Al
by Robert Dyck
Ardeco Consulting Ltd.

Aluminum ore on Earth is bauxite
Bauxite is formed by tropical rain forests:
• igneous minerals weathered by water
• tropical ecosystem depletes their needs
 iron oxide, silicon dioxide, aluminum oxide
We aren’t going to find a rainforest on Mars.

Microcline1
Andesine
Bytownite
Bronzite
Augite1
Augite3
Serpentine
Gypsum
Calcite
Dolomite
Kaolinite
Illite
Surface type 1
Model-derived modes (%)
5.8
22
21.5
5.4
12.4
11.3
4.8
1.8
3.7
0.9
2.4
9.9
RMS error
(emissivity) = 0.179
Surface type 2
Microcline1
Bytownite
Actinolite
Muscovite
Bronzite
Augite1
Forsterite
Gypsum
Dolomite
Fe-smectite
Illite
Obsidian Glass
Model derived modes (%)
5.7
27
6.1
5.7
1.6
8.4
2.9
4.5
3.3
9.2
2.2
22.8
RMS error
(emissivity)= 0.089

Anorthite
Bytownite
Labradorite
Andesine
Oligoclase
Albite
CaAl
2
Si
2
O
8
70-90% anorthite, 10-30% albite
50-70% anorthite, 30-50% albite
30-50% anorthite, 50-70% albite
10-30% anorthite, 70-90% albite
NaAlSi
3
O
8
Microcline KAlSi
3
O
8

• Bayer process extracts/purifies alumina from ore
– chemical
• Sodium hydroxide, carbon dioxide
• Hall-Héroult process de-oxidizes alumina into metal
– electrolysis
• cryolite

• Aluminum & silicon oxides dissolve in alkali NaOH
• Iron oxide and others don’t (red mud)
• Solution drawn off, CO
2
“blown through”
• Aqueous CO
2
→ carbonic acid, neutralizes alkali
• AlOH precipitates
• CO
2 gas released
• NaOH recycled
• Calcination:
2 AlOH + O
2
→ Al
2
O
3
+ H
2
O

• Alumina is not conductive, cryolite is catalyst
• Na
3
AlF
6
• 2 Al
2
O
3 dissociates into 3 Na + AlF
6
3-
→ 4 Al + 3 O
2
• Some carbon of the anode will form CO
2
• Anode regeneration: RWGS
H
2
H
2
+ CO
2
→ H
+ CO → H
2
2
O + CO
O + C
• Bake soot under pressure to form graphite
• recover hydrogen reverse fuel cell:
2 H
2
O → 2 H
2
+ O
2

• Bytownite is an alkali feldspar so an alkali like sodium hydroxide will not dissolve it. Hydrochloric acid will.
• 1.8 Al 3+ , 0.8 Ca 2+ , 0.2 Na + , 2.2 SiO
2
• Ammonia will raise pH, and evaporate when released
• Ammonium chloride pH 5.0 @ 10%
• AlOH will between pH 4.5 and 9.2
• AlOH can be calicinated: 2 AlOH + O
2
• NaCl, KCl, CaCl
2
→ Al
2
O
3
+ H
2
O are salts, they will remain in solution
• Silica scale is a problem in the Bayer process it will be more so with bytownite

NH
3
NH
4
+
+ H
2
O ↔ NH
4
+ (aq) + OH (aq)
(aq) + Cl (aq) ↔ NH
4
Cl(s)
Ammonium chloride can be contained with a spray scrubber

Working solutions have to be recycled.
Hydrochloric acid will have to be remade from salt.
Electrolysis across a membrane:
2 NaCl + 2 H
2
O → 2 NaOH + H
2
H + Cl → HCl
+ 2 Cl
K + & Ca + will not cross membrane
KOH & CaOH in diaphragm cell

SiO
2 or Si(OH)
4