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Bi374 > Iron Cycle > Flashcards

Iron Cycle Flashcards

1
Q

What are the 2 oxidation states iron cycles between in nature?

A

Fe2+ and Fe3+

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2
Q

What is Fe2+?

A

Ferrous

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3
Q

What is Fe3+?

A

Ferric iron

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4
Q

Where does biological Fe reduction take place (location)?

A
  • waterlogged soils, lake sediments
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5
Q

What organisms use Fe as an electron acceptor?

A
  • facultative anaerobes and obligate anaerobes
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6
Q

When does Fe oxidation take place?

A

in presence of O2 from water

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7
Q

Give a specific example of an iron oxidizer at a natural pH

A

Gallionella

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8
Q

Give an example of an iron oxidizer at a low pH

A

Thiobacillus (strict acidophile)

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9
Q

What is the iron reduction equation

A

Fe3+ –> Fe2+

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10
Q

What is the iron oxidation equation

A

Fe2+ –> Fe3+

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11
Q

Define pyrite

A
  • FeS2 - IRON AND SULFUR
  • natural form of iron in coal and ore
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12
Q

What conditions are easier for metal extraction from ore?

A

low pH because metals are more mobile in acidic positions

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13
Q

How does thiobacillus keep inner pH stable?

A
  • high energy for efflux pump of H+
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14
Q

What happens when thiobacillus is taken from acidic conditions?

A

they continue to pump and kill themselves

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15
Q

What is the importance of Pyrite?

A
  • Iron and sulfur cycles coming together
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16
Q

Why must pyrite be kept watered?

A
  • makes it highly mobile –> releases iron from ore and generates sulfate
17
Q

What happens once Fe2+ is stabilized from pyrite?

A

it keeps the pH down and favours metabolism via thiobacillus

18
Q

How is acidity of pyrite maintained?

A

due to amount of H+ released

19
Q

What happens to ferrous iron once it is mobilized?

A

it continues cycling (propagation cycle)

20
Q

Where is microbial leaching practiced?

A

where chemical concentration of metal is not economically feasible (not readily oxidized)

21
Q

Explain the process of microbial leaching

A
  1. Sprinkle acidic solution(Fe2+ and H2O) on CuS to make it more mobile and separate from ore (low pH on pile)
  2. Water is added to CuS and ferric iron to make Cu2+ (soluble) as well as ferrous iron and sulfate with H+ (acidic)
  3. Addition of liquid copper to Cu2+ to remove metal from scrap pile
  4. added to oxidation pond (acidic ferrous rich)
  5. propagation transformation (Fe2+ –> Fe3+ via thiobacillus)
22
Q

What does acid dumping help with?

A
  • keeping pH low for thiobacillus
  • increases mobilization
23
Q

What is the importance of free copper, sulfate and ferrous iron?

A

they keep acid content where it needs to be

24
Q

What happens when you dump liquid copper on soluble copper?

A
  • they swap electrons and take copper metal out of scrap
25
Q

When Fe2+ is transformed into Fe3+, what does it release?

A

free copper

26
Q

What is the equation after acid is added to CuS during microbial leaching

A

CuS + Fe3(+) + H2O —> Cu2(+) + Fe2+ +So4 + H+

Bi374 (8 decks)

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