Controlled addition of aged mother liquor to zeolite NaA synthesis solutions

A systematic study was conducted in which aged aluminosilicate solutions, which were known to produce zeolite NaA at elevated temperatures, were added to fresh unaged solutions having the same composition to attempt to control the number of crystals that ultimately formed at synthesis temperatures. The principle parameters in this study were the amount of aged solution added to the fresh solution and the duration of aging of the former solution. Results showed that additions of aged solutions resulted in the formation of a population of crystals that in some cases was clearly discernible from the population nucleated by the fresh solution. It was apparent that nuclei, or some nucleation catalyst, formed while aging the aluminosilicate solution at room temperature and began to grow once that solution was introduced into the fresh solution and heated. Nucleation in the fresh solution could be suppressed with sufficient addition of aged solution, which to our knowledge has not been demonstrated previously. Agglomeration occurred early in the process with excessive amounts of added aged solution. Zeolite NaX could be precipitated from a different aluminosilicate solution using the same aged solution that precipitated zeolite NaA in the standard solution. (C) Elsevier Science Inc. 1997.