Hydrothermal reaction of K‐feldspar powder in NaOHCa (OH)2 mixed medium

Abstract

AbstractThe hydrothermal reactions between K‐feldspar powder and NaOHCa (OH)2 mixed alkaline medium at 240°C were investigated. The effects of Na ratio (xNa, Na2O/(Na2O + CaO) in mole) on the phase and composition change in solid products were explored in detail. Results showed that increase in xNa led to the orderly formation of compounds following the sequence of CaOSiO2H2O → Na2OCaOSiO2H2O → Na2OAl2O3SiO2H2O, and K+ was accessible into solution after reaction. The new products after reaction was tobermorite, pectorite, nepheline hydrate, analcime, and hydroxycancrinite, depending on different xNa. The hydrothermal reaction was deduced to be a coupled dissolution and reprecipitation process, which was governed by the chemical equilibrium with the change in solution chemistry.