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 (B)</p> Signup and view all the answers

Where are alkaline soils generally located?

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

What effect does rainfall typically have on soil pH?

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

What factor contributes to the acidophilic nature of Thiobacillus ferrooxidans?

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

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

<p>High acidity (C)</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 (D)</p> Signup and view all the answers

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

<p>Atmospheric exposure due to mining (B)</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. (C)</p> Signup and view all the answers

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

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

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

<p>Ferric hydroxide (A)</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. (C)</p> Signup and view all the answers

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

<p>Oxygen (D)</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 (A)</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. (C)</p> Signup and view all the answers

What is released from rock due to acid mine drainage?

<p>Acid (B)</p> Signup and view all the answers

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

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

What is a common physical property of gold?

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

Gold is typically bonded to which of the following metals?

<p>Silver (D)</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. (B)</p> Signup and view all the answers

At what temperature does the smelting process typically occur?

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

What term is used for impurities in the smelting process?

<p>Slag (D)</p> Signup and view all the answers

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

<p>Gossan (B)</p> Signup and view all the answers

What is the natural pH range for most plants?

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

Why do sulfide minerals like pyrite underwater not weather significantly?

<p>Lack of oxygen prevents oxidation. (D)</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 (B)</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 (A)</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 (C)</p> Signup and view all the answers

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

<p>Bactericides (C)</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. (A)</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. (D)</p> Signup and view all the answers

Where are acid soils predominantly located?

<p>Rainforests and jungles (B)</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. (C)</p> Signup and view all the answers

Which statement about buffers is true?

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

Where are alkaline soils primarily found?

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

What natural pH range is most suitable for plant growth?

<p>Between 5.5 - 7.0 (D)</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. (A)</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. (C)</p> Signup and view all the answers

What is the LC50 for inhalation of gaseous hydrogen cyanide?

<p>100-300 parts per million (A)</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. (B)</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. (A)</p> Signup and view all the answers

What health effect occurs due to cyanide exposure?

<p>Cellular suffocation leading to respiratory arrest (A)</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. (A)</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 (D)</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 (A)</p> Signup and view all the answers

Flashcards

Logarithmic nature of pH scale

A small change in pH value represents a significant change in the concentration of H+ ions.

What are buffers?

Substances that resist changes in pH by absorbing excess H+ ions.

Buffering Capacity

The ability of a solution to resist changes in pH.

Where are acid soils found?

Acidic soil is common in areas with high rainfall and poor buffering capacity.

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Where are alkaline soils found?

Alkaline soils are common in areas with low rainfall and high mineral content.

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What effect does rainfall have on soil pH?

Rainfall can lower the pH of soil over time, making it more acidic.

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Pyrite Oxidation

The chemical process where pyrite reacts with oxygen and water, producing hydrogen ions (H+) and contributing to acid mine drainage.

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Pyrite

A mineral composed of iron sulfide (FeS2) with a characteristic brassy yellow color.

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Ferric Hydroxide

The chemical compound formed during pyrite oxidation, often found as a yellow-orange precipitate.

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Acid Mine Drainage (AMD)

Acidic water runoff from mines, often caused by the oxidation of pyrite in the surrounding rocks.

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Thiobacillus ferrooxidans

A type of bacteria that accelerates the oxidation of pyrite, greatly increasing the production of acid mine drainage.

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Gold Cyanidation

The process of extracting gold using cyanide, often used in mining operations.

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Baia Mare Cyanide Spill

A major cyanide spill that occurred in Romania, highlighting the risks associated with gold mining.

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Preventing Acid Mine Drainage

A strategy to reduce or eliminate acid mine drainage by preventing the contact of pyrite with oxygen and water.

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What is the pH scale?

A measure of the acidity or alkalinity of a solution. It is logarithmic, meaning a small change in pH represents a large change in hydrogen ion concentration.

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What is the pH of clean rainwater and why?

Rainwater naturally combines with carbon dioxide in the atmosphere to form carbonic acid, which makes it slightly acidic. This results in a pH range of 5.6 to 5.7 for clean rainwater.

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Where are acid soils commonly found?

Typically found in environments with heavy rainfall and decomposing organic matter, such as rainforests and jungles.

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Where are alkaline soils commonly found?

Often found in drier regions with low rainfall, such as deserts, where weathering processes lead to the accumulation of alkaline minerals.

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What is the natural pH range for most plants?

The natural pH range for most plants is acidic, typically between 5.5 and 7.

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Why do sulfide minerals like pyrite not weather significantly underwater?

The weathering of sulfide minerals like pyrite occurs in the presence of oxygen and water. When these minerals are submerged underwater, they are sheltered from oxygen, significantly slowing down the weathering process.

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

A visible manifestation of geological weathering processes. It is characterized by reddish or yellowish hues caused by the presence of iron oxide compounds, commonly formed through the oxidation of sulfide minerals.

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What is silica's importance in inorganic coatings?

Silica is a material used in inorganic coatings and is valued for its stability, acid resistance, and longevity.

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What causes acid mine drainage?

Acid mine drainage happens when sulphides in exposed rocks react with air and water.

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Where does acid mine drainage travel?

Acid mine drainage can contaminate nearby water sources like streams, rivers, lakes, and groundwater.

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What are the effects of acid mine drainage on the environment?

Acid mine drainage negatively affects the physical, chemical, and biological aspects of aquatic environments.

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What are some physical properties of gold?

Gold is soft and malleable, meaning it can be hammered into thin sheets or drawn into thin wires.

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What metals is gold often bonded to?

Gold is often found combined with other metals, like silver.

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What is the role of cyanide in gold processing?

Cyanide is used in gold processing to extract gold by dissolving it from other metals and leaching it into the surrounding water.

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What are impurities in the smelting process called?

Impurities remaining after the melting process are called slag.

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Plant pH Range

The natural pH range for most plants is slightly acidic, ranging from 5.5 to 7.

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Weathering of Sulfide Minerals in Water

Sulfide minerals like pyrite, when submerged in water, will not weather significantly due to the lack of oxygen. Oxygen is essential for the oxidation reaction that leads to weathering.

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What is gossan?

Gossan is a rusty-colored rock, often found at the surface, formed by the weathering of sulfide minerals like pyrite.

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What is Acid Mine Drainage (AMD)?

Acid Mine Drainage (AMD) is the acidic water draining from mines, often contaminated with heavy metals, caused by the oxidation of sulfide minerals.

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AMD Treatments

Some treatments for Acid Mine Drainage (AMD) include adding buffers like limestone to neutralize acidity, limiting exposed rock, compacting acid-generating rock, and covering the rock with sealing layers.

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Dry Cover for AMD Prevention

Dry cover methods involve creating a layer of material over the sulfide-bearing waste to prevent oxidation and AMD. These methods usually include a layer of plastic liners.

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Wet Cover for AMD Prevention

Wet cover methods for AMD prevention involve completely submerging the sulfide-bearing waste in water to prevent oxidation, but require high maintenance costs.

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Limitations of AMD Treatments

While various AMD treatments are used to delay or prevent oxidation, they all have limitations. Physical barriers like wet or dry covers offer short-term effectiveness, while bactericides are toxic and only work on fresh tailings. Chemical barriers are effective but expensive.

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Cyanide

A chemical compound used in gold mining that can be highly toxic to aquatic life and humans.

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LC50

The minimum concentration of a substance that is lethal to 50% of the exposed population.

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Biodegradable

The ability of a substance to break down naturally in the environment.

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Cellular Suffocation

The inability for cells to use oxygen effectively, often caused by cyanide poisoning.

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Absorption Through Eyes and Skin

The process by which a substance is absorbed through the eyes or skin.

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Oxidation

The chemical breakdown of a compound by reacting with oxygen, often producing acidic byproducts.

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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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