Acid Mine Drainage Concepts
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Questions and Answers

What does a small change in pH represent on the pH scale?

  • No significant change in acidity
  • A minor change in ion concentration
  • A large change in H+ concentration (correct)
  • An inverse change in alkalinity

    • What are solutions that resist changes to pH known as?

  • Acidic solutions
  • Buffers (correct)
  • Alkaline solutions
  • Solvents

    • What type of capacity do fluids in living organisms and seawater exhibit?

  • Conductive capacity
  • Buffering capacity (correct)
  • Absorptive capacity
  • Evaporative capacity

    • Where are acid soils typically found?

    <p>In tropical rainforests</p> Signup and view all the answers

    Where are alkaline soils generally located?

    <p>In arid regions</p> Signup and view all the answers

    What effect does rainfall typically have on soil pH?

    <p>It lowers soil pH</p> Signup and view all the answers

    What factor contributes to the acidophilic nature of Thiobacillus ferrooxidans?

    <p>Energy obtained through iron oxidation</p> Signup and view all the answers

    What characteristic of Acid Mine Drainage (AMD) is commonly associated with Thiobacillus ferrooxidans?

    <p>High acidity</p> Signup and view all the answers

    What is the oxidation state change of iron in the reaction of pyrite oxidation?

    <p>From +2 to +3</p> Signup and view all the answers

    Which environment is primarily responsible for accelerating the oxidation of pyrite?

    <p>Atmospheric exposure due to mining</p> Signup and view all the answers

    What role do microbes like Thiobacillus ferrooxidans play in the oxidation of pyrite?

    <p>They accelerate the oxidation process.</p> Signup and view all the answers

    In which type of geological formation is pyrite most commonly found?

    <p>Shales interbedded with coal seams</p> Signup and view all the answers

    What is produced in large quantities as a result of the oxidation of pyrite?

    <p>Ferric hydroxide</p> Signup and view all the answers

    What is the effect of acid mine drainage on local water sources?

    <p>It leads to acidification of surface waters.</p> Signup and view all the answers

    What is the primary oxidizing agent in the oxidation of pyrite?

    <p>Oxygen</p> Signup and view all the answers

    What environmentally harmful phenomenon can result from the mining of pyrite-rich coal seams?

    <p>Acid mine drainage</p> Signup and view all the answers

    What is the most notable property of silica as an inorganic coating?

    <p>It is stable and long lasting.</p> Signup and view all the answers

    What is released from rock due to acid mine drainage?

    <p>Acid</p> Signup and view all the answers

    Which of the following ecological impacts is caused by acid mine drainage?

    <p>Degradation of stream habitat</p> Signup and view all the answers

    What is a common physical property of gold?

    <p>Doesn't rust or tarnish</p> Signup and view all the answers

    Gold is typically bonded to which of the following metals?

    <p>Silver</p> Signup and view all the answers

    What role does cyanide play in the process of gold extraction?

    <p>It helps extract gold from other metals.</p> Signup and view all the answers

    At what temperature does the smelting process typically occur?

    <p>1500 degrees Celsius</p> Signup and view all the answers

    What term is used for impurities in the smelting process?

    <p>Slag</p> Signup and view all the answers

    What is the geological name for a rusty exposure of rock?

    <p>Gossan</p> Signup and view all the answers

    What is the natural pH range for most plants?

    <p>5.5 - 7</p> Signup and view all the answers

    Why do sulfide minerals like pyrite underwater not weather significantly?

    <p>Lack of oxygen prevents oxidation.</p> Signup and view all the answers

    Which of the following is NOT a treatment for acid mine drainage?

    <p>Increasing exposure of sulfide rocks</p> Signup and view all the answers

    Which method is effective in delaying oxidation related to acid mine drainage?

    <p>Applying chemical barriers on sulfide surfaces</p> Signup and view all the answers

    What is a limitation of using wet cover as a treatment for acid mine drainage?

    <p>Significant maintenance costs</p> Signup and view all the answers

    Which approach is NOT suitable for long-term effectiveness against acid mine drainage?

    <p>Bactericides</p> Signup and view all the answers

    What is a potential drawback of using bactericides in treating acid mine drainage?

    <p>They may harm aquatic organisms.</p> Signup and view all the answers

    What is the primary characteristic of the pH scale?

    <p>It is logarithmic, indicating small changes reflect large shifts in H+ concentration.</p> Signup and view all the answers

    Where are acid soils predominantly located?

    <p>Rainforests and jungles</p> Signup and view all the answers

    What effect does rainfall have on soil pH?

    <p>Rainwater forms a weak acid when combined with carbon dioxide.</p> Signup and view all the answers

    Which statement about buffers is true?

    <p>Buffers act like sponges to absorb excess H+ ions.</p> Signup and view all the answers

    Where are alkaline soils primarily found?

    <p>Deserts and arid regions</p> Signup and view all the answers

    What natural pH range is most suitable for plant growth?

    <p>Between 5.5 - 7.0</p> Signup and view all the answers

    Which of the following statements is incorrect regarding sulfide minerals submerged underwater?

    <p>They have no weathering process occurring.</p> Signup and view all the answers

    What was the consequence of the 2000 Baia Mare cyanide spill?

    <p>It contaminated the Someș River and affected water supply.</p> Signup and view all the answers

    What is the LC50 for inhalation of gaseous hydrogen cyanide?

    <p>100-300 parts per million</p> Signup and view all the answers

    Why has cyanide been banned for gold extraction in certain regions?

    <p>Its high toxicity poses significant environmental and health risks.</p> Signup and view all the answers

    What is one requirement imposed by the European Union after the Baia Mare cyanide spill?

    <p>Cyanide concentration must be reduced to the lowest possible level.</p> Signup and view all the answers

    What health effect occurs due to cyanide exposure?

    <p>Cellular suffocation leading to respiratory arrest</p> Signup and view all the answers

    What was a significant impact of cyanide on the ecosystem after the Baia Mare spill?

    <p>Large-scale fish deaths in Hungary and Romania.</p> Signup and view all the answers

    What is the LC50 value for cyanide absorption through the skin and eyes?

    <p>100 milligrams per kilogram of body weight</p> Signup and view all the answers

    Which two parties were involved in the joint venture responsible for the cyanide spill?

    <p>Esmeralda Exploration and the Romanian government</p> Signup and view all the answers

    Study Notes

    Acid Mine Drainage

    • Pyrite Oxidation: A chemical reaction where pyrite (FeS₂) reacts with oxygen and water, producing ferric hydroxide, sulfuric acid, and hydrogen ions. The chemical formula is 4FeS₂ + 15O₂ + 14H₂O → 4Fe(OH)₃ + 8SO₄²⁻ + 16H⁺
    • Pyrite Locations: Pyrite is commonly found in shales, often interbedded with coal seams, particularly those formed in marine coastal swamps.
    • Microbial Action: Bacteria like Thiobacillus ferrooxidans accelerate pyrite oxidation. This process dramatically increases the rate of oxidation by 1,000,000x compared to oxygen alone. These bacteria convert insoluble metals to their soluble state and are highly acidophilic (pH 1.5 to 2.0).
    • Acid Mine Drainage Prevention: Methods to prevent acid mine drainage include buffer materials like limestone, limiting exposed rock areas, compacting acid-generating rock, and covering the rock with sealing layers. Water cover (flooding) and inorganic/organic coatings are also mentioned as possible solutions.
    • pH Scale: The pH scale is logarithmic, meaning a small change in pH represents a large change in H⁺ concentration.
    • Buffer Solutions: Solutions that resist changes to pH are called buffers. They act like sponges, absorbing excess H⁺.
    • Natural pH Range for Plants: Most plants have an acidic pH range between 5.5 and 7.
    • What is Gossan? The geological name for a rusty exposure of rock is gossan.
    • Impact of Rainfall: Rainfall combines with atmospheric CO₂ to form a weak acid (H₂CO₃). Clean rainwater has a pH of 5.6-5.7.
    • Gold Cyanidation: Cyanide is used in 90% of gold production. Cyanide dissolves gold from its ores. The chemical formula for gold dissolution is: 4Au(s) + 8NaCN(aq) + O₂(g) + 2H₂O(l) → 4NaAu(CN)₂ + 4NaOH(aq).
    • Cyanide Remediation: Cyanide remediation involves oxidizing cyanide (CN⁻) to OCN⁻, then converting OCN⁻ into HCO₃⁻ and NH₃.
    • Cyanide Spills: Infamous cyanide spills include the 2000 Baia Mare spill in Romania, which polluted the Tisza and Danube rivers, killing numerous fish.
    • Health Effects of Cyanide: Cyanide is highly toxic. Inhalation, ingestion, or skin/eye absorption can cause respiratory arrest and other severe health problems.

    Gold Extraction and Processing

    • Gold Properties: Gold is a soft, malleable metal that can be pounded thin, drawn into wire, and shaped into various forms. It does not rust or tarnish.
    • Gold Bonding: Gold frequently occurs bonded to other metals such as silver.
    • Cyanide in Gold Processing: Cyanide helps extract gold from other metals and leach it into the surrounding water.
    • Smelter Temperature: The smelting process typically takes place at 1600 degrees Celsius.
    • Impurities in Smelting: Impurities in the smelting process are called slag.

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    Related Documents

    ERTH308 Lecture 15: Acid Mine Drainage + Gold Cyanidation PDF

    Description

    Explore the critical concepts surrounding acid mine drainage, including the chemical reactions involved in pyrite oxidation and the role of microbes. This quiz will also cover prevention strategies against acid mine drainage, highlighting methods and materials used in industry. Test your knowledge on these environmental challenges!

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