Atelier PARIS Extraction, ICSM, 10-11 décembre 2009

Study of DTPA and malonic acid extraction system for Ln(III)/An(III)

separationIrena Špendlíková, Petr DISTLER

CTU Prague, Czech Republic

Manuel Miguirditchian, Fabien Burdet

CEA Marcoule, France

2 ACSEPT semestrial meeting Manchester, april 4-7 2011

Extraction system

Results important• for understanding the chemistry of the process• for modelling and simulating the process

Selective stripping of actinides (Am, Cm) from lanthanidesChange of the stripping solution from HEDTA-citric acid to DTPA-malonic acidEasier degradation of DTPA and malonic

PUREX raffinateHNO3 3M

DMDOHEMA + HDEHP/HTP

EXTRACTION

FP non extracted HNO3

SCRUBBING

Mo

Mo STRIPPING

pH buffer

HEDTA + citric acidpH 3 (NaOH)

Am + Cm

ACTINIDE STRIPPINGLn SCRUBBING

Ln + Y + Zr + Fe TEDGA, oxalic acidHNO3

Ln, Zr, Fe STRIPPING

DTPA + malonic acidpH 2.5 (NH2OH)

3 ACSEPT semestrial meeting Manchester, april 4-7 2011

Content

• Experimental procedure

• Stability constants with DTPA

• Impact of malonic acid

• pH dependence

• Temperature dependence

• Kinetics experiments– Inactive / active experiments

– Influence of saturation

– Influence of pH

– Influence of temperature

• Conclusions

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Experimental Procedure

Preequilibration of organic phase (0.3M HDEHP-0.6M DMDOHEMA/TPH)

with malonic acid at different pH

Loading of organic phase

with tracers (241Am, 152Eu, 139Ce)

or/and other cations (La, Ce, Nd, Eu, Y, Pd, Zr, Fe)

Stripping experiments with DTPA-malonic acid solutions

15 minutes mechanic shaking, thermostated, centrifuged

Organic and aqueous samples measured by gamma spectrometry or ICP-

AES

5 ACSEPT semestrial meeting Manchester, april 4-7 2011

DTPA Dependence

Extracted complexes:DTPA : Eu, Ce, Am = 1:1

Aq: 10-6 M – 0.025 M DTPA at pH 2

Org: 0.3 M HDEHP, 0.6 M DMDOHEMA in TPH

0.1

1

10

100

1000

10000

0.0000001 0.000001 0.00001 0.0001 0.001 0.01 0.1

[DTPA]tot [mol/l]

D(M)

D(Am)

D(Eu)

D(Ce)

y = -0.98x - 0.748R2 = 0.9994

y = -0.95x - 1.98R2 = 0.998

y = -0.86x + 0.2338R2 = 1

-1

-0.5

0

0.5

1

1.5

2

2.5

3

3.5

-6 -4 -2 0

log [DTPA]tot

log

D(M

) AmEuCe

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DTPA Stability constants

Element Log β(app)

Am3+ 23.45

Eu3+ 22.93

Ce3+ 21.65

pK1 1.8pK2 2.55pK3 4.31pK4 8.54

pK5 10.51

Acidity constants of DTPA

Aq: 10-6 M – 0.025 M DTPA at pH 2

Org: 0.3 M HDEHP, 0.6 M DMDOHEMA in TPH

y = 187895x + 30.042R2 = 0.9971

y = 56883x + 3.4428R2 = 0.9995

y = 2956.6x + 1.1105R2 = 0.9978

0.1

1

10

100

1000

10000

0 0.005 0.01 0.015 0.02 0.025 0.03

[DTPA]tot (mol/L)

Do/

D -

1

Ce

Eu

Am

βapp includes βMDTPA and βMHDTPA

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Impact of malonic acid

• no complexation with malonic acid => no ternary complex with DTPA• just used as a buffer

• decrease in D values• NH2OH as complexing agent ? => include in calculations

Aq: 10mM DTPA, 0-1M malonic acid at pH 2

Org: 0.3 M HDEHP, 0.6 M DMDOHEMA in TPH

0

10

20

30

40

50

60

70

80

90

100

110

0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1 1,1

[Malonic acid] (mol/l), NH2OH

D(M

)

1

10

100

1000

SF

CeEuAmSF(Ce/Am)SF(Eu/Am)

NH2OH

0

10

20

30

40

50

60

70

80

90

100

0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1 1,1

[Malonic acid] (mol/l), NaOH

D(M

)

1

10

100

1000

SF

CeEuAmSF(Ce/Am)SF(Eu/Am)

NaOH

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pH dependence

y = 65733.9x-8.7

y = 15183.3x-9.5

y = 712.1x-9.3

0.01

0.1

1

10

100

1 1.5 2 2.5 3 3.5

pH (NH2OH)

D

CeEuAm

y = 1035x-3

y = 165.9x-3.7

y = 14.5x-4.3

0.01

0.1

1

10

100

1 1.5 2 2.5 3 3.5 4

pH (NaOH)D

Ce

Eu

Am

Org: 0.3 M HDEHP-0.6 M DMDOHEMA in TPH preequilibrated and loaded with 241Am, 139Ce,152Eu

Aq: 0.01M DTPA, 0.3M malonic acid at different pH adjusted by NH2OH or NaOH

• Stronger impact on pH with NH2OH Power 9 compare to power 4

9 ACSEPT semestrial meeting Manchester, april 4-7 2011

y = -1.2404x + 0.2039R2 = 0.9998

y = -1.148x + 1.252R2 = 0.9985

y = -1.1159x + 2.0767R2 = 0.9914

-4.5

-4.0

-3.5

-3.0

-2.5

-2.0

-1.5

-1.0

-0.5

0.0

2.0 2.2 2.4 2.6 2.8 3.0 3.2 3.4 3.6

pH (NaOH)

log

(D*[

H4D

TPA

]) Ce Eu Am

y = -2.0046x + 1.8146R2 = 0.9909

y = -2.036x + 3.1525R2 = 0.9889

y = -2.1207x + 4.3826R2 = 0.9931

-5.0

-4.5

-4.0

-3.5

-3.0

-2.5

-2.0

-1.5

-1.0

-0.5

0.0

2.0 2.2 2.4 2.6 2.8 3.0 3.2 3.4

pH (NH2OH)

log

(D*[

H4D

TPA

])

Ce Eu Am

pH dependence

H1)HDEHP(3)DTPA(AmDTPAH)HDEHP()DEHP(Am

OHNHH2)HDEHP(3)DTPA(AmOHNHDTPAH)HDEHP()DEHP(Am

22

433

222

3433

1H+ exchanged with NaOH : no impact of the base 2H+ exchanged with NH2OH : impact of the base in the stripping

Complexation of NH2OH after deprotonation ? Ternary complex Am(DTPA)(NH2OH)2- ? Extraction of NH3OH+ by HDEHP: impact of saturation in organic phase

xH)HDEHP(3)DTPA(AmDTPAH)HDEHP()DEHP(Am 22Base)n5(

n33

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Impact of pH and the base on the selectivity

No impact of the base on the separation factors

xH)HDEHP(3)DTPA(AmDTPAH)HDEHP()DEHP(Am 22Base)n5(

n33

0,1

1

10

100

1000

1 1,5 2 2,5 3 3,5 4

pH

SF L

n/A

m

Ce/Am (NH2OH)Eu/Am (NH2OH)Ce/Am (NaOH)Eu/Am (NaOH)

11 ACSEPT semestrial meeting Manchester, april 4-7 2011

Temperature dependence xH)HDEHP(3)DTPA(AmDTPAH)HDEHP()DEHP(Am 2

2Base)n5(n33

pH 2.00 NH2OH

y = 4083.5x - 9.4925R2 = 0.9976

y = 1597.3x - 3.0308R2 = 0.9865

y = 3274.1x - 11.555R2 = 0.998

-2.50

0.00

2.50

5.00

7.50

0.003 0.0031 0.0032 0.0033 0.0034 0.0035 0.0036 0.00371/T [K-1]

lnD(

M)

Ce Eu Am

pH 2.50 NaOH

y = 4544.4x - 11.711R2 = 0.9913

y = 1571.6x - 3.913R2 = 0.952

y = 3201.3x - 12.315R2 = 0.9974

-5.00

-2.50

0.00

2.50

5.00

0.003 0.0031 0.0032 0.0033 0.0034 0.0035 0.0036 0.00371/T [K-1]

lnD(

M)

Ce Eu Am

ΔH [kJ/mol]

2.00 NH2OH 2.50 NH2OH 2.50 NaOH

Ce -34.0 ± 0.8 -33.3 ± 1.0 -37.8 ± 1.8

Eu -13.3 ± 0.8 -7.2 ± 1.1 -13.1 ± 1.5

Am -27.2 ± 0.6 -20.5 ± 0.2 -26.6 ± 0.7

ΔS [J/mol]

2.00 NH2OH 2.50 NH2OH 2.50 NaOH

Ce 78.9 ± 2.8 86.3 ± 3.1 97.4 ± 5.9

Eu 25.2 ± 2.8 16.8 ± 3.7 32.5 ± 4.8

Am 96.1 ± 2.0 85.7 ± 0.6 102.4 ± 2.2

0.01M DTPA – 0.3M malonic acid pH 2-2.5 (NH2OH or NaOH) - 5°-55°Cvan’t Hoff method

12 ACSEPT semestrial meeting Manchester, april 4-7 2011

Stripping Kinetics

Element [mmo/l]

Ce 3.8

Eu 3.5

Fe 12.6

Nd 5.8

Pd 0.4

Y 4.7

Zr 9.3

Total 39.9

Initial concentrations of cations in loaded organic phase

Stripping of the loading organic phase with 0.01M DTPA – 0.3M malonic acid

at different pH (2.0 ; 2.5 and 3.0)at different temperature (25, 35, 45°C)in FOC (and one experiment in FAC)spiked with 241Am, 139Ce and 152Euwith macroconcentrations of cations or with tracers only

13 ACSEPT semestrial meeting Manchester, april 4-7 2011

Stripping Kinetics

Slow kinetics of stripping of Fe(III), Pd(II) and Zr(IV)Relatively fast for Am and EuGood agreement between inactive and active experiments

0.01

0.1

1

10

100

1000

0 10 20 30 40 50 60 70Time [min]

D(M

)

Fe Pd Zr

Eu (ina) Eu(152) Am

0.01M DTPA – 0.3M malonic acid pH 2.5 (NH2OH) - 25°C

14 ACSEPT semestrial meeting Manchester, april 4-7 2011

Stripping Kinetics0.01M DTPA – 0.3M malonic acid

00.20.40.60.81

1.21.41.61.82

0 5 10 15 20 25 30time [min]

D(Am

)

2 2.5 3

00.20.40.60.81

1.21.41.61.82

0 5 10 15 20 25 30time [min]

D(Am

)

25°C

35°C

45°C

0

1

2

3

4

5

6

0 5 10 15 20 25 30time [min]

D(Eu

)

2 2.5 3

0

1

2

3

4

5

6

0 5 10 15 20 25 30time [min]

D(Eu

)

25°C

35°C

45°C

pH temperature

at pH 2.03, 2.48 and 2.84 at 25°C at pH 2.46 (25°C), 2.46 (35°C), 2,47 (45°C)

15 ACSEPT semestrial meeting Manchester, april 4-7 2011

Stripping Kinetics0.01M DTPA – 0.3M malonic acid – pH 2.8 (NH2OH) – 25°C

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0.45

0 5 10 15 20 25 30time [min]

D(Am

)

FOC

FAC

0.00.51.01.52.02.53.03.54.04.5

0 5 10 15 20 25 30time [min]

D(Eu

)

FOC

FAC

• no huge difference• at 30 s FOC seems to be quicker

FOC- fonctionement organique continous- dispersed aqueous phase in the organic one

16 ACSEPT semestrial meeting Manchester, april 4-7 2011

Conclusions and outlooks

• No ternary complex observed between DTPA and malonic acid– Different from HEDTA-citric acid

• No influence of malonic acid on D-values– Different from citric acid and lactic acid (Talspeak system)

• Strong influence of pH on D-values (with NH2OH in particular)

• Influence of NH2OH on the stripping– Formation of ternary complex Am(DTPA)(NH2OH) or extraction of

NH2OH+ by HDEHP

• Exothermic ethalpies of extraction• Stripping kinetics of Am, Ln fast compared to Zr, Fe and Pd• Strong influence of pH on the stripping kinetics

=> Results will be used for modelling of the process and for better understanding of its chemistry

17 ACSEPT semestrial meeting Manchester, april 4-7 2011