GLGY 308 Lecture Notes - Lecture 13: Acidithiobacillus, Gold Cyanidation, Iron Oxide
28 Dec 2019
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Document Summary
Pyrite (4 fes2) + oxidizing agent (15 o2) + water (14 h2o) > iron hydroxide (4 fe(oh)3) Fe experiences a change in valence number from +2 in pyrite to +3 in ferric hydroxide. The fe is getting oxidized, because its valence number increases. The most common oxidizing agent in environments in contact with the atmosphere is o2. 4 moles of pyrite reacts with oxygen and water to release 16 moles of h+ into the environment. The reaction occurs naturally during pyrite weathering at or near the surface of the earth. Process is accelerated by mining or quarrying. Mining and quarrying is exposing underground pyrite to the atmosphere (o2) to push the forward reaction, producing h+ Insoluble yellow-orange precipitate, also known as ferric hydroxide or yellow iron oxide is formed. Iron hydroxide is a solid precipitate, and can be varying shades of orange, yellow and red. Sulfate isn"t as big of a concern as iron hydroxide.
