Half-decomposition of salt-bearing dolomite

Half-calcined dolomites (HCDs) have been widely used in environmental remediation, medicine, and construction. However, advanced calcination technologies are required to modify their microstructure and thus improve their working performance. Herein, we investigated the effects of a variety of inorganic salts on the decomposition of dolomite based on thermogravimetric, compositional, and morphological analysis. The thermogravimetric data showed that certain salts significantly lowered the half-decomposition temperature of dolomite, which included LiCl, CaCl₂, MgCl₂, AlCl₃, LiNO₃, KNO₃, K₂CO₃, Li₂CO₃, Li₂SO₄, Na₃PO₄, and K₃PO₄. Compositional analysis demonstrated that only half-decomposition occurred when salt-bearing dolomite was calcined at a temperature of 723-923 K, leading to the formation of CaO-free HCDs composed of periclase and Mg-calcite having a Mg level of 2.0-10.5 mol%. Morphological analysis showed that porous HCDs were feasibly obtained by calcining salt-bearing dolomite at 723-923 K. MgO coarsening occurred at a temperature above 873 K, but it could be avoided by controlling the calcination time. The mechanism of salts may be related to the heterovalent doping effect, which may lead to an increase in the concentration of vacancies in the dolomite lattice.