A preliminary investigation on kinetics of zeolite - A crystallisation using optical diagnostics

Preliminary data concerning the monitoring in situ of the zeolite A crystal lisation from clear solutions are reported. Experiments were performed at 6 0 and 70 degrees C with fresh and aged solutions having the following compo sition: 8.6Na(2)O0.18SiO(2)Al(2)O(3). 150H(2)O. The formation of early phas es in the crystallisation process were followed using diagnostics such as d ynamic light scattering (DLS), X-ray diffraction (XRD) and scanning electro n microscopy (SEM). The comparison of the available data seems to indicate the formation of a p recursor phase (like gel) in the case of not aged solution. Conversely, cry stallisation in aged solution seems to proceed without intermediate phases. At the same time, an investigation on the kinetics aspects of the zeolite A crystallisation was carried out. As far as the reproducibility test is co ncerned, the chemical system selected showed good results on a large number of tests. (C) 2000 Published by Elsevier Science S.A.