CA1323985C - Process for the separation of metals from aqueous solutions using dialkyl substituted amides - Google Patents
Process for the separation of metals from aqueous solutions using dialkyl substituted amidesInfo
- Publication number
- CA1323985C CA1323985C CA 519626 CA519626A CA1323985C CA 1323985 C CA1323985 C CA 1323985C CA 519626 CA519626 CA 519626 CA 519626 A CA519626 A CA 519626A CA 1323985 C CA1323985 C CA 1323985C
- Authority
- CA
- Canada
- Prior art keywords
- separation
- metals
- aqueous solution
- actinides
- uranium
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
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Classifications
-
- G—PHYSICS
- G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
- G21C—NUCLEAR REACTORS
- G21C19/00—Arrangements for treating, for handling, or for facilitating the handling of, fuel or other materials which are used within the reactor, e.g. within its pressure vessel
- G21C19/42—Reprocessing of irradiated fuel
- G21C19/44—Reprocessing of irradiated fuel of irradiated solid fuel
- G21C19/46—Aqueous processes, e.g. by using organic extraction means, including the regeneration of these means
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E30/00—Energy generation of nuclear origin
- Y02E30/30—Nuclear fission reactors
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W30/00—Technologies for solid waste management
- Y02W30/50—Reuse, recycling or recovery technologies
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- Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- Plasma & Fusion (AREA)
- General Engineering & Computer Science (AREA)
- High Energy & Nuclear Physics (AREA)
- Extraction Or Liquid Replacement (AREA)
Abstract
ABSTRACT
The present invention relates a process for the separation of actinides, fission products and some group 8 and group lb metals from aqueous solutions, by means of solvent and/or chromatographic extraction using dialkylsubstituted amides as extracting agents.
The process according to the invention may be used both in the separation of nuclear materials (Pu, U, Th) and in the separation and recovery of more directly commercial materials (Au, Pt, Ir, Pd).
The present invention relates a process for the separation of actinides, fission products and some group 8 and group lb metals from aqueous solutions, by means of solvent and/or chromatographic extraction using dialkylsubstituted amides as extracting agents.
The process according to the invention may be used both in the separation of nuclear materials (Pu, U, Th) and in the separation and recovery of more directly commercial materials (Au, Pt, Ir, Pd).
Description
01737-26/GW~-~/fs 13239~
The present invention relates to a process for the selective extraction of actinides and Au, Pt, Ir and Pd metals from aqueous solutions using techniques of liquid-liquid extraction in the presence of an organic phase or techniques of chromatography in the presence of a solid phase, comprising the operations of;
adjusting the acidity of said aqueous solution to obtain a value of the distribution coefficient such as to enable said actinides and/or metals to be transferred to said organic phase or solid phase; subjecting said acidified aqueous solution to extraction or chromatography by said organic or solid phase, r~spectively, containing as extracting agents dialkysubstituted amides of formula (I) n - c - N
O R"
in which ~ is a straight or branched aliphatic chain with 8 or less carbon atoms, and R' and R" are straight or branched aliphatic chains in which the sum of the carbon atoms in R' + R"
is less than or equal to 8, and contacting said organic or solid phase containing said actinides and/or metals with a fresh aqueous solution to reextract said actinides and/or rnetals from said organic or solid phase and transfer them to said ~resh aqueous solution for further processing.
Although these amides are known in the literature, they have been used mainly as plasti~ying agents.
The process according to the invention may be applied in a range of applications, including conventional nuclear technologies for the recovery, separation and purification of metals in solutions, in particular for the separation of natural and/or enriched uranium and/or plutonium and thorium from .. . .
-:
, ~32398~
solutions of dissolved spent nuclear fuel.
Currently uranium and plutonium are separated using liquid liquid extraction, but with tributyl-phosphate (TBP) as selective extracting agent.
Known as the PUREX process, it offers the dis-advantage, especially with highly active fuels, of producing breakdown products of tributylphosphate which can interfere with the process because they are not soluble in water or they form slightly soluble complexes with some metals which are difficult to remove. These complexes distribute themselves in a semisolid phase between the two phases, progressively blocking the extraction process and necessitating the replacement of the organic phase.
The process according to the invention prevents the problems cited above since breakdown of the di-substituted amides gives rise mainly to secondary amines and carboxylic acids, according to the following general formula:
The present invention relates to a process for the selective extraction of actinides and Au, Pt, Ir and Pd metals from aqueous solutions using techniques of liquid-liquid extraction in the presence of an organic phase or techniques of chromatography in the presence of a solid phase, comprising the operations of;
adjusting the acidity of said aqueous solution to obtain a value of the distribution coefficient such as to enable said actinides and/or metals to be transferred to said organic phase or solid phase; subjecting said acidified aqueous solution to extraction or chromatography by said organic or solid phase, r~spectively, containing as extracting agents dialkysubstituted amides of formula (I) n - c - N
O R"
in which ~ is a straight or branched aliphatic chain with 8 or less carbon atoms, and R' and R" are straight or branched aliphatic chains in which the sum of the carbon atoms in R' + R"
is less than or equal to 8, and contacting said organic or solid phase containing said actinides and/or metals with a fresh aqueous solution to reextract said actinides and/or rnetals from said organic or solid phase and transfer them to said ~resh aqueous solution for further processing.
Although these amides are known in the literature, they have been used mainly as plasti~ying agents.
The process according to the invention may be applied in a range of applications, including conventional nuclear technologies for the recovery, separation and purification of metals in solutions, in particular for the separation of natural and/or enriched uranium and/or plutonium and thorium from .. . .
-:
, ~32398~
solutions of dissolved spent nuclear fuel.
Currently uranium and plutonium are separated using liquid liquid extraction, but with tributyl-phosphate (TBP) as selective extracting agent.
Known as the PUREX process, it offers the dis-advantage, especially with highly active fuels, of producing breakdown products of tributylphosphate which can interfere with the process because they are not soluble in water or they form slightly soluble complexes with some metals which are difficult to remove. These complexes distribute themselves in a semisolid phase between the two phases, progressively blocking the extraction process and necessitating the replacement of the organic phase.
The process according to the invention prevents the problems cited above since breakdown of the di-substituted amides gives rise mainly to secondary amines and carboxylic acids, according to the following general formula:
2 0 RCO-NR ' R " -- - -- - > RCOOH ~ HNR ' R "
These compounds are not as strong complexing agents as the breakdown products of tributylphosphate.
Furthermore, as a function of the length of the ali-phatic chains on the carbon and nitrogen, -the product carboxylic acid and secondary amine may be soluble in water and so eliminated automatically from the '` , , : ~ ' ' ':
~323~
These compounds are not as strong complexing agents as the breakdown products of tributylphosphate.
Furthermore, as a function of the length of the ali-phatic chains on the carbon and nitrogen, -the product carboxylic acid and secondary amine may be soluble in water and so eliminated automatically from the '` , , : ~ ' ' ':
~323~
organic phase during the extraction.
It should also be considered that while re-extrac tion of the uranium in aqueous phase with tributyl-phosphate offers some difficulties, with the amides said extraction is simple and quantitative.
Therefore an object of this invention is a process for the separation of uranium and plutonium comprising:
a first step for separation of uranium and plutonium from the solutlon of dissolved spent nuclear fuel;
10a second step for treatment with a reducing agent to convert the Pu (IV) to Pu (III); and a third step of liquid-liquid extraction to extract the uranium into the organic phase, wherein the extracting agents used are dialkylsubstituted amides of formula (I) / R' R - C - N ~I) O \ R'' where R, R' and R" are as defined above.
20NN'-di-n-butyloctanamide has been found particularly suitable for separation of uranium from plutonium.
This new process has been called AMDEX.
It has also been found that the disubstituted amides used in the process for separation of uranium from plutonium show a high selectivity in the separa-~ tion of hexavalent actinides with respect to tetra-': ~ ,, ' :.; ' . ' . ", ' :' - - . , '' , ' :' ' ' ~' 1323~5 valent actinides, particularly as a function of the acidity of the solution.
Therefore a further object of the present invention is a process for the separation using liquid-liquid S extraction techniques, of hexavalent actinides from tetravalent actinides, wherein amides of formula (I) are used as extracting agents in the organic phase.
/ R' R - C - N \ (I) O R~
where R, R' and R" are as defined above.
The advankage of this process, applied in particular to the separation of U(VI) from Th(IV) (called the TAMDEX process) and to the separation of U~VI) from Pu(IV) (called the.PAMIDEX process) lies in the fact that no previous reduction of plutonium to valence 3 is required and in the high selectlvity of the process itself.
For the separation of uranium and thorium, N,N'-di-n-butyl-2-ethylhexanamide has been found advan-tageous as the dialkylsubstituted amide; for that of urani.um and plutonium, N,N'-dibutyl-3,3'-dimethyl-butyramide is preferred.
It has also been found tha-t the disubsti.tuted amides show interesti.ng properties also for the separa-.: ~ . :-` ~L32398~
tion of non-nuclear elements of high commerc.ial or strategic interest, such as gold, platinum, irid.ium, palladium.
Therefore another object of this invention is a process for the liquid-liqu:id extraction and/or for the separation or quantitative recovery of one of the metals cited above (Au, Pt, Ir, Pd) from aqueous solutions prepared by dissolving the metals or from industrial waste solutions at low concentration, wherein amides of formula (I) are used as selective extracting agents:
R' R - C - N (I) O Ra where R, R' and R" are as described above.
This process has been called AUMIDEX.
In this process as well the acidity plays an im-portant role in determining selectivity.
As mentioned above, the amides of formula (I~
. / R' R - C - N \ (I) O R~
where R, R' and R" are as described above, used in the process for separation of metals from aqueous solution according to the invention were previously used mainly as plastifying agents.
- ~
323~
_ fi _ Therefore another object of the present invention ~` is the use of amides of formula (I) as sequestrants or extracting agents in separation chromatography or in liquid-liquid extraction of all the metals S cited above from acqueous solution.
The dialkylsubstituted amides used according to the invention have a different structure as a function of their use. Amides with completely straight chains, ` such as N,N'-dibutyloctanamide or N,N'-dibutylhexan-amide are particularly suitable as alternatives to , tributylphosphate in a PUREX type process with parti-; tion of plutonium by means of reduction (AMDEX pro-', cess). They are also suitable for extraction of gold (AUMIDEX process).
15Dialkylsubstituted amides with a branch in the alpha position with respect to the carbonyl, for example N,N'-dibutyl-2-ethylhexanamide, are parti-cularly suitable for the separation of hexavalent . actinides fxom tetravalent actinides (TAMIDEX).
20Dialkyl amides with other types of branching, for example N,N'-dibutyl-3,3'-dimethylbutyramide, are particularly suitable for the separation of hexa-valent uranium from tetravalent plutonium with no reduction of the plutonium to valence three (PAMIDEX
process).
Extraction of these metals is more rapid and phase . .. , . ~ , . . .
. . . . . .
. ~ . . ~ - . ~ .
3239~
separation is quicker than in analogous tests with tributylphosphate.
I'he possibility of saturation of the metal in the organic phase is highly dependent not only on the experimental condltions but also on the degree of branching of the aliphatic or aromatic chain.
The concentration of the amides, generally dissolved in an aromatic solvent, depends on the quantity of metal to be extracted.
Table 1 reports the principle properties of the amides used.
Table_l Properties of the_amides ~olubility 15 Amide B.P. nD2o d ~2 dode- mesi-cane thylene N,N'-di-n-butyl- 100-112 1.452 0.861 <0.01 >1000 >1000 octanamide (760) N,N'-di-n-butyl-2- 111-112 1.451 0.861 <0.001 >1000 >1000 ethyl- (1) butyramide N,N'-di-n-butyl-3,3'- 145-150 1.449 0.833 <0.001 >1000 >1000 methyl- (28) butyramide N,N'-di-sec-butyl- 130-150 1.490 0.856 <0.01 >1000 >1000 hexanamide (50) _ _ _ . _ _ Tables 2 and 3 below report several distribution coefficients D for the liquid-liquid separation process :, ' ' ~ . :
, ~
- . , ,, - : , .
~ 13239~
in which the amides according to the invention are used.
Table 2 Distribution coefficients Organic plase: di-n-butyloctanamide or di-n-butyl-hexanamide (lM in mesithylene) Aqueous phase: 4M HN03 + 4M HCl (1:3) metal D(o/a) Au10000 Fe 10 Sn Hg, Zn, Ag 0.1 Cu, Pb 0.01 Table 3 Distribution coeficients for U(VI) ! Pu(IV) and PU(III) and some flssion products (lM amide in mesithylene; phase ratio - l) Nitric acid in aqueous phase 2 0 Di-n-butyl-actanamide D U(VI) 13 18 D Pu(IV) 30 50 D Pu(III) 0.]
D Zr 0.1-0.01 D Ru 0.0001 Di-sec-butyl-hexanamide D U(VI) 10 14 .
'' ' ' ~ ' `~` t323~5 . , D Pu(IV) 9 24 Di-3,3'~di-methyl-butyl-butYramide D U(VI) 5 11 D Pu(IV) 3 12 Di-n-butyl-2-ethyl-octanamide D U(VI~ 5 11 D Pu(IV) 3 9 The liquid-liquid extraction processes for which the dialkylsubstituted ami~es according to the invention are proposed consist essentially in placing the aqueous solution containing many metals, including those to be separated, in intimate contact with an organic solution immiscible with water, containing a substance (in this case an amide) capable of 'binding' and so extracting selectively and quantitatively from the aqueous phase to the organic phase the metal or metals of interest, separating them from the others.
The organic phase containing the metal(s) is then placed in contact in the same way with a suitable aqueous solution to re-extract all or some of the metals in the organic phase and return them to an aqueous phase.
Slightly acidic or reducin~ solutions are normally used which, by changing the valence of the metal, make it less extractable. This is the case for the separation of uranium from plutonium in the PUREX process, where .~ .
3239~
the tetravalent plutonium extracted with tributylphosphate into the organic phase is reduced to trivalent plutonium, which is not soluble and so returns to the aqueous phase.
In other cases competitive water-soluble extracting agents are used.
The apparatus used for these extraction operations consists of multistep contactors of various types, such as: banks of mixer settlers, pulsed columns and centrifugal contactors.
The amides proposed may also be used in columns (pure or dissolved in solvent) dispersed on a finely divided inert support. In this case the aqueous solution containing the metals of interest is passed through the column and the metals remain 'bound' to the material in the column. They are then recovered by passing a suitable aqueous solution through the column. This process is no longer liquid-liquid extraction, but rather extractive chromatography.
~XAMPL~S
The invention will be illustrated with reference to the attached drawings, in which:
figure 1 shows an example of the AMDEX process;
figure 2 shows and example of the TAMIDEX process;
figure 3 shows an example of the PAMIDEX process;
and figure 4 shows an example of the AUMIDEX process.
~3239~5 The following examples are exemplificative only and do not in any way limit the scope of the invention.
Example 1 _(AMDEX process) With reference to figure 1, a lM solution of N,N'-di-n-butylactanamid~ (DBOA) in mesithylene i9 passed at a ~low rate of 6.5 liters/hour through a multistep contactor in the opposite direction to an aqueous solution containing 250 g/liter of uranium and 2.5 g/liter of plutonium, which flows at a rate of 2j.2 liters/hour.
This 2M acid solution contains fission products as well.
After the extraction step, the fission products are found in the extract in the same quantity, while the concentration of uranium has fallen to 5.9 x 10~2 g/liter and that of plutonium to 8.7 x 10-6 g/liter.
The organic solution is then treated with a reducing agent to separate the Pu(III) Erom the uranium according to the classic PUREX process, from which the AMDEX process differs in its use of N,N'-di-n-butyloctanamide instead of tributylphosphate.
Example 2 (TAMDEX process) Figure 2 shows an example of a process for the separation of U(VI) from Th(IV) using a lM solution of N,N'-di-n-butyl-2-ethylhexanamide in mesithylene.
A solution containing 13.75 g/liter of uranium and 236.7 g/liter of thorium is separated chromatographically to give an aqueous soluti'on containing approximately , ,. , -. : -""` 1323~
120 g/liteL of thorium and ~ 0.015 g/liter of uranium and an organic phase enriched in uranium. The final extract contains more than 3.4 g/liter of uranium and no detectable thorium.
Example 3_(PAMIDEX process) Figure 3 shows a process for the separation of U(VI) from Ph(IV). In this case N,N'-dibutyl~3,3'-dimethyl-butyramide is used.
Example 4 (AUMIDEX process) Figure 4 shows the broad outline of a process for the separation and recovery of gold from solutions for working and cleaning the metal or its minerals Starting from a solution containing lOOOppm of gold and 2 g/liter of iron, after varying the phase ratio and acidity, a final solution is obtained with 37.4 mg/liter of gold and only 0.02 mg/liter of iron. The amide used in this process is N~N'-di-n-butyloctanamide~ In this case it should be noted that favourable distribution coefficient of gold (see table 2) (in general dissolved in HCl/HNO3 mixtures) and the low concentration of the metal allow the use of very low concentrations of extracting agent~
,.: . ' . . , ~ :
: , ;. ` ~ . . . :
.
It should also be considered that while re-extrac tion of the uranium in aqueous phase with tributyl-phosphate offers some difficulties, with the amides said extraction is simple and quantitative.
Therefore an object of this invention is a process for the separation of uranium and plutonium comprising:
a first step for separation of uranium and plutonium from the solutlon of dissolved spent nuclear fuel;
10a second step for treatment with a reducing agent to convert the Pu (IV) to Pu (III); and a third step of liquid-liquid extraction to extract the uranium into the organic phase, wherein the extracting agents used are dialkylsubstituted amides of formula (I) / R' R - C - N ~I) O \ R'' where R, R' and R" are as defined above.
20NN'-di-n-butyloctanamide has been found particularly suitable for separation of uranium from plutonium.
This new process has been called AMDEX.
It has also been found that the disubstituted amides used in the process for separation of uranium from plutonium show a high selectivity in the separa-~ tion of hexavalent actinides with respect to tetra-': ~ ,, ' :.; ' . ' . ", ' :' - - . , '' , ' :' ' ' ~' 1323~5 valent actinides, particularly as a function of the acidity of the solution.
Therefore a further object of the present invention is a process for the separation using liquid-liquid S extraction techniques, of hexavalent actinides from tetravalent actinides, wherein amides of formula (I) are used as extracting agents in the organic phase.
/ R' R - C - N \ (I) O R~
where R, R' and R" are as defined above.
The advankage of this process, applied in particular to the separation of U(VI) from Th(IV) (called the TAMDEX process) and to the separation of U~VI) from Pu(IV) (called the.PAMIDEX process) lies in the fact that no previous reduction of plutonium to valence 3 is required and in the high selectlvity of the process itself.
For the separation of uranium and thorium, N,N'-di-n-butyl-2-ethylhexanamide has been found advan-tageous as the dialkylsubstituted amide; for that of urani.um and plutonium, N,N'-dibutyl-3,3'-dimethyl-butyramide is preferred.
It has also been found tha-t the disubsti.tuted amides show interesti.ng properties also for the separa-.: ~ . :-` ~L32398~
tion of non-nuclear elements of high commerc.ial or strategic interest, such as gold, platinum, irid.ium, palladium.
Therefore another object of this invention is a process for the liquid-liqu:id extraction and/or for the separation or quantitative recovery of one of the metals cited above (Au, Pt, Ir, Pd) from aqueous solutions prepared by dissolving the metals or from industrial waste solutions at low concentration, wherein amides of formula (I) are used as selective extracting agents:
R' R - C - N (I) O Ra where R, R' and R" are as described above.
This process has been called AUMIDEX.
In this process as well the acidity plays an im-portant role in determining selectivity.
As mentioned above, the amides of formula (I~
. / R' R - C - N \ (I) O R~
where R, R' and R" are as described above, used in the process for separation of metals from aqueous solution according to the invention were previously used mainly as plastifying agents.
- ~
323~
_ fi _ Therefore another object of the present invention ~` is the use of amides of formula (I) as sequestrants or extracting agents in separation chromatography or in liquid-liquid extraction of all the metals S cited above from acqueous solution.
The dialkylsubstituted amides used according to the invention have a different structure as a function of their use. Amides with completely straight chains, ` such as N,N'-dibutyloctanamide or N,N'-dibutylhexan-amide are particularly suitable as alternatives to , tributylphosphate in a PUREX type process with parti-; tion of plutonium by means of reduction (AMDEX pro-', cess). They are also suitable for extraction of gold (AUMIDEX process).
15Dialkylsubstituted amides with a branch in the alpha position with respect to the carbonyl, for example N,N'-dibutyl-2-ethylhexanamide, are parti-cularly suitable for the separation of hexavalent . actinides fxom tetravalent actinides (TAMIDEX).
20Dialkyl amides with other types of branching, for example N,N'-dibutyl-3,3'-dimethylbutyramide, are particularly suitable for the separation of hexa-valent uranium from tetravalent plutonium with no reduction of the plutonium to valence three (PAMIDEX
process).
Extraction of these metals is more rapid and phase . .. , . ~ , . . .
. . . . . .
. ~ . . ~ - . ~ .
3239~
separation is quicker than in analogous tests with tributylphosphate.
I'he possibility of saturation of the metal in the organic phase is highly dependent not only on the experimental condltions but also on the degree of branching of the aliphatic or aromatic chain.
The concentration of the amides, generally dissolved in an aromatic solvent, depends on the quantity of metal to be extracted.
Table 1 reports the principle properties of the amides used.
Table_l Properties of the_amides ~olubility 15 Amide B.P. nD2o d ~2 dode- mesi-cane thylene N,N'-di-n-butyl- 100-112 1.452 0.861 <0.01 >1000 >1000 octanamide (760) N,N'-di-n-butyl-2- 111-112 1.451 0.861 <0.001 >1000 >1000 ethyl- (1) butyramide N,N'-di-n-butyl-3,3'- 145-150 1.449 0.833 <0.001 >1000 >1000 methyl- (28) butyramide N,N'-di-sec-butyl- 130-150 1.490 0.856 <0.01 >1000 >1000 hexanamide (50) _ _ _ . _ _ Tables 2 and 3 below report several distribution coefficients D for the liquid-liquid separation process :, ' ' ~ . :
, ~
- . , ,, - : , .
~ 13239~
in which the amides according to the invention are used.
Table 2 Distribution coefficients Organic plase: di-n-butyloctanamide or di-n-butyl-hexanamide (lM in mesithylene) Aqueous phase: 4M HN03 + 4M HCl (1:3) metal D(o/a) Au10000 Fe 10 Sn Hg, Zn, Ag 0.1 Cu, Pb 0.01 Table 3 Distribution coeficients for U(VI) ! Pu(IV) and PU(III) and some flssion products (lM amide in mesithylene; phase ratio - l) Nitric acid in aqueous phase 2 0 Di-n-butyl-actanamide D U(VI) 13 18 D Pu(IV) 30 50 D Pu(III) 0.]
D Zr 0.1-0.01 D Ru 0.0001 Di-sec-butyl-hexanamide D U(VI) 10 14 .
'' ' ' ~ ' `~` t323~5 . , D Pu(IV) 9 24 Di-3,3'~di-methyl-butyl-butYramide D U(VI) 5 11 D Pu(IV) 3 12 Di-n-butyl-2-ethyl-octanamide D U(VI~ 5 11 D Pu(IV) 3 9 The liquid-liquid extraction processes for which the dialkylsubstituted ami~es according to the invention are proposed consist essentially in placing the aqueous solution containing many metals, including those to be separated, in intimate contact with an organic solution immiscible with water, containing a substance (in this case an amide) capable of 'binding' and so extracting selectively and quantitatively from the aqueous phase to the organic phase the metal or metals of interest, separating them from the others.
The organic phase containing the metal(s) is then placed in contact in the same way with a suitable aqueous solution to re-extract all or some of the metals in the organic phase and return them to an aqueous phase.
Slightly acidic or reducin~ solutions are normally used which, by changing the valence of the metal, make it less extractable. This is the case for the separation of uranium from plutonium in the PUREX process, where .~ .
3239~
the tetravalent plutonium extracted with tributylphosphate into the organic phase is reduced to trivalent plutonium, which is not soluble and so returns to the aqueous phase.
In other cases competitive water-soluble extracting agents are used.
The apparatus used for these extraction operations consists of multistep contactors of various types, such as: banks of mixer settlers, pulsed columns and centrifugal contactors.
The amides proposed may also be used in columns (pure or dissolved in solvent) dispersed on a finely divided inert support. In this case the aqueous solution containing the metals of interest is passed through the column and the metals remain 'bound' to the material in the column. They are then recovered by passing a suitable aqueous solution through the column. This process is no longer liquid-liquid extraction, but rather extractive chromatography.
~XAMPL~S
The invention will be illustrated with reference to the attached drawings, in which:
figure 1 shows an example of the AMDEX process;
figure 2 shows and example of the TAMIDEX process;
figure 3 shows an example of the PAMIDEX process;
and figure 4 shows an example of the AUMIDEX process.
~3239~5 The following examples are exemplificative only and do not in any way limit the scope of the invention.
Example 1 _(AMDEX process) With reference to figure 1, a lM solution of N,N'-di-n-butylactanamid~ (DBOA) in mesithylene i9 passed at a ~low rate of 6.5 liters/hour through a multistep contactor in the opposite direction to an aqueous solution containing 250 g/liter of uranium and 2.5 g/liter of plutonium, which flows at a rate of 2j.2 liters/hour.
This 2M acid solution contains fission products as well.
After the extraction step, the fission products are found in the extract in the same quantity, while the concentration of uranium has fallen to 5.9 x 10~2 g/liter and that of plutonium to 8.7 x 10-6 g/liter.
The organic solution is then treated with a reducing agent to separate the Pu(III) Erom the uranium according to the classic PUREX process, from which the AMDEX process differs in its use of N,N'-di-n-butyloctanamide instead of tributylphosphate.
Example 2 (TAMDEX process) Figure 2 shows an example of a process for the separation of U(VI) from Th(IV) using a lM solution of N,N'-di-n-butyl-2-ethylhexanamide in mesithylene.
A solution containing 13.75 g/liter of uranium and 236.7 g/liter of thorium is separated chromatographically to give an aqueous soluti'on containing approximately , ,. , -. : -""` 1323~
120 g/liteL of thorium and ~ 0.015 g/liter of uranium and an organic phase enriched in uranium. The final extract contains more than 3.4 g/liter of uranium and no detectable thorium.
Example 3_(PAMIDEX process) Figure 3 shows a process for the separation of U(VI) from Ph(IV). In this case N,N'-dibutyl~3,3'-dimethyl-butyramide is used.
Example 4 (AUMIDEX process) Figure 4 shows the broad outline of a process for the separation and recovery of gold from solutions for working and cleaning the metal or its minerals Starting from a solution containing lOOOppm of gold and 2 g/liter of iron, after varying the phase ratio and acidity, a final solution is obtained with 37.4 mg/liter of gold and only 0.02 mg/liter of iron. The amide used in this process is N~N'-di-n-butyloctanamide~ In this case it should be noted that favourable distribution coefficient of gold (see table 2) (in general dissolved in HCl/HNO3 mixtures) and the low concentration of the metal allow the use of very low concentrations of extracting agent~
,.: . ' . . , ~ :
: , ;. ` ~ . . . :
.
Claims (5)
1. A process for the selective extraction of actinides and Au, Pt, Ir and Pd metals from aqueous solutions using techniques of liquid-liquid extraction in the presence of an organic phase or techniques of chromatography in the presence of a solid phase, comprising the operations of:
a) adjusting the acidity of said aqueous solution to obtain a value of the distribution coefficient such as to enable said actinides and/or metals to be transferred to said organic phase or solid phase;
b) subjecting said acidified aqueous solution to extraction or chromatography by said organic or solid phase, respectively, containing as extracting agents dialkysubstituted amides of formula (I) in which R is a straight or branched aliphatic chain with 8 or less carbon atoms, and R' and R" are straight or branched aliphatic chains in which the sum of the carbon atoms in R' + R" is less than or equal to 8, and c) contacting said organic or solid phase containing said actinides and/or metals with a fresh aqueous solution to reextract said actinides and/or metals from said organic or solid phase and transfer them to said fresh aqueous solution for further processing.
a) adjusting the acidity of said aqueous solution to obtain a value of the distribution coefficient such as to enable said actinides and/or metals to be transferred to said organic phase or solid phase;
b) subjecting said acidified aqueous solution to extraction or chromatography by said organic or solid phase, respectively, containing as extracting agents dialkysubstituted amides of formula (I) in which R is a straight or branched aliphatic chain with 8 or less carbon atoms, and R' and R" are straight or branched aliphatic chains in which the sum of the carbon atoms in R' + R" is less than or equal to 8, and c) contacting said organic or solid phase containing said actinides and/or metals with a fresh aqueous solution to reextract said actinides and/or metals from said organic or solid phase and transfer them to said fresh aqueous solution for further processing.
2. Process as claimed in claim 1, applied to the separation or uranium and plutonium, in which said separation is effected after reducing the plutonium to Pu(III) with a suitable reducing agent and using N,N'-di-n-butyloctanamide as extracting agent.
3. Process as claimed in claim 1, for the separation of uranium (VI) from an aqueous solution containing thorium (IV), in which N,N'-di-n-butyl-2-ethylhexanamide is used as extracting agent.
4. Process as claimed in claim 1, for the selective extraction of uranium (VI) from plutonium (IV), in which N,N'-dibutyl-3,3'-dimethylbutyramide is used as extracting agent.
5. Process as claimed in claim 1, for the selective extraction of gold from aqueous solutions containing other metal ions in which N,N'-di-n-butyloctanamide is used as extracting agent.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| IT48667A85 | 1985-10-15 | ||
| IT4866785A IT1184656B (en) | 1985-10-15 | 1985-10-15 | METAL SEPARATION PROCESS FROM THEIR AQUOUS SOLUTIONS BY SUBSTITUTED AMOXES |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1323985C true CA1323985C (en) | 1993-11-09 |
Family
ID=11267934
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 519626 Expired - Fee Related CA1323985C (en) | 1985-10-15 | 1986-10-02 | Process for the separation of metals from aqueous solutions using dialkyl substituted amides |
Country Status (5)
| Country | Link |
|---|---|
| AU (1) | AU595248B2 (en) |
| CA (1) | CA1323985C (en) |
| GB (1) | GB2183078B (en) |
| IT (1) | IT1184656B (en) |
| ZA (1) | ZA867431B (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6231784B1 (en) | 1995-02-16 | 2001-05-15 | Henkel Corporation | Water insoluble composition of an aldoxime extractant and an equilibrium modifier |
| FR3062128B1 (en) * | 2017-01-26 | 2019-04-19 | Commissariat A L'energie Atomique Et Aux Energies Alternatives | DISSYMETRIC N, N-DIALKYLAMIDES, PARTICULARLY USEFUL FOR SEPARATING URANIUM (VI) FROM PLUTONIUM (IV), THEIR SYNTHESIS AND USES THEREOF |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3218132A (en) * | 1963-05-24 | 1965-11-16 | Abbott Lab | Radioactive phosphorus process |
-
1985
- 1985-10-15 IT IT4866785A patent/IT1184656B/en active
-
1986
- 1986-09-30 ZA ZA867431A patent/ZA867431B/en unknown
- 1986-10-02 CA CA 519626 patent/CA1323985C/en not_active Expired - Fee Related
- 1986-10-14 AU AU63873/86A patent/AU595248B2/en not_active Ceased
- 1986-10-15 GB GB8624680A patent/GB2183078B/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| AU595248B2 (en) | 1990-03-29 |
| IT1184656B (en) | 1987-10-28 |
| GB2183078B (en) | 1990-01-24 |
| GB2183078A (en) | 1987-05-28 |
| IT8548667A0 (en) | 1985-10-15 |
| AU6387386A (en) | 1987-04-16 |
| GB8624680D0 (en) | 1986-11-19 |
| ZA867431B (en) | 1987-06-24 |
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