Iron Oxy/Hydroxides

Question 1

What is the name of alpha - Fe2O3 ? And colour? And packing type ?

Answer 1

Hematite, blood red, HCP

Question 2

What is the name of gamma - Fe2O3 ? And colour ? And packing type?

Answer 2

Maghemite, brown, CCP

Question 3

What is the name of Fe3O4 ? And colour? And packing type ?

Answer 3

Magnetite, CCP

Question 4

What is the name of delta - FeOOH ? And colour? And packing type ?

Answer 4

Feroxyhyte, brown, HCP

Question 5

What is the name of alpha - FeOOH ? And colour? And packing type ?

Answer 5

Goethite, yellow/brown, HCP

Question 6

What is the name of beta - FeOOH ? And colour? And packing type ?

Answer 6

Akaganeite, rust brown, HCP

Question 7

What is the name of FeOOH•0•4H2O ? And colour? And packing type ?

Answer 7

Ferrihydrite, red/brown, HCP

Question 8

What is the name of gamma - FeOOH? And colour? And packing type ?

Answer 8

Lepidocrocite, orange, CCP

Question 9

What is the name of Fe(II)Fe(III)(OH)x ? And colour? And packing type ?

Answer 9

Green rusts, green, HCP

Question 10

How is Goethite produced ?

Answer 10

1) Nucleation and growth from Fe 3+ ions @ pH > 1
2) oxidation of green rusts with carbonate
3) dissolution and reprecipitation of ferrihydrite

Question 11

How is akaganeite produced?

Answer 11

1) hydrolysis of Fe 3+ with Cl-

Question 12

How is ferrihydrite produced ?

Answer 12

1) direct precipitation of Fe 3+ @ pH > 2

Question 13

How is lepidocrocite produced?

Answer 13

1) direct oxidation of Fe2+

2) oxidation from green rusts @ pH 5-7

Question 14

How are green rusts produced?

Answer 14

1) slow hydrolysis of goethite/ferrihydrite/haemitite with Fe2+ ions
2) rapid hydrolysis of Fe(II) solution or ferrihydrite

Question 15

How is maghemite produced ?

Answer 15

1) thermal dehydroxylation of lepidocrocite

2) careful oxidation of magnetite

Question 16

How is hematite produced ?

Answer 16

1) thermal transformation from feroxyhyte, maghemite, goethite @200-400 degrees C
2) dehydration and rearrangement of nano-sized ferrihydrite

Question 17

How is feroxyhyte produced?

Answer 17

1) rapid oxidation of iron II salts

Question 18

How is magnetite produced?

Answer 18

1) oxidation and dehydration of Fe(II) salts at pH >8

2) from ferrihydrite with Fe2+ ions at pH 9-10

Question 19

What happens to Fe3+ ions/what are they converted to and how?

Answer 19

Deprotonation to Fe(OH)^(3-x)_x

Question 20

What happens to Fe2+ ions/what are they converted to and how?

Answer 20

Oxidation and Deprotonation to Fe(OH)^(3-x)_x and Fe(OH)^(2-x)_x

Question 21

Which forms of iron oxides/hydroxides are strongly magnetic? What is the disadvantage of these compounds ?

Answer 21

Maghemite and magnetite are stongly magnetic (superparamagnetic) but have small SA, needed for adsobence capacity
(High SA = ferrihydrite)