an extractant selected from organophosphorous compounds and mixtures thereof.
  • the de-ironing method according to the invention may be successfully implemented with all these organophosphorous extractants, used alone or as a mixture.
  • the organic extraction system may comprise an extractant selected from acid organophosphorous compounds such as dialkylphosphoric acids, bifunctional organophosphorous compounds, neutral phosphine oxides such as trialkylphosphine oxides, and mixtures thereof.
  • acid organophosphorous compounds such as dialkylphosphoric acids, bifunctional organophosphorous compounds, neutral phosphine oxides such as trialkylphosphine oxides, and mixtures thereof.
  • the extraction system may comprise the mixture of an acid organophosphorous compound and of a neutral phosphine oxide.
  • the acid organophosphorous compound may be selected from di(2-ethylhexyl) phosphoric acid (Di 2 EHPA), bis(1,3-dibutoxy, 2-propyl) phosphoric acid (BIDIBOPP) and bis(1,3-dihexyloxy, 2-propyl) phosphoric acid (BIDIHOPP); and the neutral phosphine oxide is selected from trioctylphosphine oxide (TOPO), and di-n-hexyl octyl methoxy phosphine oxide (DinHMOPO).
  • DI 2 EHPA di(2-ethylhexyl) phosphoric acid
  • BIDIBOPP bis(1,3-dibutoxy, 2-propyl) phosphoric acid
  • BIDIHOPP bis(1,3-dihexyloxy, 2-propyl) phosphoric acid
  • the neutral phosphine oxide is selected from trioctylphosphine oxide (TOPO), and
  • the extractant system may be selected from the following mixtures of extractants:
  • the extraction system may comprise a mixture of a trialkylphosphoric acid and a trialkyl phosphate, such as TBP.
  • the extraction system may comprise as extractant a compound which corresponds to the following general formula (I):
  • R 1 and R 2 are a hydrocarbon group, saturated or unsaturated, linear or branched, comprising from 6 to 12 carbon atoms;
  • R 3 is:
  • the compound (extractant) of formula (I) may correspond:
  • R 2 is a hydrocarbon group, saturated or unsaturated, linear or branched, comprising from 6 to 12 carbon atoms; whereas
  • R 3 is:
  • hydrocarbon group saturated or unsaturated, linear or branched, comprising from 6 to 12 carbon atoms
  • alkyl alkenyl or alkynyl group, with linear or branched chain, which comprises 6, 7, 8, 9, 10, 11 or 12 carbon atoms.
  • hydrocarbon group saturated or unsaturated, linear or branched, comprising from 2 to 8 carbon atoms
  • alkyl alkenyl or alkynyl group, with linear or branched chain, which comprises 2, 3, 4, 5, 6, 7 or 8 carbon atoms.
  • hydrocarbon group saturated or unsaturated, linear or branched, comprising from 1 to 12 carbon atoms and optionally one or more heteroatoms
  • hydrocarbon chain linear or branched, which comprises 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 or 12 carbon atoms, of which the chain may be saturated or, conversely, comprise one or more double or triple bonds and of which the 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.
  • heteroatom is taken to mean any atom other than carbon or hydrogen, said atom being typically a nitrogen, oxygen or sulphur atom.
  • “monocyclic hydrocarbon group, saturated or unsaturated, comprising from 3 to 8 carbon atoms and optionally one or more heteroatoms” is taken to mean any cyclic hydrocarbon group that only comprises a single ring and of which the ring comprises 3, 4, 5, 6, 7 or 8 carbon atoms.
  • This ring may be saturated or, conversely, comprise one or more double or triple bonds, and may 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.
  • this group may notably 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, tetrahydrothiophenyl, pyrrolidinyl or piperidinyl group), an unsaturated but non-aromatic heterocyclic group (for example, pyrrolinyl or pyridinyl), an aromatic group or instead a heteroaromatic group.
  • a cycloalkyl, cycloalkenyl or cycloalkynyl group for example, a cyclopropane, cyclopentane, cyclohexane, cyclopropenyl, cyclopentenyl or cyclohex
  • aromatic group is taken to mean any group of which the ring meets the Hückel aromaticity rule and thus has a number of delocalised ⁇ electrons equal to 4n+2 (for example, a phenyl or benzyl group), whereas “heteroaromatic group” is taken to mean any aromatic group as has just been defined but in which the ring comprises one or more heteroatoms, this or these heteroatoms being typically selected from nitrogen, oxygen and sulphur atoms (for example, a furanyl, thiophenyl or pyrrolyl group).
  • —(CH 2 ) n — group in which n is a whole number ranging from 1 to 4 may be a methylene, ethylene, propylene or butylene group.
  • R 1 and R 2 which may be identical or different, are advantageously an alkyl group, linear or branched, comprising from 6 to 12 carbon atoms.
  • R 1 and R 2 are identical to each other and both are a branched alkyl group, comprising from 8 to 10 carbon atoms, the 2-ethylhexyl group being quite particularly preferred.
  • R 3 is a hydrogen atom, a methyl, n-octyl or phenyl group.
  • R 4 is, preferably, an alkyl group, linear or branched, comprising from 2 to 8 carbon atoms and, better still, from 2 to 4 carbon atoms such as an ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl or tert-butyl group, ethyl and n-butyl groups being quite particularly preferred.
  • ethyl 1-(N,N-diethyl-hexylcarbamoyl)nonylphosphonate and especially butyl 1-(N,N-diethylhexylcarbamoyl)nonylphosphonate (DEHCNPB) are quite particularly preferred.
  • R 1 is advantageously an alkyl group, linear or branched, comprising from 6 to 12 carbon atoms.
  • a compound of the above specific formula (I-b) which has these characteristics is notably ethyl (N-dodecylpyrrolidone)-1-phosphonate which corresponds to the specific formula (I-b) in which R 1 is a n-dodecyl group, R 2 and R 3 form together an ethylene group (—CH 2 —CH 2 —), R 4 is an ethyl group whereas R 5 is a hydrogen atom.
  • the extractant system is selected from Di 2 EHPA, for example at a concentration of 0.5 M; a mixture of Di 2 EHPA, preferably at a concentration of 0.5 M, and TOPO, preferably at a concentration of 0.125 M; a mixture of Di 2 EHPA, preferably at a concentration of 0.2 M, and TBP, preferably at a concentration of 0.2 M; and butyl 1-(diethylhexyl carbamoyl) nonyl phosphonate (DEHCNPB) at a concentration of 0.1 M or 0.5 M.
  • Di 2 EHPA for example at a concentration of 0.5 M
  • a mixture of Di 2 EHPA preferably at a concentration of 0.5 M, and TOPO, preferably at a concentration of 0.125 M
  • a mixture of Di 2 EHPA preferably at a concentration of 0.2 M, and TBP, preferably at a concentration of 0.2 M
  • DEHCNPB butyl 1-(diethylhexyl carbamoy
  • the method according to the invention may be successfully implemented with an organic phase resulting from the extraction of uranium by a first organic phase, or solvent phase, from an aqueous uranium bearing solution of mineral, inorganic acid, such as phosphoric acid, nitric acid or sulphuric acid. It has also been shown (see examples) that the method according to the invention could be successfully implemented whatever the origin of this aqueous uranium bearing solution of inorganic acid.
  • this aqueous uranium bearing solution of inorganic acid may equally well be an aqueous uranium bearing solution of phosphoric acid, such as industrial phosphoric acid, derived from the lixiviation, attack, of a natural phosphate ore, generally based on apatite, by sulphuric acid, as an aqueous uranium bearing solution of sulphuric acid or nitric acid derived from the lixiviation, attack, of a non-phosphate uranium bearing ore, for example non-apatite based, by respectively sulphuric acid or nitric acid.
  • phosphoric acid such as industrial phosphoric acid, derived from the lixiviation, attack, of a natural phosphate ore, generally based on apatite, by sulphuric acid
  • an aqueous uranium bearing solution of sulphuric acid or nitric acid derived from the lixiviation, attack, of a non
  • the initial organic phase contains from 0.5 to 10 g/L of uranium; and from 0.1 to 10 g/L of iron.
  • the inorganic acid of the aqueous de-ironing (iron removal, deferrization) solution is selected from sulphuric acid, nitric acid, hydrochloric acid, phosphoric acid, and mixtures thereof.
  • the preferred inorganic acid of the aqueous de-ironing solution is sulphuric acid.
  • 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.
  • 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 uranium saturation of the organic phase.
  • 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.
  • the aqueous iron removal solution does not contain iron.
  • the initial organic phase is mixed with the aqueous de-ironing solution, then said mixture is decanted.
  • de-ironed iron-removed, deferrized, from which iron has been removed
  • de-ironed iron-removed, deferrized, from which iron has been removed
  • the placing in contact is implemented in a battery of 1 to 5 mixers-decanters, for example 3 mixers-decanters, counter-current supplied with the initial organic phase and with the aqueous de-ironing solution.
  • the placing in contact may be carried out at a temperature of 0° C. to 70° C. within the limit of the flash point temperature of the organic diluent, preferably at a temperature from 40° C. to 45° C.
  • the O/A ratio of the flow rate of the initial organic phase to the flow rate of the aqueous de-ironing solution is from 1/5 to 5/1, for example 1/1.
  • 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
  • the de-ironed (iron removed, deferrized, from which iron has been removed) 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.
  • the final organic phase referred to as de-ironed (iron removed, deferrized) organic phase contains less than 10 ppm of iron, preferably 0 ppm of iron (is free of iron).
  • a selective elimination of iron is obtained which may be greater than 90%, in one contact.
  • the Fe/U weight ratio in the de-ironed organic phase is generally less than 0.15%, which complies with the ASTM specifications.
  • the invention further relates to a method 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:
  • the first aqueous solution of inorganic acid is contacted with a first liquid organic phase; by means of which 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 (uranium removed, from which uranium has been removed) 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;
  • 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 (iron removal, deferrization) solution, by means of which 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 (deferrized, from which iron has been removed) organic phase;
  • aqueous de-ironing iron removal, deferrization
  • the aqueous de-ironing solution contains an inorganic acid and uranium, and does not contain iron.
  • the phrase “does not contain iron” is generally taken to mean that the aqueous de-ironing solution contains from 0 to 10 ppm of iron, preferably contains 0 ppm of iron (is free of iron).
  • step b) is carried out by the de-ironing method according to the invention as has been described above, and all of the description of the de-ironing method provided above applies integrally 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 de-ironing method according to the invention.
  • the third aqueous solution referred to as aqueous iron removal solution corresponds to the aqueous de-ironing solution used in the de-ironing method according to the invention and has been described in detail above.
  • the first liquid organic phase differs from the second organic phase in that it does not contain either uranium, or iron and that it is thus exclusively constituted of organic compounds.
  • this first organic phase may be constituted by 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.
  • an organic extraction system has already been described in detail above.
  • 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 (from which uranium has been removed) 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).
  • 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
  • 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 method according to the invention differs fundamentally from methods of the prior art in that the step of de-ironing b) is carried out with a specific aqueous de-ironing solution which contains an inorganic acid and uranium, and which does not contain iron.
  • the step of de-ironing b) is carried out by implementing the de-ironing method according to the invention as has been described above, and thus has all the advantages inherent in this de-ironing method.
  • This aqueous de-ironing solution makes it possible, in a surprising manner, to eliminate selectively iron from the second organic phase, or solvent phase loaded with uranium and with iron.
  • step a) when the organic phase or solvent phase obtained in step a) in placed in contact with the aqueous de-ironing solution according to the invention a chemical displacement of iron by uranium to the aqueous phase takes place, which thereby ensures selective iron removal from the organic phase, loaded with uranium and with iron.
  • the method according to the invention notably on account of the implementation of the aforementioned specific solution during the de-ironing (iron removal) step, does not have the drawbacks, defects, limitations and disadvantages of methods of the prior art and solves the problems of methods of the prior art.
  • the method according to the invention notably during the de-ironing step, only uses inorganic reagents that are already present on phosphoric acid production sites.
  • sulphuric acid which is widely available on phosphoric acid production sites because large amounts of sulphuric acid are consumed during the lixiviation of phosphate ores.
  • the method according to the invention while being more economical, enables among others a selective elimination of iron by chemical displacement while avoiding losses of uranium and phenomena of precipitation of iron which hinder the carrying out of the method.
  • the method according to the invention limits the number of unitary operations and eliminates disadvantageous impurities by saturation of the solvent with the beneficiable materials, namely uranium.
  • 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.
  • 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.
  • first aqueous solutions of inorganic acid whatever their origin, namely for example 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 as described previously.
  • aqueous uranium bearing solution of phosphoric acid such as industrial phosphoric acid
  • step a) is carried out at a temperature from 30° C. to 35° C., in a battery of 5 mixers-decanters counter-current supplied with organic phase and with aqueous phase, and with an O/A ratio of the flow rate of organic phase to the flow rate of aqueous phase of 1/6 to 1/8, for example 1/7.
  • the method according to the invention may further comprise a step c) wherein the de-ironed (iron removed) organic phase obtained in step b) is placed in contact with an aqueous solution of a complexing base; by means of which 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 the complexing base.
  • the complexing base is a carbonate of an alkali or alkaline-earth metal such as sodium carbonate.
  • the method according to the invention may further comprise a step d) wherein the organic phase free of uranium, further containing the complexing base obtained in step c), is placed in contact 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.
  • the method according to the invention may further comprise a step e) in which the aqueous phase loaded with uranium obtained in step c), is contacted with a base such as sodium hydroxide, whereby a uranate precipitate, such as a sodium urinate precipitate, which is separated, and an aqueous solution which is sent to step c) after addition of a complexing base, are obtained.
  • a base such as sodium hydroxide
  • all or part of the uranate precipitate such as sodium uranate, obtained in step e
  • an inorganic acid such as sulphuric acid
  • the aqueous solution obtained containing an inorganic acid and uranium is sent to step b) after having optionally adjusted the concentration of inorganic acid.
  • FIG. 1 is a block diagram of the method according to the invention.
  • FIG. 2 is a graph which shows the kinetic profiles of the yield of selective de-ironing (iron removal) 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.
  • FIG. 3 is a graph which gives the de-ironing yield (or removal of Fe in %) from the loaded solvents A, B, C, D, E, F, G, H, L, I, J, K, and M prepared in example 4, in one contact, either with pure 1.5 M sulphuric 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 sulphuric acid containing uranium (for each test: right bar).
  • 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.
  • 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 2 O 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 2 O 5 .
  • 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]).
  • 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).
  • 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.
  • This aqueous solution is generally an aqueous solution, known as attack solution, obtained during the attack of phosphate ores by sulphuric acid.
  • 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.
  • the cooling step makes it possible for example to cool the attack solution, which is hot.
  • the Solid/Liquid separation step makes it possible to separate the gypsum in super saturation in the solution.
  • the oxidation step for example by hydrogen peroxide or by another oxidant such as NaClO 3 , makes it possible to oxidise uranium in the form of U (IV) into uranium in the form of U (VI).
  • 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.
  • 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.
  • Preferred extractants used alone are Di 2 EHPA, preferably at a concentration of 0.5 M.
  • 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.
  • 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.
  • the acid-organophosphorous compound of the mixture such as a dialkylphosphoric acid
  • a dialkylphosphoric acid is selected from bis 2-ethylhexyl phosphoric acid (Di 2 EHPA), 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).
  • TOPO trioctylphosphine oxide
  • DinHMOPO di-n-hexyl octyl methoxy phosphine oxide
  • Preferred extractant mixtures of this type are the following:
  • a particularly preferred synergistic extractant mixture is a mixture of D 2 EHPA and TOPO, preferably a mixture of 0.5 M D 2 EHPA and 0.125 M TOPO.
  • Another synergistic mixture of extractants is a mixture of D 2 EHPA and TBP, preferably a mixture of 0.2 M D 2 EHPA and 0.2 M TBP: this is the mixture used in the “DAPEX” method.
  • the organic diluent, non-miscible and non-reactive with water is generally selected from liquid hydrocarbons.
  • liquid hydrocarbons may be selected from aromatic hydrocarbons such as benzene, aliphatic hydrocarbons such as n-heptane and n-octane, and mixtures thereof.
  • aromatic hydrocarbons such as benzene
  • aliphatic hydrocarbons such as n-heptane and n-octane
  • a mixture of hydrocarbons that is suitable as diluent according to the invention is kerosene.
  • Aliphatic kerosenes such as the products available under the denomination ShellSol®, may thus be suitable for use in the organic diluent.
  • 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.
  • This extraction step may be carried out in static mode or in dynamic mode.
  • 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.
  • 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.
  • the number of mixers-decanters may range from 1 to 10, notably from 1 to 5.
  • 5 mixers-decanters in other words 5 mixing-decanting stages are implemented.
  • 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.
  • 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.
  • O/A designates the ratio of the flow rate of organic phase to the flow rate of aqueous phase.
  • 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.
  • 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.
  • 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.
  • 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%.
  • 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.
  • 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).
  • 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.
  • 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 2 O 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.
  • 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 2 O 5 from 26% to 32% by weight, preferably from 28% to 32% by weight
  • 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.
  • step b) the organic phase ( 5 ) obtained in step a) is placed in contact with an aqueous de-ironing solution ( 9 ).
  • the aqueous de-ironing solution ( 9 ) contains an inorganic acid and uranium, and does not contain iron.
  • 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.
  • the preferred inorganic acid of the aqueous de-ironing solution is sulphuric acid.
  • the concentration of inorganic acid of the aqueous de-ironing solution such as sulphuric acid is from 1 to 1.5 M.
  • the concentration of uranium of the aqueous de-ironing solution is preferably from 35 to 40 g/L, for example 40 g/L.
  • 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.
  • This step of the method is generally carried out at a temperature from 10° C. to 50° C.
  • 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.
  • 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.
  • this step de-ironing (iron removal step) ( 8 ) is carried out with a battery of mixers-decanters in dynamic counter-current operation.
  • the number of mixers-decanters may range from 1 to 5.
  • 3 mixers-decanters in other words 3 mixing-decanting stages are implemented.
  • stage 1 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”.
  • 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.
  • 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 aqueous supply stage, and 3 minutes for the two other stages.
  • the dwell time in the decanter is generally 5 minutes at the most.
  • 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.
  • 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.
  • 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 ).
  • a step c also called back extraction of uranium ( 12 )
  • 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 ).
  • 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 from 1 to 2 M, for example 1.5 M.
  • 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.
  • This step of back extraction ( 12 ) is generally carried out with a battery of mixers-decanters in dynamic counter-current operation.
  • the number of mixers-decanters may range from 1 to 5.
  • 3 mixers-decanters in other words 3 mixing-decanting stages are implemented.
  • 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.
  • 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.
  • a preferred overall O/A ratio is 1/1.
  • This step of back extraction of uranium ( 12 ) of the method is generally carried out at a temperature from 10° C. to 50° C.
  • 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.
  • 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.
  • 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.
  • 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.
  • This step of acidification of the solvent ( 16 ) may be carried out in static mode or in dynamic mode.
  • This step of acidification ( 16 ) may be carried out in any suitable contacting apparatus.
  • 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.
  • a single mixer-decanter in other words a single mixing-decanting stage is implemented.
  • 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.
  • a preferred overall O/A ratio is 1/1.
  • 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.
  • the step of acidification ( 16 ) is thereby carried out preferably at a temperature from 40° C. to 45° C.
  • 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.
  • 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.
  • 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 ).
  • 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.
  • a base such as sodium hydroxide
  • 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.
  • the complexing base is an alkali or alkaline-earth metal carbonate, such as sodium carbonate
  • the uranium is in the form of uranyl tricarbonate of alkali or alkaline-earth metal, such as sodium uranyl tricarbonate.
  • 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.
  • a base such as sodium hydroxide
  • uranate precipitate for example a sodium diuranate precipitate (SDU) or sodium uranate precipitate, if sodium hydroxide was used for the precipitation.
  • SDU sodium diuranate precipitate
  • sodium uranate precipitate if sodium hydroxide was used for the precipitation.
  • This uranate precipitate is separated by any suitable solid-liquid separation method, for example by filtration.
  • 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.
  • an inorganic acid such as sulphuric acid
  • 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.
  • the preferred inorganic acid is sulphuric acid.
  • a dissolution aqueous solution is thereby obtained containing an inorganic acid such as sulphuric acid, and uranium in the form of uranyl sulphate.
  • 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 ).
  • an input of inorganic acid ( 26 ), such as sulphuric acid, could be made on the pipe carrying the dissolution aqueous solution ( 25 ).
  • 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.
  • 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 ).
  • 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 4 ( 32 ) is obtained, which may be optionally separated by any suitable solid-liquid separation method, for example by filtration.
  • the precipitate of uranium peroxide may then be placed in vessels such as drums during a step referred to as “UO 4 drumming” ( 33 ).
  • the method according to the invention implements for example twelve mixing-decanting stages.
  • 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.
  • 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.
  • 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.
  • 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.
  • FIG. 2 shows the kinetic profiles of the yield of selective iron removal (de-ironing) of the solvent for different initial concentration of uranium (namely 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 complementary tests of example 2.
  • uranium namely 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
  • 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.
  • MD 3 mixers-decanters
  • 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.
  • solvents or extraction systems loaded with uranium are prepared by placing the attack liquors loaded with uranium in contact with solvents.
  • a sulphuric attack liquor or solution a phosphoric attack liquor or solution, and a nitric attack liquor or solution are prepared.
  • the phosphoric and sulphuric attack liquors are prepared from industrial liquors, juices.
  • the sulphuric attack liquor comes from an ore lixiviation liquor, juice doped with vanadium and with zirconium (see Table IV).
  • the phosphoric attack liquor comes from an American industrial phosphoric acid SIMPLOT diluted twice and doped with uranium (see Table V).
  • the nitric attack liquor was, for its part, prepared from nitric acid, uranyl nitrate and iron sulphate (III) (see Table VI).
  • 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)).
  • the solvents are prepared.
  • 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).
  • 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.
  • 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.
  • 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.
  • 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.
  • the mixture D 2 EHPA/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.
  • 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 2 EHPA/TBP for which the concentration of iron is two times lower.
  • 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.
  • 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.
  • the tests carried out with the reference solution 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.
  • 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.
  • the analytical uncertainty is comprised between 5 and 10% depending on the considered element.
  • 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.
  • 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.
  • 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.
  • the analytical uncertainty is comprised between 5 and 10% depending on the considered element.
  • 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.
  • 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.
  • 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.
  • the analytical uncertainty is comprised between 5 and 10% depending on the considered element.
  • 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.
  • the yields of iron removal are represented in FIG. 3 for all of the tests of examples 6, 7, and 8 as a function of the aqueous iron removal solutions used, namely the pure 1.5 M sulphuric acid solution (which does not comply with the aqueous iron removal solution used in the method of the invention) which constitutes the reference aqueous solution, and the 1.5 M sulphuric acid solution containing uranium in an amount of 40 g/L, which complies with the aqueous iron removal solution used in the method of the invention).
  • 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.
  • 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%.

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US15/738,441 2015-06-30 2016-06-29 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 Abandoned US20180187290A1 (en)

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FR1556181A FR3038326A1 (fr) 2015-06-30 2015-06-30 Procede de separation du fer d'une phase organique contenant de l'uranium et procede d'extraction de l'uranium d'une solution aqueuse d'acide mineral contenant de l'uranium et du fer
PCT/EP2016/065169 WO2017001494A1 (fr) 2015-06-30 2016-06-29 Procede de separation du fer d'une phase organique contenant de l'uranium et procede d'extraction de l'uranium d'une solution aqueuse d'acide mineral contenant de l'uranium et du fer

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CN117587277A (zh) * 2023-11-13 2024-02-23 湖南中核金原新材料有限责任公司 一种分步沉淀制备重铀酸盐的方法

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CN111254296B (zh) * 2020-01-21 2020-12-22 中南大学 一种具有苯乙烯基膦酸双酯结构的铀萃取剂及其应用

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US4105741A (en) * 1976-03-08 1978-08-08 Freeport Minerals Company Process for recovery of uranium from wet process phosphoric acid
FR2442796A1 (fr) 1978-11-28 1980-06-27 Commissariat Energie Atomique Procede de recuperation de l'uranium present dans les solutions d'acide phosphorique
FR2459205A2 (fr) 1979-06-15 1981-01-09 Commissariat Energie Atomique Procede de recuperation de l'uranium present dans une solution d'acide phosphorique
FR2461681A1 (fr) * 1979-07-20 1981-02-06 Rhone Poulenc Ind Perfectionnement au procede de recuperation de l'uranium d'un acide phosphorique impur
FR2494258A1 (fr) 1980-11-14 1982-05-21 Commissariat Energie Atomique Procede de recuperation de l'uranium present dans des solutions d'acide phosphorique
FR2596383B1 (fr) * 1986-03-28 1990-10-26 Cogema Procede de separation du fer a partir d'une solution organique contenant de l'uranium
IL79999A0 (en) 1986-09-10 1986-12-31 Yeda Res & Dev Bifunctional organophosphorus extractants and polymers for uranium recovery
US6645453B2 (en) * 2001-09-07 2003-11-11 Secretary, Department Of Atomic Energy, Government Of India Solvent extraction process for recovery of uranium from phosphoric acid (25-55% P205)
FR2990206B1 (fr) 2012-05-07 2014-06-06 Commissariat Energie Atomique Nouveaux composes bifonctionnels utiles comme ligands de l'uranium(vi), leurs procedes de synthese et leurs utilisations
CN103397184B (zh) * 2013-07-31 2014-12-03 南昌航空大学 一种反萃取分离叔胺有机相中铀和铁的方法

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