Transformation of Calcite CaCO3 to Fluorite CaF2 by Action of KF Solution

Abstract

Abstract Conversion of microcrystalline calcium carbonate powder to fluorite by reacting it with potassium fluoride solution is studied. The reaction occurs at room temperature and yields a white flowing powder. Rhombohedral CaCO3 microcrystals are replaced by an ensemble of CaF2 nanoparticles sized ca. 20 nm, which in part fill in the volume of the precursor microcrystals. The product calcium fluoride contains about 2 mol% KF. KCaF3 is not produced by the reaction, and KCaF3 is a high-temperature compound stable above 500 оС.