Zeolite Synthesis and Steam: Preliminary Data Using Coal Fly Ash As Raw Material

In this work, vapor-phase crystallization method (VPC) was used to form sodalite from coal fly ash, a waste material obtained from burning coal in thermoelectric power plants. During the experiments, raw material was contacted only with steam from distilled water heated at 45, 60 and 90 °C. The preliminary results indicated that VPC treatment controls the zeolite synthesis through an intermediate mechanism between solid-state transformation and hydrothermal synthesis. The increasing sodalite-cancrinite interzeolite formation up to 90 °C confirms this mechanism. In detail, the data show the sodalite crystallization at 45 °C. The amount of this newly formed phase increases up to 60 °C, showing a better defined shape at this temperature. VPC treatment at 90 °C determines a progressive sodalite transformation into cancrinite and/or nosean. Compared to other conventional methods for zeolite synthesis, the steam assisted process results in less liquid waste production thus offering many advantages for the environment.