Extraction and separation of Rare Earths - EREANerean.eu/papers/Lecture III - Extraction and separation... · · 2014-10-17Ore Beneficiation Mine Concentrates Ore attack Rare Earths

Extraction and separation of Rare Earths

Dr. Alain LEVEQUEformer R&D global director Rare Earths

SUMMER SCHOOL LEUVEN UNIVERSITY 2014 Aug19

Rare EarthsSystems

AGENDA

KU Leuven Summer School 2014 Aug 19Extraction and separation of Rare Earths2

1. Solvent extraction is the only industrialtechnology for RE separation

2. Raw materials processing3. Basics of Solvent Extraction

• chemistry• technology

4. Examples of process flow sheet5. Conclusions & Prospects

Rare EarthsProducers

3

Separations : a key step in the value chainMiningOperators

Rare earths users

oil refiningcatalysts phosphors magnets special

alloysglass andpolishing

depollutioncatalysts

ceramicsand others

End Users Markets(cars,electronics,computers,lighting,glass,medical,energy,nuclear,communications,…)

Ore Beneficiation

Mine Concentrates

Ore attack

Rare Earths mix concentrate

Salts & OxidesSpecialties

Metals &Alloys

Separations

KU Leuven Summer School 2014 Aug 19Extraction and separation of Rare Earths

4

Rare Earths are difficult to separate

Electronic structure 4f 0-14 5d1 6s2 Very similar chemical propertiesPhysical properties > numerous applications

Ionic radius

Monotonic evolution from La3+ to Lu3+

rLa3+ = 1.16Ắ → rLu3+ = 0.7Ắ The regular variation of Ln3+ ionic

radii makes the separation between two ions very difficult and only possible by complexation.

Exception for Ce4+ and Eu2+

proximity with uranides and alkaline earths beneficial for their separation

Ioni

cra

dius

(Å)


5

Since 1965-1970 solvent extraction is the onlyindustrial technology for RE separation

0

20 000

40 000

60 000

80 000

100 000

120 000

140 000

160 00019

5019

5219

5419

5619

5819

6019

6219

6419

6619

6819

7019

7219

7419

7619

7819

8019

8219

8419

8619

8819

9019

9219

9419

9619

9820

0020

0220

0520

0720

09

China(bastnaesite+ionics)USA (bastnaesite Molycorp)Others (incl. Monazite Solvay)

Fractionnatedcristallization

Selectiveprecipitation(Ce)

Ion-exchangeresins

Solvent extraction

Global production of Rare Earths (tpa REO)


Where are the RE separation plants located today

6

For a global production of # 130.000 T/year REO

KazakhstanUst Kamenogorsk

China> 20 plants

FranceSolvay

USAMolycorp

MalaysiaLynas

IndiaIndian RE

EstoniaSilmet-Moly

JapanShinEtsu

VietnamJapanese coll


AGENDA

7






Classical raw materials

NB Loparite (a [RE-Ca-Nb-Ti]mix-oxide) is specificallyused in Russia at low level production

Raw materialsFour main ore types are processed for RE production

MonaziteW.AustraliaMount Weld

XenotimeMalaysia

BastnaesiteUSA

MontainPass

BastnaesiteChina

(In.Mongolia)Bayan Obo

Ionic ClayChinaXunwu

LopariteRussia

Light R

E La2O3

94,7

23,9

3,5

0,4

98,7

32

97,7

23

74,5

30

97,9

28

CeO2 47,6 1,4 50,5 50 7 57,4

Pr6O11 5,2 0,5 4,2 6,2 7,5 3,7

Nd2O3 18,1 1,2 12 18,5 30 8,8

Med

ium

RE

Sm2O3

5,3

2,4

96,5

1,1

1,3

0,8

2,3

0,8

25,5

6

2,1

0,92

Eu2O3 0,53 0,01 0,12 0,2 0,5 0,13

Gd2O3 1,1 4 0,15 0,7 4 0,22

Heavy RE

Tb4O7 0,09 1,2 0,01 0,1 0,4 0,07

Dy2O3 0,25 6,6 0,03 0,1 2 0,09

Ho2O3 0,03 2,5 0,01 - 0,4 0,03

Er2O3 0,06 6,1 0,01 0,1 1 0,07

Tm2O3 0,01 9 0,02 0,1 0,3 0,07

Yb2O3 0,03 0,9 0,01 0,1 0,6 0,3

Lu2O3 0 0,8 0,01 - 0,3 0,05

Y2O3 0,76 64,3 0,1 0,1 10 0,15

8KU Leuven Summer School 2014 Aug 19Extraction and separation of Rare Earths

9

o Number of new projects are based on minerals showing a very complex mineralogy

o Some of them contain not only RE (i.e. Zr, Nb, Ta, U),

o These complex minerals have never been processed and require specific and new process development .

Formulae of major minerals containing rare earthsRare earth

mineral Formula Type of REE Existingprocess

Bastnaesite LRE Yes

Monazite LRE Yes

Xenotime HRE YesFergusonite HRE No

Eudyalite HRE No

fluocarbonate CeFCO3

phosphate (Ce,Y)PO4

phosphate YPO4

(Y,U,Th)[Nb,Ta,Ti]O4

Na4(Ca,Ce)2(Fe,Mn,Y)ZrSi8O22(OH,Cl)2

New RE mining projects evaluate new minerals

Raw materials - issues impacting separations


10

All Rare Earths raw materials contain natural radioactivity(Thorium and Uranium)

Radioactivity is a relatively complex technical challenge due to the fact that separationprocesses make cuts in radioactive families of Thorium and Uranium. The main isotopes to consider are

bastnaesite monazite pyrochlore xenotime apatite eudyalite

REO contentsin deposit 0,5%-10% 3%-15% 1% 0,6%-6%

(max12%) 0,6%-0,8% 0,90%

Thorium / REO 0,50% 0,5%-15% 7% 3% 2% 0,15%-0,3%

Uranium / REO - 0,05%-0,5% 2% 0,1%-0,2% 0,3%-0,8% 0,20%

Raw materials - issues impacting separations

Radioactive isotopes groups [Th232,Th228,Th230] [U238,U234,U235] [Ra228,Ra226] [Pb210] and [Ac227] have a complex chemistry and are split according various behaviours during separations by precipitation or SX.

232Th family 232Th, 228Ra, 228Th238U family 238U, 234U, 230Th,226Ra, 210Pb235U family 235U, 227Ac.


11

Ce(OH)4

REsulfatesoln

Ce oxidation

H2SO4leaching

Roasting

CeO2concentrate

REchloridesoln

RoastingCeIII>CeO2

SelectiveHCl

leaching

bastnaesiteRECO3F

monazite,xenotimeREPO4

Na phosphate

NaOHcracking

acidleaching

Th hydroxide

RE chl/nitrsoln

RE+Thnitrate soln

RE hydroxide

neutralization

Two main process routes for ore cracking

H2SO4Roasting (*)

waterleaching

MgSO4(Th)

neutralization

RE sulfatesoln

HF,SO2

CaPO4(Th)

mixRE concentrateSX separations(*) different temperatures are used


12

Process route for ionic ores The principal ionic clays are muscovite and kaolinite [(Al,Si)Ox(OH-)3,(RE3+)] .

SX separations

RE cation adsorption clays

Ammoniumsulphateleaching

Mix RE carbonate

Mining and concentration

Ore concentrate

Ore crakingH2SO4 or NaOH

Mix RE concentrate

Non RE purification

Heap leaching

In situ leaching

RE Carbonate precipitation

2 [(Al,Si)Ox(OH-)3,(RE3+)] + 3 [(NH4+)2,SO4

2-] → 2 [(Al,Si)Ox(OH-)3,3NH4+] + 2 (RE)2(SO4)3

Ion exchange leaching

ionic ore leaching solution solid waste leachate solution


AGENDA

13






Basics of Solvent Extraction (*)

14

Definitions

Solvents

Chemistry of solvent extractiono Extractant classes and selectivitieso Case of non RE3+ (CeIV and EuII)

Technology and process design

Choice of a separation system

RE mix concentrate

Pure RE solutions

(*) SX Or « Liquid-Liquid Distribution » according to IUPACOr Liquid-Liquid Extraction


Definitions

Equilibrium Constant KTR = [RE S]org/[RE] aq* [Sorg]

Partition Coefficient PRE = [RE S]org/[RE] aq

Separation Factor expresses the selectivity of the system, its faculty to separate two species RE1 et RE2

F = PRE1/PRE2

Equilibrium Distribution of a specie between two immiscible phases RE aq + S org RE S org

Initial aqueoussolution

An organic immiscible solvent is added

mixing

Settlingseparation


The solvent is the heart of the processA « solvent » is an organic mixture which includes mainly

- an extracting agent, active player of the system,which chemically reacts with species to beextracted. It should be insoluble in water (alkyl chains C4 to C15). EA are usually viscous liquids(some are solids).

-a diluent , usually a mixture of aliphatic and/or aromatic hydrocarbons, it helps hydrodynamic, acting on solubility of the extracted species and giving a lower viscosity.

Industrial diluentshydrocarbons

-aliphatic (kerosene)-aromatic (i.e.solvesso)

Extracting agents - acidic (cations)

- neutral (molecules)- basic (anions)

Sometime are added> a modifier to improve some properties (solubility,viscosity/hydrodynamic,kinetics)> a synergistic agent (or anti-synergistic) which modifies partition coefficients and/or selectivity.

Modifiers-alcohols C8-C12

-phenols C9

SynergisticAgent

i.e.TBP , TOPO


The chemistry of Rare Earths extraction 3 classes of extracting agents

17

RE3+ + 3 (HA)org (RE A3)org + 3 H+

extraction by compound formationAcidic and chelating extractants = cation exchangers

RE3+ + 3 NO3- + (B+NO3

-)org (B+,RE(NO3)4-)org

extraction by ion-pair formationBasic extractants = anion exchangers

RE3+ +3 NO3- + (S)org (S,RE(NO3)3)org

extraction by solvationNeutral extractants = molecules exchangers

In hydrometallurgy it is convenient to consider 3 types of distribution systems (*).A large number of extractants are available for Rare Earths among the productsespecially designed for metal separation and purification purpose.

For all of them the exchange equilibrium for 2 REE characterizes the selectivityRE1 + RE2 org RE2+ RE1 org (separation factor F1/2= kTR1/kTR2 )

(*) Y.Marcus


18

HEHEHP, HEHEHPA, PC88A, P507, Ionquest 801 - 2-ethylhexyl hydrogen-2-ethylhexyl phosphonate- PHOSPHONIC ACID (2-ETHYLHEXYL)-

MONO(2-ETHLHEXYL)ESTERC16H35O3P

HDEHP, DEHPA , P204- BIS(2-ethylhexyl) hydrogen phosphate- PHOSPHORIC ACID BIS(2-ETHYLHEXYL)ESTERC16H35O4P

1- Acidic extractants / cationic exchangers

Strongly acidic Alkylphosphoric derivatives P

O-H

R1R2

O

Incr

easi

ngac

idity

Cyanex 272, P229DI-ISOOCTYLPHOSPHINIC ACIDC16H35O2PIonquest 290BIS (2,4,4-TRIMETHYLPENTYL) PHOSPHINIC ACID


19

Weakly acidic Carboxylic acids R-(C=O)-O-H

C

O-OH

R1

R2 CH3

C

Versatic acidsR1+R2=C7, versatic 10R1+R2=C6-C8, versatic 911

1- Acidic extractants / cationic exchangers

Chelating extractants which have been developped for hydrometallurgy show no real interest for RE separations

Kelex 100 7-(4-ethyl-1-methylocty)-8-hydroxyquinoline

Oxime serie i.e. LIX 860 5-dodecyl-2-hydroxybenzaldehyde oxime

ß-diketone LIX 54

R1

R2

R=naphtene

Naphtenic acidsR1-R4= alkyl Ex: NOR 180

(CH2)nCOOH

R1R2

R3 R4

CA-100Sec-Nonylphenoxyacetic acidC17H26O3M 278.39

R=phenoxy


1- Extraction by acidic extractants

20

RE3+ + 3 (HL)org (RE L3)org + 3 H+ (kRE) The general reaction is

1) Alkylphosphoric acids (R*)(R*)(P=O)O-H

and equilibrium constant kRE is linked to the dielectric constant of the diluent, kRE decreases whenεincreases (kRE kerosene > kRE cyclohexan > kRE benzene > kRE chloroform)

o Extraction mechanism varies with diluent (for HDEHP)

-aliphatic RE3+ + 2,5 (H2L2)org [RE L(HL2)2]org + 3 H+ kRE = PRE [H+]3/[H2L2]2,5

kRE = PRE [H+]3/[H2L2]3 RE3+ + 3 (H2L2)org [RE (HL2)3]org + 3 H+-aromatic

P

O-H

R*R*

OP

H-O R*R*

O

> only 1 H+ can be exchanged by a dimer

(H2L2)org (HL2)org + H+

o Strong extractants and associated in organic diluant in a dimeric form

o Extract RE in acidic mediumPRE is strongly dependent on acidity of the aqueous phase. PRE = kRE [H2L2]3 / [H+]3

With the less acidic extractants a saponification is required to extract REE

RE3+ + 3OH- + 3 (HL)org (RE L3)org + 3 H2O

o Polymerisation of extracted species occures for concentrated solutions and can generate some gel formation which gives limitations in use.


21

2) carboxylic acids R(C=O)O-H

Extraction reactions are similar to that of strongly acidic extractants

o Extracted species are often solvated by extractant molecules (REL3,xHL), concentrated organic solutions are viscous and can generate some gel formation especially with HRE.

o Much less acidic than phosphorous acidic extractants they extract in neutralaqueous solutions

-Versatic extracts RE in pH 4-6 range.-Naphtenic have been widely used but the composition of the extractant is often not stable-CA-100 extracts at lower pH value than Versatic.

o Low cost extractants but some losses by solubility and high viscosity with HRE.


RE3+ + 3/2 (H2L2)org [RE L3]org + 3 H+

o They are associated in a dimer form (but all H+ can be exchanged)


Comparative extraction power for acidic extractants

22

Y‐HDEHP‐kerosene

Y‐PC88A‐kerosene

Y‐VERSATIC‐kerosene

La‐PC88A/kerosene

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0,1110 N N N pH2 pH3 pH4 pH5 acidity

o The extraction power depends on the acidity of the extractantalkylphosphoric > alkylphosphonic > alkylphosphinic >>> carboxylic acids(RO)2PO-OH (RO)RPO-OH R2PO-OH R(CO)OH

o Alkyl-phosphoric are the stronger extractants but more difficult to back-extract(increasing reactant costs in processes).



23

o Alkylphosphoric acids

-Extraction increases with the atomicnumber of REE ,

-Y is between Ho and Er (FY/Ho#2) in accordance with its atomic number.

-Among SX extractants they have the highest selectivity for the RE family.

-Extented scale is 105-106 units and the mean separation factor is #2,4-3.

-Anions and diluents have a verylimited impact on selectivity.

HEHEHP is a bit more selective than HDEHP.

Its main advantage comes from itslower extraction constant for REE

∆pKE# 2+/-0,5 1

10

100

1000

10000

100000

1000000

10000000

La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu

HEHEHP

HDEHP

Y

1- Extraction by acidic extractants - Selectivity


o Carboxylic acids

The selectivity of is rather low(extended scale <20) and HRE are at the same level with no possible separation.

But Y shows a special behaviorbeing moved towards LRE.This behavior has been used for some process design.

0,1

1

10


versatic 911

ethyl‐2‐hexanoïc

naphtenic NOR180

alkylphosphonic PC88A

Y

Selectivity of carboxylic acids PY=1

With CA-100 Y is with HRE.

For Yttrium production Naphtenicand Versatic are used in separationschemes

1- Extraction by acidic extractants - Selectivity


Table from Marcus & KertesIon Exchange & solvent Extraction of Metal

Complexes 1969

Al3+

Extraction of various cations by versatic acidpH 1 2 3 4 5 6 7 8

% metal extracted

50% RE3+ extraction range

Fe3+

Cu2+

Ni2+

Co2+

Mn2+ Mg2+Be2+

Important to consider for purification of RE against impurities of

the raw materials (i.e.ores) recovery of RE in recycling processes

(end-of-life products or scraps).

Extraction of various cations byHDEHP 50% in toluene in HCl medium

HCl (M) 0,01 0,1 1

Th

La

Y

Ni

Partition coefficient

1- Selectivity of acidic extractants towards non-REE

25

Fe

Zr

TaAl3+


26

2- Neutral extractants / molecular extractants

P = OR3

R1

R2

Phosphorous derivatives

Others Ethers R-O i.e. isopropyletherAlcohols R-OH i.e. isobutanolKetones R-(C=O)-R i.e. MIBK

have no interest for REE separations

They extract RE nitrate – no or limited extraction of RE chloride or sulfate

Increasingbacidity

TBPTri-n butyl phosphate C12H27O4P

DBBPDibutyl butyl phosphonateC12H27O3P

TOPO, Cyanex 921Trioctylphosphine oxide (solid)

C24H51OPCyanex 923 & 925 liquid mixture of four trialkyl-phosphine oxides


2- Extraction by neutral extractant -TBP

27

The most important is TBP which extracts RE nitrate salts

o Partition coefficients are highly dependant of nitrate concentration PTR = kTR .[NO3

-]3.[TBP ]3 . o Extraction can be increased by a salting out effect with non-extracted salts (i.e Na or

NH4 nitrate). o HNO3 is extracted and decreases partition coefficients.o Back-extraction is achieved by water.

TR3+ + 3 NO3- + 3 (TBP)org ((TBP)3,TR(NO3)3)org

0,00

0,10

0,20

0,30

0,40

0,50

0,60

0,70

0,80

0 1 2 3 4 5

PCe function of HNO3 (M)

Ceaq 1,7 mol.l -1

TBP 75-kerosene 25 vol%

0,00

0,20

0,40

0,60

0,80

1,00

1,20

0 1 2 3 4 5

PCe function of NH4NO3 (M)

Ceaq 0,35 mol.l -1

TBP 60-kerosene 40 vol%


o TBP selectivity is relatively low and highly influenced by RE concentration in aqueous phase- LRE selectivity increases with the REO concentration- Y moves towards LRE when REO decreases- for HRE poor selectivity

0,5

1

1,5

2

2,5

0 100 200 300 400 500

F(Sm/Nd)

F(Pr/Ce)

F(Ce/La)

F(Nd/Pr)

F(Dy/Gd)

F(Gd/Sm)

F(Er/Ho)

F(Ho/Dy)

F(Yb/Er)

Separation factors with aq .conc. of RE nitrates (TBP 50 vol% in Shellsol A)

REO g.l -1

0,01

0,1

1

10

La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Y

REO 460 g/l

REO 430 g/l

REO 310 g/l

REO 220 g/l

REO 125 g/l

REO 60 g/l

Variation of the selectivity with aq .conc. of RE nitrates(TBP 50 vol% in Shellsol A)

2- Extraction by neutral extractant -TBP selectivity


2-Selectivity of neutral extractants towards non-REE

La

UVI Th

Na

FeIII

Ni

Co


Ca

HNO3 1 M 3,5 6 11 14

Undiluted TBP in HNO3 medium


CeIII

Ni

Ca

Co

FeIII

UVI

Th

HCl M 1 4 6 9 12

Undiluted TBP in HCl medium

Tables from Marcus & Kertes in Ion Exchange & solvent Extraction of Metal Complexes 1969

29

Nb

Ta

Zr

Nb

Ta


30

3- Basic extractants / anion exchangers

Alkylamines

Primary amines

ALIQUAT 336, ADOGEN 464Tricaprylmethylammonium chlorideCH3N[(CH2)7CH3]3Cl

Quaternary ammonium salts

Primary amines extrat RE sulphate Quaternary ammonium salts extract RE nitrate or RE thiocyanate

No extraction occures in chloride medium

PRIMENE™ JM-T (C16-22)-tertC –alkyl amine

N1923SecC-alkyl amine R2CNH3R

RR - C - NH2

R


3- Extraction by basic extractants - Amines

31

1) Primary amines

They extract RE sulphates, but no extraction occures in chlorure or nitrate solution

H2SO4 + 2 (RNH2)org (RNH3)2(SO4)org

2 RE(SO4)33- + 3[(RNH3)2 SO4 ]org 2[(RNH3)3,RE(SO4)3]org + 3 SO4

2-

2 RE3+ + 3 SO42- 2 RE(SO4)3

3-

Th

La

U

Extraction by Primene JMT

H2SO4 0,01 0,1 1 10 N

Primary amines are efficient extractant to separate Th from U and RE. They have been studied in that purposefrom solutions obtained after sulfuric attackof the monazite (ORNL 1959). The selectivity between adjacent RE israther low (F=1,2-1,9) and not really large enough for separations.

Table from Marcus & Kertes in Ion Exchange & Solvent Extraction of Metal Complexes 1969


104

103

102

10

1


NH4NO3 M

Influence of ammonium nitrate on Y nitrate extraction by

ALIQUAT 336Aliquat 0,5M

Y(NO3)3 0,5 mol.l -10

0,1

0,2

0,3

0,4

0,5

0,6

0 2 4 6 8

P Yttrium

2) Quaternary ammonium salts

- they extract RE-thiocyanates and RE-nitrates, by the simplified reaction ( i.e.NO3)

- anion concentration is the key parameter for partition coefficients PRE = kRE .[NO3

-]3.[R4N+NO3-] .

- back-extraction is achieved by water.

RE3+ + 3 NO3- + (R4N+NO3

-)org (R4N+,RE(NO3)4-)org


32

NH4NO3 (M)


33

o in organic phase associated species and water molecules are involvedin the extraction mechanism which is slighly different for LRE and HREFor Aliquat 336 :

RE3+,(H2O)x+ 3 NO3- + [(R4N+NO3

-)2,(H2O)y ]org [(R4N+)2 RE3+(NO3-)5 ,z H2O]org

• Heavy RE extraction

RE3+,(H2O)t + 3 NO3- + 3/2 [(R4N+NO3

-)2,(H2O)y ]org [(R4N+)3 RE3+(NO3-)6 ,v H2O]org

• Light RE extraction

o At high concentration in organic phase, aggregation and strongassociation lead to polymer evolution with precipitation and/or an increase of viscosity . Adding a modifier could change these complexreactions but often decreases the extraction efficiency.

Amine extraction is a complex chemistry :



34

Characteristics for Aliquat 336

o Medium selectivity-an extended scale of # 100-150-F #1,4-1,5 between adjacent RE

o Reverse evolution in the extraction order for RE-in nitrate medium PLa < PLu-in thiocyanate PLa > PLu

o Y has a special behavior- Y # HRE in nitrate - Y # LRE in SCN.

0,100

1,000

10,000

100,000


Aliquat NO3

Aliquat SCN

Pyttrium=1YY

3- Extraction by basic extractantsAliquat 336 selectivity


35

The chloride medium in whichthe rare earths are not extractedoffers possibilities for separationof non-RE elements by amine extractants.

Tri-isooctylamine HCl

Example :Triisooctylamine in HCl medium


Table from Marcus & KertesIon Exchange & solvent Extraction of Metal Complexes 1969

HCl 1 4 8 12 M

La

Eu

Y

CoZn

Ga

Fe


3- Selectivity of amine extractant towards non-REE

Zr

Ta

Nb


36

Separation factorF2/1=PRE2/PRE1

Yttrium shows a particular behavior-link to the ionic radius-link to the complexformation chemistry

SELECTIVITY Overall Comparison of extractants for RE

0,00001

0,0001

0,001

0,01

0,1

1

10

100


Aliquat NO3

Aliquat SCN

HEHEHP

HDEHP

TBP NO3

Versatic

Naphtenic

PRE

PY = 1


37

Ce4+ and Eu2+ can be separated by Solvent Extraction with a very high selectivity

Ce4+

Extraction is very efficient with acidic (alkyl phosphorous acids,carboxylic) or neutralextractants

Ce4+ + 4 NO3- + 2 TBP <=> Ce(NO3)4 (TBP)2

In nitrate medium TBP gives a separation factor F(Ce4+/RE3+) > 105

The main issue is the back-extraction which necessarily requires a reducing agent (NaNO2,formol,NaCl,méthanol,H2O2,Fe2+,hydroxylamine,hydrazine have been proposed)

Ce4+ -> Ce(OH)4 insoluble in acidic mediumi.e. oxidation by Na-hypochlorite 2 Ce3+ + ClO- + 6 OH- + H2O -> 2 Ce(OH)4↓ + Cl-

Ce3+ - e- -> Ce4+

Eu2+

Extraction of RE3+ vs Eu2+ is very selective with acidic extractantsF(Sm3+ /Eu2+) > 106 with HDEHP or HEHEHP.

Eu3+ + e- -> Eu2+ i.e. reduction by Zn 2 Eu3+ + Zn0 -> 2 Eu2+ + Zn2+

and selective precipitation of EuSO4


AGENDA

38






TechnologyCalculation of separations

Equilibrium Constant KTR = [RE S]org/[RE] aq* [Sorg]

Partition Coefficient PRE = [RE S]org/[RE] aq

Separation Factor F1/2 = PRE1/PRE2

Equilibrium Distribution of a specie between two immiscible phases RE aq + S org RE S org

Distribution or Partition curveor partition isotherm

- different shapes- P varies with concentration

in aqueous phase- maximum loading of organicphase

0

2

4

6

8

10

0 5 10

A

B

C

D

Conc.in aqueous phase

Conc.in organic phase

P


McCabe &Thiele construction (principles)

40

0123456789

10

0 5 10

Equilibrium

CF

COE

A/O

Extraction 1 stage

0123456789

10

0 5 10

EquilibriumOp.LineStages

COF

COE

CR

CF

Ph.ratio flowrate A/O

Counter-current Extraction 3 stages

Washing 2 stages

0123456789

10

0 2 4 6 8 10 12

COE

COEW

CW

Back-extraction 4 stages

0123456789

10

0 5 10

Equilibrium

chem tool

COEW

CE

CR

Action on chemistry


Two conditions are required to get an effective separation

1- extraction zoneextraction coefficient for RE1 >1E RE1 = PRE1.O/( F+W) > 1

2- washing or scrubbing zone washing coefficient for RE2 >1 SRE2=1/ERE2=(1/PRE2).W/O > 1

McCabe & Thiele construction for a separation battery(general case)

Separation of two species RE1>RE2

Flowrate F+W F W E E

Feed(RE1+RE2)

Washingsoln

ExtractRE1

RaffinateRE2

Washingsoln

Flowrate O

solvent

1 2 3 4 5 6 7 8

extractionwashing orscrubbing back-extraction

Concentration organic ph.

RE1

RE2

Concentration aqueous ph.

RE1 raf RE2 raf RE2 Feed RE1 Feed


For Rare Earths separationsthe reaction is an exchange between 2 RE

42

RE1 + RE2 org RE2+ RE1 org

The separation factor F1/2= kTR1/kTR2 is the equilibrium constant of the exchange reaction (F>1) of RE between the two phases

RE2+RE1

RE1+RE2

RE1RE2+RE1

RE1+RE2 RE1RE2

RE2

For a counter-current operation

In a battery with n stages

organicaqueous


n stages

Feed RE1+RE2Pure RE2

Pure RE1

reflux

loading

43

For Rare Earths separationsMcCabe & Thiele construction applied to molar fractions

Mol

arfra

ctio

n R

E1

in s

olve

nt

Molar fraction RE1 in aqueous soln

0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8

0,9

1

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

F1/2

Feed

Extract

Raffinate

Operating line for scrubbing zone slope SCR = (1/PTOTAL) .vS/V solvent

Operating line for extraction zoneslope EXT = (1/PTOTAL) . (vS+vFeed)/ Vsolv.


refluxraffinate

extractnE stages nS stages

Feed RE1+RE2Pure RE2

Pure RE1

loading Extraction zone Scrubbing zone

44

solvent

reflux

extractionnE stages

scrubbingnS stages

back-extractionnR stages

extract RE1

feed RE1+RE2

raffinateRE2

back-extractionsolution

To reach high purity for individual Rare Earths99% up to 99,999%

the total number of stages required for one cut(nE+nS+nR) ranges from ~30 up to 100.

Solvent extraction battery for RE separations


00,10,20,30,40,50,60,70,80,9

1

0 10 20 30 40 50

mol

arfra

ctio

n La

Ce

étages

La 5 N Ce 3N

0,00001

0,0001

0,001

0,01

0,1

10 5 10 15 20 25 30 35 40 45 50

mol

arfra

ctio

n La

Ce

stages

Ce

La

Example 1 : calculation for a binary mixture Ce 90:La10

Proprietary softwares have been developped To make calculation of separation To drive the industrial batteries

KU Leuven Summer School 2014 Aug 19Extraction and separation of Rare Earths45

SX 2 aqueous R EO co ncent rat ion as a f unct ion o f st age number

0

50

100

150

200

250

300

0 5 10 15 20 25 30 35 40 45 50

st age number

Lanthanum

Cer ium

Pr aseodymium

Neodymium

Samar ium

Gadol inium

Dyspr osium

Yttr ium

Ce

La

Dy

Gd

SmNd

Y

Pr

FeedLa 25,8% Sm 1,4%Ce 46,0% Gd 0,8%Pr 5,5% Dy 0,8%Nd 14,7% Y 3,6%

others HRE 1,4%

REO

con

cent

ratio

n in

aqu

eous

phas

e

Stage number

46

Proprietary softwares have been developped

Example 2 : Separation La,Ce,Pr,Nd / Sm,Eu,Gd,…Y


47

Aqueous exit

Organic feed

Aqueous feed

Organic exit

Counter-current battery

moto - agitateur canne de phase aqueuse

recylage internejupeturbine

canne de solvant

hublot

DECANTEURMELANGEUR

DESCRIPTION D'UN ETAGEMixer-settler

SettlerEmusion separationMixer

motor Solvent outletaqueous outlet

Technologythe mixer-settler is the only industrial choice

for RE separation batteries

Initial aqueoussolution

An organic immiscible solvent is added

mixing

Settlingseparation

Unit operation


Solvay La Rochelle

48




moto - agitateur canne de phase aqueuse

recylage internejupeturbine

canne de solvant

hublot

DECANTEURMELANGEUR

DESCRIPTION D'UN ETAGE

49

Mixer-Settler designKinetic studies are required mixing during extraction phase separation for settling

Mixer-settlers areo relatively easy to design and flexible to run in operation

(high capacity, phases ratio, stop and go )o the efficiency of each stage is close to one theoretical stage.

Main advantages• possibility to adjust the phase ratio in the mixer

using internal recycling ;• possibility to control the emulsion by the mixing

power ;• a relatively high contact time between phases .

Main drawbacks• require a large surface area to be installed ,• the hold-up of the solvent could be important.• could be difficult to run when solids particules

exist in the phases

Light phase

Heavy phase emulsionband

SettlerEmulsion separationMixer

Light phase exit Heavy phase exit

Internal recycling




Mixer-settler : sedimentation and coalescence

Sedimentation front

coalescence front

aqueous phase dispersed =organic continue w/o

organic phase dispersed =aqueous continue o/w

Case density of organicphase < density of

aqueous phase

The nature of the continuous phase is a key parameter for settlingWater-in-oil or oil-in-water emulsion type determines separation behaviour

Remark: the continuous phase can be identified by conductivitymeasurement

Ostwald Law3 domaines to be considered with the Aqueous/Organic ratio:•continuous aqueous phase is the only possible •continuous organic phase is the only possible •ambivalence domain where both systems are possible

continuousorganicphase

continuousaqueous

phaseNot determined

0,33 3A/O ratio


marine propellerwith 3 bladesturbine with 4 inclined blades

disc turbine, Rushton type

turbine with curvedbladesclosed turbine with disc and curved blades

Mixer-Settler design

o MixerBatch test in standardized tank withdifferent turbines to reach equilibriumand create emulsion characteristics

Continuous test on a mixer settler unit model for sizingVariation of the height of the emusion band H withthe specific flow-rate Q/S of the dispersed phase.

o Settler

Example : Ryon lineslog H = log K + n log Q/S

for 2 temperatures T1 & T2 1

10

0,1 1 10

T2

T1

H cm

Q/S m3.m-2.h -1

51

m3 small medium largeMixer < 0,1 0,5 - 1 15Settler 0,3 - 0,4 4 40

Typical size for RE separation batteries


AGENDA

52






Select an extraction process

To define an extraction process two choices are to be considered the solvent the technology

Moreover in the case of Rare Earths separations a certain sequence of successive cuts must be considered.

Purity and yield are obtained by the definition of operating conditions (stages number, flow rates and reflux) when the selection of the solvent has been made.

in order to reach targeted objectiveso Purity and Yieldo Environment and safetyo Economy (capital investment CAPEX and operaing costs OPEX)


Select a extraction processis to find an optimum economic

the solvent is the first choice whichdetermines for a great part the economy of the process

- selectivity of the solvent- maximum loading of the solvent- concentration of metal ions in aqueous phase- hydrodynamic (> volume of stages) - corrosion > material choice

The type of the solvent : cation or moleculesits solubility in water and eventual dégradationits viscosity <> temperature to improve phase separation

+

OPEX o Reactants : acid, base,…saltso Energy (steam for

concentration or T° adjustment) Solvents losses Effluent treatment Taxes on discharge streams

CAPEX the battery number and volume of stages material Annex equipments linked to the

solvent characteristics Hold-up Induced equipments specific effluent treatment

(*) both dependent on local conditions


55

There are two industrial SX process routes for RE separation :

Make the good choice

Advantages Drawbacks

Nitrate route Lower OPEX Higher CAPEXNitrate liquid effluent to deal with

Chloride route Lower CAPEX Higher OPEXN or NH4 chloride liquid effluent

Solvay uses both routes chloride in its two Chinese plants and nitrate in its La Rochelle plant. Chloride route is used by Chinese producers and new comers

Solvent choiceselectivity solvent

loading solvent reactantcosts

possible routeLRE HRE chloride nitrate

++ ++ ‐ stronglyacidic ‐ ‐ yes yes

++ ++ ‐ mediumacidic ‐ yes yes

+ ‐ ‐except Y

+/‐ lowacidic +/‐ yes yes

+ ‐ ‐ + neutral + no yes

+ + ‐ basic + no yes+ favorable- unfavorable


56

LRE / HRE

Pr / Nd

La / Ce,Pr,Nd

Ce / Pr,Nd

La,Ce,Pr / Nd

La,Ce / Pr

La / Ce

4 RE to separate

11 REto separate

What process flow sheet for the refinery ?

or

A lot of processes are possible for RE separationsaccording to

- raw material (ore,concentrate,..)- targeted products and purity (99% to 99,999%)- ….

HRE Separations

Sm/Eu/Gd/Tb/Dy/Y…

Ore attack

Separation Non-RE impurities

Incl. R* / TREO

Mix-REchemical

concentrate


Typical process flow sheets

57

Molycorp process for Europium (1965)

Megon process for yttrium from xenotime (1975)

Typical chinese process for all purified Rare Earths

Rhone-Poulenc/Solvay process for all purifiedRare Earths


Molycorp for Eu from bastnaesite

58

RECl3solution

Calcination HClLeaching

Ce concentrateREO 75% (Ce 92%)

BastnaesiteConcentrate

REO 70%

LRE concentrates La,Pr,Nd

5 stages 4 stages

HDEHP-kerosene

2 stages 4 stages

HDEHP-kerosene

HCl

HCl

Sm,Eu,Gd,..HRE

separations

Jones Zn reduction

Sm,Gd,HREconcentrate

EuIISO4Eu2O3

Years ‘70


Megon for Y from Xenotime

59

Years ‘70

STEP 3

Y2O3 5NTm,Yb,Lu

26 extraction + 6 scrubbing SCN

ALIQUAT SCN-Solvesso150

8 back-extn

NH4NO3 0,5NH4SCN 0,1 HNO3 0,1 NH4SCN

Y 99,999% REOYb 2,5 ppm, Er 3 ppm

others <1ppm

STEP 2 26 extraction + 6 scrubbing 3 back-extn

ALIQUAT NO3 -Solvesso150

NH4NO3 1,75M

Gd…Er

HNO3 0,001

Y concentrate 95%REONH4NO3 4,9M+SCN 0,1M

STEP 1

H2SO4Attack-Dissolution

RE sulphate solution REO 20 gpl (Y 65%)

XenotimeConcentrate

LRE + non-RELa,Ce,Pr,(Nd)

Nd,Sm,Eu,(Gd,Tb) (Tb),Yb,Lu

4 extraction

HDEHP-Shellsol

8 Scrubbing B4 Scrubbing A 4 Back-extraction

HNO3 1,5M H2SO4 0,5MHNO3 6M

NH3

Y concentrate 75%REONH4NO3 6M


Rare Earths separation in China Typical process flow sheet

Solvent used

P 507 (HEHEHP)

Naphtenic acid

Mix RECl3

Mix RE concentrate

Ho Er Tm, Yb LuheaviesY

Ho / Er

Tm, Yb / Lu

Ho, Er / Tm, Yb, Lu

Y / Ho … Lu

Tb

recycling

recycling

Sm Eu Gd

Sm,Eu,Gd / Tb, Dy / Ho,Y …. Lu

ɛSmEu,Gd / Tb / Dy

Gd, Tb / ɛDy

Gd / Tb

Sm, Eu / Gd

Sm / Eu Gd / ɛTb

ɛEu / Gd

Dy

La ..Nd / Sm .. Dy / Ho,Y … Lu

Larecycling

Ce Pr Nd

LRE separations HRE separations

MRE separations

La / Ce / Pr

La / Ce, Pr / Nd

60

NH4 or Na chloride

Liquideffluents


Solvay separation schemecapacity 9.000 TREO/year

61

Sm,Eu / HRE,…

Sm/Eu

Sm Eu

HRE separ

Ho Er Tm Yb LuGd Tb Dy Y

All Solventtypes are usedin 18 batteries and #1200 MS

RE concentratesConcentratesfrom recycling

Mix RE nitratessolubilization

LRE / HRE separation

La Ce Pr Nd

La,Ce / Pr,Nd

La / Ce Pr / Nd valorization

Ammoniumnitrate

monazitebastnaesitexenotime

RE/Th/U

Th

UAlcaliattack

Acid HNO3 solubilization Th/U

Mix RE-Th-Uhydroxide

Ore processing until 1994


AGENDA

62






63

In the recent plants improvements are dedicated to environmental concerns-limitation of solid wastes, air emission reduction, controlled management of radioactivity,

-better power generation and use.-recycling of reagents (i.e.NaCl electrolysis) and process water

but no real improvement has been made on separation technology-use of the classical solvent (phosphonic acid ester) and quite classical mixer-settler.

The SX technology for RE separation is mature . It has largely demonstrated its efficiency since 50 years. Improvements are made continuously and experience is a key factor for performance.

For the RE industry major weaknesses are pointed out and need to be adressed gazeous emissions during sulfuric ore treatment, radioactive wastes and more widely radioactivity management,

and some others which are more specifically linked to separation technology large amount of salt containing liquid effluents, high costs for reagents and water use, high capital investment .

Conclusions & Prospects


64

For RE recycling and new raw materials, existing technologies for separations are efficient enough but the flexibility of the processes vs.various sources is a key factor to handle.

New solvents would help in some specific aspects better separation properties (selectivity) reduction of salt effluent generation more friendly solvents (limitation of use of petroleum derivative solvents) New molecules

New synergistic formulations

Ionic Liquids is a new approach but still at the very begining of R&D stage.

The development of new technologies others than solvent extraction is certainly a real challenge.

Conclusions & Prospects


Thanks for yourattention


Documents

Extraction and separation of Rare Earths - EREANerean.eu/papers/Lecture III - Extraction and separation... · · 2014-10-17Ore Beneficiation Mine Concentrates Ore attack Rare Earths