Influence of pH, starting material and synthesis duration on kaolinite crystallinity

Kaolinites were synthesized at 220 degrees C, for 2 to 182 days, at pH 5 an d 1, from an amorphous gel and from a gel partly transformed into kaolinite . Whatever the starting material and the run time, the final pH of synthesi s and the kaolinite crystallinity are inversely correlated. For a given fin al pH and for the studied temperature, the increase of the synthesis durati on improves the kaolinite crystallinity, which however is stabilized progre ssively and reaches an optimum after 3 months. ((C) Academie des sciences / Elsevier, Paris.).