1. European Metallurgical Conference 27.6.2017
Leaching of Eudialyte concentrate and REE-precipitation
- Pilot plant Treatment of Eudialyte Concentrate -
Yiqian Ma, Srecko Stopic, Bernd Friedrich

2. Introduction Rare earth resources Rare earth resources
Polinares project, Fact sheet: rare earth oxides, released in 2012
Rare earth resources
Polinares project, Fact sheet: rare earth oxides, released in 2012

3. About EURARE project

4. Eudialyte from Norra Kärr and Tanbreez
*Both without radioactivity
Norra Kärr

5. Eudialyte from Tanbreez and Norra Kärr
Metal
Norra Kärr
Tanbreez Al
3.32%
3.36% Ca
1.44%
4.33% Fe
5.54%
6.08% Hf
0.09%
0.11% Y
0.45%
0.33% Nb
0.12%
0.44% Yb
0.03%
0.04% Zr
2.28%
5.08% Ce
0.30%
0.52% Dy
0.01%
0.06% Gd
0.02% La
0.14%
0.25% Nd
0.15%
0.21%
TREE
1.20%
1.60%
Eudialyte
Na4(Ca, Ce,Fe)2ZrSi6O17(OH, Cl)2
Norra Kärr
Tanbreez

6. Main aims of large-scale test
Treatment of Eudialyte concentrates in demonstration scale in order to produce >20 kg rare earth carbonate
Removal of iron and aluminium in order to produce fine product with % REE-oxide content
Improvement of efficiency and automisation degree of the demonstration plant
Eudialyte concentrate
Residue after REE extraction

7. Flowsheet and parameters of lab-scale
Variable
Norra Kärr
Tanbreez
Con.: HCl/(kg/L)
1:1
1:1.2
Con.: Water/(kg/L)
1: 3
1: 4
Leaching Temperature/℃
Room temperature
Reaction time/min 60
*Dry digestion(fuming) with
concentrated acid can prevent
silica gel formation

8. Metal balance of lab-scalepH
pH ~6.0

9. General flowsheet of demo plant
Eudialyte
Norra Kärr
Tanbreez
Fuming
Leaching
Neutralization (CaCO3)
Filtration
Precipitation
(Na2CO3)
Filtration
% TREE
Norra Kärr : 1.2
Tanbreez : 1.6
REE-carbonate
SX-MEAB

10. Continuous process for leaching of eudialyte
leaching cascade containing four stirred glas reactors
(3x10L, 1x8,5L)
filter press
stirred collecting container (250L)
leaching reactor(2x100L)
fuming reactor(2x40L)

11. Parameters for large scale processing of eudialyte
Unit
Norra Kärr 1
Norra Kärr 2
(optimal)
Tanbreez
Total quantity each day kg - 36 30
Fuming temperature oC
70-80
Fuming time
min 60
Addition of Eudialyte concentrate
7.5 per reactor
(overload)
6 per reactor
Addition of HCl (31% w/w) L
5 per reactor
Leaching temperature 50
Room temperature
Leaching time h 1
Addition of water in leaching reactor
30 per reactor
20 per reactor
Extraction efficiency %
85.4
84.8
84.2

12. Dry digestion(fuming) - the heart of this process
Characteristics:
Average treatment rate (kg/hour): 6
Reactor volume (L): 40
Digestion media HCl, 31% (L): 6-7.2
Fuming time (min): 60
Temperature: RT, due to exothermic effect increase to °C
Flux- air operated diafragm pump
Flow rate (30 L/min)
Operated pressure

13. pH adjustment using CaCO3
At pH 4 (first stage of leach purification), mainly Zr, Al, Fe transferred to the residue, while REEs remain in solution.

14. Filtration using a semi-continuous chamber filter press
pH of solution higher than 4.0
Max pressure: 6 bar
Flow rate of suspension: L/min
Maximum Capacity: 6kg wet residue

15. Material balance diagram

16. videos

17. Leach residue composition after separation in filter press
Metal
Norra Kärr /%
Tanbreez/% Al
4.960
4.360 Ca
1.370
1.330 Fe
0.408
0.810 Hf
0.044
0.103 Y
0.045
0.057 Nb
0.020
0.069 Yb
0.006
0.008 Zr
2.320
5.390 Ce
0.023
0.049 Dy
0.005
0.007 Gd
0.004 La
0.083
0.019
TREE
0.180
0.210
The overall yields reached 85.1% and 84.4% respectively.
Washing residue after filtration makes a new concentrate for recovery of Zr, Hf and Nb.

18. REE precipitation efficiency with Na2CO3
After precipitation with sodium carbonate pH~6.0, more than 95 % of REEs transferred to REE-carbonate

19. Removal of iron from the produced REE-Carbonate
Element Al Ca Fe Hf Zr Na Nb Si
TREE
REE Carbonate (%)
3.33
6.0
7.86
0.002
0.05
4.73
0.007
0.031
15.1
REE carbonate re-dissolved with HCl
Oxidation of Fe(II) to Fe(III) using 4 ml 30 % H2O2 per liter solution
pH value adjusted using diluted NaOH to pH 3.5 to 3.8
Need of flocculants, filtration

20. Separation using flocculant
Removal of iron
REE precipitation

21. Produced REE CarbonateLa Ce Nd Tb Gd Y Sm Dy Eu %
5.23
10.5
3.90
0.20
0.85
7.15
0.93
1.17
0.08 Er Sc Fe Al Zr Na Ca Mn
TREE
0.78
<0.01
3.31
0.05
0.02 
4.18
0.23
31.00 

22. Summary Conclusions Outlook
Based on the results obtained from the small scale experiments, the large scale experiments were carried out successfully.
The fuming process should start with addition of concentrate first and then the acid in appropriate ratio to avoid silica gel formation.
During neutralization with CaCO3 (pH~ 4.0), more than 95% of Zr, Al and Si go into the residue
During precipitation with Na2CO3 (pH~ 6.0), more than 95% of REEs are precipitated for both the concentrates, thus increasing the amount of REEs in the REE-carbonate produced.
Outlook
Reducing loss of REE during precipitation processes
The residue can be used as a potential source of Zr, Hf, Nb recovery

23. Thank you for your attention!