Summary
Molten salts are ionic compounds of (usually) alkali metal or alkali earth positive ions and halogen ions or polyatomic negative ions. They have relatively high melting points. A commonly encountered subcategory are the Molten Alkali Salts (MAS) compounds formed from alkali metal atoms and anions. Familiar alkali salts include sodium chloride (table salt), potassium carbonate (potash), and alkali sulfates, nitrates and phosphates. When they are solid, they are non-conducting, crystalline and usually white or transparent. They tend to have high melting points - on the order of 1000C - and they tend to be relatively non-reactive or chemically stable. When they melt, they become very good electrical conductors, good heat transfer fluids, and have high heat storage capacity.
Mixtures of salts often form a “eutectic” mixture - a particular combination of two or more salts with a minimal melting point, lower than the melting point of the individual salts alone. Mixtures of the subject salts that differ from the precise eutectic composition will form a melt that has the eutectic composition together with solid phase crystals of one or more ingredients that are present in excess.
Molten alkali salts have potential applications in CDR for the formation of biochar, and for direct air capture.
Variations
use in biochar
use in DAC
“low melting”: https://www.sciencedirect.com/science/article/abs/pii/S0927024819304362
Exemplars
Molten Salts are used in solar power towers, of which there are several demonstration projects, however none of them have direct CDR applications associated at this time. Examples:
http://www.emsp.uevora.pt/
http://www.solarreserve.com/en/global-projects/csp/crescent-dunes
More Information
Need references, data, etc.