View source for Lunar Aluminum Production

Our satellite lacks of bauxite, therefore, anorthite will be used instead.<ref>http://www.permanent.com/l-minera.htm#aluminum</ref> [[Anorthite]] (CaAl<sub>2</sub>Si<sub>2</sub>O<sub>8</sub>) could be separed from [[Anorthosite]] with mechanical and chemical methods to produce [[Alumina]] (aluminium oxide, Al<sub>2</sub>O<sub>3</sub>). <ref> http://en.wikipedia.org/wiki/Anorthosite</ref>

There are several proposed methods to obtain aluminium (even those that doesn't require electrolysis). However, almost all include an importation of catalysts and/or reactants. It is true that reactants can be recycled but they limit the total output to the total amount of reactant present and to the speed that the process can recycle them. Another process would be [[Ion-sputtering]] to obtain other material and as a residue [[Aluminium]].
Aluminium is a strong reducing agent, therefore it cannot undergo a normal [[Reduction]] by carbon. <ref>http://en.wikipedia.org/wiki/Anorthite</ref>

== Proposed Anorthite Production Process ==

Anorthosite is a mix of [[Plagioclase]]s, [[Olivine]]s, and [[Pyroxene]]s. To separate the anorthite, anorthosite a must be grind. Then, magnets could be put in contact with the powder to separate everything from the non-magnetic anorthite.

The magnetic materials (even [[Ilmenite]], iron oxide, silica and magnesia) could be stored for production of [[Titanium]] and other metals.

== Proposed Alumina Production Process ==

On Earth aluminium is subjected to the Hall-Heroult process where bauxite undergoes the Bayer process to become alumina.

On the Moon [[Alumina]] could be produced from Anorthite by boiling the impurities (between 1500 ºC - 2000 ºC ). The resulting material would be calcium aluminate (CaAlO<sub>4</sub>). That can be leached in sulfuric acid. The following reaction would be:

CaAl<sub>2</sub>O<sub>4</sub> + 4H<sub>2</sub>SO<sub>4</sub> ==> CaSO<sub>4</sub> + Al<sub>2</sub>(SO<sub>4</sub>)<sub>3</sub> + 4H<sub>2</sub>O

Aluminium sulfate in hexadecahydrate form (Al<sub>2</sub>(SO<sub>4</sub>)<sub>3</sub>) is then separated from calcium sulphate (CaSO<sub>4</sub> + Al<sub>2</sub>(SO<sub>4</sub>)<sub>3</sub>) by filtering and from water by evaporation (and then recovered).

Finally Alumina is obtained by roasting the aluminium sulfate releasing S<sub>2</sub>.<ref>http://www.moonminer.com/Lunar_Aluminum.html</ref>

== Future Hall-Heroult Adaptation ==

Alumina is dissolved in molten cryolite ([[Sodium]] hexafluoroaluminate, Na<sub>3</sub> AlF<sub>6 </sub>) around 1400 ºC. This mix is electrolyzed to separate two byproducts: aluminium and CO<sub>2</sub>.

Pure alumina can be electrolyzed, but, it melts around the impractical 2000 ºC without the addition of cryolite. It is not known how refractory containers are going to be made on the Moon, neither if the Hall-Heroult process can be adapted with or without the importation of fluorine for the cryolite.<ref>http://en.wikipedia.org/wiki/Hall-H%C3%A9roult_process</ref>

== Subchloride Process ==

Chlorine and carbon would be imported from Earth. The alumina is then carbochlorinated (carbonated and chlorinated) to yeild AlCl<sub>3</sub> which is electrolyzed. Electrolysis of AlCl<sub>3</sub> does not consume the precious lunar carbon electrodes as does conventional Hall-Heroult electrolysis of alumina.  The carbochlorination byproduct CO<sub>2</sub> must be [[recycled]]. <ref>http://www.moonminer.com/Lunar_Aluminum.html</ref>

== Proposed Carbothermal Reduction ==

Carbon would be imported from Earth. Then the alumina would be mixed with silica and carbon and melted near 2000 ºC. An aluminium-silicon alloy will form. This could be separated by cooling the Al-Si mixture to 700 ºC-1000 ºC. and the silicon will solidify and settle out of the melt. CO<sub>2</sub> must be recovered and carbon recycled. <ref>http://www.moonminer.com/Lunar_Aluminum.html</ref>

== Other Electrolysis Methods ==

There are two process that doesn't require importation on Earth.

The first one is just boil the anothite and to obtain gases at different temperatures, first silica glass then calcium aluminate. With more temperature we obtain alumina and calcium oxide the temperature is reduced and the gases condensed and the liquid is electrolyzed to obtain aluminium, calcium and oxygen (all of them pure). This would require temperatures over 2560 ºC, very efficient super-refractories and a tremendous input of energy. <ref>http://www.moonminer.com/Lunar_Aluminum.html</ref>

The second is not going that far with just electrolyzing anorthite at about 1600 ºC. The other byproduct would be calcium oxide.<ref>http://www.moonminer.com/Lunar_Aluminum.html</ref>


== See Also ==

[[Aluminium]]



== References == 
<references/>