DEVELOPMENT OF AMMONIUM-SAPONITES FROM GELS WITH VARIABLE AMMONIUM CONCENTRATION AND WATER-CONTENT AT LOW-TEMPERATURES

Ammonium-saponite is hydrothermally grown at temperatures below 300-de grees-C from a gel with an overall composition corresponding to (NH4)0 .6Mg3Si3.4Al0.6O10(OH)2. The synthetic saponite and coexisting fluid h ave been characterized by means of X-rav powder diffraction, X-ray flu orescence. Induced Coupled Plasma-Atomic Emission Spectroscopy, thermo gravimetric analysis, transmission electron microscopy, CEC determinat ion using an ammonia selective electrode, and pH measurement. In the c rystallization model developed, crystallization started with the growt h of individual tetrahedral layers with an aluminum substitution not c ontrolled by the Al(IV)/Al(VI) ratio in the gel and hydrothermal fluid , on which the octahedral Mg layers can grow. During the synthesis, in dividual sheets stacked to form thicker flakes while lateral growth al so took place. The remaining Al(VI) partly replaced ammonium as the in terlayer cation.