Aluminum extraction from Feldspar

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Aluminum extraction from Feldspar
Al

• by Robert Dyck
• Ardeco Consulting Ltd.

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Traditional ore

• 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 arent going to find a rainforest on Mars.

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MGS-TES
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Plagioclase feldspar
Anorthite CaAl2Si2O8
Bytownite 70-90 anorthite, 10-30 albite
Labradorite 50-70 anorthite, 30-50 albite
Andesine 30-50 anorthite, 50-70 albite
Oligoclase 10-30 anorthite, 70-90 albite
Albite NaAlSi3O8
Orthoclase feldspar
Microcline KAlSi3O8
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Traditional smelting

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

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Bayer process

• Aluminum silicon oxides dissolve in alkali NaOH
• Iron oxide and others dont (red mud)
• Solution drawn off, CO2 blown through
• Aqueous CO2 ? carbonic acid, neutralizes alkali
• AlOH precipitates
• CO2 gas released
• NaOH recycled
• Calcination
• 2 AlOH O2 ? Al2O3 H2O

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Hall-Héroult process

• Alumina is not conductive, cryolite is catalyst
• Na3AlF6 dissociates into 3 Na AlF63-
• 2 Al2O3 ? 4 Al 3 O2
• Some carbon of the anode will form CO2
• Anode regeneration RWGSH2 CO2 ? H2O COH2
  CO ? H2O C
• Bake soot under pressureto form graphite
• recover hydrogenreverse fuel cell2 H2O ? 2 H2
  O2

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Bytownite to Alumina

• Bytownite is an alkali feldspar so an alkali like
  sodium hydroxide will not dissolve it.
  Hydrochloric acid will.
• 1.8 Al3, 0.8 Ca2, 0.2 Na, 2.2 SiO2
• Ammonia will raise pH, and evaporate when
  released
• Ammonium chloride pH 5.0 _at_ 10
• AlOH will between pH 4.5 and 9.2
• AlOH can be calicinated 2 AlOH O2 ? Al2O3
  H2O
• NaCl, KCl, CaCl2 are salts, they will remain in
  solution
• Silica scale is a problem in the Bayer processit
  will be more so with bytownite

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Side reactions ammonium chloride

• NH3 H2O ? NH4(aq) OH-(aq)
• NH4 (aq) Cl-(aq) ? NH4Cl(s)
• Ammonium chloride can be
• contained with a spray scrubber

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Acid Recycling

• Working solutions have to be recycled.
• Hydrochloric acid will have to be remade from
  salt.
• Electrolysis across a membrane
• 2 NaCl 2 H2O ? 2 NaOH H2 2 Cl
• H Cl ? HCl
• K Ca will not cross membrane
• KOH CaOH in diaphragm cell

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Precipitating Silica

• SiO2 or Si(OH)4