An investigation was conducted to find out formation and is mechanism of kaolinite from pyrophyllite under hydrothermal conditions. First, a pyropyllite sample from the Heenam district, Korea, was activated by heat-treating at 400℃ for 3 hrs. The kaolinite powder was successfully obtained by subjecting the dried feedstock to autoclaving at 200℃, 15atm, pH<1 for 5days with addition of 17.4mol/l AlCl3. Evidently, the AlCl3 addition as a mineralizer strongly promoted incorporation of Al3+ ion into pyrophyllite structure which was subdequently converted into kaolinite. It also indicated that the formation of octahedral feed solution. The final pH of the solution was decreased to ∼0.3. The transformation reaction was not noticeably accelerated when 10wt% natural kaolinite was added as the seeds, suggesting that the transformation was not reconstructional, but substitutional type.
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