Thermal study of the hydrocalumite–katoite–calcite system
Alejandro Jiménez, V. Rives, Miguel Á. Vicente
Abstract
Hydrocalumite (Ca2Al(OH)6Cl·2H2O) samples were prepared by the coprecipitation method, using Al3+ obtained from an aluminum slag, extracted in NaOH solutions and purified removing silica by precipitation with HCl. Hydrocalumite aging was assisted by microwave irradiation, and carried out under different temperatures. Very pure hydrocalumite was obtained under certain conditions, but samples impurified with katoite (Ca3Al2(OH)12) and calcite (CaCO3) were obtained in other cases. The thermal decomposition of hydrocalumite is complex and is not completely elucidated, compounds such as Ca12Al14O33 (mayenite), Ca(OH)Cl and CaO have been proposed. The thermal characterization of this system was studied, also considering samples impurified with katoite and calcite, as a valuable and rapid method for identifying these phases.