Europäisches Patentamt *EP001019322B1* (19) European Patent Office

Office européen des brevets (11) EP 1 019 322 B1

(12) EUROPEAN PATENT SPECIFICATION

(45) Date of publication and mention (51) Int Cl.7: C01D 3/18, G21C 19/48 of the grant of the patent: 18.07.2001 Bulletin 2001/29 (86) International application number: PCT/GB98/02743 (21) Application number: 98944035.9 (87) International publication number: (22) Date of filing: 16.09.1998 WO 99/14160 (25.03.1999 Gazette 1999/12)

(54) TREATMENT OF MOLTEN REPROCESSING WASTES VERFAHREN ZUR BEHANDLUNG VON SALZSCHMELZEN AUS WIEDERAUFBEREITETEN ABFÄLLEN TRAITEMENT DE DECHETS DE RETRAITEMENT PAR SELS FONDUS

(84) Designated Contracting States: • ROONEY, David, William FR GB Belfast BT9 5AG (GB)

(30) Priority: 16.09.1997 GB 9719551 (74) Representative: Harrison Goddard Foote Tower House, (43) Date of publication of application: Merrion Way 19.07.2000 Bulletin 2000/29 Leeds LS2 8PA (GB)

(73) Proprietor: British Nuclear Fuels PLC (56) References cited: Risley Warrington Cheshire, WA3 6AS (GB) WO-A-98/06106 US-A- 5 336 450

(72) Inventors: • SEDDON K R: "IONIC LIQUIDS FOR CLEAN • FIELDS, Mark TECHNOLOGY" JOURNAL OF CHEMICAL Askam-in-Furness, Cumbria CA16 7HT (GB) TECHNOLOGY AND BIOTECHNOLOGY • THIED, Robert, Charles (INTERNATIONAL JOURNAL OF Seascale, Cumbria CA20 1PG (GB) BIOTECHNICAL AND CHEMICAL PROCESSES), • SEDDON, Kenneth, Richard vol. 68, no. 4, April 1997, pages 351-356, Belfast BT9 5AG (GB) XP000659374 • PITNER, William, Robert Belfast BT9 5AG (GB)

Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention). EP 1 019 322 B1

Printed by Jouve, 75001 PARIS (FR) 1 EP 1 019 322 B1 2

Description [0007] E. S. Lane, J. Chem. Soc. (1953), 1172-1175 describes the preparation of certain alkylpyridinium ni- [0001] This invention relates to the treatment of trate ionic liquids, including sec-butylpyridinium nitrate. and, more particularly, the treatment of salts previously No use of the liquids is mentioned but reference is made used in molten form in the reprocessing and treatment 5 to the pharmacological activity of decamethylenebis(py- of nuclear materials. ridinium nitrate). [0002] Molten salts are known for their use as sol- [0008] Ionic liquids based on various anions, includ- vents and they have in fact been proposed for use in the ing nitrate, fluoroborate and ethanoate, are disclosed by reprocessing or treatment of irradiated fuels from light J S Wilkes et al., J. Chem. Soc. Chem. Commun., water reactors (LWRs) and fast reactors. In such a meth- 10 965-967 (1992). The use as solvents for catalysis of ion- od, an irradiated fuel is dissolved into molten ic liquids based on non-nucleophilic ions such as chlorides. The dissolved uranium and plutonium spe- tetrafluoroborate and hexafluorophosphate is described cies are extracted from the salt and, optionally, proc- by Y. Chauvin et al., Angew. Chem. Int. Edit. Engl., 34, essed into fuel, and the molten salt is re-used. Eventu- 2698-2700 (1995). ally the molten salt becomes significantly contaminated 15 [0009] L. Heerman et al., J. Electroanal. Chem., 193, with fission products which must be removed before the 289 (1985) describe the dissolution of UO3 in a system salt can be re-used. One process which uses molten comprising N-butylpyridinium chloride and aluminium salts for reprocessing irradiated fuel uses chlo- (III) chloride. ride/ chloride eutectic [{LiCl + KCl} eutectic] [0010] WO 95/21871, WO 95/21872 and WO and another uses chloride/ 20 95/21806 relate to ionic liquids and their use to catalyse eutectic [{NaCl + KCl} eutectic]. When used herein, the hydrocarbon conversion reactions (e.g. polymerisation term "molten salt" refers to a salt, or a mixture of salts, or oligomerisation of olefins) and alkylation reactions. having inorganic cationic and anionic species, and hav- The ionic liquids are preferably 1-(C1-C4 alkyl)-3-(C6- ing a melting point in excess of 100°C, usually at least C30 alkyl) imidazolium chlorides and especially 1-me- 25 300°C. The term "metal salt", when used herein, refers thyl-3-C10 alkyl-imidazolium chloride, or 1-hydrocarbyl to a material which gives rise to a molten salt when melt- pyridinium halides, where the hydrocarbyl group is for ed. In addition to chloride salts such as those mentioned example ethyl, butyl or other alkyl. above, other molten salts with which this invention may [0011] The present invention provides a method of re- be concerned include fluorides and carbonates. moving from a metal salt ionic species therein, which [0003] Recently, salts, mixtures of salts, or mixtures 30 method comprises contacting the metal salt with an ionic of components which produce salts, which melt below liquid to dissolve the metal salt, the ionic species or both, or just above room temperature have become known. thereby to form a resultant ionic liquid composition and, (In the terms of this invention, a salt consists entirely of at least in the case where both the molten salt and the cationic and anionic species). Such liquids are known ionic species are dissolved, said ionic liquid composition as "ionic liquids" although this term can be used for salts 35 is treated to separate the ionic species therefrom and which melt at relatively high temperatures, including for subsequently processed to recover the metal salt. example temperatures of up to 100°C. They normally [0012] The method of the invention has the advantage include at least an organic cation. Common features of that it can be performed at relatively low temperatures ionic liquids include a zero vapour pressure at room tem- (e.g. of about 50 °C or less), for example at tempera- perature, a high solvation capacity and a large liquid 40 tures at or close to room temperature. range (for instance, of the order of 300°C). [0013] The ionic species with which this invention is [0004] When used herein, the term "ionic liquid" refers concerned include ions of fission products, minor acti- to a salt, a mixture of salts, or a mixture of components nides, activation products, corrosion products, fuel ad- which produce salts and which melts at a temperature ditives and process additives. up to 100°C and/or includes an organic cation. 45 [0014] The metal salt is preferably an alkali metal hal- [0005] Other ionic liquids are, for example, nitrates, ide or a mixture of alkali metal halides, for example a fluoroborates, ethanoates or hexafluorophosphates, of mixture of and potassium chloride or a which nitrates and fluoroborates are discussed in PCT/ mixture of and potassium chloride. GB97/02057,. Mixtures of any of the previously de- Such alkali metal halide mixtures are suitably eutectics. scribed ionic liquids may likewise be used. 50 [0015] The species removed from the metal salt may [0006] Known ionic liquids include halides such as an comprise fission product ions, for example as their chlo- imidazolium halide, a pyridinium halide or a phosphoni- rides, fluorides or nitrates. Exemplary fission products um halide as well as such materials in combination with, include Cs, Sr, Ba and those of the actinides and lan- for instance, a metal halide such as aluminium chloride. thanides. The invention is particularly concerned with Examples of ionic liquids include 1-ethyl-3-methylimida- 55 methods in which the ionic species comprise cations of zolium chloride, N-butylpyridinium chloride, tetrabutyl- the lanthanides (for example Sm. Gd and Ce) and the phosphonium chloride and a mixture of 1-ethyl-3-meth- metals Cs, Sr and Ba. ylimidazolium chloride and aluminium(III) chloride. [0016] In preferred processes, the metal salt and the

2 3 EP 1 019 322 B1 4 ionic species are dissolved in the ionic liquid and known to solution. Such leaching is desirably aided by reducing techniques may be used to separate the dissolved prod- the particle size by, for instance, mechanically dividing ucts. Suitable separation techniques include salting out, (e.g. crushing or grinding) the salt. electrochemical methods, precipitation and ion ex- [0023] The ionic liquid mixture is then treated to sep- change. In one class of methods, the solution is treated 5 arate the alkali metal halides from the fission products, to separate the ionic species, typically fission product for example by using one or more techniques known per chlorides, therefrom and subsequently processed to re- se for separating solutes. Suitable separation proce- cover the metal salt. dures include salting out, other precipitation methods, [0017] Alternatively, a component from the metal salt ion exchange, and electrochemical separation. The fis- and contaminant fission product mixture is dissolved in 10 sion products may not have been completely dissolved the ionic liquid. The presence of an insoluble component in the ionic solvent because, for instance, they may be leads to the first step in the separation sequence. "locked" within the particles of an insoluble component. [0018] In one preferred class of processes, LiCI + KCl A further washing step may be necessary in these cir- or NaCI + KCI, in either case containing dissolved fis- cumstances. In such cases, the invention normally in- sion products, is contacted at, for example, room tem- 15 cludes the decontaminating of such insoluble residues perature with an ionic liquid system in which the alkali remaining after the dissolution of the alkali metal halide metal halides as well as fission products to be separated composition. Each of the foregoing procedures will now therefrom are soluble. The invention contemplates in be considered in turn with specific reference to the treat- particular ionic liquids containing an organic halide, op- ment of reprocessing salt compositions. tionally in combination with a metal halide such as alu- 20 minium(III) chloride; such ionic liquids include in combi- Salting Out of Chlorides nation with an imidazolium halide, a pyridinium halide or a phosphonium halide as well as these materials in [0024] A majority of radioactive fission product hali- combination with aluminium (III) chloride. Examples of des (but not Cs halides) have lattice energies, which are organic halide ionic liquids include 1-ethyl-3-methylimi- 25 considerably greater than those of the alkali metal hali- dazolium chloride, N-butylpyridinium chloride and des. Thus, when the salts have been dissolved in an tetrabutylphosphonium chloride. Preferred ionic liquids ionic liquid the fission product chlorides may be precip- include 1-ethyl-3-methylimidazolium chloride and a mix- itated by the addition of a species (for example toluene, ture of basic (that is, Franklin basic) 1-ethyl-3-methyl- benzene or other organic solvent) which makes the ionic imidazolium chloride and aluminium(III) chloride ("[em- 30 liquid more like an organic solvent, thereby destabilising im]Cl-AlCl3"). Of course, the aforegoing ionic liquids the fission product complexes: as the ionicity of the so- may be used to dissolve salt compositions other than lution decreases a fission product chloride is precipitat- LiCl + KCl or NaCl + KCl. ed when the stabilisation energy of the complex in the [0019] A further preferred option is combining the ion- solution becomes less than the lattice energy of the ic liquids to form a mixture, such as 1-ethyl-3-methyl- 35 chloride. Thus. lanthanide and alkaline earth chlorides imidazolium chloride and 1-octyl-3-methyl-imidazolium are generally precipitated before alkali metal chlorides. chloride. [0025] The precipitated chlorides may in practice be [0020] The composition of the [emim]C1-AlCl3 mix- pyrohydrolysed prior to disposal. ture determines whether the liquid has Franklin acidic, [0026] Alternatively the salt may be dissolved in water 40 basic or neutral properties. A basic melt has an AlCl3: or similar solvent, the resulting solution being added to [emim]Cl ratio < 1.0. whilst an acidic melt has an AlCl3: an ionic liquid. Upon removal of the water by [emim]Cl ratio > 1.0. A neutral melt has an AlCl3:[emim] evaporation , the soluble component(s) of the solute Cl ratio = 1.0. may be extracted into the ionic liquid and any compo- [0021] The invention will now be described in more nents which are insoluble in the ionic liquid will form a detail primarily in relation to alkali metal halide salts pre- 45 precipitate. viously used in reprocessing and contaminated with fis- sion products. It will be understood, however, that the Precipitation of Phosphates invention may equally be applied to other metal salts, especially to remove contaminants. [0027] As an alternative to precipitation by salting out [0022] Thus, in the treatment of salt compositions re- 50 (or even to supplement it), fission product salts, espe- sulting from reprocessing and treatment of nuclear ma- cially phosphates, may be precipitated from the ionic liq- terials, the ionic liquid (e.g. basic [emim]Cl-AlCl3) may uid solution by addition of, in particular, a phosphate be used to dissolve one or more of the alkali metal halide such as, for example, Na3PO4 or K[H2PO4]. [s] and/or (usually by complexing) the bulk of the fission product halides (normally chlorides). If the alkali metal 55 Ion Exchange halide component of the composition is relatively insol- uble in the ionic liquid, as in the case of NaCI in basic [0028] After precipitation of lanthanide fission prod- [emim]Cl-AlCl3, the fission products may be leached in- ucts as phosphates, the LiCl + KCl or NaCI + KC1 salt

3 5 EP 1 019 322 B1 6 mix is likely to be significantly contaminated by, in par- (iii) then optionally removing contaminants remain- ticular, alkali and alkaline earth metal halides. The dis- ing in the solution by ion exchange; and solved contaminants may be removed by ion exchange, for example using a zeolite. (iv) recovering the alkali metal halide composition 5 from the solution and, if necessary, adjusting its Electrochemical Separation composition to the eutectic.

[0029] As an alternative to precipitation to separate [0034] In some of these methods a residue compris- out fission products, electrochemical separation may be ing alkali and/or alkaline earth metal halides remains un- considered, for example the reduction of lanthanide(III) 10 dissolved in the ionic liquid. The residue is dissolved in to lanthanide(0). Electrochemical separation requires a an acidic ionic liquid, especially acidic [emim]Cl-AlCl3, solvent which is not significantly destroyed in the elec- to obtain a mixture from which contaminants are re- trowinning process. moved especially by precipitation or electrochemical re- duction and/or by ion exchange. Decontamination of Halides Insoluble in the Initial 15 [0035] Also included in the invention is the use of an Ionic Liquid Solvent ionic liquid as a solvent for an ionic composition in the selective removal from the dissolved composition of one [0030] Halides not dissolved in the chosen ionic liquid or more species contained in the composition. may be treated to remove radioactive ions by contacting [0036] In order that the present invention may be the undissolved residue with another ionic liquid com- 20 more fully understood, examples will now be given by position. For example, halides not dissolved in the basic way of illustration only with reference to the accompa- ionic liquid used in the initial dissolution may be treated nying drawings of which: to remove radioactive ions by contacting the undis- solved residue with acidic [emim]Cl-AlCl3, in which it Figure 1 is a graph illustrating the effect of changing 25 may be dissolved. The radioactive ions (fission prod- the composition of AlCl3 in the ionic liquid [emim]Cl- ucts) may be removed from the resulting solution by, for AlCl3 on LiCI and KCl solubility. example, any of the separation techniques mentioned above, especially ion exchange. Acidic [emim]Cl-AlCl3 Figure 2 is a flowsheet diagram illustrating a proc- is not suitable for dissolving mixtures containing signif- ess for the extraction of metal chloride from a mol- icant NaCI, because this ionic liquid reacts with NaCl to 30 ten salt mixture using [emim]Cl; yield neutral, buffered [emim]Cl-AlCl3 composition which will not dissolve fission product chlorides. Figure 3 is a flowsheet diagram illustrating a proc- [0031] Acidic [emim]Cl-AlCl3 may be used as solvent ess for the extraction of metal chloride from a mol- in other contexts. Moreover, irrespective of the context, ten salt mixture using concentrated HCl and an [em- other acidic ionic liquids (e.g. those based on substitut- 35 im]Cl/[omim]Cl mixture; ed imidazolium and/or containing AlCl3) may be used in place of [emim]Cl-AlCl3. Some preferred methods of the Figure 4 is a flowsheet diagram illustrating a proc- invention therefore involve dissolving a metal halide in ess for the extraction of metal chloride from a mol- an acidic ionic liquid. ten salt mixture using water and an [emim]Cl/[omim] [0032] The cleaned salt composition is then recov- 40 Cl mixture; ered from the ionic liquid and, if required, has its com- position adjusted to the eutectic. In one variant, the Figure 5 is a flowsheet diagram illustrating a proc- cleaned salt composition is dissolved in water or another ess for the extraction of metal chloride from a mol- aqueous medium and then extracted with a water-insol- ten salt mixture using methanol and 1-butyl-3-meth- 45 uble ionic liquid (e.g. [bmim][PF6], where [bmim] = ylimidazolium tetrafluoroborate ([bmim][BF4]). 1-butyl-3-methylimidazolium cation). The salt composi- tion may then be re-used. Figure 6 is a flowsheet diagram illustrating a proc- [0033] It will be appreciated, therefore, that the inven- ess for the extraction of metal chloride from a mol- tion includes a method of removing radioactive contam- ten salt mixture using 1-butyl-3-methylimidazolium 50 inants from an alkali metal halide composition used in hexafluorophosphate ([bmim][PF6]) and [emim]Cl. the reprocessing of nuclear fuel, comprising: [0037] In order to show the effectiveness of the (i) dissolving in an ionic liquid said contaminants to present invention a series of experiments were under- obtain an ionic liquid solution; taken in order to determine the maximum amount of in- 55 dividual salts which could be dissolved by [emim]Cl. In (ii) separating said contaminants from the solution these experiments 10g of [emim]Cl was heated to 150° by precipitation, solvent extraction or electrochem- and small quantities (0.5g) of LiCl, KCl and NaCl were ical reduction; added.

4 7 EP 1 019 322 B1 8

[0038] The mixture was stirred for a minimum of eight methanol may be used. The resultant LiCl solution is hours or until no solid remained. The results are given separated from KCI and GdCl3 by filtration, both being in table 1 below which gives the percentage by weight insoluble in concentrated HCI in the separation vessel for each salt dissolved in the ionic liquid. The column 38. The LiCI solution is removed to an evaporator 40 headed mix refers to a eutectic mixture of LiCI and KCl. 5 where the concentrated HCl is evaporated off and re- used. The LiCI is then washed 42 and can then be sent TABLE 1 for recycle in the reprocessing plant. The KCl and GdCl3 % Weight are dissolved in water 46 and a mixture of the ionic liq- uids [emim]Cl and [omim]Cl are added 50 to the solution Chloride Run 1 Run 2 Mix 10 48. Sodium 0.76 0.74 - [0046] The resultant mixture is added to vessel 52 in Potassium 0.19 0/17 0.24 which the water is evaporated off, causing the formation Lithium 26.35 25.93 13.78 of a KCl precipitate and leaving GdCl3 dissolved in the ionic liquid. GdCl3 is recoyered by addition of an organic 15 solvent such as chloroform at 54. The GdCl can thus [0039] It can therefore be seen that LiCl is more sol- 3 be filtered off and sent to a further vessel for conversion uble in [emim]Cl than KCl or NaCl. to oxide. The organic solvent can be removed from the [0040] In addition, it has been found that the addition ionic liquid mixture by distillation. The ionic liquid which of AlCl to a mixture of LiCl and [emim]Cl results in the 3 remains can be recycled in the process by adding at 50. precipitation of LiCl. This allows the control of the LiCl 20 All solvents are thus recycled. LiCl and KCl are now solubility by the addition of AlCl . 3 clean and can be returned to the reprocessing plant. [0041] Figure 1 further shows that an increase in the [0047] Referring to figure 4, the flow sheet schematic concentration of AlCl in the ionic liquid [emim]Cl de- 3 diagram 70 shows a process for the removal of metal creases the solubility of LiCl and in addition, if the con- chlorides from a salt mixture comprising NaCl, KCl and centration of AlCl is further increased, the solubility of 3 25 GdCl . KCl increases. 3 [0048] The cooled molten salt 72 first passes through [0042] Referring to Figure 2, the flow sheet schematic a particle reduction step. The salt is then combined with diagram 10 shows a process for the removal of metal water 74. At this stage any insoluble products are filtered chloride ionic species in this case gadolinium chloride off. To the resultant aqueous solution 76 is added a mix- from a salt mixture. The molten salt mixture of KCI, LiCI 30 ture of the ionic liquids [omim]Cl and [emim]Cl 78. The and GdCl is placed in a bath 12 and cooled to a solid. 3 water is evaporated off from this mixture. The GdCl is [0043] The solid is removed to a particle size reduc- 3 soluble in the ionic liquid mixture but the NaCl and KCl tion vessel 14 and from there it is combined with the ionic are insoluble. As this water is removed, the NaCl and liquid [emim]Cl and added to a reaction vessel 18 in KCl precipitate from the mixture and are passed to ves- which LiCl and GdCl dissolve in [emim]Cl and KCl is 3 35 sel 84 for working with an organic solvent. The GdCl is present as an insoluble solid. The insoluble KCl is re- 3 separated from the ionic liquid using an organic solvent moved from reaction vessel 18 to filter 20 where it is such as chloroform. The GdCl is then sent to vessel for filtered, washed and then recycled to the reprocessing 3 oxide conversion, in readiness for vitrification. The or- plant. LiCl and GdCl are then removed into reaction 3 ganic solvent is removed from the ionic liquid by distil- vessel 22. The gadolinium may be removed by elec- 40 lation. Thus both the ionic liquid and the organic solvent trodeposition and hence extraction from the lithium, or can be recycled to the process (point 78 for the ionic by, for instance, precipitation of a gadolinium phosphate liquid). NaCl and KCl can now be recycled to the reproc- by the addition of a phosphate precursor. essing plant. [0044] The LiCI can then be removed from the ionic [0049] Referring to figure 5. the flowsheet schematic liquid using an organic solvent. The LiCI is then clean 45 diagram 90 shows a process for the removal of metal and the organic solvent can be removed from the ionic chlorides from a salt mixture comprising NaCl, KCl and liquid by evaporation and can be sent for re-use at the GdCl . Salt from the molten salt bath 92 is first cooled, reprocessing plant. Both the ionic liquid and the molten 3 then sent for mechanical particle size reduction 94 salt can then be recycled to this extractor process. Methanol 96 is then used as a solvent, dissolving LiCl [0045] Referring to Figure 3, the flow sheet schematic 50 and GdCl chlorides, but leaving behind KCl in vessel diagram 30 shows a process for the removal of metal 3 98. The KCl can be filtered, washed in an organic sol- chlorides ionic species, in this case gadolinium chloride vent 100, and returned to the molten salt bath 92. The from a salt mixture. The molten salt mixture comprising LiCI / GdCl solution is then treated with another ionic KCl, LiCI and GdCl is cooled in a bath 32, the solid mix- 3 3 liquid such as hot l-butyl-3-methylimidazolium tetrafluor- ture is then sent for particle size reduction in the particle 55 oborate, [bmim][BF ] (140°C) in vessel 102. The meth- size reduction vessel 34. From here the mixture is 4 anol is distilled off 104, and returned to the first dissolu- passed to vessel 38, concentrated HCl 38 being added tion step 96. LiCl will be soluble in the hot [bmim][BF ] to dissolve LiCl. As an alternative to the use of HCl, 4 whereas GdCl3 will form a precipitate. The GdCl3 pre-

5 9 EP 1 019 322 B1 10 cipitate can be filtered off 106, sent to oxide conversion, 3. A method of Claim 2 wherein the metal salt is mix- and vitrification. ture of LiCl and KCl or a mixture of NaCl and KCl. [0050] The LiCl could be precipitated from the [bmim] [BF4] by saturation of the solution 108, followed by cool- 4. A method of any of Claims 1 to 3 wherein the ionic ing and filtering off the solid LiCl 110. The [bmim]Cl can 5 species comprise one or more species selected then be recycled to the process. This process has the from cations of the lanthanides, the alkali metals advantage that all solvents are thus recycled. and the alkaline earth metals. [0051] Referring to figure 6, the flowsheet schematic diagram 120 shows a process for the removal of metal 5. A method of Claim 4 wherein the ionic species com- chlorides from a salt mixture comprising NaCl, KCl and 10 prise one or more cations of Sm, Gd, Cs, Ba and Sr. GdCl3. Salt form the molten salt bath 122 is first cooled, then sent for mechanical particle size reduction 124. 6. A method of any of Claims 1 to 5 wherein the ionic The salt particles are then dissolved in an ionic liquid liquid comprises at least one imidazolium halide, a [bmim][BF4] 126 which dissolves LiCl in vessel 128. The pyridinium halide or a phosphonium halide, option- 15 remaining solid KC1 and GdCl3 can be filtered off, and ally in combination with AlCl3. sent to the next stage. The LiCl solution in [bmim]Cl, is then contacted with water or methanol 130, to extract 7. A method of Claim 6 wherein the ionic liquid is the lithium chloride 132, and the [bmim]Cl can be recy- 1-ethyl-3-methylimidazolium chloride. cled to the process. The KCl and LnCl3 solids are mixed with an ionic liquid such as [emim]Cl 134, into which the 20 8. A method of Claim 6 wherein the ionic liquid is GdCl3 will dissolve 136. The insoluble KCl precipitate 1-ethyl-3-methylimidazolium chloride in combina- can be filtered off, washed and dried and returned to the tion with 1-octyl-3-methylimidazolium chloride. molten salt bath 138. The gadolinium laden ionic liquid stream, can be thermally decomposed to leave the ox- 9. A method of Claim 6 which includes the features of ides for vitrification 140. 25 claims 3 and 4 and wherein the ionic liquid is basic [0052] The method of the present invention may also 1-ethyl-3-methylimidazolium chloride-AlCl3 or an- be used for the extraction of more than one lanthanide other basic ionic liquid. salt or other fission products from a eutectic mix. For example, a eutectic mixture comprising 45g LiCl and 10. A method of Claims 1 to 9 wherein said treatment 30 KCl, 2.5g SmCl3 and 2.5g GdCl3 was combined with 45g comprises one or more of salting out, another pre- of methanol or 45g of concentrated hydrochloric acid cipitation method, ion exchange and electrochemi- and stirred for eighteen hours. The sample was then fil- cal separation. tered and the resulting solids were collected and dis- solved in 50g distilled water. In addition 5g of [emim]Cl 11. A method of Claim 10 wherein the ionic solution and 5g of [omim]Cl were added to the aqueous solution. 35 contains [LiCl and KCl] or [NaCl and KCl] and at The sample was then heated to 100°C for 1 hour and least one lanthanide, and wherein the solution is subsequently allowed to cool. 20g of methanol was add- treated to separate the or each lanthanide there- ed and the mixture was filtered, the methanol was ex- from and is subsequently processed to recover the tracted from the resultant liquid to leave a liquid com- [LiCl and KCl] or [NaCl and KCl], the treatment com- 40 prised of [emim]Cl, [omim]Cl SmCl3 and CdCl3. prising at least one of the steps of salting out the or [0053] A similar method was used to extract SmCl3 each lanthanide as the chloride or chlorides thereof, and GdCl3 from KCL and NaCl. precipitating out the or each lanthanide as the phos- phate or phosphates thereof, or electrochemically separating the or each lanthanide. Claims 45 12. A method of Claim 10 or Claim 11 wherein the ionic 1. A method of removing from a metal salt ionic spe- solution further contains alkali and/or alkaline earth cies therein, which method comprises contacting metal halides other than [LiCl and KCl] or [NaCl and the metal salt with an ionic liquid to dissolve the met- KCl] and said other halides are removed by ion ex- al salt, the ionic species or both, thereby to form a 50 change. resultant ionic liquid composition and, at least in the case where both the metal salt and the ionic species 13. A method of any of Claims 1 to 12 which comprises are dissolved, said ionic liquid composition is treat- dissolving a metal halide in acidic 1-ethyl-3-methyl- ed to separate the ionic species therefrom and sub- imidazolium chloride-AlCl3 or another acidic ionic sequently processed to recover the metal salt. 55 liquid.

2. A method of Claim 1 wherein the metal salt is one 14. A method of Claim 13 wherein said metal halide is or more alkali metal halides. a residue, insoluble in basic 1-ethyl-3-methylimida-

6 11 EP 1 019 322 B1 12

zolium chloride-AlCl3, remaining after performing a genannte ionische, flüssige Zusammensetzung be- process of claim 1. handelt um die ionische Spezies daraus abzutren- nen und anschließend bearbeitet, um das Metall- 15. A method of Claim 14 wherein the performing of a salz zurückzugewinnen. process of claim 1 involves performing a method of 5 claim 7. 2. Ein Verfahren nach Anspruch 1, worin das Metall- salz ein oder mehrere Alkalimetallhalogenide ent- 16. A method as defined in claim 1 for removing radio- hält. active contaminants from an alkali metal halide composition used in the reprocessing of nuclear fu- 10 3. Ein Verfahren nach Anspruch 2, worin das Metall- el, comprising: salz eine Mischung aus LiCl und KCl oder eine Mi- schung aus NaCl und KCl ist. (i) dissolving in an ionic liquid said contami- nants to obtain an ionic liquid solution; 4. Ein Verfahren nach einem der Ansprüche 1 bis 3, (ii) separating said contaminants from the so- 15 worin die ionische Spezies eine oder mehrere Spe- lution by precipitation or electrochemical reduc- zies ausgewählt aus Kationen der Lanthaniden, Al- tion; kalimetalle und der Erdalkalimetalle umfasst. (iii) then optionally removing contaminants re- maining in the solution by ion exchange; and 5. Ein Verfahren nach Anspruch 4, worin die ionische (iv) recovering the alkali metal halide composi- 20 Spezies ein oder mehrere Kationen von Sm, Gd, Ba tion from the solution and, if necessary, adjust- und Sr umfasst. ing its composition to the eutectic. 6. Ein Verfahren nach einem der Ansprüche 1 bis 5, 17. A method of Claim 16 wherein the ionic liquid is worin die ionische Flüssigkeit wenigstens ein Imi- 1-ethyl-3-methylimidazolium chloride or acidic 25 dazolium-halogenid, ein Pyridiniumhalogenid oder 1-ethyl-3-methylimidazolium chloride-AlCl3. ein Phosphoniumhalogenid umfasst, optional in Kombination mit AlCl3. 18. A method of Claim 16 or Claim 17 wherein a residue comprising alkali and/or alkaline earth metal halides 7. Ein Verfahren nach Anspruch 6, worin die ionische remains undissolved in the ionic liquid, which resi- 30 Flüssigkeit 1-Ethyl-3-methylimidazoliumchlorid ist. due is dissolved in acidic 1-ethyl-3-methylimidazo- lium chloride-AlCl3 to obtain a mixture from which 8. Ein Verfahren nach Anspruch 6, worin die ionische contaminants are removed by precipitation or elec- Flüssigkeit 1-Ethyl-3-methylimidazoliumchlorid in trochemical reduction and/or by ion exchange. Kombination mit 1-Octyl-3-methylimidazoliumchlo- 35 rid ist. 19. A method of any of Claims 16 to 18, wherein the recovery of the alkali metal halide composition in- 9. Ein Verfahren nach Anspruch 6, das die Merkmale volves its being extracted into an aqueous medium der Ansprüche 3 und 4 einschließt und worin die and then extracted into a water-insoluble ionic liq- ionische Flüssigkeit basisches 1-Ethyl-3-methylimi- 40 uid. dazolium-chlorid-AlCl3 oder eine andere basische, ionische Flüssigkeit ist. 20. A method of any of Claims 16 to 18, wherein the recovery of the alkali metal halide composition in- 10. Ein Verfahren nach den Ansprüchen 1 bis 9, worin volves its being extracted into an aqueous medium genannte Behandlung ein oder mehrere Schritte followed by addition of a water miscible ionic liquid 45 des Aussalzens, andere Fällungsverfahren, lonen- and removal of the water. austausch und elektrochemische Trennung um- fasst.

Patentansprüche 11. Ein Verfahren nach Anspruch 10, worin die ionische 50 Lösung [LiCl und KCl] oder [NaCl und KCl] und we- 1. Ein Verfahren zum Entfernen von in einem Metall- nigstens ein Lanthanid enthält, und worin die Lö- salz befindlichen ionischen Spezies, das Verfahren sung behandelt wird, um das oder jedes Lanthanid umfasst das in Kontakt bringen des Metallsalzes mit daraus abzutrennen, und anschließend bearbeitet einer ionischen Flüssigkeit, um das Metallsalz, die wird, um das [LiCl und KCl] oder [NaCl und KCl] zu- ionische Spezies oder beide zu lösen, wodurch sich 55 rückzugewinnen, die Behandlung wenigstens einen eine ionische, flüssige Zusammensetzung bildet der Schritte des Aussalzens des oder jeden Lantha- und wenigstens in dem Fall, in dem beide, das Me- nids als Chlorid oder deren Chloride, Ausfällen des tallsalz und die ionische Spezies, gelöst sind, wird oder jeden Lanthanids als Phosphat oder deren

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Phosphate, oder elektrochemisches Trennen des Kontaminationen durch Fällung oder elektrochemi- oder jeden Lanthanids umfasst. sche Reduktion und/oder durch Ionenaustausch entfernt werden. 12. Ein Verfahren nach Anspruch 10 oder Anspruch 11, worin die ionische Lösung weiterhin andere Alkali- 5 19. Ein Verfahren nach irgendeinem der Ansprüche 16 und/oder Erdalkalimetallhalogenide als [LiCl und bis 18, worin die Rückgewinnung der Alkalimetall- KCl] oder [NaCl und KCl] enthält und genannte an- halogenid-Zusammensetzung deren Extraktion in dere Halogenide durch Ionenaustausch entfernt ein wässriges Medium und dann deren Extraktion werden. in eine wasserunlösliche, ionische Flüssigkeit ein- 10 schließt. 13. Ein Verfahren nach irgendeinem der Ansprüche 1 bis 12, welches das Lösen eines Metallhalogenids 20. Ein Verfahren nach irgendeinem der Ansprüche 16 in saurem 1-Ethyl-3-methylimidazoliumchlorid- bis 18, worin die Rückgewinnung der Alkalimetall- AlCl3 oder einer anderen sauren, ionischen Flüssig- halogenid-Zusammensetzung deren Extraktion in keit, umfasst. 15 ein wässriges Medium, gefolgt von der Zugabe ei- ner mit Wasser mischbaren ionischen Flüssigkeit 14. Ein Verfahren nach Anspruch 13, worin genanntes und Entfernen des Wassers einschließt. Metallhalogenid ein in basischem 1-Ethyl-3-methy- limidazoliumchlorid-AlCl3 unlöslicher Rückstand ist, welcher nach Durchführung eines Verfahrens 20 Revendications nach Anspruch 1 zurückbleibt. 1. Procédé pour enlever des espèces ioniques d'un 15. Ein Verfahren nach Anspruch 14, worin die Durch- sel métallique, lequel procédé comporte la mise en führung eines Verfahrens nach Anspruch 1 die contact du sel métallique avec un liquide ionique Durchführung eines Verfahrens nach Anspruch 7 25 pour dissoudre le sel métallique, les espèces ioni- einschließt. ques ou les deux, pour former ainsi une composi- tion liquide ionique résultante, et au moins dans le 16. Ein Verfahren gemäß Anspruch 1, zum Entfernen cas où à la fois le sel métallique et les espèces io- von radioaktiven Kontaminationen aus einer in der niques sont dissous, ladite composition liquide io- Wiederaufbereitung von Kernbrennstoff verwende- 30 nique est traitée pour séparer les espèces ioniques ten Alkalimetallhalogenid-Zusammensetzung, um- de celle-ci et subséquemment traitée pour récupé- fassend: rer le sel métallique.

(i) das Lösen genannter Kontaminationen in ei- 2. Procédé selon la revendication 1, caractérisé en ce ner ionischen Flüssigkeit, um eine ionische, 35 que le sel métallique est constitué d'un ou plusieurs flüssige Lösung zu erhalten; halides métalliques alcalis. (ii) das Abtrennen genannter Kontaminationen von der Lösung durch Fällung oder elektroche- 3. Procédé selon la revendication 2, caractérisé en ce mische Reduktion; que le sel métallique est un mélange de LiCl et KCI (iii) dann gegebenenfalls das Entfernen in der 40 ou un mélange de NaCl et KCI. Lösung verbleibender Kontaminationen durch Ionenaustausch; und 4. Procédé selon l'une des revendications 1 à 3, ca- (iv) das Rückgewinnen der Alkalimetallhaloge- ractérisé en ce que les espèces ioniques compor- nid-Zusammensetzung aus der Lösung und, tent une ou plusieurs espèces choisies parmi des falls nötig, Einstellen ihrer Zusammensetzung 45 cations de lanthanides, les métaux alcalis et les mé- zur eutektischen Zusammensetzung. taux terre alcalins.

17. Ein Verfahren nach Anspruch 16, worin die ionische 5. Procédé selon la revendication 4, caractérisé en ce Flüssigkeit 1-Ethyl-3-methylimidazoliumchlorid que les espèces ioniques comportent un ou plu- oder saures 1-Ethyl-3-methylimidazoliumchlorid- 50 sieurs cations de Sm, Gd, Cs, Ba et Sr. AlCl3 ist. 6. Procédé selon l'une des revendications 1 à 5, ca- 18. Ein Verfahren nach Anspruch 16 oder Anspruch 17, ractérisé en ce que les liquides ioniques comportent worin ein Rückstand, umfassend Alkali- und/oder au moins un halide imidazolium, un halide pyridi- Erdalkalimetallhalogenide, ungelöst in der ioni- 55 nium, ou un halide phosphonium, et optionnelle- schen Lösung verbleibt, der Rückstand in saurem ment en combinaison avec AlCl3. 1-Ethyl-3-methylimidazoliumchlorid-AlCl3 gelöst wird, um eine Mischung zu erhalten, aus welcher 7. Procédé selon la revendication 6, caractérisé en ce

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que le liquide ionique est 1-éthyle-3-méthylimidazo- lide métallique alcali utilisée dans le retraitement de lium chlorure. combustible nucléaire, comprenant :

8. Procédé selon la revendication 6, caractérisé en ce (i) dissoudre dans un liquide ionique lesdits que le liquide ionique est 1-éthyle-3-méthylimidazo- 5 contaminants pour obtenir une solution liquide lium chlorure en combinaison avec 1-octyle-3-mé- ionique ; thylimidazolium chlorure. (ii) séparer lesdits contaminants de la solution par précipitation ou réduction électrochimique ; 9. Procédé selon la revendication 6 incluant les carac- (iii) ensuite de manière optionnelle, enlever les téristiques des revendications 3 et 4, et caractérisé 10 contaminants restant dans la solution par en ce que le liquide ionique est un basique 1-éthyle- échange d'ion ; et 3-méthylimidazolium chlorure-AlCl3 ou un autre li- (iv) récupérer la composition halide alcali métal quide ionique basique. de la solution et si nécessaire ajuster sa com- position à l'eutectique. 10. Procédé selon l'une des revendications 1 à 9, ca- 15 ractérisé en ce que ledit traitement comporte une 17. Procédé selon la revendication 16, caractérisé en ou plusieurs désalinisations, une autre méthode de ce que le liquide ionique est 1-éthyle-3-méthylimi- précipitation, d'échange d'ion et de séparation élec- dazolium chlorure ou acidique 1-éthyle-3-méthyli- trochimique. midazolium chlorure-AlCl3. 20 11. Procédé selon la revendication 10, caractérisé en 18. Procédé selon la revendication 16 ou 17, caracté- ce que la solution ionique contient [LiCl et KCl] ou risé en ce qu'un résidu comprenant des halides mé- [NaCl et KCI] et au moins un lanthanide, et en ce taux terre alcalis et/ou alcalins reste non dissout que la solution est traitée pour séparer le ou chaque dans le liquide ionique, lequel résidu est dissout lanthanide de celle-ci, et est subséquemment trai- 25 dans acidique 1-éthyle-3-méthylimidazolium chlo- tée pour récupérer le [LiCI et KCI] ou [NaCI et KCI], rure-AlCl3 pour obtenir un mélange à partir duquel le traitement comprenant au moins l'une des étapes les contaminants sont enlevés par précipitation ou de désalinisation du ou de chaque lanthanide ou du réduction électrochimique et/ou par échange d'ion. ou des chlorures de celle-ci, précipitation du ou de chaque lanthanide du phosphate ou des phospha- 30 19. Procédé selon l'une des revendications 16 à 18, ca- tes de celle-ci, ou la séparation électrochimique du ractérisé en ce que la récupération de la composi- ou de chaque lanthanide. tion halide métallique alcali implique l'extraction de celle-ci dans un milieu aqueux et ensuite extraction 12. Procédé selon la revendication 10 ou 11, caractéri- dans un liquide ionique insoluble dans l'eau. sé en ce que la solution ionique contient de plus des 35 halides métaux terre alcalis ou alcalins, autres que 20. Procédé selon l'une des revendications 16 à 18, ca- [LiCl et KCI] ou [NaCl et KCI] et lesdits autres hali- ractérisé en ce que la récupération de la compos- des sont enlevés par échange d'ion. tion halide métallique alcali implique son extraction dans un milieu aqueux suivie par de l'addition de 13. Procédé selon l'une des revendications 1 à 12, ca- 40 liquide ionique missible dans l'eau et enlèvement ractérisé en ce qu'il comporte l'étape de dissolution de l'eau. d'un halide métallique dans 1-éthyle-3-méthylimi- dazolium chlorure-AlCl3 acidique ou un autre liqui- de ionique acidique. 45 14. Procédé selon la revendication 13, caractérisé en ce que le métal halide est un résidu, insoluble dans basique 1-éthyle-3-méthylimidazolium chlorure- AlCl3, restant après réalisation d'un procédé selon la revendication 1. 50

15. Procédé selon la revendication 14, caractérisé en ce que la mise en oeuvre du procédé de la reven- dication 1 implique la réalisation du procédé de la revendication 7. 55

16. Procédé selon la revendication 1 pour l'enlèvement de contaminants radioactifs d'une composition ha-

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