Regeneration of Aluminum Fluoride From Pure Bath

Commercial aluminum fluoride production is currently dependent on fluorspar, listed by the USGS and EU as a critical mineral, as a feedstock. Surplus pure bath, continuously generated during aluminum electrolysis from a reaction between the sodium oxide present in alumina and the molten cryolitic bath, presents an option as an alternative fluoride source for the production of aluminum fluoride. Solidified cryolitic bath is composed of numerous different fluoride phases including cryolite, chiolite, calcium cryolite, and neighborite. An elevated temperature, solid-state reaction between aluminum sulfate and solidified cryolitic bath is capable of converting the fluoride components of the bath to aluminum fluoride and sodium, calcium, and magnesium sulfates. The sulfates can then be separated from the aluminum fluoride fraction through a sequence of aqueous washes. Due to the low aqueous solubility of aluminum fluoride, this results in a solid fraction with purity comparable to commercially available smelter grade aluminum fluoride.