Characterization and Dehydration Behavior of a Natural, Ammonium Hydroxide, and Thermally Treated Zeolitic Tuff

Abstract

Aqueous NH 4 OH-treated and subsequently calcined forms of local natural zeolitic tuff were characterized by different techniques including scanning electron microscopy (SEM), X-ray powder diffraction, inductively coupled plasma-atomic emission spectroscopy (ICP-AES), volumetric N 2 adsorption at À196 C, thermogravimetry (TG), differential scanning calorimetry (DSC), and transmittance infrared spectroscopy. The dehydration behavior of the samples was investigated using an in situ temperature-programmed diffuse reflectance Fourier transform infrared spectroscopy (TP-DRIFTS) method under vacuum. The DRIFTS spectra recorded yielded information about the effect of the NH 4 OH treatment and subsequent calcination on the dehydration behavior of the natural zeolite. Changes in the infrared bands corresponding to vibrations of the OÀH and NÀH bonds upon in situ heating under vacuum were analyzed.Keywords Ammonium hydroxide treatment; Characterization;Clinoptilolite; Dehydration; DRIFTS INTRODUCTIONNatural zeolites constitute a group of minerals having open aluminosilicate frameworks containing channels and cavities that accommodate cations and water molecules. Generally, these cations are exchangeable and the water molecules can be removed or replaced reversibly without disrupting the framework. The presence of water in the pores hinders adsorption of other molecules; thus adsorption and catalytic properties of zeolites are directly related to their water content. Water is adsorbed into zeolites by filling oxygen-lined channels and hydrating the cations present in the channels. The observed macroscopic thermal behavior of a zeolite depends on the type, amount, and position of the extraframework cations within the structure, their coordination to water molecules, their interactions with framework oxygen atoms, the presence of other water molecules, Si=Al ratio, time, temperature, pressure, and heating rate.Dehydration behaviors of clinoptilolite have been investigated by various analytical techniques including

Impact of Surface Chemistry on Microwave-Induced Degradation of Atrazine in Mineral Micropores

“…The presence of water molecules in the micropores of zeolites affects their sorption and catalytic properties through hindering adsorption of other molecules, and thermogravimetric analysis has been commonly used to identify the different types of water sorbed in zeolites and other microporous minerals. − Figure c shows the DSC thermographs of the wet Y zeolites. A major endotherm was observed for all the zeolites in the 30–300 °C region, and the endotherms of the hydrophilic zeolites Mg/CBV-100, Ca/CBV-100, CBV-400, CBV-100, CBV-300, and CBV-712 were broader than those of the hydrophobic ones (CBV-720, CBV-760, and CBV-780).…”

Structure Features and Physicochemical Performances of Fe-Contained Clinoptilolites Obtained via the Aqueous Exchange of the Balanced Cations and Isomorphs Substitution of the Heulandite Skeletons for Electrocatalytic Activity of Oxygen Evolution Reaction and Adsorptive Performance of CO2

“…The band at 796 cm −1 was assigned to the O-T-O stretching vibrations (T = Si or Al), which may be due to the presence of a quartz impurity in the samples [ 34 ]. The absorption peaks at approximately 1638 cm −1 were related to the deformation vibrations of H 2 O and stretching vibrations of -OH [ 35 ]. In accordance with works by Verdonck et al [ 36 ], the prominent IR bands at 665 cm −1 , as shown in Figure S8b,c , can be assigned to Fe-O stretching vibrations or Fe-O-H bending vibrations.…”

Application of model-free kinetic analysis methods to dehydration of a HEU-type zeolite rich tuff from Turkey

“…Evacuation of the zeolitic tuff at room temperature resulted in a decrease in the intensities of the infrared bands associated with water (3610, 3410 and 1630 cm À1 ), especially those at 3410 cm À1 and 1630 cm À1 . The bands at 3610 cm À1 and 3410 cm À1 were assigned to the ''tightly bound'' water and ''loosely held'' water, respectively (Narin et al, 2011). The latter band was associated with the vibrations of OH groups bound to the framework oxygen atoms via hydrogen bonds and disappeared above 132ºC under vacuum.…”

“…The latter band was associated with the vibrations of OH groups bound to the framework oxygen atoms via hydrogen bonds and disappeared above 132ºC under vacuum. Evacuation at room temperature caused this band to shift to a lower wavenumber (Narin et al, 2011). This implied an increase in the strength of the hydrogen bonds as a result of the decreased distance between water molecules and the framework oxygen atoms (Bertsch & Habgood, 1963).…”