CA1103035A

CA1103035A - Removal of actinide metals from solution

Info

Publication number: CA1103035A
Application number: CA295,775A
Authority: CA
Inventors: Ronald D. Hancock; Ian V. Howell
Original assignee: BP PLC
Current assignee: BP PLC
Priority date: 1977-12-08
Filing date: 1978-01-26
Publication date: 1981-06-16
Also published as: ZA78489B; AU514813B2; GB1569346A; AU3431078A

Abstract

ABSTRACT OF THE DISCLOSURE
Actinide metals including uranium, thorium and plutonium are removed from solution by contact with a substrate produced by reacting an inorganic solid containing surface hydroxyl groups, e.g. silica, with a silane having amino function groups, e.g. (C2H5O)3 Si (CH2)3 NH2.

Description

11(~3~35 The present invention relates to the removal of actinide metalsfrom solution.
Aooompanying the growth in nuolear chemistry there has been a oorresponding inorease in interest in removing aotinide metals from solution. In partioular the reoovery of uranium from its natural surroundings, partioularly by solutlon mining, has fooussed interest on methods for removing it from solution. One suoh method is provided by the present invention.
Aooording to the present invention thre is provided a prooess for the removal of an a¢tinide metal, as hereinafter defined, from solution whioh prooess oompri~ea oontaoting the ~olution oontaining the aotinide metal ln the form of a soluble oompound thereof with a substrate oomprising the produot obtained by reaoting an inorganic solid oontain-ing surfaoe ~droxyl groups with a oompound of formula:
Rl X CH2 R - Si - Y (I) wherein Y is an - oR3 group in whloh R3 represents a hydrogen atom or an alkyl, aryl or aoyl group oontaining up to 20 oarbon atoms or Y i8 a halogen atom, X represents an - NR4R5 group in whioh R4 and R5 which may be the same or different are hydrogen atoms or alkyl or aryl groups oontaining up to 20 oarbon atoms or groups of formula:
- (CR2 )nNR7R8 in whioh R , R7 and R8 represent a H atom, an alkyl or aryl group oontaining up to 20 oarbon atoms, n is an integer between l and lO
and whereln R4, R5, R , R7 and R8 may be the same or different ,~ :

~3~3S

or X is a saturated or unsaturated cyclic group in which one or more ring positions are occupied by nitrogen atoms, R is a divalent organic group containing up to 20 carbon atoms and R ;
and R are organic radicals containing up to 20 carbon atoms, under conditions w~ich effect reaction between the group Y- and an -OH
group on the surface of the inorganic solid thereby bonding the compound (I) to the inorganic solid.
The term actinide metal within the context of the present specification is defined as a metal with an atomic number equal to or greater than 89 in the Periodic Table of the elements.
Thus the term aotlnide metal includes thorium, uranium and plutonium for exanple, The inorganic solid containing surface hydroxyl groups may be alumina, titania, zirconia, glass, sepiolite, or a zeolitic molecular sieve. Preferably the inorganic solid is silica and more preferably silica gel. In addition mixtures of inorganic solids may be used. Unless they have been sub3ected to severe treatments eg, heating above 1000 C all commercial silicas contain surface hydroxyl groups. ~lowever for -the rcmoval of metals from alkaline media, under whioh condition silioa would be chemlcally attacked, it is preferred to employ an alkali resistant inorganlc solid contalning surface hydro~yl groups.
Rl and R2 in the compound o~ ~ormula (I) may be alkyl, aryl, aryloxy or aLkoxy radicals or halogen atoms and may be the same or dlfferent. Preferably R and R are halogen a-toms, aLkoxy or aryloxy groups. Preferably the group Y is an alkoxy sroup ~nd the groups R and R2 and Y are identical alkoxy groups.
R in the oompound of ~ormula (I) is suitably an alkylene group oontaining up to 6 carbon atoms and is preferably a ~o dimethylene group.

:
~1~3035 Examples of suitable groups X in the compound of formula (I) include -NH2, -NHR4, -NR4R5J -NH(CH2)2NH2~ -NR4(CH2)2NR7R , Examples of suitable compounds of formula (I) are (CH30)3Si(C ~ )3~H(CH2)2NH~ (CH30)3Si(CH2)3CH2 ~ N and (C2H50)3Si (CH2)3NH2-In the oase of silioa the substrate is believed to be formed by the raction represented by the following equation:
Rl .
- Si OH + Y li R - CH2 Rl 1, 1 - Si - O Si - R CH2 X + HY

However the invention is not intended to be restrioted in any way by the above equation representing the formation of the substrate.
The substrate may be Produced by reaoting the inorganio solid oontaining surfaoe hydroxyl groups~with the oompound of formula (I) in a single stage or in two or more stages. m us in a single stage the reaotion may be effeoted by warming the two together eg, under reflux in the presenoe of an inert solvent for the compound of formula (I) for 1 to 3 hours and thereafter separating the produot, A suitable solvent for the oompound of formula (I) is toluene. In two stages the substrate may be produoed by reacting the inorganic solid containing surfaoe hydroxyl groups with a ~3~35 compound of formula:
Rl :
Y Si R C~ Z (III) wherein Y, R, Rl and R have the same identity as in formula (I) above and Z is a halogen atom, preferably chlorine, in a first stage and in a seoond stage reaoting the produot from the first stage with a oompound of formula:

~C(R9)2M (rv) wherein R9 is a hydrogen atom or an alkyl group oontaining less than 20 oarbon atoms, preferably less than 12 oarbon atoms and M
is an alkali metal, preferably lithium, and thereafter reoovering the produot from the seoond stage. Preferably the oompound of formula (III) is (MeO)~i(CH2)~Cl and the compound of formula (IV) ls N ~ CH2Li. Preferably the produc-t ~rom the first stage is treated to ellminate any remalning unreaoted -OH groups on the surfaoe of the inorganio solld by reaotlon with a sllylating agent eg, heXamethyl dlsilazane, before reaotion in the seoond stage, The treatment may be effeoted by refluxing for ~ to 2 hours and dlstllling off exoess sllylating agent.

The prooess of the lnvention ls partioularly applioable to the removal of the aotinide metals, in the form of a soluble inorganio oompound thereof from aqueous solutions but may also be used for their dlreot removal in the form of an organio oompound thereo~ from non-aqueous solutions. Alternatively the prooess of the lnvention may be~e~tended to aqueous solutions oontai~ing an aotinide metal in a form other than a soluble inorganio oompound thereof, for instanoe an organio 11~3~35 compound or an inorgani¢ compound insoluble in water, or as the elemental metal by converting the material to an inorganic compound soluble in water by a suitable pre-treatment.
The solution containing the metal in the form of a soluble compound thereof may be contacted with the substrate at any temperature in the range O to 200, preferably 20 to 100C. Under atmospheric pressure the temperature will normally be in the range O to 100 C, for aqueous solutions, thought if super atmospheric pressure is employed temperatures above 100 C
may be used. For organlo solutions the temperature may be in the range O to 200 C irrespective of the pressure.
The process of the invention is partioularly advantageous for the removal of uranium from aqueous solution.
When the substrate loses its aotivity for removing metal it may either be disposed of without further treatment or the metal may be reoovered therefrom by means knownto those skilled in the art. One suoh method for removing the metal from the substrate is to oontact the metal-loaded substrate with an aqueous solution followed by separatlon of the aqueous solution oontaining the metal from the substrate. The aqueous solution may be an aqueous solution of a mlneral acid, such as hydroohlorlo or sulphurio aoid. Alternatively the aqueous solution may be aoidified brine or an aqueous solution of a metal salt, such as a nitrate or carbonate. Thereafter the metal may, if desired, be recovered from the aqueous solution.
The solution oontaining the metal may be oontacted with the substrate batchwise, or, preferably, continuously by passing the 11G)3(:135 solution over a bed of the substrate mounted ln a suitable reactor. -The process of the invention is illustrated by the following Examples:
Example A
Reaction of N-aminoethylaminopropyltrimethoxysilane with silica Aoid washed U30 slllca (20 8), which had been drled at 180C, was stirred for 2 hours at room temperature with distilled water (10 ml) and toluene (250 ml), Residual water was distilled from the reaction flask and, after oooling to room temperature, the silane (MeO)3BiCH2CH2CH2NHCE~CE12NE12 (20 ml) was added . The mixture was stlrred at reflux temperature for 3 hours during which time any alcohol produoed was oolleoted ln a Dean & Stark tube whioh was perlodioally drained. After oooling, the silioa product was transferred to a Soxhlet apparatus and extraoted with dry methanol for 24 hours. The silica was finally drled ln vacuo. On analysls the silica was found to oontaln 1.8 peroent weight nitrogen.
Example B
Reaotion of N-aminoethylamlnopropyltrimethoxysil~ne with silioa Aoid washed U30 ~llloa (50 g), whloh had been dried at 180C, was stirred at room temperature for 2 hours with distilled water (5 ml) and toluene (300 ml). To this mixture was added the silane (MeO)3SiCH2CH2CH2NHCH2CH2NE12 (12.5 ml) and the stirring oontinued for a further 48 hours, The silloa produot was transferred to a Soxhlet apparatus and extraoted with methanol for 16 hours prior to drying in vaouo. On analysis the sllioa was found to oontain 2.1 peroent welght nitrogen.
Example_C
Reaotlon of ~-aminoDropyltrlmethoxysllane wlth slllca Acid washed U30 sillca (25 g), whioh had been dried at 180C, was stirred at room temperature for 2 hours with distilled water (15 ml) and toluene (300 ml). Residual water was distilled from the reaction flask and, after cooling to room temperature, the siIane (EtO)3SiCH2CH2CH2NH2 (25 ml) was added, The mixture was stirred at reflux for 3 hours during which time any alcohol produced was collected in a Dean & Stark tube which was periodically drained, After oooling, the silica product was transferred to a Soxhlet apparatus and extracted wlth methanol for 24 hours prior to drying in vacuo. On analysis the sillca ~as found to contain 0.7 peroent weight nitrogen, Examples A, B and C are not examples aooording to the invention.
They are inoluded for the purpose of demonstrating the produotlon of substrates useful in the prooess of the invention.
Example 1 200 ml of a dilute sulphurio aoid solution or uranyl sulphate oontaining 1.64 g U02S043H20 was stirred with 1,62 g of the diamine funotionalised silioa, prepared as desoribed in Example B, for 5 hours at room temperature, After allowlng the mixture to stand overnight the silioa produot was isolated by ~iltration and thcn Soxhlc* oxtr~oted with water ~or 18 hours followed by methanol ~or 8 hours. Thc silioa was finally dried in vaouo. On analysis the silioa was found to oontain 1.2 peroent weight uranium, measured as uranium metal, Example 2 200 ml of a dilute sulphurio aoid solution of uranyl sulphate containing 2.19 g U02S043H20 was stirred with 1.92 g of the primary amine functionalised silica, prepared as described in Example C
for 5 hours at room temperature. After allowing the mixture to stand overnight the silica produot was transferred to a Soxhlet apparatus and extraoted with water for 18 hours then methanol for 3~3S

8 hours. The silica was finally dried in vacuo. On analysis the silica was found to contain 0.3 percent weight uranium, measured as uranium metal.
Comparison Test 200 ml of a dilute sulphuric acid solution of uranyl sulphate containing 1.29 g U02S043H20 was stirred with 2.11 g of acid washed U30 silica for 5 hours at room temperature. After allowing the mixture to stand for 18 hours the sllica product was isolated by filtration and then Soxhlet extracted with water for 18 hours followed by methanol for 8 hours. The silica was finally dried in vacuo. On analysis the silica was found to contain 0.1 percent weight uranium, measured as uranium metal.
This is not an example according to the invention and ls inoluded only for the purpose of oomparison.
Example ~
250 ml of an aqueous solution of uranyl nitrate containing o.66 g Uo2(No3j26H2o was stirred with 1.58 g of the diamine funotionalised silioa, prepared as described in Example A for 4 hours at room temperature. After allowin~ the mixture to stand for 65 hours the silica product was isolated by filtration and then Soxhlet extracted with water for 12 hours followed by methanol for 8 hours. The silica was finally dried in vacuo.
On analysis the sllica was found to contain 5.9 percent weight uranium, measured as uranium metal.

_g_

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A process for the removal of an actinide metal, with an atomic number equal to or greater than 89 in the Periodic Table of the elements, from solution which process comprises contacting the solution containing the actinide metal, in the form of a soluble compound thereof with a substrate comprising the product obtained by reacting an inorganic solid containing surface hydroxyl groups with a compound of formula:

(I) wherein Y is an -OR3 group in which R3 represents a hydrogen atom or an alkyl, aryl or acyl group containing up to 20 carbon atoms or Y is a halogen atom, X represents an -NR4R5 group in which R4 and R5, which may be the same or different, are hydrogen atoms or alkyl or aryl groups containing up to 20 carbon atoms or groups of formula:
- (CR26)nNR7R8 in which R6, R7 and R8 represent a H atom, an alkyl or aryl group containing up to 20 carbon atoms, n is an integer between 1 and 10 and wherein R4, R5, R6, R7 and R8 may be the same or different or X is a saturated or unsaturated cyclic group in which one or more ring positions are occupied by nitrogen atoms, R is a divalent organic group containing up to 20 carbon atoms and R1 and R2 are organic radicals containing up to 20 carbon atoms, under conditions which effect reaction between the group Y- and an -OH group on the surface of the inorganic solid thereby bonding the compound (I) to the inorganic solid.

2. A process according to claim 1 wherein the inorganic solid is alumina, titania, zirconia, glass, sepiolite or a zeolitic molecular sieve.

3. A process according to claim 2 wherein the inorganic solid is silica.

4. A process according to claim 3 wherein the inorganic solid is silica gel.

5. A process according to claim 1, 2, or 3 wherein R1 and R2 in the compound of formula (I) are alkyl, aryl, aryloxy or alkoxy radicals or halogen atoms and may be the same or different.

6. A process according to claim 5 wherein R1 and R2 are halogen atoms, alkoxy or aryloxy groups.

7. A process according to claim 1, 2, or 3 wherein the group Y
in the compound of formula (I) is an alkoxy group and the groups Y, R1 and R2 are identical alkoxy groups.

8. A process according to claim 1 wherein R in the compound of formula (I) is an alkylene group containing up to 6 carbon atoms.

9. A process according to claim 8 wherein the alkylene group is a dimethylene group.

10. A process according to claim 1, 2, or 3 wherein the group X
in the compound of formula (I) is -NH2, -NHR4, -NR4R5, -NH(CH2)2NH2, -NR4(CH2)2NR7R8, , , or .

11. A process according to claim 1, 2, or 3 wherein the compound of formula (I) is:
(CH3O)3Si(CH2)3NH(CH2)2NH2

12. A process according to claim 1, 2, or 3 wherein the compound of formula (I) is

13. A process according to claim 1, 2, or 3 wherein the compound of formula (I) is (C2H5O)3Si(CH2)3NH2.

14. A process according to claim 1 wherein the substrate is produced in a single stage by warming the inorganic solid containing surface hydroxyl groups with the compound of formula (I) in the presence of an inert solvent for the compound of formula (I) for 1 to 3 hours and thereafter separating the product.

15. A process according to claim 14 wherein the inert solvent is toluene.

16. A process according to claim 1 wherein the substrate is produced in two stages by reacting the inorganic solid containing surface hydroxyl groups in a first stage with a compound of formula:

(II) wherein Y, R, R1 and R2 have the same identity as in the formula (I) and Z is a halogen atom, and in a second stage reacting the product from the first stage with a compound of formula:

(III) wherein R9 is a hydrogen atom or an alkyl group containing less than 12 carbon atoms and M is an alkali metal, and thereafter recovering the product from the second stage.

17. A process according to claim 16 wherein the alkali metal in the formula (III) is lithium and Z in the formula (II) is a chlorine atom.

18. A process according to claim 16 or 17 wherein the compound of formula (II) is (MeO)3Si(CH2)3Cl and the compound of formula (III) is .

19. A process according to claim 16 or 17 wherein the product from the first stage is treated to eliminate any remaining unreacted -OH groups on the surface of the inorganic solid by reaction with a silylating agent before reaction in the second stage.

20. A process according to claim 1 wherein the solution containing the metal in the form of a soluble compound thereof is contacted with the substrate at a temperature in the range from 0 to 200°C.

21. A process according to claim 20 wherein the solution is an aqueous solution and the temperature is in the range 20 to 100°C
at atmospheric pressure.

22. A process according to claim 1, 2, or 3 wherein uranium is removed from an aqueous solution thereof.

23. A process according to claim 1, 2, or 3 wherein the actinide metal is recovered from the substrate.