1. Understanding and managing acid mine drainage
Dr Talitha Santini
Lecturer, School of Geography, Planning, and Environmental Management and Centre for Mined Land Rehabilitation, UQ

2. Mt Morgan map

3. pH 3.2 (≈ lemon juice)
Al: 730 mg/L
Fe: 250 mg/L
Cu: 35 mg/L
Mn: 80 mg/L
SO42-: mg/L

5. Outline Acid mine drainage: Mount Morgan as a case study to illustrate
How does it occur?
How do we manage or prevent it?
Mount Morgan as a case study to illustrate

6. Image courtesy Crystal Jasperson, DEEDI
History of Mt Morgan
Largest gold mine in Australia
1881: Gold discovered
1882: Mining started
Initially underground then open cut
1906: Cu production
1981: Extraction ended
247 T Au
390,000 T Cu
37 T Ag
Image courtesy Crystal Jasperson, DEEDI

7. Image courtesy Crystal Jasperson, DEEDI

8. Copper extraction

9. Copper extraction Chalcopyrite (CuFeS2); 80%
Rankin WJ (2011) Minerals, metals and sustainability. CSIRO Publishing, Collingwood Australia, 419 p.

10. Copper extraction Copper oxides; 20%
Rankin WJ (2011) Minerals, metals and sustainability. CSIRO Publishing, Collingwood Australia, 419 p.

11. Mining Most deposits exploited by surface mining
Ore typically crushed and concentrated via froth flotation to separate copper sulfides prior to further processing
Escondida, Chile
Chuquicamata, Chile

12. Froth flotation CuFeS2 tailings
Rankin WJ (2011) Minerals, metals and sustainability. CSIRO Publishing, Collingwood Australia, 419 p;

13. 2CuFeS2 + 4O2 + SiO2 → Cu2S + Fe2SiO4 + 3SO2
Smelting
SO2
(SiO2)
2CuFeS2 + 4O2 + SiO2 → Cu2S + Fe2SiO4 + 3SO2
Cu2S
Fe2SiO4
Rankin WJ (2011) Minerals, metals and sustainability. CSIRO Publishing, Collingwood Australia, 419 p.

14. British Geological Survey (2007) Mineral profile: Copper
British Geological Survey (2007) Mineral profile: Copper. National Environment Research Council, Swindon UK.

15. Images courtesy Crystal Jasperson, DEEDI
Mine closure
1990: Mine closure
1992: QLD Govt accepts liability for the site
2000: Commencement of rehabilitation studies
2003: Rehab Plan developed
Site is managed under the QLD Government’s Abandoned Mines Land Program
Images courtesy Crystal Jasperson, DEEDI

16. Image courtesy Crystal Jasperson, DEEDI

17. Management Water: AMD seepage and spills, water-filled pit
Overflowed in Jan 2013
87000 ML released into Dee River
25000 fish killed
Impacts up to 65 km downstream

18. Management Water: AMD seepage and spills, water-filled pit
Heritage: building maintenance, OHS
Land: weeds, pests, fire risks
Social: historical value, economic transition in town

19. Chalcopyrite: CuFeS2
Chalcocite: Cu2S
Pyrite: FeS2

20. Pyrite
FeS2

21. Acid mine drainage (AMD)
Oxidation of sulfides (esp. pyrite) on exposure to O2(g) generates acid:
2FeS2(s) + 7O2(g) + 2H2O(l)  2Fe2+(aq) + 4SO42-(aq) + 4H+(aq)
4Fe2+(aq) + O2(g) + 4H+(aq)  4Fe3+(aq) + 2H2O(l)
Fe3+(aq) + 3H2O(l)  Fe(OH)3(s) + 3H+(aq)
FeS2(s) + Fe3+(aq) + 8H2O(l)  2Fe2+(aq) + 2SO42-(aq) + 16H+(aq)
Rate limiting step;
microbially mediated

22. 4Fe2+(aq) + O2(g) + 4H+(aq)  4Fe3+(aq) + 2H2O(l)
Ferroplasma acidarmanus: isolated from a mixed metal sulfide mine; optimum growth pH 1.2; pH lower limit 0
Leptospirillum ferrooxidans: isolated from a mixed metal sulfide mine; optimum growth pH 3; pH lower limit 1.5
Edwards et al. (2000) Science, 287, ; Schrenk et al. (1998) Science, 279,
Image courtesy Mansour Edraki, CMLR

23. Acid mine drainage (AMD)
Oxidation of sulfides (esp. pyrite) on exposure to O2(g) generates acid:
2FeS2(s) + 7O2(g) + 2H2O(l)  2Fe2+(aq) + 4SO42-(aq) + 4H+(aq)
4Fe2+(aq) + O2(g) + 4H+(aq)  4Fe3+(aq) + 2H2O(l)
Fe3+(aq) + 3H2O(l)  Fe(OH)3(s) + 3H+(aq)
FeS2(s) + Fe3+(aq) + 8H2O(l)  2Fe2+(aq) + 2SO42-(aq) + 16H+(aq)
Rate limiting step;
microbially mediated

24. Acid mine drainage (AMD)
My Lyell copper mine, Tasmania
Mamut copper mine, Malaysia

25. Grey (1997) Environmental impact and remediation of acid mine drainage: a management problem. Environ Geol 30,

26. Management options - prevention
2FeS2(s) + 7O2(g) + 2H2O(l)  2Fe2+(aq) + 4SO42-(aq) + 4H+(aq)
4Fe2+(aq) + O2(g) + 4H+(aq)  4Fe3+(aq) + 2H2O(l)
Fe3+(aq) + 3H2O(l)  Fe(OH)3(s) + 3H+(aq)
FeS2(s) + Fe3+(aq) + 8H2O(l)  2Fe2+(aq) + 2SO42-(aq) + 16H+(aq)
Johnson and Hallberg (2005) Acid mine drainage remediation options: a review. Sci Tot Environ 338, 3-14.

27. Management options - prevention
Johnson and Hallberg (2005) Acid mine drainage remediation options: a review. Sci Tot Environ 338, 3-14.

28. Management options - remediation
Hydrated lime: Ca(OH)2(s) + 2H+(aq) + SO42-(aq)  CaSO4(s) + 2H2O(l)
Limestone: CaCO3(s) + 2H+(aq) + SO42-(aq)  CaSO4(s) + H2O(l) + CO2(g)
Johnson and Hallberg (2005) Acid mine drainage remediation options: a review. Sci Tot Environ 338, 3-14.

29. Hydrated lime (Ca(OH)2) dosing plant: 3 ML/day of water treated
Ca(OH)2(s) + 2H+(aq) + SO42-(aq)CaSO4(s) + 2H2O(l)

30. Evaporators: treat 2 ML/day
Ca(OH)2(s) + 2H+(aq) + SO42-(aq)CaSO4(s) + 2H2O(l)

31. Management options - remediation
Fe3+ → Fe2+
CH2O + SO H+ →
S2- + 2H2O + HCO3-
S2- + M2+ → MS
FeS
SO42- → S2-
Johnson and Hallberg (2005) Acid mine drainage remediation options: a review. Sci Tot Environ 338, 3-14.

32. Biological treatment wetlands
Fe3+, H+, Na+,
Cu2+, Cl-, SO42-
Na+, Cl-, DOC
2CH2O + SO H+ →
H2S + 2H2O + 2CO2
H2S + M2+ → MS + 2H+
Degens (2009)
Images courtesy Brad Degens

33. Biological treatment wetlands
Fe3+, H+, Na+,
Al3+, Pb4+,
Cl-, SO42-
Inflow pH
Outflow pH
Na+, Al3+, Cl-,
DOC
2CH2O + SO H+ →
H2S + 2H2O + 2CO2
H2S + M2+ → MS + 2H+
Degens (2009)
Images courtesy Brad Degens

34. Biological treatment wetlands
Fe3+, H+, Na+,
Al3+, Pb4+,
Cl-, SO42-
Inflow pH
Outflow pH
Na+, Al3+, Cl-,
DOC
2CH2O + SO H+ →
H2S + 2H2O + 2CO2
H2S + M2+ → MS + 2H+
FeS2
Degens (2009)
Images courtesy Brad Degens

35. Summary Acid mine drainage (AMD) is caused by oxidation of sulfides
Common in copper sulfide deposits
Treatment can be active or passive, using abiotic or biotic approaches
After lunch: lab session!
Learn how to calculate treatment rates for AMD