Note: Descriptions are shown in the official language in which they were submitted.
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)
R2
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
R2
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)
R2
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
--5--
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
--6--
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,
3035
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
--8--
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_
