Abstract
Desilication and dealumination techniques were used to obtain mesoporous ZSM-5 and mordenite zeolites. The study provides insight into specific structural, textural, and sorption properties of obtained materials with different Si/Al ratios. Subsequent dealumination and desilication procedures were found to be efficient methods of generating a secondary system of mesopores in mordenite and ZSM-5 crystals while preserving their microporous character. The investigated materials were evaluated in terms of their sorption properties of selected heavy metal cations (Cd2+, Cr3+, and Pb2+). Particular emphasis was placed on the structural examination of the materials via infrared spectroscopy (FT-IR). Other research methods included X-ray diffraction (XRD), X-ray fluorescence (XRF), nuclear magnetic resonance (NMR) and atomic absorption spectrometry (AAS).
Highlights
Zeolites that belong to tecto-aluminosilicates are crystalline, nanoporous materials built of a three-dimensional framework of superimposed aluminate [AlO4 ] and silicate [SiO4 ] tetrahedra linked by shared oxygen atoms
The obtained results show that the sequential treatment of zeolites with alkaline and acid solutions is a very effective method of generating a secondary mesopore system
The nuclear magnetic resonance (NMR) and IR spectra revealed changes in zeolite structures induced by both demetalation processes and the sorption of heavy metal cations
Summary
Zeolites that belong to tecto-aluminosilicates are crystalline, nanoporous materials built of a three-dimensional framework of superimposed aluminate [AlO4 ] and silicate [SiO4 ] tetrahedra linked by shared oxygen atoms. Owing to their good sorption and ion-exchange properties as well as thermal and chemical stability, zeolites are successfully used in environmental protection and in many industries [1,2]. The framework includes other channels with an eight-member ring cross-section, connected to big channels, parallel to the [010] direction, with sizes of 4.8 Å × 3.4 Å [7] Both types of Materials 2019, 12, 3271; doi:10.3390/ma12193271 www.mdpi.com/journal/materials
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