Preliminary investigation on kinetics of zeolite a crystallization using optical diagnostics

Preliminary data concerning the monitoring in situ of the zeolite A crystallisation from clear solutions are reported. Experiments were performed at 60 and 70 °C with fresh and aged solutions having the following composition: 8.6Na 2O·0.18SiO 2·Al 2O 3·150H 2O. The formation of early phases in the crystallization process were followed using diagnostics such as dynamic light scattering (DLS), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The comparison of the available data seems to indicate the formation of a precursor phase (like gel) in the case of not aged solution. Conversely, crystallization 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 carded out. As far as the reproducibility test is concerned, the chemical system selected showed good results on a large number of tests.