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Understanding and managing acid mine drainage

Understanding and managing acid mine drainage. Dr Talitha Santini (t.santini@uq.edu.au) Lecturer, School of Geography, Planning, and Environmental Management and Centre for Mined Land Rehabilitation, UQ. Mt Morgan map. pH 3.2 (≈ lemon juice). Al: 730 mg/L Fe: 250 mg/L Cu: 35 mg/L

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Understanding and managing acid mine drainage

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  1. Understanding and managing acid mine drainage Dr Talitha Santini (t.santini@uq.edu.au) 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-: 11500 mg/L

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

  5. 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

  6. Image courtesy Crystal Jasperson, DEEDI

  7. Copper extraction http://www.youtube.com/watch?v=89r8fIR34Gc

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

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

  10. 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 http://www.riotinto.com/ourbusiness/escondida-4740.aspx#; www.miningaustralia.com.au/features/world-s-largest-copper-mine-moves-underground-imag

  11. Froth flotation CuFeS2 tailings Rankin WJ (2011) Minerals, metals and sustainability. CSIRO Publishing, Collingwood Australia, 419 p; http://advanceseng.com/chemical-engineering/the-use-of-rhamnolipid-biosurfactants-as-a-frothing-agent-and-a-sample-copper-ore-response/; http://web.utk.edu/~ammonst/research.html

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

  13. British Geological Survey (2007) Mineral profile: Copper. National Environment Research Council, Swindon UK. http://www.bgs.ac.uk/downloads/start.cfm?id=1410

  14. 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

  15. Image courtesy Crystal Jasperson, DEEDI

  16. 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

  17. 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

  18. Chalcopyrite: CuFeS2 Chalcocite: Cu2S Pyrite: FeS2

  19. Pyrite FeS2

  20. 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

  21. 4Fe2+(aq) + O2(g) + 4H+(aq) 4Fe3+(aq) + 2H2O(l) Ferroplasmaacidarmanus: isolated from a mixed metal sulfide mine; optimum growth pH 1.2; pH lower limit 0 Leptospirillumferrooxidans: isolated from a mixed metal sulfide mine; optimum growth pH 3; pH lower limit 1.5 Edwards et al. (2000) Science, 287, 1796-1799; Schrenk et al. (1998) Science, 279, 1519-1522 Image courtesy Mansour Edraki, CMLR

  22. 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

  23. Acid mine drainage (AMD) Mamut copper mine, Malaysia My Lyell copper mine, Tasmania http://epa.tas.gov.au/epa/mt-lyell-acid-drainage-remediation; http://www.thestar.com.my/story.aspx/?file=%2f2007%2f10%2f2%2flifefocus%2f18911210&sec=lifefocus

  24. Grey (1997) Environmental impact and remediation of acid mine drainage: a management problem. Environ Geol30, 62-71.

  25. 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.

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

  27. 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.

  28. 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)

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

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

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

  32. Fe3+, H+, Na+, Al3+, Pb4+, Cl-, SO42- Na+, Al3+, Cl-, DOC Inflow pH 2.8-3.5 Outflow pH 4.0-6.5 2CH2O + SO42- + 2H+ → H2S + 2H2O + 2CO2 H2S + M2+ → MS + 2H+ Biological treatment wetlands Degens (2009) Images courtesy Brad Degens

  33. Fe3+, H+, Na+, Al3+, Pb4+, Cl-, SO42- Na+, Al3+, Cl-, DOC Inflow pH 2.8-3.5 Outflow pH 4.0-6.5 2CH2O + SO42- + 2H+ → H2S + 2H2O + 2CO2 H2S + M2+ → MS + 2H+ Biological treatment wetlands FeS2 Degens (2009) Images courtesy Brad Degens

  34. 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

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