LOW COST SYNTHESIS AND CHARACTERIZATION OF ZEOLITES FROM SILICON NATURAL SOURCES FOR ENVIRONMENTAL APPLICATIONS

Abstract

The synthesis of hierarchical zeolites for their future environmental application in the removal of heavy metals and pharmaceutics is presented. A low cost, abundant and renewable amorphous silica extracted from a waste of the Cuban agricultural industry, the rice husk, was employed as alternative silicon source for the synthesis. The effect of Si/Al ratio, aging time, used template and time and temperature of reaction, on the structural characteristics of the obtained material was investigated. The elemental, structural and morphological characterization of the ash and the zeolites was performed by XRD, SEM, EDS and TG. The SEM images of zeolites synthesized with Si/Al = 1 (serie I) show a uniform morphology - cubic of smoothed edge- characteristics of zeolite A, with mean particle size of about 0.5 μm. The diffraction patterns of the samples matched the reference peaks of NaA zeolite. The zeolites synthesized with Si/Al = 2 (serie II) have an octahedral morphology characteristic of the faujasite phase, with particle sizes of about 1 μm, and the diffraction patterns matched with that reported for X zeolite. The increase of the aging time and surfactant concentration slightly decrease the particle size, which is evidenced in the increase of the half-width of the diffraction peaks. The global results demonstrated that it is possible to synthesize A and X zeolites at moderate temperatures, short crystallization times, without seeding, and with a good purity starting from rice husk ash as silicon source.