Synthesis of nano-porous molecular sieve from some natural materials

Abstract

Zeolites due to their structures can be used as molecular sieves for purification of materials and solutions. Zeolites with PHI and SOD structure are so common and applicable for this purpose. Hydroxy sodalite and phillipsite are the more abundant members of zeolites which display good selectivity for very small molecules and some ions such as Sr, Pb, Zn, Cu and Rb. There is not any pure natural deposit of these zeolites and purify methods are not cost-effective. Therefore, introducing an effective method to prepare these zeolites is necessary. In this study, hydroxy sodalite and phillipsite have been synthesized respectively from clinoptilolite and volcanic ash at hydrothermal conditions in the presence of alkaline solutions. Mineralogical studies show that K, Na and Cl ions are necessary in SOD and PHI structure. The effect of K⁺ concentrations and temperature in the presence of constant value of Na⁺ and Cl^-are being considered as the variable parameters in the present experiment. NaCl used as source of Na⁺ and Cl^- ions. Alkaline solutions were prepared by using 2 to 12 grams KOH powder and synthesize mixture were heated at temperatures of 100 and 150˚C. Results of this study show that phillipsite is synthesized at 100 and 150˚C in all runs. Hydroxy sodalite is appeared just in 150˚C by using clinoptilolite as initial material. Analcime formed as by-product of volcanic ash phase transition at 150˚C.