Chapter 1: Physical Metallurgy of Aluminum

Question 1

How much of earth’s crust is aluminum?

Answer 1

8.2%

Question 2

Aluminum is the ____ most abundant element in the earth’s crust

Answer 2

3rd

Question 3

Name the two common aluminum minerals

Answer 3

Alumina (Al2O3)
Alum (KAl(SO4)2.12H20)

Question 4

Which common ore contains hydrated alumina?

Answer 4

Bauxite (Al2O3.2H2O)

Question 5

Why was there no aluminum metal before the 1880s?

Answer 5

Extraction of the oxide was difficult from the ore
Reduction of the oxide was very difficult and expensive

Question 6

What are the charges of the electrodes in an electrolytic cell?

Answer 6

Cathode - negative
Anode- positive

Question 7

What is the movement of charges in an electrolytic cell

Answer 7

Cations move towards the cathode
Anions move towards the anode

Question 8

What is the name of the electrolytic process by which aluminum is recovered?

Answer 8

The Hall-Heroult process

Question 9

What does the Hall-Heroult process involve?

Answer 9

It involves the electrolysis of alumina dissolved in an electrolyte called cryolite (Na3AlF6)

Question 10

What is the Bayer process?

Answer 10

It is a process designed to extract alumina from bauxite via caustic soda (NaOH) leach

Question 11

What are the steps of the Bayer process?

Answer 11

1. Pressure Leaching
2. Filtration
3. Precipitation
4. Filtration
5. Evaporation

Question 12

Purification (filtration) step of Bayer process

Answer 12

Ore is placed in caustic soda solution
Sodium aluminate (NaAlO2) is produced
Clay and other impurities filtered out

Question 13

Reprecipitation step of Bayer process

Answer 13

Aluminate is reprecipitated by adding H+ to it

Question 14

Calcination step of Bayer process

Answer 14

Calcination in rotary kilns or fluidized beds
Hydrated aluminum oxide is converted into alumina

Question 15

What are the anodes and cathodes in a Hall-Heroult cell?

Answer 15

Cathode: Iron Cell Wall
Anode: Carbon

Question 16

What is the Cathode reaction in the Hall-Heroult cell?

Answer 16

Aluminum ions are reduced to the metal at the cathode

Question 17

What is the Anode reaction in the Hall-Heroult celll?

Answer 17

Oxygen is liberated at the anode, also producing CO, CO2, and fluorocarbons

Question 18

Cathode reaction in Hall-Heroult

Answer 18

4Al + 12e = 4Al

Question 19

Another reaction in Hall-Heroult

Answer 19

3C + 6O = 3CO2 + 12e

Question 20

Overall reaction of Hall-Heroult Process

Answer 20

2Al2O3 + 3C = 4Al + 3CO2

Question 21

How pure is electrolytically refined aluminum?

Answer 21

about 99% pure
impurities of Cu, Si, and Al2O3 are still present

Question 22

How much aluminum can you produce with 3.5-4.0 tonnes of bauxite?

Answer 22

1.0 tonnes of aluminum (1.95 tonnes of alumina)

Question 23

How much anode coke is required for 1 tonne of aluminum?

Answer 23

0.5 tonnes of anode coke

Question 24

How much electricity is needed for 1 tonne of aluminum produced?

Answer 24

13 000 kWh
energy intensive process
plants are cost effective at large capacity

Question 25

What is the aluminum world production?

Answer 25

60 M tonnes

Question 26

What is Canada’s rank for aluminum production?

Answer 26

It is 4th in the world for aluminum production

Question 27

What are some properties of aluminum?

Answer 27

• Light
• Conductive
• Effective heat conductor
• Good corrosion resistance
• Highly formable
• Can be very strong when alloyed
• Can be very reflective

Question 28

Why is aluminum often used for transmission lines if it is less conductive than copper?

Answer 28

Because of it’s light weight

Question 29

Major uses of aluminum

Answer 29

• Construction
• Furniture
• Containers and packaging
• Car bodies
• Aircraft fuselage
• Engine blocks

Question 30

What is aluminum’s forecast for use in the automotive industry?

Answer 30

• Lightweight construction will be necessary for EVs, requiring more aluminum
• This will also reduce CO2 emissions and increase vehicle fuel economy