Ionic liquid-acid aqueous two-phase system

Abstract

Disclosed is a process for extracting or separating metal ions using a composition including: an ionic liquid of formula C.sup.+,−X, in which: C.sup.+ is an onium cation including at least one hydrocarbon chain R.sup.1 including from 6 to 20 carbon atoms; X.sup.P− is an anion of charge p, the ionic liquid having a solubility in water at 20° C. of at least 10 g/l; an acid; and water. The composition includes two liquid phases: a phase enriched in ionic liquid ϕ.sub.IL; and a phase enriched in water ϕ.sub.w, the pH of which is less than or equal to 4.7. The composition is useful for extracting a metal ion from an acidic aqueous medium including a metal ion, for separating metal ions from an aqueous medium including at least two metal ions or for purifying an acidic aqueous solution including a metal ion.

Claims

1. Method for extracting a metal ion M from a medium, comprising the steps of: a) contacting an ionic liquid of formula C.sup.+,(X.sup.p−).sub.1/p, in which: C.sup.+ is an onium cation comprising at least one atom selected from N, S, P or O, the onium cation comprising at least one hydrocarbon chain R.sup.1 comprising from 6 to 20 carbon atoms, optionally interrupted by one or more groups selected from —S—, —O—, —(C═O)—O—, —O—(C═O)—, —NR.sup.10—(C═O)—, —(C═O)—NR.sup.11— or —NR.sup.12R.sup.13—, and/or optionally substituted with one or more groups selected from halogen, —OR.sup.14, —(C═O)R.sup.15, —(C═O)NR.sup.16R.sup.17—, —NR.sup.18R.sup.19R.sup.20, —S—R.sup.21, —(C═O)—OR.sup.22, wherein R.sup.10, R.sup.11, R.sup.12, R.sup.13, R.sup.14, R.sup.15, R.sup.16, R.sup.17, R.sup.18, R.sup.19, R.sup.20 and R.sup.21 independently represent H or a linear or branched hydrocarbon chain comprising from 1 to 6 carbon atoms and R.sup.22 represents a linear or branched hydrocarbon chain comprising from 1 to 6 carbon atoms, and X.sup.p− is an anion charge of p, the ionic liquid having a solubility in water at 20° C. of at least 10 g/L,  with an aqueous medium comprising a metal ion M and an acid, wherein a composition is obtained at a temperature T.sub.i, the composition comprising a single liquid phase, b) varying the temperature to obtain a composition at a temperature T.sub.f different from T.sub.i comprising two liquid phases φ.sub.IL and φ.sub.W, the liquid phase φ.sub.IL being a phase enriched in ionic liquid and the liquid phase φ.sub.W being a phase enriched in water, the pH is less than or equal to 4.7,  with the proviso that, at temperature T.sub.f, the partition coefficient of the metal ion between the two phases φ.sub.IL and φ.sub.W:
K(M).sub.Tf=[M]φ.sub.IL/[M]φ.sub.W in which [M].sub.φIL is the concentration in M in the phase φ.sub.IL at the temperature T.sub.f and [M]φ.sub.W is the concentration in M in the phase φ.sub.W at the temperature T.sub.f, is greater than 1, c) separating the phases φ.sub.IL and φ.sub.W of the composition obtained in step b), then d) optionally extracting the metal ion M from the phase φ.sub.IL.

2. Method for separating metal ions M.sub.1 and M.sub.2, comprising the steps of: a′) contacting an ionic liquid of formula C.sup.+,(X.sup.p−).sub.1/p, in which: C.sup.+ is an onium cation comprising at least one atom selected from N, S, P or O, the onium cation comprising at least one hydrocarbon chain R.sup.1 comprising from 6 to 20 carbon atoms, optionally interrupted by one or more groups selected from —S—, —O—, —(C═O)—O—, —O—(C═O)—, —NR.sup.10—(C═O)—, —(C═O)—NR.sup.11— or —NR.sup.12R.sup.13—, and/or optionally substituted with one or more groups selected from an halogen, —OR.sup.14, —(C═O)R.sup.15, —(C═O)NR.sup.16R.sup.17—, —NR.sup.18R.sup.19R.sup.20, —S—R.sup.21, —(C═O)—OR.sup.22, wherein R.sup.10, R.sup.11, R.sup.12, R.sup.13, R.sup.14, R.sup.15, R.sup.16, R.sup.17, R.sup.18, R.sup.19, R.sup.20 and R.sup.21 independently represent H or a linear or branched hydrocarbon chain comprising from 1 to 6 carbon atoms and R.sup.22 represents a linear or branched hydrocarbon chain comprising from 1 to 6 carbon atoms, and X.sup.p− is an anion of charge p, wherein the ionic liquid has a solubility in water at 20° C. of at least 10 g/L,  with an aqueous medium comprising two metal ions M.sub.1 and M.sub.2 (of different natures) and an acid, wherein a composition is obtained at a temperature T.sub.i, and wherein the composition comprises a single liquid phase, b′) varying the temperature to obtain a composition at a temperature T.sub.f different from T.sub.i comprising two liquid phases φ.sub.IL and φ.sub.W, the liquid phase φ.sub.IL being a phase enriched in ionic liquid and the liquid phase φ.sub.W being a phase enriched in water, of which the pH is less than or equal to 4.7, provided that, at the temperature T.sub.f, the separation factor b(M.sub.1/M.sub.2).sub.Tf corresponding to the ratio between the partition coefficients of M.sub.1 and M.sub.2 β
β(M.sub.1/M.sub.2).sub.Tf=K(M.sub.1).sub.Ti/K(M.sub.2).sub.Tf=([M.sub.1]φ.sub.IL/[M.sub.1]φ.sub.W)/([M.sub.1]φ.sub.IL/[M.sub.1]φ.sub.W) in which: K(M.sub.1).sub.Ti is the partition coefficient at the temperature T.sub.f of the metal ion M.sub.1 between the two phases φ.sub.IL and φ.sub.W, with K(M.sub.1).sub.Tf=[M.sub.1]φ.sub.IL/[M.sub.1]φ.sub.W, K(M.sub.1).sub.Ti is the partition coefficient at the temperature T.sub.f of the metal ion M.sub.2 between the two phases φ.sub.IL and φ.sub.W, with K(M.sub.2).sub.Tf=[M.sub.2]φ.sub.IL/[M.sub.2]φ.sub.W [M.sub.1].sub.φIL is the concentration in M.sub.1 in the phase φ.sub.IL at the temperature T.sub.f and [M.sub.1]φ.sub.W is the concentration in M.sub.1 in the phase φ.sub.W at the temperature T.sub.f, [M.sub.2].sub.φIL is the concentration in M.sub.2 in the phase φ.sub.IL at the temperature T.sub.f and [M.sub.2]φ.sub.W is the concentration in M.sub.2 in the phase φ.sub.W at the temperature T.sub.f, is greater than 1, c′) separating the phases φ.sub.IL and φ.sub.W of the composition obtained in step b′), then d′) optionally extracting the metal ion M.sub.1 from the phase φ.sub.IL, e′) optionally extracting the metal ion M.sub.2 from the phase φ.sub.W.

3. Method for separating metal ions M.sub.1 and M.sub.2 comprising the steps of: a″) contacting an ionic liquid of formula C.sup.+,(X.sup.p−).sub.1/p, wherein: C.sup.+ is an onium cation comprising at least one atom selected from N, S, P or O, the onium cation comprising at least one hydrocarbon chain R.sup.1 comprising from 6 to 20 carbon atoms, optionally interrupted by one or more groups selected from —S—, —O—, —(C═O)—O—, —O—(C═O)—, —NR.sup.10—(C═O)—, —(C═O)—NR.sup.11— or —NR.sup.12R.sup.13—, and/or optionally substituted with one or more groups selected from a halogen, —OR.sup.14, —(C═O)R.sup.15, —(C═O)NR.sup.16R.sup.17—, —NR.sup.18R.sup.19R.sup.20, —S—R.sup.21, —(C═O)—OR.sup.22, wherein R.sup.10, R.sup.11, R.sup.12, R.sup.13, R.sup.14, R.sup.15, R.sup.16, R.sup.17, R.sup.18, R.sup.19, R.sup.20 and R.sup.21 independently represent H or a linear or branched hydrocarbon chain comprising from 1 to 6 carbon atoms and R.sup.22 represents a linear or branched hydrocarbon chain comprising from 1 to 6 carbon atoms, and X.sup.p− is an anion of charge p,  wherein the ionic liquid has a solubility in water at 20° C. of at least 10 g/L, with an aqueous medium comprising an acid and two metal ions M.sub.1 and M.sub.2 (of different natures), wherein a composition is obtained at a temperature T.sub.i, the composition comprising: either a single liquid phase, or two liquid phases φ.sub.IL and φ.sub.W, the liquid phase φ.sub.IL being a phase enriched in ionic liquid and the liquid phase φ.sub.W being a phase enriched in water, whose pH is less than or equal to 4.7, provided that at temperature T.sub.i: the partition coefficient of the metal ion M.sub.1 between the two phases φ.sub.IL and φ.sub.W:
K(M.sub.1).sub.Ti=[M.sub.1]φ.sub.IL/[M.sub.1]φ.sub.W  is greater than 1, the partition coefficient of the metal ion M2 between o the two phases φIL and φW:
K(M.sub.1).sub.Ti=[M.sub.1]φ.sub.IL/[M.sub.1]φ.sub.W  is greater than 1, b″) when a composition comprising a single liquid phase is obtained in step a″), varying the temperature to obtain a composition at a temperature Tf different from Ti comprising two liquid phases φIL and φW, the liquid phase φIL being a phase enriched in ionic liquid and the liquid phase φW being a phase enriched in water, whose pH is less than or equal to 4.7, provided that at the temperature Tf: the partition coefficient of the metal ion M1 between the two phases φIL and φW:
K(M.sub.1).sub.Tf=[M.sub.1]φ.sub.IL/[M.sub.1]φ.sub.W is greater than 1, the partition coefficient of the metal ion M.sub.2 between the two phases φIL and φW:
K(M.sub.2).sub.Tf=[M.sub.2]φ.sub.IL/[M.sub.2]φ.sub.W is greater than 1, c″) to separate the phases φ.sub.IL and φ.sub.W of the composition obtained in step a″) or b″), then d″) contacting, at a temperature T.sub.Ω, the φ.sub.IL phase with an aqueous solution such that: the solubility in the aqueous solution at the temperature T.sub.Ω of M.sub.1 is greater than or equal to 0.01 mol/l, the solubility in the aqueous solution at the temperature T.sub.Ω of M.sub.2 is less than or equal to 0.001 mol/l, wherein M.sub.2 precipitates and a medium Ω comprising a solid comprising M.sub.2 and at least one liquid phase comprising M.sub.1 is obtained, e″) optionally filtering the medium Ω to recover the solid comprising M.sub.2, f″) optionally extracting the metal ion M.sub.1 from the liquid phase.

4. Method for purifying an acidic aqueous solution comprising a metal ion M comprising the steps of: i) contacting an ionic liquid of formula C.sup.+,(X.sup.p−).sub.1/p, in which: C.sup.+ is an onium cation comprising at least one atom selected from N, S, P or O, the onium cation comprising at least one hydrocarbon chain R.sup.1 comprising from 6 to 20 carbon atoms, optionally interrupted by one or more groups selected from —S—, —O—, —(C═O)—O—, —O—(C═O)—, —NR.sup.10—(C═O)—, —(C═O)—NR.sup.11— or —NR.sup.12R.sup.13—, and/or optionally substituted with one or more groups selected from halogen, —OR.sup.14, —(C═O)R.sup.15, —(C═O)NR.sup.16R.sup.17—, —NR.sup.18R.sup.19R.sup.20, —S—R.sup.21, —(C═O)—OR.sup.22, wherein R.sup.10, R.sup.11, R.sup.12, R.sup.13, R.sup.14, R.sup.15, R.sup.16, R.sup.17, R.sup.18, R.sup.19, R.sup.20 and R.sup.21 independently represent H or a linear or branched hydrocarbon chain comprising from 1 to 6 carbon atoms and R.sup.22 represents a linear or branched hydrocarbon chain comprising from 1 to 6 carbon atoms, and X.sup.p− is an anion of charge p, the ionic liquid having a solubility in water at 20° C. of at least 10 g/L,  with an aqueous solution S comprising a metal ion M at a [M].sub.S concentration and an acid, wherein a composition is obtained at a temperature T.sub.i, the composition comprising a single liquid phase, ii) varying the temperature to obtain a composition at a temperature T.sub.f different from T.sub.i comprising two liquid phases φ.sub.IL and φ.sub.W, the liquid phase φ.sub.IL being a phase enriched in ionic liquid and the liquid phase φ.sub.W being a phase enriched in water, the pH is less than or equal to 4.7, provided that, at the temperature T.sub.f, the partition coefficient of the metal ion between the two phases φ.sub.IL and φ.sub.W:
K(M).sub.Tf=[M]φ.sub.IL/[M]φ.sub.W  is greater than 1, iii) separating the phases φ.sub.IL and φ.sub.W of the composition obtained in stage ii), wherein a phase φ.sub.W is obtained which is an acidic aqueous solution whose concentration of metal ion M[M]φ.sub.W is lower than the concentration [M].sub.S.

5. Method according to claim 1, comprising before step a), a step a.sub.0) of preparing the aqueous medium comprising a metal ion M and an acid by leaching.

6. Method according to claim 1, wherein the ionic liquid has one of the following formulas: ##STR00003## in which: R.sup.1 and X.sup.p− are as defined in claim 1, R.sup.2, R.sup.3 and R.sup.4 independently represent a hydrocarbon chain comprising from 1 to 20 carbon atoms, optionally interrupted by one or more groups chosen from —S—, —O—, —(C═O)—O—, —O—(C═O)—, —NR.sup.110—(C═O)—, —(C═O)—NR.sup.111— or —NR.sup.112R.sup.113—, and/or optionally substituted by one or more groups chosen from a halogen, —OR.sup.114, —(C═O)R.sup.115, —(C═O)NR.sup.116R.sup.117—, —NR.sup.118R.sup.119R.sup.120, —S—R.sup.121, —(C═O)—OR.sup.122, wherein R.sup.110, R.sup.111, R.sup.112, R.sup.113, R.sup.114, R.sup.115, R.sup.116, R.sup.117, R.sup.118, R.sup.119, R.sup.120, R.sup.121 and R.sup.122 independently represent H or a linear or branched hydrocarbon chain comprising from 1 to 6 carbon atoms, wherein two groups selected from R.sup.1, R.sup.2, R.sup.3 and R.sup.4 may be connected to form a ring.

7. Method according to claim 6 wherein the R.sup.1 chain comprises at least 8 carbon atoms.

8. Method according to claim 5, wherein the C.sup.+ cation comprises, in addition to the hydrocarbon chain R.sup.1, a hydrocarbon chain R.sup.2 comprising from 2 to 20 carbon atoms, in particular from 4 to 20 carbon atoms optionally interrupted by one or more groups selected from —S—, —O—, —(C═O)—O—, —O—(C═O)—, —NR.sup.210—(C═O)—, —(C═O)—NR.sup.211— or —NR.sup.212R.sup.213—, and/or optionally substituted with one or more groups selected from halogen, —OR.sup.214, —(C═O)R.sup.215, —(C═O)NR.sup.216R.sup.217—, —NR.sup.218R.sup.219R.sup.220, —S—R.sup.221, —(C═O)—OR.sup.222, wherein R.sup.210, R.sup.211, R.sup.212, R.sup.213, R.sup.214, R.sup.215, R.sup.216, R.sup.217, R.sup.218, R.sup.219, R.sup.220, R.sup.221 and R.sup.222 independently represent H or a linear or branched hydrocarbon chain comprising from 1 to 6 carbon atoms, wherein the groups R.sup.1 and R.sup.2 may be connected to form a ring.

9. Method according to claim 6, wherein the ionic liquid has one of the following formulas ##STR00004## in which X.sup.p− is an anion of charge p.

10. Method according to claim 6, wherein the anion X.sup.p− is selected from anions BF.sub.4.sup.−, PF.sub.6.sup.−, CF.sub.3SO.sub.3.sup.−, HSO.sub.4.sup.−, SO.sub.4.sup.2−, NO.sub.3.sup.−, CH.sub.3COO.sup.−, CF.sub.3CO.sub.2.sup.−, ClO.sub.4.sup.−, HPO.sub.4.sup.2−, H.sub.2PO.sub.4.sup.−, halides, anions BR.sup.5.sub.4.sup.−, RCO.sub.2.sup.− or R.sup.5SO.sub.3.sup.−, R.sup.5 being a linear or branched alkyl group having from 1 to 4 carbon atoms.

11. Method according to claim 1, wherein the pH of the water-enriched phase φW is less than 4.0.

12. Method according to claim 1, wherein the acid is: an organic acid chosen from formic acid, acetic acid, oxalic acid, lactic acid, uric acid, p-toluenesulphonic acid, trifluoromethanesulphonic acid or a mixture thereof, an inorganic acid chosen from hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid or a mixture thereof, or a mixture thereof.

13. Method according to claim 1, wherein the acid has the formula H.sub.p(X.sup.p−), where is X.sup.p− is the anion of charge p of the ionic liquid of the composition.

Description

FIGURES

(1) FIG. 1 shows a phase diagram formed by ionic liquid [P.sub.44414][C1] and HCl at four different temperatures, namely 24° C., 36° C., 45° C. and 56° C. For each temperature, the biphasic system/monophasic system transition is represented as a function of the [P.sub.44414][Cl] mass concentration (ordinate) and the HCl mass concentration (abscissa).

(2) FIG. 2 shows a diagram of the protocol followed in Example 3.

(3) FIG. 3 shows a diagram of the protocol followed in Example 4.

EXAMPLE 1: BIPHASIC SYSTEM [P.SUB.44414.][Cl]—HCl—H.SUB.2.O

(4) Compositions comprising water, HCl and tributyltetradecylphosphonium chloride [P.sub.44414][Cl] (Cytec Industries) were prepared by varying the mass concentrations of ionic liquid [P.sub.44414][Cl] and HCl at four temperatures (24° C., 36° C., 45° C. and 56° C.). Depending on the proportions and the temperatures, a monophasic or biphasic medium was obtained.

(5) FIG. 1 shows a phase diagram for each of the temperatures tested.

(6) The system is biphasic when the prepared mixture corresponds to a point located in the right zone of the curve shown in FIG. 1. The system then corresponds to a composition according to the invention.

(7) On the other hand, since the mixture prepared corresponds to a point situated in the zone to the left of the curve presented in FIG. 1, the system is monophasic (a homogeneous phase) and these systems are therefore not compositions according to the invention.

(8) At 45° C., the biphasic system is formed at lower HCl concentrations than those required at 25° C. This is characteristic of an LCST type behavior.

EXAMPLE 2: USE OF A BIPHASIC SYSTEM [P.SUB.44414.][Cl]—HCl—H.SUB.2.O TO EXTRACT Fe(III) IONS

(9) Iron has been used as an example of a metal whose presence in aqueous solution requires the use of acid to avoid the formation of iron hydroxide and the precipitation of the metal ion.

(10) 0.015 g of FeCl.sub.3.6H.sub.2O (supplied by Alfa Aesar) was dissolved in 50 mL at 10 M HCl (supplied by Roth). The solution was yellow. 1 ml of this solution was mixed with 0.25 g of [P.sub.44414][Cl] (supplied by Cytec) at 25° C. A biphasic composition was obtained, comprising: a yellow upper phase: the phase enriched in ionic liquid φ.sub.IL comprising Fe(III), and an almost colorless lower phase: the phase enriched in water φ.sub.W.

(11) The partition coefficient of the Fe(III) metal ion between the two phases φ.sub.IL and φ.sub.W was
K(Fe(III)).sub.n=[Fe(III)]φ.sub.IL/[Fe(III)]φ.sub.W>750

(12) Fe(III) was quantitatively extracted with acidic ABS [P.sub.44414][Cl]—HCl—H.sub.2O. More than 99.7% of the Fe(III) is extracted from the acidic aqueous phase as measured by flame absorption spectroscopy.

EXAMPLE 3: USE OF A BIPHASIC SYSTEM [P.SUB.44414.][Cl]—HCl—H.SUB.2.O TO SEPARATE Ni AND Co IONS

(13) In 50 mL of an 18 wt % HCl aqueous solution, 0.065 g of NiCl.sub.2 and 0.12 g of CoCl.sub.2.6H.sub.2O (supplied by Alfa Aesar) were mixed at 25° C. In 1 mL of this solution, 0.25 g of [P.sub.44414][Cl] was added. The mixture was monophasic at 25° C., blue in color. The mixture was heated to 50° C., which induced phase separation, namely: a blue upper phase: the phase enriched in φ.sub.IL ionic liquid comprising cobalt (II), and an almost colorless lower phase: the water-enriched phase φ.sub.W in which the nickel (II) remained.

(14) The protocol followed is illustrated in FIG. 2. The analyzes were carried out by flame absorption spectroscopy.

(15) The partition coefficient of the Co(II) metal ion between the two phases φ.sub.IL and φ.sub.W was
K(Co(II)).sub.Ti=[Co(II)]φ.sub.IL/[Co(II)]φ.sub.W=190

(16) The partition coefficient of the Fe(III) metal ion between the two phases φ.sub.IL and φ.sub.W was
K(Ni(II)).sub.Ti=[Ni(II)]φ.sub.IL/[Ni(II)]φ.sub.W=0.14

(17) A one-step and quantitative separation of cobalt and nickel was thus achieved, which is an advantage over the methods usually used in the prior art. The nickel-cobalt separation is not effective with conventional methods and requires several consecutive extraction steps to obtain a quantitative separation of the two metal ions.

EXAMPLE 4: USE OF A BIPHASIC SYSTEM [P.SUB.44414.][Cl]—HCl—H.SUB.2.O TO SEPARATE Pt AND Co IONS

(18) Platinum is known as a noble metal which dissolves only in very acid aqueous solutions (typically in aqua regia: a mixture of hydrochloric acid and nitric acid concentrated in a proportion of 2 to 4 volumes of hydrochloric acid for 1 volume of nitric acid.

(19) To 1 mL of a 10M aqueous HCl solution comprising 0.005M Co (II) and 0.01M Pt(IV) added as H.sub.2PtClO.sub.6.3H.sub.2O and CoCl.sub.2.6H.sub.2O (supplied by Alfa Aesar) at 25° C. were introduced 0.25 g of [P.sub.44414][Cl]. Without heating, a phase separation takes place, namely: a green upper phase: the phase enriched in φ.sub.IL ionic liquid comprising cobalt (II) and platinum (IV), and an almost colorless lower phase: the phase enriched in water φ.sub.W.

(20) The partition coefficient of the metal ion Pt(IV) between the two phases φ.sub.IL and φ.sub.W was
K(Pt(IV)).sub.Ti=[Pt(IV)]φ.sub.IL/[Pt(IV)]φ.sub.W>100

(21) [P.sub.44414][Cl]—HCl—H.sub.2O thus made it possible to obtain a quantitative extraction of platinum and cobalt towards the phase rich in ionic liquid φ.sub.IL.

(22) The two phases φ.sub.IL and φ.sub.W were separated. To the phase enriched in isolated φIL ionic liquid was added 1.5 ml of 1M aqueous HCl solution, which induced the precipitation of platinum (in the form of an insoluble salt of PtCl.sub.6.sup.2−), since platinum is not soluble in an aqueous solution so little acidic. A mixture comprising: a salt which precipitates at the bottom which consists of PtCl.sub.6.sup.2 and a single liquid phase comprising water, cobalt, [P.sub.44414][Cl] and HCl, was obtained.

(23) The protocol followed is shown in FIG. 3.