Study of K‐Feldspar and Lime Hydrothermal Reaction at 190 °C: Phase, Kinetics and Mechanism with Reaction Time

Abstract

AbstractAn artificial silicate composite material prepared by the hydrothermal reaction of K‐feldspar and lime, showed excellent performance in remediating the soil. To elucidate the physicochemical properties of the artificial silicate composite material, K‐feldspar and lime were reacted in mild hydrothermal conditions (T=190 °C; P∼12.4 atm; t=0∼36 h). The hydrothermal product was systematically investigated using various techniques such as X‐ray powder diffraction (XRPD), scanning electron microscopy, and inductively coupled plasma‐optical emission spectrometry (ICP–OES). Quantitative evaluation of the extent of reaction by ICP–OES and XRPD methods enabled the analysis of hydrothermal evolution with prolonged time. The hydrothermal treatment of K‐feldspar with lime exhibits complex product phases, including leftover K‐feldspar, calcium hydroxide, calcite, grossular, tobermorite, alpha‐dicalcium silicate hydrate, potassium carbonate, bütschliite, and amorphous calcium silicate hydrate. The analysis of the reaction reveals that the K‐feldspar dissolution showed a clear transition, with the hydrothermal reaction beginning to slow down after 20 h. The slowdown of the K‐feldspar dissolution was essentially caused by different reaction kinetics and mechanisms before and after 20 h. The study yields vital and valuable insights into comprehending the chemistry and mineralogy of the artificial silicate composite material and producing a multielement reservoir from potassium‐rich rocks.