Synthesis and mineralogical characterization of calcium ferrate hydrates and their application as reservoir minerals in waste dumps

摘要

The objective of the study was to present basic chemical and mineralogical data on lamellar calcium ferrate hydrates 3CaO*Fe_2O_3*Ca(X_2,Y)*nH_2O for application in cement chemistry or as reservoir minerals for immobilization of hazardous ions. Crystallization in lime stabilized waste mixtures is leading to an intimate inter growth with the other non reactive particles. Additionally pollutants in the mixture can be immobilized by incorporation in the crystal structure of calcium ferrate hydrates. In a first step of the presented investigation, the relevant anions and cations were selected. They are representing the bulk chemical composition in mixtures of red mud and calcium rich waste products. After synthesis of 3CaO*Fe_2O_3*Ca(X_2,Y)*nH_2O with anionic components X = Cl~-, Br~-, I~-, NO_3~- and with Y = SO_4~(2-), CrO_4~(2-), HBO_3~(2-) the calcium ferrate hydrates were characterized by XRD, thermal and chemical analysis. Finally solid solution or formation of intermediate phases were studied in selected binary systems with substitution of cations or anions.