Transformation of Kaolin to Kalsilite: Effect of KOH Concentration and Reaction Temperature

Abstract

Kalsilite was synthesized via a hydrothermal method using kaolin as a silica and alumina precursor and potassium hydroxide (KOH) as a potassium source. The effects of KOH concentration and reaction temperature were investigated. X-ray diffraction (XRD) and scanning electron microscope (SEM) analyses indicated that kalsilite was formed as a result of the hydrothermal reaction of kaolin at 190 °C in 0.75 M KOH for 24 hours. Higher KOH molarity was found to increase the crystallinity of the product while 190 °C was sufficient to convert kaolin to kalsilite. However, zeolite W was the dominant product at lower KOH concentrations and temperatures.