Hydrothermal synthesis of zeolites from low-cost natural silica-alumina sources

Abstract Sardinian perlite and Sicilian tuff have been subjected to hydrotermal synthesis in NaOH media. The influence of the nature and chemical composition of the starting material, pH and concentration of the mineralizing agent (NaOH) and reaction temperatures and time on the zeolitization process is discussed and compared to the performance of Lipari pumice. The chemical composition, in particular the SiO 2 Al 2 O 3 ratio, of volcanic glasses is the most important factor in the dissolution process leading to formation of zeolitic products.