Zeolite Y is one of the earliest known and most widely used synthetic zeolites. Many experimental investigations verify the valuable ion exchange capability of this zeolite. In this study, we assessed the effects of ion exchange on its vibrational spectra. We applied classical lattice dynamics methods for IR and Raman intensity calculations. Computed spectra of optimized zeolite Y structures with different cations were compared with experimental data. The spectra obtained in this study are in agreement with previous experimental and computational studies on zeolites from the faujasite group.
7 November 2017 in Polish Journal of Environmental Studies
This study investigated the influence of alkali activation process conditions on the amount and types of zeolites in the resultant geopolymers. The products were formed during the alkaline activation of coal fly ash with the use of aluminium and sodium hydroxide solution. Geopolymers were cured at 80ºC for 24 h. The effects of reaction systems’ constitution (expressed as SiO2/Al2O3 and Al2O3/Na2O molar ratios) on the phase composition and structure of obtained products were determined. The results indicated that the products obtained from such hydrothermal treatment demonstrated the characteristics of zeolite-like materials – sodalite. By using the appropriate composition of the initial solution (sufficiently high concentration of NaOH and aluminum carrier), it is possible to synthesize the sodalite phase efficiently in an amorphous matrix.
1 September 2009 in Journal of Hazardous Materials
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).
Zeolites can be obtained in the process of the alkali-activation of aluminosilicate precursors. Such zeolite–geopolymer hybrid bulk materials merge the advantageous properties of both zeolites and geopolymers. In the present study, the effect of the type and concentration of an activator on the structure and properties of alkali-activated metakaolin, and metahalloysite was assessed. These two different kaolinite clays were obtained by the calcination of kaolin and halloysite, and then activated with sodium hydroxide and water glass. The phase compositions were assessed by X-ray diffraction, the microstructure was observed via scanning electron microscope, and the structural studies were conducted on the basis of the infrared spectra. The structure and properties of the obtained alkali-activated materials depend on both the type of a precursor and the type of an activator. The formation of zeolite phases was observed when the activation was carried out with sodium hydroxide alone, or with a small addition of water glass, regardless of the starting material used. The higher proportion of silicon in the activator solution does not give crystalline phases, but only an amorphous phase. Geopolymers based on metahalloysite have better compressive strength as the result of the better reactivity of metahalloysite compared to metakaolin.
19 June 2024 in Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy