Phase equilibrium simulation and optimal experimentation for the hydrothermal alkali treatment of Rb-rich microcline

Abstract

The hydrothermal alkaline decomposition of Rb-rich microcline was systematically investigated using KOH and Ca(OH) 2 as combined additives. By integrating quantitative analyses of liquid-phase composition with crystallographic evolution of solid products, this study addresses three central aspects of the KAlSi 3 O 8 –KOH–Ca(OH) 2 –H 2 O system: reaction kinetics, process optimization, and thermodynamic partitioning behavior of major and trace elements. Under optimized conditions, potassium and rubidium extraction efficiencies reached 93.0% and 90.56%, respectively. Tobermorite (Ca 5 Si 6 O 16 (OH) 2 ·4H 2 O) was identified as the dominant solid-phase product. These results demonstrate that the coupled KOH–Ca(OH) 2 hydrothermal system enables efficient potassium recovery while simultaneously enriching rubidium in the alkaline solution, providing a potential pathway for the integrated utilization of feldspar resources.