Síntese de zeólitas a partir de perlita e diatomita como fonte alternativa de silício e alumínio

Abstract

The synthesis of zeolites from natural materials such as perlite and diatomite was studied. The obtained and starting materials were characterized by several complementary techniques, such as X-ray diffraction, X-ray fluorescence, textural analysis by N2 adsorption, thermal analysis, nuclear magnetic resonance of 27Al and 29Si, infrared spectroscopy, scanning electron microscopy and mercury porosimetry. Firstly the properties of natural materials were studied: expanded perlite and three diatomites from different origins. The materials have a significant amount of SiO2 (73 to 94%) and considerable amounts of Al2O3 (3.4 to 15%), and are suitable for use as alternative sources of these elements. They are amorphous materials and have Si and Al in the tetrahedral form that are suitable for the synthesis of zeolites. Both materials possess adsorptive properties, proven by the adsorption of dyes Methylene blue (max of 96%) and Rhodamine B (max 66% for diatomites). With the use of perlite, the topology zeolites OFF, GIS and ERI were obtained as phase mix and the LTA zeolite as pure phase. The phase mixtures were used in adsorptive processes using the Rhodamine B dye, resulting in better adsorbents than the expanded perlite (93% vs 80%). With the perlite and the three diatomites from different sources, the synthesis of the LTA zeolite was studied, and it was obtained in pure phase. Crystallinity differences are observed when using different materials (12% to 52% compared to traditional LTA). It is believed that longer synthesis time will lead to more crystalline phases with a greater conversion of the natural materials into zeolites. Finally, the lamellar zeolite Fu-1 was obtained for the first time using two diatomites of the RN. This material seems to be very promising for new applications. It is concluded that it is possible to employ different alternative sources of Si and Al, such as perlite and diatomite in obtaining different zeolitic structures. The obtained materials can be applied in several processes, in this work the adsorptive capacity was proved. A good characterization of starting materials is important to target a given zeolitic structure.