New hydrothermal route for the synthesis of high purity nanoparticles of zeolite Y from kaolin and quartz

Abstract

Reducing the activation temperature of kaolin for the synthesis of zeolites and other materials is a not only cost-effective but also green strategy. Hydrothermal alkaline activation (HAA) has been proposed as an effective technique for replacing the traditional high-temperature calcination route. However, one major obstacle to the exisiting HAA routes for the synthesis of zeolite Y is that the required addition of quartz leads to the formation of the acid insoluble analcime, resulting in an inefficient use of kaolin ores. In this study, a systematic investigation has been performed to develop a new HAA route for avoiding acid-insoluble aluminosilicates. Kaolin and quartz (KQ) as the sources for this new HAA route were then used to form hydroxycancrinite, which is readily dissolved in HCl solution and then neutralized by using the recycled alkali solution to form a uniform silica-alumina gel. The uniform gel promises the crystallization of zeolite Y with high purity and controllable morphologies and grain sizes, including nanoparticles. In particular, zeolite Y crystallized from the new HAA route depends on the SiO2/Al2O3 ratios of the starting materials but is independent of the types of the starting materials, i.e., irrespective of chemical reagents or raw minerals. Therefore, our work opens a new way for the synthesis of other mesoporous and macroporous materials e.g. aerogel, using low-cost natural kaolin and quartz in comparison with the conventional technique requiring expensive chemical reagents.