Oxygen Extraction Pilot Plant
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Processes for Getting Oxygen on the Moon

Larry Friesen

There are about ten major oxides/silicates among lunar minerals. This is a list of seven possible extraction techniques, with a few comments about some of the techniques. Of course, this should not be considered an exhaustive list; other techniques may also exist.

1. Hydrogen reduction of ilmenite

This has been the most publicized and researched, perhaps because (on first examination, at least), it looks easy to do.

However, it only retrieves a small portion of the oxygen bonded in the lunar regoltith. Illemite also only contains iron and titanium, so the scope of metal production as a spinoff is limited.

2. Hydrogen sulfide reduction

Although the yield is greater than with the hydrogen reduction, H2S is difficult to work with.

3. Carbothermic technique

This reduces only iron and titanium. Iron is only ~ 8-9% of the soil by weight.

4. Carbonate - oxygen

This reaction is quite complex, but has a low yield.

5. Flourine exchange

This is an attractive process, which can extract all metals and oxygen. The metal flourides can be sorted and processed.

However, flourine is notorious for being nasty to handle. As a result, if the oxygen is to be used for breathing, the oxygen must be very thoroughly cleansed.

There is a possible source for flourine from lunar apatite. Apatite also provides phosphorous, if phosphorous is needed for any purpose.

6. Chlorine exchange

Theis process is somewhat similar to flourine exchange, with the exception that chlorine only reacts with three or four of the oxides.

7. Electolytic reduction with NaOH

This process also extracts all of the oxygen. It also extracts all of the metals, albeit as a mixed slag.

On the other hand, building an inventory of sodium is required. Also needed are nickel electrodes, which are available from meteoritic particles in lunar soil. Electrode consumption may also be a problem.

Oxygen Extraction Pilot Plant

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