Abandoned Coal Mine Drainage Cleanup Through Domestic Production of Critical Minerals for National Security – Sarma V. Pisupati, Mohammad Rezaee, and Dr. Barbara Arnold, Penn State University

1. Center for Critical Minerals (C2M)
Abandoned Coal Mine Drainage Cleanup Through Domestic
Production of Critical Minerals for National Security
July 29, 2021
Sarma V. Pisupati,
Mohammad Rezaee,
Barbara J. Arnold
Center for Critical Minerals (C2M),
EMS Energy Institute,
John and Willie Leone Department of Energy and
Mineral Engineering
College of Earth and Mineral Sciences
The Pennsylvania State University
2022 PA ABANDONED MINE RECLAMATION CONFERENCE

2. Center for Critical Minerals (C2M)
AMD Formation
1. Oxidation of sulfide
(also known as initiator reaction or oxidation by oxygen)
𝐹𝑒𝑆! + ⁄
"
! 𝑂! + 𝐻!𝑂 = 𝐹𝑒!# + 2𝑆𝑂$
!%
+ 2𝐻#
2. Oxidation of ferrous iron
𝐹𝑒!# + ⁄
&
$ 𝑂! + 𝐻# = 𝐹𝑒'# + ⁄
&
! 𝐻!𝑂
3. Oxidation by ferric iron
(also known as propagation)
𝐹𝑒𝑆! + 14𝐹𝑒'# + 8𝐻!𝑂 = 15𝐹𝑒!# + 2𝑆𝑂$
!%
+ 16𝐻#
Akcil & Koldas, (2006), Journal of Cleaner Production, 14:1139-1145

3. Center for Critical Minerals (C2M)
Pennsylvania and Critical Mineral Resources
3
Potential Environmental Benefits from Production:
• Remining and Reclamation of Abandoned Mined Lands
• Remediation of Acid Mine Drainage
• Reclamation of Mineral Processing and Metallurgical Waste Dumps
Purple poly-lines - rivers that have pollution levels higher than state-acceptable
levels
Yellow poly-points - locations of abandoned mines
Abandoned Mine Drainage (AMD) is one of the largest sources of stream impairment in Pennsylvania. Billions of
gallons of AMD impair over 5,500 miles of streams within the Commonwealth. - PA DCED

4. Center for Critical Minerals (C2M)
Pennsylvania Susquehanna River Basin - AMD
discharge and Treatment Sites
https://www.srbc.net/minedrainageportal/
Maphttps://www.srbc.net/minedrainagepor
tal/Map
Drs. Klima and Pisupati sampling
AMD sludge from a pond in Central PA

5. Center for Critical Minerals (C2M)
AMD and REE contents
• A strong function of pH.
• For flows with pH <4 the
Average is 371 g/ton (PA and
WV data).
• For flows with pH >4 the
Average is 88 g/ton.
• REEs produced from AMD can
vary between 771 and 3,400
tons per annum.
Distribution of the total REEs concentration in various AMD
samples as a function of solution pH (After [16]). The red circle
represents the samples reported in this study.

6. Center for Critical Minerals (C2M)
Research Objectives
q The main objective is to study the fundamental aspects of precipitation of rare earth
elements which provide guidance to develop an efficient, environmentally friendly, and
economically feasible process for recovery of Critical Minerals including Co and Mn from AMD
while treatment for environmental compliance.
Ø Characterization and evaluation of AMD and sludge material
Ø Study the behavior of REE precipitation in AMD treatment process
Ø Evaluation of various ligands and ions in precipitation behavior of REEs during AMD
neutralization
Ø Determining the effective ligand for REE recovery of over 90%
Ø Study the structure and kinetics of formations for individual and complex systems
Ø Optimization of the process parameters to maximize the selectivity and recovery of critical
elements including Co and Mn from AMDs

7. Center for Critical Minerals (C2M)
Pourbaix Diagrams
Y Nd Eu Tb
Dy Al Fe Mn
D. G. Brookins, Eh-pH Diagrams for Geochemistry, Berlin Heidelberg: Springer-Verlag, 1988.

8. Center for Critical Minerals (C2M)
AMD TREATMENT
Characterization of Acid Mine Drainages and Sludge Material
EDS-Mapping

9. Center for Critical Minerals (C2M)
AMD Sites
Site C
Site B
Site A

10. Center for Critical Minerals (C2M)
AMD Treatment Process
Sludge
Pond
Settling
Pond
Discharge
AMD
pH
Adjustment

11. Center for Critical Minerals (C2M)
REE Distribution of Samples
Sample Material pH
Eh
(mV)
TREE
(ppm)
CREE 1
(ppm)
HREE 2
(ppm)
LREE 3
(ppm)
H/L
Ratio
Site A:
AMD
3.66 188.1 0.54 0.31 0.31 0.23 1.35
Site B: 4.00 168.5 0.43 0.21 0.18 0.25 0.72
Site C: 3.72 184.5 0.47 0.23 0.21 0.26 0.81
Site A:
Sludge
1043 600 595 447 1.33
Site B: 2787 1332 1175 1612 0.73
Site C: 2487 1233 1131 1356 0.83
1. CREE: Nd, Eu, Tb, Dy, Y
2. HREE: Y, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu
3. LREE: Sc, La, Ce, Pr, Nd, Sm

12. Center for Critical Minerals (C2M)
AMD TREATMENT
Effect of various ligands on precipitation

13. Center for Critical Minerals (C2M)
Elemental Content of Site A
HREE
(ppbv)
Y Eu Gd Tb Dy Ho Er Tm Yb Lu
157.90 6.29 38.31 6.36 34.17 6.85 19.80 2.26 12.33 1.80
LREE
(ppbv)
Sc La Ce Pr Nd Sm HREE LREE TREE H/L
6.98 24.56 79.15 12.21 66.25 22.79 286 212 500 1.35
Major
Cations
(ppmv)
Al Ca Fe Mg Mn Si Co Ni Cu Zn
33.73 178 0.17 324.06 33.36 18.35 0.72 1.21 0.04 2.51
Major
Anions
(ppmv)
F Cl SO4
2– NO3
–
1.05 0.76 2.03 0.11

14. Center for Critical Minerals (C2M)
REE Precipitation Patterns
0
10,000
20,000
30,000
40,000
50,000
0
20
40
60
80
100
pH 4.5 pH 5.0 pH 6.0 pH 7.0 pH 8.0 pH 9.0
Grade
(ppm)
Cumulative
Recovery
(%)
NaOH
Grade
Recovery
0
10,000
20,000
30,000
40,000
pH 4.5 pH 5.0 pH 6.0 pH 7.0 pH 8.0 pH 9.0
0
20
40
60
80
100
Grade
(ppm)
Cumulative
Recovery
(%)
(NH₄)OH
Grade
Recovery
0
10,000
20,000
30,000
40,000
pH 4.5 pH 5.0 pH 6.0 pH 7.0 pH 8.0 pH 9.0
0
20
40
60
80
100
Grade
(ppm)
Cumulative
Recovery
(%)
Na₂SO₄
Grade
Recovery
0
20,000
40,000
60,000
80,000
100,000
120,000
140,000
pH 4.5 pH 5.0 pH 6.0 pH 7.0 pH 8.0 pH 9.0
0
20
40
60
80
100
Grade
(ppm)
Cumulative
Recovery
(%)
Na₂CO₃
Grade
Recovery
Na2CO3
0
10,000
20,000
30,000
40,000
0
20
40
60
80
100
pH 4.5 pH 5.0 pH 6.0 pH 7.0 pH 8.0 pH 9.0
Grade
(ppm)
Cumulative
Recovery
(%)
Na₂HPO₄
Grade
Recovery
Na2HPO4

15. Center for Critical Minerals (C2M)
REE Precipitation Patterns
0
10,000
20,000
30,000
40,000
50,000
0
20
40
60
80
100
pH 4.5 pH 5.0 pH 6.0 pH 7.0 pH 8.0 pH 9.0
Grade
(ppm)
Cumulative
Recovery
(%)
NaOH
Grade
Recovery
Na2CO3
0
20,000
40,000
60,000
80,000
100,000
120,000
140,000
pH 4.5 pH 5.0 pH 6.0 pH 7.0 pH 8.0 pH 9.0
0
20
40
60
80
100
Grade
(ppm)
Cumulative
Recovery
(%)
Na₂CO₃
Grade
Recovery
Na2CO3

16. Center for Critical Minerals (C2M)
Precipitation Patterns
0
20
40
60
80
100
4.5 5 6 7 8 9
Cumulative
Al
Recovery
(%)
pH
CO₃
NaOH
4.5 5 6 7 8 9
0
20
40
60
80
100
pH
Cumulative
REE
Recovery
(%)
CO₃
NaOH

17. Center for Critical Minerals (C2M)
Two-Step Treatment Process
5.10
85.41
93.66
5.70
0
20
40
60
80
100
pH 5.0 pH 7.0
Recovery
(%)
TREEs Al

18. Center for Critical Minerals (C2M)
Two-Step Treatment Process
Recovery:
Al 90%
TREE 85%
Grade:
Al 30%
TREE 16,000 ppm

19. Center for Critical Minerals (C2M)
AMD TREATMENT
Selective Precipitation of REEs by CO₂ Mineralization Process

20. Center for Critical Minerals (C2M)
Chemicals and Filtration
• In CO₂ mineralization
experiments, CO₂ was
purged into AMD for 24
hours before pH
adjustment using NaOH
pH Adjustment
and treatment
Filtration
100 psi
(0.45 µm)
Filter Cake
Filtrate
NaOH
AMD
CO₂ Purge
24hrs CO₂
Treatment

21. Center for Critical Minerals (C2M)
TREE Recovery and Grade
0
10,000
20,000
30,000
40,000
50,000
0
20
40
60
80
100
4.5 5.0 6.0 7.0 8.0 9.0
pH
Concentration
(ppm
s
)
TREE
Recovery
(%) Concentration
Cumulative
Recovery
NaOH

22. Center for Critical Minerals (C2M)
TREE Recovery and Grade
CO₂/NaOH
0
3,000
6,000
9,000
12,000
15,000
0
20
40
60
80
100
4.5 5 6 7 8 9
pH
Concentration
(ppm
s
)
Cumulative
TREE
Recovery
(%)
Concentration
Cumulative
Recovery
REE Step

23. Center for Critical Minerals (C2M)
Al and Fe Precipitation
0
20
40
60
80
100
4.5 5 6 7 8 9
Cumulative
Recovery
(%)
pH
Al (CO₂/NaOH)
Fe (CO₂/NaOH)
Al (NaOH)
Fe (NaOH)
Al Step REE Step

24. Center for Critical Minerals (C2M)
Two-Step Treatment Process

25. Center for Critical Minerals (C2M)
AMD Treatment
• Recovery of Co and Mn

26. Center for Critical Minerals (C2M)
Effect of Various Ligands
0
10
20
30
40
50
60
70
80
90
100
PH 4.5 PH 5.0 PH 6.0 PH 7.0 PH 8.0 PH 9.0
RECOVERY
(%)
Mn
NaOH
Na₂CO₃
(NH₄)HCO₃
(NH₄)OH
(NH₄)₂SO₄
Na₂SO₄
Na₂HPO₄
0
10
20
30
40
50
60
70
80
90
100
PH 4.5 PH 5.0 PH 6.0 PH 7.0 PH 8.0 PH 9.0
RECOVERY
(%)
Co
NaOH
Na₂CO₃
(NH₄)HCO₃
(NH₄)OH
(NH₄)₂SO₄
Na₂SO₄
Na₂HPO₄

27. Center for Critical Minerals (C2M)
AMD Treatment
• Development of a Process Flowsheet

28. Center for Critical Minerals (C2M)
A flow chart for multimetal recovery

29. Center for Critical Minerals (C2M)
Final Products Grade
Stage Element
Elemental
Content
(%)
Mineral
(Formation) [fraction]
Mineral Grade
(%)
Stage I R2 Al 32
Boehmite
AlO(OH)
[78.3%] 55.7
92.8
Dawsonite
NaAl(OH)2(CO3)
[21.7%] 37.1
Stage II R3 TREE 42
Adamsite-(REE)
Na(REE)(CO3)2
88.5
Stage III
R2
Mn 43
Ramsdellite
MnO2
68.0
Co 1.3
Cobalt(II,III) oxide
Co3O4
6.9

30. Center for Critical Minerals (C2M)
Conclusions
• Pennsylvania AMDs can be a viable source for REE recovery.
• A product of high REE concentration can be produced with well controlled
staged precipitation process using carbonate ligands.
• Carbonate ions (carbonate chemicals or through CO₂ mineralization process)
increase REE recovery in AMD treatment process.
• A two-step treatment process was formulated for recovery of critical
elements from AMD.
• Over 90% Al and REE can be recovered separately using the proposed two-
step treatment process.
• The neutralized AMD can be further treated for recovery of Co and Mn.