Cristalização Induzida por Semente na Síntese Hidrotérmica de Zeólita com Estrutura FAU a partir de Pó de Vidro Residual

Abstract

The production of microporous materials at a low cost by using waste raw materials as the main precursors in synthetic routes has been widely studied. Thus, in this work, we evaluated the best experimental conditions for the use of colorless glass powder as an alternative source of silicon in the conversion into zeolites with FAU-X structure. Firstly, the optimal parameters for acid leaching on glass powder were statistically studied using Response Surface Methodology (RSM). Then, hydrothermal syntheses were assisted by seed crystals (0% to 5%, wt.) of the structure itself to induce the growth of FAU zeolite, evaluating the crystallization time (12, 24, 36, and 48 h) and the variation in silicon source (treated and untreated waste). The obtained samples were characterized by X-ray diffractometry and X-ray fluorescence. The statistical analysis points to the treatment that resulted in greater calcium leaching, mainly as a function of time and acid concentration. Regarding the syntheses, for the zeolites synthesized from the untreated residue a phase competition between the GIS, LTA, SOD, and FAU structures was observed, in which with the addition of seed from 0% to 5% enabled the proper targeting to the FAU structure, but with a low structural ordering. On the other hand, the efficiency in the acid treatment for the residue resulted in the formation of the faujasite phase as the main phase and as a second phase the presence of the Na-P1 zeolite (GIS structure), obtaining a higher degree of structure ordering the zeolite with higher amount of seed and shorter crystallization time. Therefore, the need for a prior treatment in the residue to obtain a purer phase in the synthesized material and the addition of seed to decrease the crystallization time and obtain greater structural ordering were required.