Use of an organic-inorganic hybrid material for extracting uranium(VI) from a sulfuric acid aqueous solution, issued notably from the sulfuric leaching of a uranium-bearing ore

Abstract

The invention relates to the use of an organic-inorganic hybrid material, comprising an inorganic solid support on which are grafted organic molecules having the general formula (I) below: ##STR00001##
in which: x, y and z=0 or 1, with at least one of x, y and z different from 0; m=1 to 6; v and w=0 or 1, with v=1 when w=0, and v=0 when w=1; if x=0, R.sup.1H or a saturated or unsaturated, linear or branched, C.sub.1 to C.sub.12 hydrocarbon group, whereas, if x=1, R.sup.1=a group bound to the inorganic solid support by at least one covalent bond; if y=0, R.sup.2H or a saturated or unsaturated, linear or branched, C.sub.1 to C.sub.12 hydrocarbon group, whereas, if y=1, R.sup.2=a group bound to the inorganic solid support by at least one covalent bond; if z=0, R.sup.3H or a saturated or unsaturated, linear or branched, C.sub.1 to C.sub.12 hydrocarbon group, whereas, if z=1, R.sup.3=a group bound to the inorganic solid support by at least one covalent bond; R.sup.4 and R.sup.5H, a saturated or unsaturated, linear or branched, C.sub.2 to C.sub.8 hydrocarbon group, or a monocyclic aromatic group;
for extracting uranium(VI) from a sulfuric acid aqueous solution. The invention also relates to a method that makes it possible to recover the uranium(VI) present in a sulfuric acid aqueous solution, selectively with respect to the other metal cations that may also be present in said solution.

Claims

1. A method of extracting uranium(VI) from a sulfuric acid aqueous solution, comprising: (i) contacting the sulfuric acid aqueous solution with an organic-inorganic hybrid material, which comprises an inorganic solid support on which is grafted in a covalent manner a plurality of organic molecules of formula (I): ##STR00007## wherein: x, y and z are equal to 0 or 1, with the proviso that at least one of x, y and z is equal to 1; m is a whole number ranging from 1 to 6; v and w are equal to 0 or 1, with the proviso that v is equal to 1 when w is equal to 0 and that v is equal to 0 when w is equal to 1; if x is equal to 0, R.sup.1 represents a hydrogen atom or a saturated or unsaturated, linear or branched hydrocarbon group, comprising 1 to 12 carbon atoms, whereas, if x is equal to 1, R.sup.1 represents a group bound to the inorganic solid support by at least one covalent bond indicated by the dotted line; if y is equal to 0, R.sup.2 represents a hydrogen atom or a saturated or unsaturated, linear or branched hydrocarbon group, comprising 1 to 12 carbon atoms, whereas, if y is equal to 1, R.sup.2 represents a group bound to the inorganic solid support by at least one covalent bond indicated by the dotted line; if z is equal to 0, R.sup.3 represents a hydrogen atom or a saturated or unsaturated, linear or branched hydrocarbon group, comprising 1 to 12 carbon atoms, whereas, if z is equal to 1, R.sup.3 represents a group bound to the inorganic solid support by at least one covalent bond indicated by the dotted line; and R.sup.4 and R.sup.5 represent, independently of each other, a hydrogen atom, a saturated or unsaturated, linear or branched hydrocarbon group, comprising 2 to 8 carbon atoms, or a monocyclic aromatic group; and then (ii) separating the sulfuric acid aqueous solution from the organic-inorganic hybrid material, wherein the sulfuric acid aqueous solution comprises 0.1 to 10 g/L of uranium, 0.1 to 2 mol/L of sulfate ions, and 0.01 to 0.5 mol/L of sulfuric acid.

2. The method of claim 1, wherein the inorganic solid support comprises a metal oxide, a mixed metal oxide, a mixture of metal oxides, or carbon.

3. The method of claim 1, wherein the inorganic solid support comprises a porous material.

4. The method of claim 3, wherein the porous material is a mesoporous material or a macroporous material.

5. The method of claim 4, in which the porous material is a mesoporous silica, a mesoporous titanium oxide, a mesoporous zirconium oxide, or a mesoporous carbon.

6. The method of claim 5, wherein the inorganic solid support is an SBA mesoporous silica or a CMK mesoporous carbon.

7. The method of claim 1, wherein R.sup.3 represents a group of formula (CH.sub.2).sub.qX.sup.1 in which q is a whole number ranging from 0 to 12, and X.sup.1 represents: ##STR00008## or CHCH.

8. The method of claim 1, wherein at least one of R.sup.1 and R.sup.2 represents a group of formula (a), (b), (c), (d), (e), (f) or (g):
(CH.sub.2).sub.pC(O)NH(CH.sub.2).sub.qX.sup.2(a)
(CH.sub.2).sub.pNHC(O)(CH.sub.2).sub.qX.sup.2(b)
(CH.sub.2).sub.pC(O)O(CH.sub.2).sub.qX.sup.2(c)
(CH.sub.2).sub.pOC(O)(CH.sub.2).sub.qX.sup.2(d)
(CH.sub.2).sub.pO(CH.sub.2).sub.qX.sup.2(e)
(CH.sub.2).sub.p-triazole-(CH.sub.2).sub.qX.sup.2(f)
(CH.sub.2).sub.qX.sup.2(g) wherein p is a whole number ranging from 1 to 6, q is a whole number ranging from 0 to 12, and X.sup.2 represents: ##STR00009## or CHCH.

9. The method of claim 8, wherein R.sup.3 represents a group of formula (CH.sub.2).sub.qX.sup.1 in which q is a whole number ranging from 0 to 12, and X.sup.i is identical to X.sup.2.

10. The method of claim 1, wherein the organic molecules have a formula (Ia): ##STR00010## wherein x, y, z, m, R.sup.1, R.sup.2, R.sup.3, R.sup.4 and R.sup.5 are as defined in formula (I).

11. The method of claim 10, wherein x and y are 0, R.sup.1 and R.sup.2 represent, independently of each other, a linear or branched alkyl group comprising 1 to 12 carbon atoms; z is 1 and R.sup.3 represents a group bound to the inorganic solid support by at least one covalent bond, and R.sup.4 and R.sup.5 represent, independently of each other, a hydrogen atom or a linear or branched alkyl group, comprising 2 to 8 carbon atoms.

12. The method of claim 11, wherein R.sup.1 and R.sup.2 are identical to each other and represent a branched alkyl group, comprising 6 to 12 carbon atoms.

13. The method of claim 11, wherein R.sup.4 and R.sup.5 represent, independently of each other, a hydrogen atom or a linear or branched alkyl group, comprising 2 to 4 carbon atoms.

14. The method of claim 10, wherein the inorganic solid support comprises a metal oxide, a mixed metal oxide, or a mixture of metal oxides, and R.sup.3 represents a group: ##STR00011## wherein q is equal to 1 to 5.

15. The method of claim 10, wherein the inorganic solid support comprises carbon and R.sup.3 represents a group: ##STR00012## wherein q is equal to 0 to 5.

16. The method of claim 1, wherein the sulfuric acid aqueous solution is obtained from leaching of a uranium-bearing ore by sulfuric acid.

17. A method of recovering uranium(VI) from a first sulfuric acid aqueous solution, comprising: a) extracting uranium(VI) from the first sulfuric acid aqueous solution, by (i) contacting the first sulfuric acid aqueous solution with an organic-inorganic hybrid material, which comprises an inorganic solid support on which is grafted in a covalent manner a plurality of organic molecules of formula (1): ##STR00013## wherein: x, y and z are equal to 0 or 1, with the proviso that at least one of x, y and z is equal to 1; m is a whole number ranging from 1 to 6; v and w are equal to 0 or 1, with the proviso that v is equal to 1 when w is equal to 0 and that v is equal to 0 when w is equal to 1; if x is equal to 0, R.sup.1 represents a hydrogen atom or a saturated or unsaturated, linear or branched hydrocarbon group, comprising 1 to 12 carbon atoms, whereas, if x is equal to 1, R.sup.1 represents a group bound to the inorganic solid support by at least one covalent bond indicated by the dotted line; if y is equal to 0, R.sup.2 represents a hydrogen atom or a saturated or unsaturated, linear or branched hydrocarbon group, comprising 1 to 12 carbon atoms, whereas, if y is equal to 1, R.sup.2 represents a group bound to the inorganic solid support by at least one covalent bond indicated by the dotted line; if z is equal to 0, R.sup.3 represents a hydrogen atom or a saturated or unsaturated, linear or branched hydrocarbon group, comprising 1 to 12 carbon atoms, whereas, if z is equal to 1, R.sup.3 represents a group bound to the inorganic solid support by at least one covalent bond indicated by the dotted line; and R.sup.4 and R.sup.5 represent, independently of each other, a hydrogen atom, a saturated or unsaturated, linear or branched hydrocarbon group, comprising 2 to 8 carbon atoms, or a monocyclic aromatic group; and then (ii) separating the first sulfuric acid aqueous solution from the organic-inorganic hybrid material; b) washing the separated organic-inorganic hybrid material obtained in a) with water; and c) stripping uranium(VI) from the washed organic-inorganic hybrid material obtained in b) by contacting the organic-inorganic hybrid material with a second sulfuric acid aqueous solution, then separating the organic-inorganic hybrid material from the second sulfuric acid aqueous solution, wherein the first sulfuric acid aqueous solution comprises 0.1 to 10 g/L of uranium, 0.1 to 2 mol/L of sulfate ions, and 0.01 to 0.5 mol/L of sulfuric acid.

18. The method of claim 17, wherein the first sulfuric acid aqueous solution is obtained from leaching of a uranium-bearing ore by sulfuric acid.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) FIG. 1 schematically illustrates the preparation of a first useful organic-inorganic hybrid material according to the invention, in which the inorganic solid support is a mesoporous silica and in which the organic molecules comply with the general formula (I) above in which m and v are 1, R.sup.1 and R.sup.2 both represent a 2-ethylhexyl group, R.sup.3 represents a (CH.sub.2).sub.3SiO.sub.3 group, R.sup.4 represents an ethyl group, whereas R.sup.5 represents a hydrogen atom.

(2) FIG. 2 schematically illustrates the preparation of a second useful organic-inorganic hybrid material according to the invention, in which the inorganic solid support is a mesoporous carbon and in which the organic molecules comply with the general formula (I) above in which R.sup.1 and R.sup.2 both represent a 2-ethylhexyl group, R.sup.3 represents a CH.sub.2C(O)NHCH.sub.2C group, R.sup.4 represents an ethyl group, whereas R.sup.5 represents a hydrogen atom.

(3) FIG. 3 schematically illustrates the reaction scheme of the synthesis of an organic compound useful for the preparation of the hybrid organic-inorganic materials shown in FIGS. 1 and 2.

DETAILED DESCRIPTION OF PARTICULAR EMBODIMENTS

Example 1: Preparation of a First Useful Organic-Inorganic Hybrid Material According to the Invention

(4) A first useful organic-inorganic hybrid material is prepared according to the invention, below designated material M1, which comprises a mesoporous silica with periodic hexagonal structure, of SBA-15 type, on which are grafted organic molecules complying with the general formula (I) above in which: m is 1; v is 1 (and thus w is 0); R.sup.1 and R.sup.2 both represent a 2-ethylhexyl group, R.sup.3 represents a (CH.sub.2).sub.3SiO.sub.3 group, R.sup.4 represents an ethyl group, whereas R.sup.5 represents a hydrogen atom.

(5) This organic-inorganic hybrid material is prepared by the method illustrated in FIG. 1, which includes:

(6) (1) the functionalisation of the mesoporous silica with amine functions, which is carried out by a silanisation reaction, that is to say by making the silanol functions (SiOH) of this silica react with the ethoxysilane functions of 3-aminopropyltriethoxysilane (commercially available), noted APTS in FIG. 1; then

(7) (2) the grafting of 3-(N,N-di(2-ethylhexyl)carbamoyl)-3-(ethoxy)-hydroxyphosphono)propanoic acid, or compound RT141, on the amine functions of the silica thereby functionalised, which is carried out by peptide coupling, that is to say by making said amine functions react with the carboxylic acid functions of this compound.

(8) 1.1Synthesis of the Mesoporous Silica

(9) The mesoporous silica is synthesised by following an operating protocol identical to that described by Zhao et al. in Science 1998, 279, 548-552, reference [7]. It has pores of 9.1 nm diameter (as determined according to the BJH method) and a BET specific surface area of 800 m.sup.2/g (as determined by nitrogen adsorption-desorption).

(10) 1.2Functionalisation of the Mesoporous Silica

(11) After activation (that is to say heating under vacuum to 130 C. for 24 hours), the mesoporous silica (1.8 g) is suspended in a solution containing 0.5 g of

(12) 3-aminopropyltriethoxysilane in 20 mL of toluene. The mixture is heated to 90 C. for 48 hours under nitrogen, then filtered and washed with acetone before being treated with acetone in a Soxhlet for 48 hours. The aminosilica thereby obtained is dried in an oven (80 C.) for 20 hours.

(13) Its physical-chemical characteristics are the following: diameter of the pores (BJH method): 8.4 nm; BET specific surface area (nitrogen adsorption-desorption): 460 m.sup.2/g; weight loss (ATG analysis): 9%; elementary analysis found: C, 5.0%; N, 1.7%; P, 0%; quantity of amine functions grafted: 1.4 mmol/g of mesoporous silica.

(14) 1.3Synthesis of the Compound RT141

(15) The compound RT141 is synthesised using the reaction scheme comprising the steps A, B, C and D which is illustrated in FIG. 3.

(16) As may be seen in this figure, this synthesis consists in making react in a first step, noted A, 2,2-diethylhexylamine, noted 1, with chloroacetyl chloride, noted 2, to obtain 2-chloro-N,N-diethylhexylacetamide, noted 3 in this figure.

(17) To do so, potassium carbonate (2 eq.) is added under stirring to a 0.7 mol/L solution of 2,2-diethylhexylamine in dichloromethane. The suspension thereby obtained is cooled to 0 C. and chloroacetyl chloride (1.5 eq.) is added to it drop by drop. The mixture is left to return to room temperature. Once the amine has been consumed (which is verified by thin layer chromatography (TLC) using ethyl acetate as eluant and ninhydrin as developer), 4 equivalents of water are added drop by drop to the mixture, which causes an effervescence. When this effervescence has finished, a quantity of water equal to half the volume of dichloromethane having been used to dissolve the amine is added to this mixture. The mixture is maintained under stirring for 15 minutes. The aqueous and organic phases are then separated and the organic phase is dried over Na.sub.2SO.sub.4, filtered and concentrated. The expected compound is thereby obtained (Yield: 97%) of which the characterisations by .sup.1H and .sup.13C NMR are given below.

(18) .sup.1H NMR (400 MHz, CDCl.sub.3) (ppm): 0.85-0.91 (m, 12H, CH.sub.3); 1.23-1.33 (m, 16H, CH.sub.2); 1.55-1.60 (m, 1H, CHCH.sub.2N); 1.67-1.73 (m, 1H, CHCH.sub.2N); 3.18 (d, 2H, J=7.5 Hz, CH.sub.2N); 3.22-3.32 (m, 2H, CH.sub.2N); 4.09 (s, 2H, CH.sub.2Cl);

(19) .sup.13C NMR (100 MHz, CDCl.sub.3) (ppm): 10.7; 11.0; 14.1 (CH.sub.3); 23.1; 23.9; 24.0; 28.7; 28.9; 30.4; 30.6 (CH.sub.2); 36.8; 38.5 (CH); 41.6 (CH.sub.2Cl); 48.8 (CH.sub.2N); 51.7 (CH.sub.2N); 167.1 (CO).

(20) In a second step, noted B in FIG. 3, 2-chloro-N,N-diethylhexylacetamide is subjected to an Arbuzov reaction to obtain diethyl 1-(N,N-diethylhexylcarbamoyl)methylphosphonate, noted 4 in this figure.

(21) This Arbuzov reaction is carried out by taking a mixture composed of 2-chloro-N,N-diethylhexylacetamide (1 eq.) and triethylphosphite (1.2 eq.) to 160 C. at reflux for 3 hours. Once the acetamide has been consumed (which is verified by TLC using dichloromethane as eluant and UV or phosphomolybdic acid as developer), the excess of phosphite is distilled under reduced pressure. The expected compound is thereby obtained (Yield: quantitative) of which the characterisations by .sup.1H, .sup.13C and .sup.31P NMR are given below.

(22) .sup.1H NMR (400 MHz, CDCl.sub.3) (ppm): 0.81-0.86 (m, 12H, CH.sub.3); 1.21-1.32 (m, 22H, CH.sub.2, OCH.sub.2CH.sub.3); 1.51-1.57 (m, 1H, CHCH.sub.2N); 1.64-1.71 (m, 1H, CHCH.sub.2N); 3.02 (d, 2H, J=22.0 Hz, COCH.sub.2P); 3.21-3.27 (m, 4H, CH.sub.2N); 4.08-4.16 (m, 4H, OCH.sub.2CH.sub.3);

(23) .sup.13C NMR (100 MHz, CDCl.sub.3) (ppm): 10.6; 11.0; 14.1; 14.2 (CH.sub.3); 16.3; 16.4 (OCH.sub.2CH.sub.3); 23.1; 23.2; 23.5; 23.9; 28.8; 28.9; 30.4; 30.6 (CH.sub.2); 33.1; 34.5 (d, J=134.0 Hz, CH.sub.2P); 37.0; 38.6 (CH); 48.9; 52.3 (CH.sub.2N); 62.5 (d, J=6.5 Hz, OCH.sub.2CH.sub.3); 165.2 (d, J=6.0 Hz, CO);

(24) .sup.31P NMR (160 MHz, CDCl.sub.3) (ppm): 21.8.

(25) In a third step, noted C in FIG. 3, diethyl 1-(N,N-diethylhexylcarbamoyl)methylphosphonate is subjected to a C-alkylation reaction to obtain ethyl 3-(N,N-di(2-ethylhexyl)carbamoyl)-3-(diethoxy)phosphono)propanoate, noted 5 in this figure.

(26) To do so, a solution of diethyl 1-(N,N-diethylhexylcarbamoyl)-methylphosphonate (dried beforehand for 2.5 hours at 80 C. under vacuum) in anhydrous tetrahydrofuran (THF1 eq.1 mol/L) is added, drop by drop and under stirring, to a suspension of sodium hydride (1.5 eq.washed beforehand with pentane) in anhydrous THF (2 mol/L). The mixture is stirred for 1 hour at room temperature then the solution is cooled to 0 C. and a solution of ethyl acetate bromide (1.5 eq.) is added drop by drop. This mixture is left to return to room temperature which is then stirred for 1 hour, after which the crude is acidified up to pH 1 using a 1 mol/L aqueous solution of hydrochloric acid and extracted with dichloromethane. The aqueous and organic phases are separated and the organic phase is dried over Na.sub.2SO.sub.4, filtered and concentrated. The excess bromide is eliminated by distillation under vacuum. The expected compound is thereby obtained (Yield: quantitative) of which the characterisations by .sup.1H, .sup.13C and .sup.31P NMR are given below.

(27) .sup.1H NMR (400 MHz, CDCl.sub.3) (ppm): 0.77-0.89 (m, 12H); 1.16-1.28 (m, 27H); 1.63-1.70 (m, 1H); 1.74-1.83 (m, 1H); 2.68-2.76 (m, 1H); 2.70-2.90 (m, 1H); 3.01-3.18 (m, 2H); 3.50-3.75 (m, 3H); 4.01-4.13 (m, 6H);

(28) .sup.13C NMR (100 MHz, CDCl.sub.3) (ppm): 10.3; 10.5; 10.6; 10.9; 14.0; 14.1; 16.3; 16.4; 23.1; 23.5; 23.7; 24.0; 28.6; 28.7; 28.8; 28.9 30.2; 30.3; 30.6; 30.7; 32.7; 37.0; 37.1; 37.2; 37.3; 37.7-39.1 (d, J=132.0 Hz); 38.6; 38.7; 38.9; 50.2; 50.6; 50.9; 51.2; 51.9; 52.4; 60.8; 62.4; 62.5; 63.1; 63.2; 63.3; 167.4; 168.5; 171.3-171.5 (dd, J=18.5 Hz, d=4.5 Hz);

(29) .sup.31P NMR (160 MHz, CDCl.sub.3) (ppm): 23.1.

(30) In a final step, noted D in FIG. 3, ethyl 3-(N,N-di(2-ethylhexyl)carbamoyl)-3-(diethoxy)phosphono)propanoate is subjected to a saponification reaction to obtain the compound RT141.

(31) This saponification is carried out by adding, to a 0.4 mol/L solution of ethyl 3-(N,N-di(2-ethylhexyl)carbamoyl)-3-(diethoxy)phosphono)propanoate in ethanol, a 20% sodium hydroxide solution (6 eq.). The mixture is taken to reflux for 3 hours. After cooling, the mixture is acidified to pH 1 using a 1 mol/L aqueous solution of hydrochloric acid, then extracted twice with dichloromethane. The aqueous and organic phases are separated and the organic phase is dried over Na.sub.2SO.sub.4, filtered and concentrated. The expected compound is thereby obtained (Yield: quantitative) of which the characterisations by .sup.1H, .sup.13C and .sup.31P NMR are given below.

(32) .sup.1H NMR (400 MHz, CDCl.sub.3) (ppm): 0.82-0.92 (m, 12H); 1.22-1.38 (m, 19H); 1.66-1.73 (m, 1H); 1.74-1.82 (m, 1H); 2.88-3.0 (m, 2H); 3.01-3.23 (m, 2H); 3.46-3.80 (m, 3H); 4.07-4.17 (m, 2H); 8.96 (Is, 2H);

(33) .sup.13C NMR (100 MHz, CDCl.sub.3) (ppm): 10.3; 10.5; 10.7; 10.8; 14.0; 16.2; 16.3; 23.0; 23.4; 23.6; 23.8; 28.5; 28.6; 28.7; 30.2; 30.3; 30.4; 32.9; 37.1; 37.7-39.0 (d, J=132.0 Hz); 38.5; 38.6; 50.4; 50.6; 52.3; 52.8; 62.4 168.8; 174.2 (d, J=9.0 Hz); 174.4 (d, J=9.0 Hz);

(34) .sup.31P NMR (160 MHz, CDCl.sub.3) (ppm): 24.0.

(35) 1.4Grafting of the Compound RT141 on Aminosilica

(36) The aminosilica (1 eq. of amine functions) and the compound RT141 (2 eq.) are made to react in anhydrous THF in the presence of dicyclohexylcarbodiimide (DDC2 eq.), N-hydroxybenzotriazole (HOBt2 eq.) and diisopropylthylamine (DIPEA1.5 eq.) for 48 hours, at room temperature and under argon flow.

(37) After which, the reaction medium is filtered, the residue is washed several times with dichloromethane and methanol and dried under vacuum at 90 C.

(38) In this way is obtained the material 1 of which the characterisations by .sup.13C, .sup.31P and .sup.29Si CPMAS NMR and the physical-chemical characteristics are given below.

(39) .sup.13C NMR (ppm): 8.5; 11.73; 15.23; 22.39; 28.34; 37.23; 40.74; 48.30; 60.07; 172.44;

(40) .sup.31P NMR (ppm): 18.11;

(41) .sup.29Si NMR (ppm): 59.01; 66.05 (sites T.sup.2 and T.sup.3); 101.12; 110.01 (sites Q.sup.3 and Q.sup.4);

(42) Diameter of the pores (BJH model): 5.5 nm;

(43) BET specific surface area (nitrogen adsorption-desorption): 400 m.sup.2/g;

(44) Weight loss (ATG analysis): 19%;

(45) Elementary analysis found: C, 12.4%; N, 1.9%; P, 1.1%;

(46) Quantity of molecules of the compound RT141 grafted: 0.46 mmol/g of material M1.

Example 2: Preparation of a Second Useful Organic-Inorganic Hybrid Material According to the Invention

(47) A second useful organic-inorganic hybrid material is prepared according to the invention, below designated material M2, which includes a mesoporous carbon with periodic hexagonal structure, of CMK-3 type, on which are grafted organic molecules complying with the general formula (I) above in which: m is 1; v is 1 (and thus w is 0); R.sup.1 and R.sup.2 both represent a 2-ethylhexyl group, R.sup.3 represents a CH.sub.2C group, R.sup.4 represents an ethyl group, whereas R.sup.5 represents a hydrogen atom.

(48) This organic-inorganic hybrid material is prepared by the method illustrated in FIG. 2, which comprises:

(49) (1) the functionalisation of the mesoporous carbon with amine functions, which is carried out by a Diels-Alder reaction, that is to say by making the conjugated diene functions of this carbon react with the alkynyl functions of propargylamine, noted 9 in FIG. 2; then

(50) (2) the grafting of the compound RT141 on the amine functions of the carbon thereby functionalised, which is carried out by peptide coupling as in example 1 above.

(51) 2.1Synthesis of the Mesoporous Carbon

(52) The mesoporous carbon is synthesised following the operating protocol described by Jun et al. in Journal of the American Chemical Society 2000, 122, 10712-10713, reference [8]. It has pores of 3.5 nm diameter (as determined according to the BJH method) and a BET specific surface area of 1400 m.sup.2/g (as determined by nitrogen adsorption-desorption).

(53) 2.2Functionalisation of the Mesoporous Carbon

(54) The mesoporous carbon (0.5 g) is suspended in neat propargylamine.

(55) The mixture is placed in an autoclave heated to 100 C. for 48 hours. After which, it is washed with acetone in a Soxhlet for 48 hours.

(56) The aminocarbon thereby obtained is dried in an oven (80 C.) for 20 hours.

(57) Its physical-chemical characteristics are the following: diameter of the pores (BJH method): 3.0 nm; BET specific surface area (nitrogen adsorption-desorption): 600 m.sup.2/g; elementary analysis found: N, 1.1%; P, 0%; O, 2.6%. quantity of amines grafted: 0.79 mmol/g of mesoporous carbon.

(58) 2.3Grafting of the Compound RT141 on the Aminocarbon

(59) This grafting is carried out by following an operating protocol identical to that described in example 1 above for the grafting of the compound RT141 on aminosilica.

(60) It leads to the material 2 of which the physical-chemical characteristics are the following: diameter of the pores (BJH method): 2.8 nm; BET specific surface area (nitrogen adsorption-desorption): 300 m.sup.2/g; elementary analysis found: N, 1.3%; P, 0.9%; O, 3.9%; quantity of molecules RT141 grafted: 0.38 mmol/g of material M2.

Example 3: Properties of the Useful Hybrid Organic-Inorganic Materials According to the Invention

(61) 3.1Extraction and Stripping Tests Carried Out from a Sulfuric Acid Aqueous Solution Only Comprising Uranium as Metal Cation

(62) 3.1.1Extraction Tests

(63) The capacity of the material M1, as obtained in example 1 above, to extract uranium(VI) from a sulfuric acid solution is assessed by extraction tests that are carried out in tubes and which consist: in mixing this material in powder form with 10 mL of a sulfuric acid aqueous solution, of pH equal to 2.2 and only comprising uranium(VI) as metal cation; in leaving the mixture for 24 hours under stirring (in a Turbula mixer), at room temperature (25 C.); then in separating by filtration the solid and liquid phases of this mixture.

(64) Two different tests are carried out: a first testbelow test 1in which 100.3 mg of material M1 and a sulfuric acid aqueous solution which includes 0.0125 mol/L of sulphate ions are used, and a second testbelow test 2in which 102.8 mg of material M1 and a sulfuric acid aqueous solution which includes 0.533 mol/L of sulphate ions are used. To guarantee that this solution has the same pH as the solution used in test 1, the increase in the sulphate ion content is achieved by addition of sodium sulphate salt (Na.sub.2SO.sub.4).

(65) The concentrations of uranium(VI) are determined in the aqueous solutions of sulfuric acid before they are mixed with the hybrid material M1 as well as in the filtrates.

(66) From the concentrations thereby obtained, for uranium(VI) are calculated: the quantity extracted per g of material M1, noted Q.sub.ext, and expressed in mg/g, by applying the following formula (i):

(67) $\begin{array}{cc}{Q}_{\mathrm{ext}}=\left(C_{\mathrm{ini}}-C_{\mathrm{end}}\right)\frac{V}{m}& \left(i\right)\end{array}$
with:
C.sub.ini=initial concentration in the sulfuric acid aqueous solution (in mg/L);
C.sub.end=concentration in the filtrate (in mg/L);
V=volume of sulfuric acid aqueous solution mixed with the material M1 (in L);
m=mass of material M1 used in the test (in g); the distribution coefficient, noted K.sub.d and expressed in L/g, by applying the following formula (ii):

(68) $\begin{array}{cc}\mathrm{Kd}=\frac{Q_{\mathrm{ext}}}{C_{\mathrm{end}}}& \left(\mathrm{ii}\right)\end{array}$
in which Q.sub.ext and C.sub.end have the same signification as previously.

(69) Table I below presents the results obtained for each of tests 1 and 2.

(70) TABLE-US-00001 TABLE I Test 1 Test 2 ([SO.sub.4.sup.2] = 0.0125M) ([SO.sub.4.sup.2] = 0.533M) U(VI) C.sub.ini (mg/L) 110 118 C.sub.end (mg/L) 2 18 Q.sub.ext (mg/g) 11 10 Kd (L/g) 5.5 0.555

(71) 3.1.2Stripping Tests

(72) The possibility of stripping, from the material M1, uranium(VI) having been extracted by this material in tests 1 and 2 described at point 3.1.1 above is assessed by tests that are carried out in tubes and which consist: in washing the solid phases, such as obtained at the end of these tests, 3 times with deionised water to desorb the elements physisorbed on the surface of the material M1, which makes it possible to determine the quantity of uranium(VI) having actually been complexed by this material; in mixing the solid phases thereby washed with 10 mL of an aqueous solution containing 3 mol/L of sulfuric acid; in leaving the mixture for 24 hours under stirring (in a Turbula mixer), at room temperature (25 C.); in separating by filtration the solid and liquid phases of the mixture; then in determining the quantity of uranium(VI) present in the filtrate.

(73) Table II presents the results obtained for each of the solid phases obtained at the end of tests 1 and 2.

(74) TABLE-US-00002 TABLE II Solid phase from Solid phase from test 1 test 2 ([SO.sub.4.sup.2] = ([SO.sub.4.sup.2] = U(VI) 0.0125M) 0.533M) Initial quantity 1.10 1.18 (in mg for 10 mL of solution) Quantity extracted 1.08 1.00 (in mg for 10 mL of solution) Quantity recovered after 3 0 0.02 washings with water (mg) Quantity recovered after 0.8 0.27 stripping with H.sub.2SO.sub.4 (mg) Percentage recovery 73 25 (compared to the initial quantity in the solution)

(75) Tables I and II show: on the one hand, that uranium(VI) has been almost totally complexed by the organic molecules of the material M1 during the extractions carried out at point 3.1 above since it is very little desorbed by washings with deionised water; and on the other hand, that it is possible to strip uranium(VI) from the material M1 by means of a sulfuric acid aqueous solution but that this stripping is more efficient when it is carried out from the material M1 having served to extract uranium(VI) from the sulfuric acid aqueous solution that is the least concentrated in sulphate ions.

(76) 3.2Extraction and Stripping Tests Carried Out from a First Sulfuric Acid Aqueous Solution Including a Plurality of Metal Cations

(77) 3.2.1Extraction Tests

(78) The ability of the material M1 to extract selectively uranium(VI) from a sulfuric acid aqueous solution is assessed by extraction tests that are carried out in tubes and which consist: in mixing this material in powder form with 10 mL of a sulfuric acid aqueous solution simulating an aqueous solution from the leaching by sulfuric acid of a uranium-bearing deposit of the type of that situated at Imouraren in Niger but diluted 3 times; in leaving the mixture for 24 hours under stirring (in a Turbula mixer), at room temperature (25 C.); then in separating by filtration the solid and liquid phases of this mixture.

(79) The qualitative and quantitative composition of metal cations of the sulfuric acid aqueous solution is presented in table III below.

(80) TABLE-US-00003 TABLE III Metal cations Concentrations (mg/L) U 124 Fe 1435 Ti 34.3 Zr 5.2 Mo 22.4 Al 176 Ma 3410 Mg 1800 V 68

(81) This composition has a high concentration of sulphate ions, 0.5 mol/L, i.e. a ratio of molar concentrations U(VI)]/SO.sub.4.sup.2 of 10.sup.3. Its pH is 2.1.

(82) Two different tests are carried out: a first testbelow test 3in which 100.5 mg of material M1 are used and a second testbelow test 4in which 101.1 mg of material M1 are used.

(83) The concentrations of uranium(VI), iron, titanium, zirconium and molybdenum are determined from the filtrates.

(84) From the concentrations thereby obtained, for each of these metal cations are determined: the quantity extracted per g of material M1, noted Q.sub.ext, and expressed in mg/g, which is determined by the formula (i) indicated at point 3.1.1 above; the distribution coefficient, noted K.sub.d and expressed in L/g, which is determined by the formula (ii) indicated at point 3.1.1 above.

(85) The selectivity coefficient of the material for uranium(VI) with respect to the other metal cations is also determined. This coefficient, which is noted S.sub.U/M, is determined by the following formula (iii):

(86) $\begin{array}{cc}{S}_{U/M}=\frac{{\mathrm{Kd}}_U}{{\mathrm{Kd}}_M}& \left(\mathrm{iii}\right)\end{array}$
in which Kd.sub.U is the distribution coefficient of uranium(VI), whereas Kd.sub.M is the distribution coefficient of the metal cation M with respect to which the selectivity for uranium is assessed. In this respect, it is pointed out that a selectivity coefficient S.sub.U/M>1 indicates a selectivity for uranium with respect to the metal cation M.

(87) Table IV below presents the results obtained for each of tests 3 and 4.

(88) TABLE-US-00004 TABLE IV Metal cations Tests U Fe Ti Zr Mo C.sub.ini (mg/L) Tests 3 and 4 124 1435 34.3 5.2 22.4 C.sub.end (mg/L) Test 3 71.0 1162 22.7 2.5 17.0 Test 4 74.1 1314 24.6 2.2 17.4 Q.sub.ext (mg/g) Test 3 5.3 27.2 1.1 0.3 0.5 Test 4 5.0 12.0 1.0 0.3 0.5 Kd (L/g) Test 3 0.0743 0.0234 0.0508 0.1075 0.0316 Test 4 0.0666 0.0091 0.0390 0.1349 0.0284 S.sub.U/M Test 3 3.18 1.46 0.69 2.35 Test 4 8.15 1.90 0.55 2.61

(89) This table shows that the material M1 extracts uranium preferentially to the other metal cations except in the case of zirconium since the selectivity coefficient S.sub.U/Zr is less than 1.

(90) 3.2.2Stripping Tests

(91) Stripping tests are carried out in tubes which consist: in washing the solid phases, such as obtained at the end of the extraction tests 3 and 4 carried out at point 3.2.1 above, 3 times with deionised water to desorb the elements physisorbed on the surface of the material M1 and to determine exactly the quantity of uranium(VI), iron, titanium, zirconium and molybdenum having been complexed by this material; in mixing the solid phases thereby washed with 10 mL of an aqueous solution containing 3 mol/L of sulfuric acid; in leaving the mixture for 24 hours under stirring (in a Turbula mixer), at room temperature (25 C.); in separating by filtration the solid and liquid phases of the mixture; then in determining the quantity of uranium(VI), iron, titanium, zirconium and molybdenum present in the filtrate.

(92) Table V below presents the results obtained for each of the solid phases obtained at the end of tests 3 and 4.

(93) TABLE-US-00005 TABLE V Test from which the solid phase Metal cations is derived U Fe Ti Zr Mo Initial quantity Tests 3 1.24 14.35 0.34 0.05 0.22 (in mg for and 4 10 mL of solution) Quantity Test 3 0.53 2.73 0.12 0.03 0.02 extracted (in Test 4 0.50 1.20 0.10 0.03 0.05 mg for 10 mL of solution) Quantity Test 3 0.06 2.54 0.03 0 0.02 recovered Test 4 0.13 >1.2 0.04 0 0.03 after 3 washings with water (mg) Quantity Test 3 0.51 1.15 0.11 0 0.05 recovered Test 4 0.21 0.35 0.06 0.01 0.02 after stripping with H.sub.2SO.sub.4 (mg) Efficiency Test 3 >100 >100 >100 0 >100 of the Test 4 69.5 >100 >100 21.7 >100 stripping (%)

(94) This table shows that a disparity exists in the results obtained for iron and molybdenum, probably due to analysis errors.

(95) Nevertheless, from the results presented in tables IV and V, it may be concluded: that the material M1 makes it possible to extract uranium(VI) from a sulfuric acid aqueous solution with a capacity of the order of 5 g/kg of material; that the material M1 has a very high selectivity for uranium(VI) with respect to iron and titanium and a lower selectivity but nevertheless strong with respect to molybdenum; that after the washings with water of the material M1, the selectivity of the latter for uranium(VI) with respect to iron and molybdenum is increased since the quasi-totality of the iron and molybdenum having been extracted is desorbed by these washings; that uranium(VI) is indeed complexed by the material M1 since it is not desorbed by the washings with water; that, on the other hand, the stripping by the sulfuric acid aqueous solution makes it possible to recover the quasi-totality of uranium having been extracted by the material M1; and that, if the material M1 has proved not to be selective for uranium(VI) with respect to zirconium during the extraction (see table IV), zirconium is not stripped from the material M1 by the sulfuric acid aqueous solution, which makes it possible to obtain selectivity during the stripping.

(96) 3.3Extraction and Desorption Tests Carried Out from a Second Sulfuric Acid Aqueous Solution Comprising a Plurality of Metal Cations

(97) 3.3.1Extraction Test

(98) In order to evaluate the influence of the concentration of uranium(VI) on the one hand, and the ratio of the molar concentrations SO.sub.4.sup.2/U(VI) on the other hand, on the extractive properties of the material M1, an extraction test identical to those carried out at point 3.2.1 above is carried out in tubes, except that 250.6 mg of material M1 are used and that a sulfuric acid aqueous solution simulating an aqueous solution from the leaching by sulfuric acid of a uranium-bearing deposit of the type of that situated in Imouraren of which the uranium(VI) content has been deliberately increased is used.

(99) The qualitative and quantitative composition of metal cations of the sulfuric acid aqueous solution is presented in table VI below.

(100) TABLE-US-00006 TABLE VI Metal cations Concentrations (mg/L) U 2870 Fe 1377 Ti 31.3 Zr 2.3 Mo 20.1 Al 187 Mg 1735 V 62.3

(101) Its molar concentration of SO.sub.4.sup.2 ions is 0.497.

(102) Table VII below presents, for uranium(VI), iron and titanium, their initial concentration in the sulfuric acid aqueous solution (C.sub.ini), their final concentration in the filtrate (C.sub.end), the quantity extracted per g of material M1 (Q.sub.ext), their distribution coefficient (K.sub.d) and, for iron and titanium, the selectivity coefficient of the material M1 for uranium(VI) with respect to each of these two metal cations (S.sub.U/M).

(103) TABLE-US-00007 TABLE VII Metal cations U Fe Ti C.sub.ini (mg/L) 2870 1377 31.1 C.sub.end (mg/L) 2250 1316 28.7 Q.sub.ext (mg/g) 24.74 2.43 0.10 Kd (L/g) 0.0110 0.0018 0.0033 S.sub.U/M 5.9 3.3

(104) This test, which was carried out to assess the maximum capacity of the material M1 to extract uranium(VI) from a complex sulfuric acid aqueous solution, makes it possible to demonstrate that this maximum extraction capacity is 25 g/kg and that in the presence of a sulfuric acid aqueous solution at high uranium(VI) concentration, the selectivity of the material M1 for uranium(VI) with respect to iron and titanium is good.

(105) 3.3.2Desorption Test

(106) The solid phase, such as obtained at the end of the extraction test described at point 3.3.1 above, is washed 3 times with deionised water and the quantities of uranium(VI), iron and titanium still present on this solid phase at the end of these washings are determined.

(107) The quantity of uranium(VI) is 13.17 mg per g of material M1, whereas the quantities of iron and titanium are equal to 0 mg/g of material M1, which signifies that after 3 washings with water, the material M1 has a total selectivity for uranium(VI) with respect to iron and titanium.

REFERENCES CITED

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