A and X-type zeolites synthesised from kaolinite at low temperature

A commercial Chinese well crystalline kaolinite (KCh) and a poorly crystalline kaolinite (KGa-2) from the Source Clay Repository of The Clay Minerals Society were used, after fusion with NaOH, to synthesise zeolite by hydrothermal activation. The experiments were performed at temperatures ranging from 25 to 60 °C, for 96 h, in distilled water. A large amount of X-type zeolite was crystallised from KCh at 25 °C whereas its crystallisation from KGa-2 starts at 35 °C. A-type zeolite is formed using both source materials and it is the only synthetic product detected at 25 °C. The presence of illite/mica and quartz in KCh determines the different behaviour of the two starting clay minerals.