national technical university of athens...the residue after bauxites treatment for alumina...

National Technical University of AthensSchool of Chemical Engineering

Laboratory of Inorganic and Analytical Chemistry

Lamprini-Areti TSAKANIKA, Klaus-Michael OCHSENKÜHN,Maria OCHSENKÜHN-PETROPOULOU

Laboratory of Inorganic and Analytical Chemistry, School of Chemical Engineering, NTUA Iroon Polytechniou 9, Zografou, 15773, Greece

E-mail: [email protected], [email protected]

SEPARATION AND RECOVERY OF RARE

EARTHs AFTER RED MUD LEACHING BY

CATION - EXCHANGE CHROMATOGRAPHY

Aim of the present study

The selective separation and recovery of rare earths from the

main elements co-existing in the leachate after red mud acidic

leaching.

Development and optimization of an ion exchange process using a

suitable industrial strong cation exchange resin and applying

multiple successive elutions using selective eluents firstly in lab

scale.

Application of the developed ion exchange process on a pilot

plant.

Group of 17 chemical elements

15 lanthanides (La-Lu) Yttrium (Y) Scandium (Sc)

Scandium and yttrium are considered

rare earth elements since they tend to

occur in the same ore deposits as the

lanthanides and exhibit similar

physico-chemical properties

LREEs: light rare earths (La, Ce, Pr, Nd, Pm, Sm, Eu, and Gd;

also known as the cerium group)

HREEs: heavy rare earths (Tb, Dy, Ho, Er, Tm, Yb, Lu, and Y;

also known as the yttrium group)

RARE EARTH ELEMENTS (REEs)

Source : Department of Energy, USA

The REEs with the greater demand- Their uses

Lanthanum

Cerium

Neodymium

Dysprosium

Yttrium

Europium

Cerium

Lanthanum

Terbium

Scandium

Fluid Catalytic Cracking (FCC) -

Catalysts

Permanent Magnets

Lighting

Aerospace and defense technology,

athletic equipment, solid oxide fuel

cells (SOFCs)

Source : Critical Materials Institute (Ames Lab, USA )

Five of the most critical

elements are rare earths

(Nd, Dy, Eu, Y, Tb)

(new sources, processes,

recycling, substitutes)

CRITICAL ELEMENTS

MAIN MINERALS OF REEs

Thortveitite [Sc2Si2O7] (main mineral of scandium, very rare)

Bastnasite [(REE)(CO3)F] (Light REEs,)

Monazite [(REE)PO4]

Xenotime [YPO4] (Heavy REEs)

ALTERNATIVES RESOURCES FOR REEs

Apatites (~ 1kgREEs/ton)

Exploitation byproducts of uranium (105g Sc/ton in 1000m depth,

Ukraine), tungsten, lead, tin, zirconium, titanium and mine tailings

Phosphate rocks and phosphogypsum

Bauxites (of low concentration in Al)

Red mud, bauxite residue after Bayer process

(130g Sc/ton , 1kg REEs /ton )

REEs recycling (permanent magnets, batteries, lamps, phosphors)

Rarity of economically exploitable sources (outside China

having the 97% of the annual world market of REEs)

High demand for modern and high technology applications

High commercial

values of REEs

REEs values

1

10

100

1000

10000

La Ce Nd Pr Sm Dy Eu Tb Y Sc

U$

/Kg

REEs OXIDES

YEAR

2010

YEAR

2011

YEAR

2012

YEAR

2013

Change in the price of REEs oxides (2010 to 2013)Source: Lynas Corporation (China Domestic prices), USGS (Sc, Y)

Prices of scandium oxide (US$/kg) vs % purity

Source: USGS

0

1000

2000

3000

4000

5000

6000

7000

99% 99,99% 99,9995-99,9999%

US

$/k

g

Sc oxide purity

2010 2011 2012 2013

0

50

100

150

200

250

300

scandium

fluoride, 99.9%

purity

scandium

iodide, 99.999%

purity

dendritic, metal ingot, metal scandium

chloride, 99.9%

purity

scandium

acetate, 99.99%

purity

US

$/g

2011

2012

2013

Prices (US$/g) of scandium metal and its compounds (2011-2013)

The residue after bauxites treatment for alumina production using

Bayer process (about 50 % Fe2O3)

Annual production of red mud in Greece 700.000 tons (AdG)

High alkalinity (pH>11), very fine (< 10μ)

Rich in main elements ( Fe, Ti, Si, Ca, Na )

It contains also elements of techno-economical interest

(V, Zr, Nb, REEs, etc)

Greek red mud is enriched in REEs by a factor almost 2 in

comparison to the initial bauxite (Source: M. Ochsenkühn-Petropulu, Th. Lymperopulu, G.

Parissakis, Anal Chim Acta (1994) 296, 305-313)

RED MUD

Problem

Its disposal due to its

complex character and

alkalinity combined with

its annually huge

production

Solutions Safe disposal (dry stacking, dry disposal) Neutralization Reuse of red mud Utilization (Recovery

of valuable elements)

Mineral found in bauxite

Hydroxyl-bastnaesite

(Nd,La)CO3(OH,F))

M.Ochsenkühn-Petropulu and K.M.Ochsenkühn, Microscopy and Analysis, 37, 33-34 (1995)

NC

C

N

Mineralogical analysis of Greek red mud

H

H

H

H H

H

H

D

DD

FT-IR analysis of a Greek red mud sample

G:Gibbsite, K:Kaolinite, Go:Goethite, D:Diaspore, Cn:Cancrinite, So:Sodalite, He:Hematite

Source: PhD Thesis Dr. Lamprini-Areti Tsakanika (2013)

Element

oxides

% Wt

EDX

Semi

quant

% Wt

AAS

Full

quant

Fe2O3 38.8 43.8

Al2O3 14.2 15.8

CaO 12.3 12.5

Na20 3.9 2.9

SiO2 7.7 5.6

TiO2 5.7 5.3

V2O5 0.4 0.3

Cr2O3 0.5 -

Morphology and Semi Quant composition

(surface analysis) of Greek red mud observed by SEM- EDX


Element Average concentration Average Enrichment

Factor

Bauxite R.S.D. % Red mud R.S.D.% Red mud/bauxite

La 87.2 ± 21.9 25.10 149.0 ± 40.0 26.80 1.78

Ce 224.3 ± 21.7 9.70 418.0 ± 52.9 12.70 1.87

Pr 13.9 ± 4.8 34.50 25.8 ± 7.5 29.10 2.13

Nd 62.4± 15.6 25.00 115.0 ± 27.0 23.50 1.99

Sm 13.2± 2.6 19.70 28.9 ± 5.2 17.90 2.30

Eu 2.5 ± 0.63 25.20 5.0 ± 0.9 18.00 1.89

Gd 12.8 ± 2.3 17.90 23.3 ± 3.2 13.70 1.86

Dy 7.0 ± 1.6 22.80 12.8 ± 1.9 14.80 2.15

Ho 2.0 ± 0.56 28.00 4.3 ± 1.0 23.20 2.15

Er 8.1 ± 1.6 19.70 17.2 ± 3.1 18.00 2.15

Yb 8.0 ± 1.2 15.00 15.6 ± 1.9 12.20 1.99

Y 55.9 ± 9.3 16.60 91.2 ± 15.7 17.20 1.68

Lu 1.38 ± 0.37 26.80 2.4 ± 0.32 13.30 1.76

Sc 59.0 ± 3.7 6.30 127.9 ±14.7 11.50 2.17

Mean 1.99

LREE/ HREE 10.30 09.80

ΣREE 557.68±6.47 1036.4±12.36

Average concentration of lanthanides, yttrium and scandium in Greek

bauxites and red mud samples from the alumina production and

corresponding enrichment factors (all concentrations in μg/g)

Source: M. Ochsenkühn-Petropulu, Th. Lymperopulu, G. Parissakis, Anal Chim Acta (1994) 296, 305-313

Red mud

1993

Red mud

2001

Red mud

2007

Red mud

2012

Mean

Sc 127.9 107.0 130.0 110.0 118.7±11.9

Y 91.2 94.0 94.0 115.0 98.6±11.0

La 149 101.5 132.0 147.6 132.5±22.1

Ce 418 404.0 492.0 498.0 453.0±48.9

Nd 115 86.3 88.5 92.5 95.6±13.2

Sm 28.9 20.5 22.0 24.3 23.9±3.7

Gd 23.3 23.4 20.5 21.3 22.10±1.45

Eu 5.0 3.7 4.0 4.9 4.40±0.65

Er 12.2 12.7 13.1 10.9 12.20±0.96

Yb 15.6 15.0 14.4 15.8 15.20±0.63

Total 986.1 868.0 1010.5 1040.3 976.2±75.5

(±7.7%)

Concentration [g/ton] of REEs in greek red mud batches

(1993-2012)

REEs oxides

Target price of oxides

99.5-99.9% ($/kg)

Average concentration of REEs oxides

Βauxite (g/ton) RM (g/ton)

Value($/ ton RM)

Sc 3800 92 195 741.00 (95.3%)

Y 20 71 127 2.54

La 6.5 102 175 1.14

Ce 5.5 262 490 2.70

Pr 134 16 30 4.02

Nd 69 72 134 9.25

Eu 1100 3 6 6.60

Gd 44 15 27 1.19

Dy 525 8 15 7.88

Er 69 9 20 1.38

Total 650 1219 777.70

Value of REEs / ton of Greek red mud

Source: Hefa 31 December, www.mineralsprices.com and USGS Jan 2014 (Sc)

Flow sheet of the innovative multi process method

for the recovery of REEs from red mud

Purity 99.1%

After the selective acidic

leaching of red mud under

ambient temperature and

pressure, the leachate is

enriched in Sc and other

REEs, but it contains also

the main elements of red

mud.

An ion exchange process is necessary for further

separation of Sc and other REEs from the

remaining main elements after the leaching process.

Their further purification is achieved using suitable

extraction /back-stripping processes.

[a]

[b]

Oxides

[%]

Na2O Al2O3 SiO2 CaO TiO2 V2O5 Fe2O3

Before

leaching

5.9 14.4 8.9 7.3 5.6 0.3 41.0

After

leaching

- 11.7 2.9 2.6 6.3 0.2 45.2

Semi-quantitative

analysis of red mud

samples by EDAX

before [a] and after

leaching [b]


Ion exchange process

Ion exchange

Multiple successive elutions with

mineral acids

2nd

elution

Main elements

1

Sc Y, {Lns}

23

Filtered leachate

effluent

3rd

elution

effluent 1st elution

Analysis with

ICP-OES

Optima 7000 DV

Perkin Elmer

Analysis with

AAS 240FS

Varian

Analysis with

ICP-OES

Optima 7000 DV

Perkin Elmer

Experimental conditions

I. Lab scale

Resin bed volume: V=25ml packed in glass column

Flow rate: Q=1ml∙min-1

Residence time: τ=25min

II. Pilot plant

Resin bed volume: V=5L packed in glass column

Residence time: τ=25min (same as in lab scale)

Flow rate: Q=12L∙h-1

The flow rate was calculated by the formula:

τ=V/Q where τ=25min

Lab scale Pilot plant

(School of Chem. Enginnering, NTUA)

The pilot plant unit for the utilization of red mud (Semi-Industrial Lab, School of Chemical Engineering -

National Technical University of Athens)

Breakthrough curve of Sc and Y

(Column vol.25mL, flow rate 1mL∙min-1,

bed volume=25ml)

Absorption of scandium and other REEs

Lab scale experiments

The feed solution

arising from the

leaching of red mud

with dilute HNO3


Breakthrough curve of Fe

(Column vol.25 mL, flow rate 1mL∙min-1,

bed volume=25ml)

Absorption of Fe

The feed solution

arising from the

leaching of red mud

with dilute HNO3


% removal of main elements with 1.75M HNO3

(Vfeed solution =50mL)

1st elution: Quantitatively removal of the main

elements of the leachate

Almost the same

behavior with 1.75M

HCl but lower

volumes are required

for their quantitative

removalSource: PhD Thesis Dr. Lamprini-Areti Tsakanika (2013)

1st elution: Removal of Fe with

1.75M HNO3 or 1.75M HCl

% removal of Fe with 1.75M HNO3 or 1.75 M HCl

(Vfeed solution =50mL)

Eluent to feed

solution 3:1

Eluent to feed

solution 2:1

Sc and Y remain almost

completely in the ion

exchanger, while Fe was

completely removed.

The losses of Sc and Y

were higher in HNO3

(15% for Sc and 7% for

Y) in comparison with

those in HCl (3% for Sc

and 5% for Y).

What about REEs?


2nd elution: Selective recovery of scandium (Lab scale)

I. Type of eluent

• As eluents HNO3, HCl

and H2SO4 were tested

for the recovery of Sc

• 1M H2SO4 was found to

be the most suitable eluent,

achieving selective

recovery of Sc about 80%

from the selected strong

cation exchanger

• Only Y was co-eluted

at a total percentage of

10%

Flow rate: 1ml∙min-1Elution curves (a) and % REEs recovery (b)

with H2SO4 Vfeed solution = 60ml

ScEluent to feed

solution ~1:1

Sc recovery 80%


% recovery of Sc and Y vs flow rate of 1M H2SO4

Increasing the flow

rate of the eluent, the

recovery of Sc is

decreased, while the

losses of Y remain

almost constant

II. Effect of flow rate


3rd elution: Recovery of Y and Lns

with 6M HNO3 or 5M HCl

Y

Y

6M HNO3

Quantitative recovery with

eluent to feed solution >3:1

5M HClQuantitative recovery with

eluent to feed solution 2.5:1

% Y and Lns recovery with HNO3,

Vfeed solution = 50ml

% Y and Lns recovery with HCl, Vfeed solution = 50mlSource: PhD Thesis Dr. Lamprini-Areti Tsakanika (2013)

1st elution: Removal of Fe and other main elements

1.75M

HNO3

1.75M

HCl

% main elements removal in HNO3,

Vfeed solution = 50L

% main elements removal in HCl,


Eluent to feed

solution 3:1

Eluent to feed

solution 1:1


Feed solution

(mg)

%

Removal with

effluent

%

Removal with

1.75M ΗCl

1:1

%

Total removal

Main

Elements

Fe 4676 0.0 100.0 100.0

Ca 43570 0.0 99.7 99.7

Na 5757 47.0 45.5 92.5

Al 23388 0.0 99.9 99.9

Ti 5542 0.0 100.0 100.0

V 290 18.8 81.1 99.9

Si 6767 76.3 18.0 94.3


2nd elution: Recovery of Sc

(combination of 1st and 2nd elution)

% REEs recovery in HCl and H2SO4,


% main elements removal in HCl and

H2SO4, Vfeed solution = 50LSource: PhD Thesis Dr. Lamprini-Areti Tsakanika (2013)

Feed

solution

(mg)

%

Removal in

effluent

%

Recovery in

1.75M ΗCl

1:1

%

Recovery in

1M H2SO4

1.2:1

%

Total

recovery

Composition

of

1M H2SO4

eluate (mg)

REEs

Sc 30.70 0.0 3.4 79.5 82.9 24.41

Y 28.74 0.0 5.0 24.2 29.2 6.96

La 15.34 0.0 0.0 0.0 0.0 0.0

Ce 51.8 0.0 10.8 0.0 10.8 0.0

Nd 16.58 0.0 0.0 0.0 0.0 0.0

Eu 0.903 0.0 0.0 0.0 0.0 0.0

Er 2.95 0.0 0.0 28.5 28.5 0.84

Yb 2.71 0.0 0.0 53.1 53.1 1.44

Main elements

Fe 4576 0.0 99.9 0.0 99.9 0

Ca 37570 0.0 89.7 0.6 90.3 225

Na 4757 52.0 35.7 0.7 88.4 33

Al 20088 0.0 99.5 0.1 99.6 20

Ti 4952 0.0 100.0 0.0 100.0 0

V 282 10.8 89.3 0.0 100.0 0

Si 6215 71.7 13.0 0.0 84.7 0

2nd elution: Recovery of Sc

(combination of 1st and 2nd elution)


Feed solution

(mg)

%

Recovery in 5M ΗCl

2.5:1

Composition of the

5M HCl eluate

(mg)

REEs

Y 30.84 95.5 29.45

La 18.34 99.9 18.32

Ce 62.70 87.7 54.99

Nd 19.55 95.0 18.57

Eu 1.02 90.0 0.92

Er 3.35 83.0 2.78

Yb 2.88 65.0 1.87

Ca 43570 0.3 130


An ion exchange process is developed for the separation and

purification of REEs from the main elements co-existing in the

leachate after the acidic leaching process. Further purification of the

REEs is achieved by appropriate extraction/back-stripping processes.

The quantitative removal of the main elements is achieved with

1.75M HCl, which was found to be more suitable than nitric

acid, requiring lower volumes of the eluent.

The separation and the selective recovery of Sc about 80% is

obtained using as eluent 1M H2SO4. Only few amounts of Y are co-

eluted while the other REEs remain in the column.

A third elution using 5M HCl lead to the quantitative recovery of Y

and Lns as a group.

The developed ion exchange process was successfully applied on a

pilot plant and a good agreement with the optimized parameters found

in lab experiments, was achieved.

Prof.Dr.MariaOchsenkühn-Petropoulou

( coordinator)

Dr. Klaus - Michael Ochsenkühn

Dr. Lamprini - Areti Tsakanika

Dr. Theopisti Lymperopoulou

Dr. Leonidas Mendrinos

Dr. Konstantinos Hatzilyberis

Dr. Konstantinos Salmas

Dr. Rachel Argyropoulou

Students

Anthi Psalida

Panagiotis Pagonas

Giannis Gourousis

Panagiotis Rebestekos

Emmanuel Foundoulakis

Thank you

for your attention!

national technical university of athens...the residue after bauxites treatment for alumina...

Documents