ch.4
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Ch.4. . Acid Mines Drainages (AMD) Exposure of the reduced minerals by mine excavating Oxidation of the reduced minerals producing acids Pyrite is the primary source of the acid. Pyrite FeS 2 Most frequently observed sulfide in crust - PowerPoint PPT PresentationTRANSCRIPT
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Ch.4. Acid Mines Drainages (AMD)
Exposure of the reduced minerals by mine excavating
Oxidation of the reduced minerals producing acids
Pyrite is the primary source of the acid
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Pyrite○ FeS2
○ Most frequently observed sulfide in crust○ Oxidized to produce acid, causing severe environ-
mental problems such as AMD and acid rain
http://mineralminers.com/html/pytmins.stm
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Pyrite Oxidation○ Complex multistep process (Luther, 1997; Rimstidt
and Vaughn; 2003)○ Microbial vs. abiotic○ Bulk reaction pathways:
FeS2 + 3.5O2+H2O = Fe2+ + 2SO42-+2H+ (R1)
FeS2+14Fe3++8H2O = 15Fe2++SO42-+16H+ (R2)
Fe2++0.25O2+H+ = Fe3++0.5H2O (R3)
○ Dominated by microbial oxidation in nature
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Acidithiobacillus albertis, acidophilus, ferrooxidans, thiooxidans, thioparus Leptospirillum ferrooxidans, thermoferrooxidans Sulfobacillus thermosulfidooxidans Archaea spp. Acidianus brierleyi, Sulfolobus solfataricus, Sulfolobus ambivalens, Sulfolobus acidocaldarius
Microbes capable of oxidizing pyrite
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Acidithiobacillus ferrooxidans○ (Old name: Thiobacillus ferrooxidans)○ Gram negative acidophillic chemolithoautotroph
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Imgok Creek, Imgok, Korea 1996
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http://wiki.biomine.skelleftea.se/wiki/index.php/Image:AMD_in_Rio_Tinto_river.jpgRio Tinto, Spain
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Environmental Impacts by AMD○ Atheistically bad due to the precipitation of Fe-oxy-
hydroxides○ Degrading water quality and limiting water re-
sources due toLow pHHigh concentrations of toxic metalsLack of O2Turbidity & coating by the Fe-ppts
○ Destruction of water ecosystem
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Treatment of AMD○ Active
Physical: - Aeration - Bubbling - Mechanical mixing
Chemical: - Oxidation - Dissolution - Neutralization
Biological- Accelerating the oxidation- Prohibiting the oxidation
○ PassiveSwampReactive beds
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http://pruned.blogspot.com/2008/02/treating-acid-mine-drainage-in.html
Treating Acid Mine Drainage in Vintondale
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Ch.4. Other Environmental Problems in Mining
AreaNoisesDustsAccidentsSubsidence
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From http://www.graphicshunt.com/health/images/black_lung-577.htm
Black Lung
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From http://www.courier-journal.com/cjextra/blacklung/graphics/diseasedlung.html
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From http://www.cdc.gov/niosh/programs/mining/risks.html
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From http://www.donga.com/fbin/output?n=200805240249
Subsidence in Eumsung, Choongcheongbukdo, May 24, 2008