Iron Beneficiation
Beneficiation is the process of increasing the concentration of a valuable component of an ore.
Native iron particles exist in lunar soil in fairly large quantities. They come from nickel-iron meteorites, which pulverise themselves and the lunar rocks which they impacted. Hence the iron particles are tiny (fine grained) and well mixed into the fine dust of the lunar regolith. But they are chemically distinct, and in a pure metal state therefore very little chemical processing is needed to separate the metal particles from the rocky dust particles.
Contents
Magnetic separation
Iron particles are highly sensitive to a magnetic field. There is a similar process on earth for extracting iron ore from sand dunes. The method involves passing the sand and dust over a magnetically charged rotating cylinder. The particles with some iron stick to the drum and are scraped off on the other side. 98% of the lunar soil would simply passes through and not interact with the cylinder.
Using several passes you can refine the result to about 80% pure elemental nickel-iron with the remainder as various oxides of iron-titanium. Melting this mixture with some Anorthite will cause separation the because the oxides are lighter and prefer to form a slag on top of the molten iron.
The power requirements of this mechanical separation are quite modest. A robotic unit not much bigger than a desk could conceivably roam the lunar surface extracting iron dust from the top 10 centimeters. At a concentration of 1/2% this would yield about a kilogram of iron per square meter or 1,000 tons per km2. This is a very high yield of usable material close to any lunar facility.
liquid phase separation
The density of iron is much higher than the rocky dust. Therefore, it is possible that the different particles could be separated by mixing lunar regolith into a suitable liquid, then allowing the rocky dust (mostly Basalt or similar) to float and the iron particles to sink.
density of iron is 7.86 g/cm3
density of basalt is 2.9 g/cm3
Need a liquid which has a density in between, then the iron will sink and the basalt will float.
Possible liquids:
Room Temperature
Bromine = 3.1028 g/cm3
Cryogenic
None identified to date.
High Temperature
(Basalt melts at about 1900 deg F) (Iron melts at 2800 deg F)
- Iodine pentafluoride Density and phase: 3.250 g cm−3 liquid, Melting point 9.43°C (282.58 K)
- Molten Tin at 6.99 g·cm−3 (melting point 505.08 K (231.93 °C, 449.47 °F))
- Molten salts perhaps
