How would you be able to extract aluminium and iron in the moon for example? Is there some electrolytic technique that does not use carbon?
Don Sadoway of MIT has led a team developing molten oxide electrolysis methods for use on the Moon. In 2008 he received a patent for a process using an anode made of iridium and a cathode of tungsten or molybdenum. This apparatus will produce a puddle of molten metals at the cathode, placed at the bottom of a crucible, and bubbles of oxygen around the anode at the top. The metals will be a mixed alloy of all the metals present in the feedstock.
Selection of favorable feedstock from the lunar highlands, comprised mostly of anorthite, CaAl2Si2O8, allows the alloy produced to be mostly aluminum and silicon.
More recently, Sadoway's team have developed an anode made of chromium and iron for use in producing iron on the Moon. This process also has potential application on Earth, as a method of steel production that doesn't release carbon gases as a by-product.
For iron production, other methods have also been investigated. Elemental iron is present in lunar regolith at a level of up to 1% in the maria. Simply passing magnets through a stream of the smallest regolith particles could produce a feedstock very high in iron, but with substantial contaminants.
Processing of ilmenite, FeTiO3, with hydrogen produces water, iron, and titanium dioxide. Concentrations of ilmenite in the maria can be around 10%. Reactors to process ilmenite with hydrogen have been investigated principally as a means of producing oxygen, but iron is another product.