Question

Describe the chemical reaction(s) that produce AMD

Describe, via a chemical reaction, what happens as water travels through pyrite.

Answer 1

Acid mine drainage (AMD) is caused by the oxidation of pyrite (FeS2) in the presence of water and oxygen. The resulting reactions produce ferrous sulfate (FeSO4) and sulfuric acid (H2SO4), contributing to the acidic nature of AMD.

Step-by-step explanation:

Acid mine drainage (AMD) is caused by the oxidation of pyrite (FeS2) in the presence of water and oxygen. The reaction can be represented as:

2FeS2 + 7O2 + 2H2O -> 2FeSO4 + 2H2SO4

In this reaction, pyrite reacts with oxygen and water to produce ferrous sulfate (FeSO4) and sulfuric acid (H2SO4). The sulfuric acid that is formed further reacts with water to produce hydronium ions (H3O+) and sulfate ions (SO42-), which contribute to the acidic nature of AMD.

Acid Mine Drainage (AMD) is produced through chemical reactions involving pyrite, water, and oxygen, resulting in sulfuric acid and iron ions, which can further react to form environmentally harmful compounds like ferric hydroxide.

The chemical reactions that produce Acid Mine Drainage (AMD) generally occur when water and oxygen come into contact with pyrite (FeS₂), a common mineral found in rocks. These reactions can be understood by looking into how water travels through pyrite and interacts with it chemically. When pyrite is exposed to water and oxygen, it can undergo a series of reactions. First, the pyrite reacts with water and oxygen to form sulfuric acid and iron(II) (ferrous) ions:

4FeS₂ + 14H₂O + 15O₂ → 4Fe²⁺ + 8SO₄²⁺ + 16H⁺

This release of acidic ions into the water creates an acidic environment which is harmful to local ecosystems. The ferrous ions can be further oxidized to form ferric ions, which can precipitate as ferric hydroxide, a common yellow-orange compound seen in AMD:

4Fe²⁺ + O₂ + 10H₂O → 4Fe(OH)₃↓ + 8H⁺

This secondary reaction can exacerbate the environmental damage, as ferric hydroxide coats streambeds and disrupts aquatic life. These reactions serve as examples of how the interactions of simple materials, like minerals and water, can have profound implications in natural and industrial contexts.