A study on the synthesis of [Fe,B]-MFI zeolites using hydrothermal method and investigation of their properties

Abstract

Synthesis of MFI-type zeolites with boron and iron in their framework using conventional hydrothermal method was investigated. The effect of several parameters including gel composition and pH on the crystallization of zeolites was systematically studied. The prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and N2 physical adsorption analysis. The XRD patterns showed that the crystallization of boroferrisilicate zeolite takes place at pH values higher than 9 with molar ratio of Si/(Fe+B)≥8.3. The crystallinity and BET surface area of zeolites was decreased by increasing the amount of Fe3+ ions in the synthesis gel. The SEM images revealed that Fe/B ratio of synthesis gel could also influence the morphology of zeolite particles. The drug loading capacity of boroferrisilicates with different Fe/B ratios was evaluated by loading of doxorubicin (DOX) as a model drug. Among zeolites with Fe/B ratios of 0.5, 1 and 2, higher loading efficiency was achieved for sample with lower iron content. However, for sample with Fe/B=∞ which the formation of iron oxide particles on the external surface of sample was confirmed by XRD and SEM analysis, the DOX loading efficiency was remarkably high. Since the desorption of DOX molecules from zeolites surface was prevented by the strong interaction between drug molecules and the surface of heteroatom-substituted zeolites, the release efficiency for all boroferrisilicate zeolites was low.