Extraction of Li2CO3 from Zimbabwean petalite, from the Bikita deposit, was studied using
ammonium bifluoride (ABF) digestion at temperatures ranging from room temperature
to 600 oC, and gram quantities of ore. ABF digestion bypasses the conventional hightemperature
conversion of the mineral to β-spodumene before acid roasting. The process
reaction takes place at surprisingly low temperatures – even at room temperature with slurry
formation due to the release of water. Below the melting point of ABF, the main products
are LiF, AlF3, K2NaAlF6, and (NH4)2SiF6. (NH4)2SiF6 decomposes readily to form ammonia
and gaseous SiF4. At higher temperature, the products are cryolithionite (Li3Na3Al2F12) and
eucryptite (LiAlSiO4). The fluoride solids are not readily soluble in water and may be roasted
in sulfuric acid at relatively mild conditions for a few tens of minutes, then water leached,
with 99 % pure lithium carbonate easily recovered from the aqueous phase.The Fluorochemical Expansion Initiative (FEI).http://www.satnt.ac.zaam2022Chemical Engineerin
