Understanding of iron extraction mechanisms from phosphate and sulfuric media using DEHCNPB

(1)

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Understanding of iron extraction mechanisms from

phosphate and sulfuric media using DEHCNPB

B. Fries, C. Marie, V. Pacary, H. Mokhtari, Mc. Charbonnel

To cite this version:

B. Fries, C. Marie, V. Pacary, H. Mokhtari, Mc. Charbonnel. Understanding of iron extraction mechanisms from phosphate and sulfuric media using DEHCNPB. PhD day AREVA Mines, Jun 2016, Paris, France. PhD day AREVA Mines, 2016. �hal-02417823�

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MINING BU

Perspectives

• Quantification of sulfur in the organic phase in a way to determine [SO

₄2-

_{]/ [Fe}

3+

_{] ratio (ICP-AES)}

• Study of the extraction of water during the extraction of iron (Karl-Fischer)

• EXAFS measurements of organic phase to validate proposed structures of complexes

• Comparison with iron extraction from the phosphoric medium using an analog molecule

Sulfuric medium

Phosphoric medium

PhD’s Day, June 9

th

_{2016, AREVA Paris La Défense}

Understanding of iron extraction mechanisms from

phosphate and sulfate media using DEHCNPB

FRIES Boris

a

, MARIE Cécile

a

, PACARY Vincent

a

, MOKHTARI Hamid

b

, CHARBONNEL Marie-Christine

a

a : CEA/DEN Marcoule, Département de recherche sur les procédés pour la mine et le recyclage du combustible, Service d’études des procédés de dissolution et de séparation ,

30207 Bagnols-sur-Cèze, France

b : AREVA MINES , Service d’Etudes de Procédés et Analyses, 87250 Bessines-sur-Gartempe, France

Contacts : boris.fries@cea.fr

References

[1] : Gabriel.S et al., Annals of Nuclear Energy, 58., p213-220,2013.

[2] : Brevet PCT WO 2013/167516 A1 ; 14/11/2013.

[3] : Norme ASTM C967-08.

[4] : Wilke. M et al., American Mineralogist, 86, pp714

–730, 2001

Extraction

Scrubbing

Stripping

Acid

☨

Uranium + Impurities

DEHCNPB / TPH

H

₂

SO

₄

Na

2

CO

3

Impurities

U

U, Imp

_U

Raffinate

Context

Uranium extraction from phosphate ores



Low amount of U, but large quantity available (~4Mt)

[1]



Uranium with high amounts of other metals (U/Fe selectivity)

Historic process: Synergistic mixture HDEHP/TOPO

di-(2-ethylhexyl) phosphoric acid

Novel bifunctional extractant: DEHCNPB

[2]

⇨ D

_U

~20x higher than with HDEHP/TOPO*

⇨ FS(U/Fe) ~35x higher*

⇨ Pilot scale trial demonstration

⇨ Used for the extraction of uranium from sulfuric medium

Lower performances of the « sulfate » process → U leaks in raffinates

Di-(2-ethylhexyl)carbamoyle

nonyl phosphate butyl

Objective

Explain the differences between the two processes

Understanding of extraction mechanisms, speciation in organic phases

Development of a thermodynamical model simulating both processes

U extraction process

Solvent treatment

Uranium extraction by DEHCNPB in TPH



☨

_{Phosphoric medium: [H}

3

PO

4

]=5M



☨

_{Sulfuric medium: [SO}

42-

]=1.4M , pH = 1

Iron scrubbing



Scrubbing of extracted iron by concentrated sulfuric acid

Stripping of uranium in alkali medium (carbonates)



Back-extraction of uranium in aqueous phase (concentrated U)

Fe/U< 0.15%

[3]

Mo/U<0.1%

[3]

Ti/U et Zr/U<0.01%

[3]

Experimental studies

Tri-octyl phosphine oxyde

0 50 100 150 200 250 300 350 400 450 500 0 200 400 600 800 1000 1200 1400 1600 1800 2000 1 2 3 4 5 6 7 8

Iron

conce

ntration

in

the

organi

c

ph

as

e

(mg/L

)

Ur

aniu

m

conce

ntration

i

n

the

organi

c

ph

as

e (mg/L

)

Stage number

Concentration profiles – extraction stages

[U]org

[Fe]org

0.0E+00 5.0E-04 0.1E-02 0.2E-02 0.2E-02 0 10 20 30 40 50 60 70 80 0 10 20 30 40 50 60 70

D

Fe

D

U

Contact time (min)

Extraction kinetic

Uranium Fer

0 0,5 1 1,5 2 2,5 0 5 10 15 20 25 30 35 40 45

Iron

conce

ntration

in

the

organi

c

ph

as

e

at

equi

li

brii

um

(g.

L

-1

)

Iron concentration in the aqueous phase at equilibrium (g.L

-1

₎

0.E+00 1.E-01 2.E-01 3.E-01 4.E-01 5.E-01 0 500 1000 1500 2000 2500 0 20 40 60 80 100 120

D

Fe

D

U

Contact time (min)

Extraction kinetic

D(U)

D(Fe)

y = 1.243x + 1.508

R² = 0.993

-1,00 -0,80 -0,60 -0,40 -0,20 0,00 0,20 0,40 0,60 0,80 1,00 -0.2 -0.2 -0.2 -0.1 -0.1 -0.1 -0.1

log

(D

Fe

)

log[DEHCNPB]

Graphical slope analysis

y = 1.622x – 0.137

R² = 0.999

-4 -3,5 -3 -2,5 -2 -1,5 -1 -2,20 -2,00 -1,80 -1,60 -1,40 -1,20 -1,00 -0,80

lo

g(D

Fe

)

log [DEHCNPB]

Graphical slope analysis

Conclusion

⇨ Two processes with ≠ performances → Uranium leaks in raffinates

⇨ Iron is suspected of interfering with uranium extraction from a sulfuric medium

⇨ Different iron extraction mechanisms depending on the initial medium

⇨ Predominant iron specie in sulfuric acid FeSO

₄+

_{is most likely extracted}

Comparative study

0 50 100 150 200 250 300 350 400 450 500 0 200 400 600 800 1000 1200 1400 1600 1800 2000 1 2 3 4 5

Iron

conce

ntration

in

the

organi

c

ph

as

e

(mg/L

)

Ur

aniu

m

conce

ntration

in

the

organi

c

ph

as

e

(mg/L

)

Stage number

Concentration profiles – extraction stages

[U]org

[Fe]org

⇨ Uranium leaks

⇨ Sulfate medium: Higher [Fe]

_org

⇨ How does the initial media influences the

extraction of iron?

0,E+00 1,E-02 2,E-02 3,E-02 4,E-02 5,E-02 6,E-02 7,E-02 8,E-02 7105 7107 7109 7111 7113 7115 7117

xµ

(E)

Energy (eV)

DEHCNPB 0.1M/TPH - Fe 1 g/L

DEHCNPB 0.1M/TPH - Fe 50 g/L

Fe(II) Reference

Fe(III) Reference

Uranium and iron extraction profiles during pilot scale trials; solvent: DEHCNPB 0.1M / Dodecane. Feed solution: industrial phosphoric acid,H₃PO₄ 5M, C_U=119ppm, C_Fe=5.7g/L. O/A=0.1 ; T=40°C

Uranium and iron extraction profiles during pilot scale trials; solvent: DEHCNPB 0.05M / TPH. Feed solution: Synthetic « Imouraren » solution, [SO42-]=1.42M, pH=1, CU=360ppm, CFe=4.1g/L, O/A=0.125 ; T=25°C

Uranium and iron distribution coefficients as a function of extraction time; solvent: DEHCNPB 0.1M / TPH. Aqueous phase: [H₃PO₄]=5M, C_U=1g/L , C_Fe=10g/L ; O/A=1 ; T=25°C.

Uranium and iron distribution coefficients as a function of extraction time; solvent: DEHCNPB 0.1M / TPH. Aqueous phase: [SO₄2-_{]=1.6M, pH=1, C}

U=1g/L , CFe=10 g/L ; O/A=1 ; T=25°C.

Logarithmic plot of iron distribution coefficient as a function of extractant concentration; solvent: DEHCNPB 0.01M - 0.1M / TPH. Aqueous phase: [H₃PO₄]=5M, C_Fe=3g/L ; O/A=1 ; T=25°C.

Logarithmic plot of iron distribution coefficient as a function of extractant concentration; solvent: DEHCNPB 0.022M-0.25M / TPH. Aqueous phase: [SO42-]=1.7M, pH=1, CFe=3.8g/L ; O/A=1 ; T=25°C.

Iron extraction isotherm. Solvent: DEHCNPB 0.1 M/ TPH. Aqueous phase: [SO42-]=1.7M, pH=1, CFe from 0.5g/L to

50g/L ; O/A=1 ; T=25°C. Normalized K-edge spectra of iron – pre-edge region. Samples : DEHCNPB 0.1M/TPH after extraction of iron from a sulfuric medium. Fe(II) reference: Fe₂(SO₄)₃(NH₄)₂ 0.05M with Hydroxylamine 1M. Fe(III) reference: Fe₂(SO₄)₃ 0.05M with hydrogen peroxyde 1M

Step

Phosphate process

Sulfate process

Extraction

10 ppm

23 ppm

Stripping

< 3 ppm

70 ppm

⇨ Contact time required to reach equilibrium

⇨ Sulfate medium: Higher D

_Fe

and D

_U

↘ when

iron reaches equilibrium

⇨ Selectivity issue?

Element

Phosphate medium

Sulfate medium

U

5 min

Fe

Unmeasurable

40 min

Different iron extraction mechanisms according to the initial medium?

Graphical slope analysis

⇨ Lower average stoichiometries of

Fe-DEHCNPB complexes formed from the sulfate

medium.

 

)

log(

.

)

log(

D

_Fe



n

HL

libre

Iron extraction from a sulfuric medium



Hypotheses :

✘ Extraction of Fe

2+

Solution potential measurements

allowed to estimate that 5% to

15% of iron is divalent in the

sulfuric medium

✔ Co-extraction of SO

₄

2-

Direct measurement of sulfur

Sulfur in organic phases at

equilibrium thanks to ICP-AES

⇨ Extraction of FeSO

₄+

_?

Determination of iron oxydation state in organic phases

[4]



XANES measurments: Only trivalent iron is present in the organic complexes

Fe

2+

_Fe

3+

Iron

* Extraction at 22°C of an aqueous phase containing 250mg/L of uranium several grams per liter of iron in H₃PO4 5M, DU=3.8

andSF_(U/Fe)=200 avec HDEHP/TOPO (80%/20% ; 0.25M), and D_U=72 and SF_(U/Fe)=6500 with DEHCNPB (0.1M).