Hydrothermal synthesis of zeolites from rhyolitic pumice of different geological origins

Abstract Twelve samples of rhyolitic pumice from widely different origins were subjected to zeolitization in standard hydrothermal conditions (solid/liquid ratio, 1 5 ; T , 95°C; reaction time, 5 h; alkaline solution 5 N NaOH). The Si Al ratio of the starting material was of special importance in that zeolites formed with Si Al ratios similar to or smaller than that of the parent material. Pumice with low SiO 2 Al 2 O 3 , and high Fe content, preferentially gave rise to zeolites with lower SiO 2 Al 2 O 3 ratio than in the case of lower Fe and higher SiO 2 Al 2 O 3 ratio.