Natural underground pyritic deposits that are not disturbed by mining activities do not form acidic drainage waters. Why not? Explain the critical steps in the formation of acid mine drainage in your answer
What will be an ideal response?
Answer: The initiation, or first, step in the formation of acid requires the exposure of pyrite to oxygen. If this step does not occur, the propagation cycle that produces sulfuric acid and dissolved metals cannot proceed. When pyrite is exposed to oxygen, it is slowly oxidized into sulfate. The production of sulfate slowly creates an acidic environment and reduced Fe2+ is released. Once an acidic environment with Fe2+ is established, growth of Acidithiobacillus ferrooxidans catalyzes the rapid oxidation of Fe2+ to Fe3+ under acidic conditions. The Fe3+ begins to react rapidly with the pyrite, causing a rapid release of sulfuric acid in the propagation cycle. The acid and any co-occurring metals that are dissolved by the acid then flow away from the exposed pyrite, contaminating the environment.
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for what purpose?
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