Beiträge zur Chemie des Bauxitaufschlusses. I. Untersuchungen im System Na₂OCaOAl₂O₃TiO₂H₂O bei 100°C unter Normaldruck

Abstract

Es wurde untersucht, welche kristallinen Verbindungen sich in natronalkalischen Aluminatlösungen aus TiO2 und Ca(OH)2 bei 100°C unter Normaldruck bilden. Bei niedrigen Alkalikonzentrationen entsteht das Calciumaluminat 3 CaO · A12O3 · 6 H2O. Zwei verschiedene Calciumtitanate, darunter Perowskit CaTiO3, lassen sich bei mittleren Alkaligehalten der Lösungen nachweisen, während aus hochalkalischen Lösungen das Natriumtitanat Na2TiO3 kristallisiert.

Kinetics and Mechanisms of the Hydrothermal Crystallization of Calcium Titanate Species

“…The reaction products (CaTiO 3 or Ca(TiO 2 ) 2 (OH) 2 ) were specific to the type of calcium phase used and no overlap of products was observed. This is in contrast with earlier published works which report a mix of CaTiO 3 and Ca(TiO 2 ) 2 (OH) 2 in reaction products. ,,, This study illustrates the selectivity of CaCO 3 in promoting exclusive CaTiO 3 formation. A natural follow on from this study would be to examine the reaction using mixtures of CaCO 3 and hydrogarnet and observe phase precipitation.…”

“…Shultze-Rhonhof and Winkhaus reported formation of CaTiO 3 and a second calcium titanate: Ca(TiO 2 ) 2 (OH) 2 (the mineral kassite), following the reaction of Ca(OH) 2 and TiO 2 (anatase) in alkaline sodium aluminate solution (2.6−16 M NaOH) for 20 h at 100 °C. This study was continued at 100−275 °C and the increased temperatures were found to favor CaTiO 3 stability.…”