Clinoptilolite characterization

For example. Date et al. (1983) recognized the following alteration zones in the Fukazawa Kuroko mine area of Hokuroku district from the centre (near the orebody) to the margin (1) sericite-chlorite zone (zone 111 in Figs. 1.20-1.22) characterized by quartz + sericite Mg-rich chlorite (2) montmorillonite zone (zone 11 in Fig. 1.20) characterized by Mg-Ca-type montmorillonite + quartz kaolinite calcite sericite Fe-rich chlorite and (3) zeolite zone (zone 1 in Fig. 1.20) characterized by clinoptilolite + mordenite + Mg-Na-type montmorillonite cristobalite calcite or analcime + Mg-Na-type montmorillonite + quartz calcite sericite Fe-rich chlorite (Fig. 1.20). 

Physicochemical properties of L zeolites and of clinoptilolite were studied by adsorption, chromatographic, spectral, and ther-mogravimetric methods. The sodium form of L zeolite is characterized by better adsorption with respect to water and benzene vapor and by higher retention volumes of C C hydrocarbons and CO than potassium and cesium forms. The activation energy of dehydration determined by the thermogravimetric method decreases on going from the sodium to cesium form of L zeolite. When calcium is replaced by potassium ions in clinoptilolite, the latter shows a decreased adsorption with respect to water vapor. The infrared spectra of the L zeolite at different levels of hydration show the existence of several types of water with different bond characters and arrangements in the lattice. 

TTigh silica zeolites attract great attention since they are characterized by relatively high thermal stability and considerable acid resistance. Physicochemical properties of high silica zeolites, despite a number of investigations, have not been sufficiently studied. The same is true for L- and clinoptilolite zeolite. The data on synthesis, structure, adsorption properties, decationization, dealuminization, adsorption heats, and other properties of the above-mentioned zeolites have been given (1-15). Results of studies of physicochemical properties of L zeolites and of natural and modified clinoptilolite are given here. 

Clinoptilolite has been demonstrated to be the most appropriate sorbent for strontium recovery from seawater, as well as ftom other natural waters and brines [248-250]. This most common zeolite is characterized by the composition (Na, IO4 CaAl6Si3o072 24 H2O. The main advantages of applying clinoptilolite for recovery of strontium from seawater is attributed to the ease with which it is regeneratable by ammonium salts... 

Structural characterization of the solids by X-ray diffraction showed that the materials ZSM-5 and USY zeolites studied had a high crystallinity, while a mordenite structure was observed for the natural zeolite traces of clinoptilolite were observed in this sample. 

The chemical composition of clinoptilolite resembles that of heu-landite, but it may be characterized as compared with that of heulandite by high alkali and Si content and low Ca and A1 content. Table I shows... 

Chemical compositions of the Nakanosawa tuff and clinoptilolite from it are given in Table II. The clinoptilolite is characterized by a high content of alkalies in which K exceeds Na. It contains an appreciable amount of Sr. The bulk analysis of tuff indicates that Sr is concentrated selectively by the clinoptilolite. 

Although Barrer and Makki (1) succeeded in reducing the aluminum content of clinoptilolite essentially to zero, the characterization of a fully decationized mordenite has not been reported. 

Considering that clinoptilolite is a HEU-type zeolite, characterized by a two-dimensional pore system with three different channels having pore openings of 2.6x4.7, 3.0x7.6 and 3.3X4.6 A, respectively (Baerlocher et al, 2001), it was thought worthwhile to promote a study aiming at evaluating the technological potential of this material in application connected... 

A zonal distribution of clay minerals occurs in the East Hachimantai thermal area, characterized by smectite - illite/smectite - illite/chlorite, with the latter tending to occur in the vicinity of hot upflow zones. The smectite is characteristically Ca-smectite. The occurrence of Ca-bearing zeolite minerals, such as laumontite and wairakite correspond to the presence of hot hydrothermal fluids near in the center of the geothermal resource. In contrast, Na-smectite and Na-zeolite (e.g. clinoptilolite - mordenite - analcime) in marine sediments and pyroclastic sequences tend to envelope the main thermal area. Inoue et al. (2001) and Hara et al. (2001) have described the style and distribution of alteration in the Hachimantai area. The Na-enriched alteration zones contain higher Na concentrations than... 

The uptake of hydrogen cyanide into protonic forms of synthetic zeolites Y, Beta, mordenite, as well as into naturally occurring clinoptilolite, ferrierite, stil-bite and aliunina-pillared clays were studied by Jamis et al. [954] using FTIR measurements of the C=N stretching vibration to characterize the binding of HCN to the various Br0nsted-acid sites of the molecular sieve materials. 

The hydrothermal transformation of Na-clinoptilolite to Na-Y and Na-P zeolites has been studied by the Fe NGR method [91D1]. The RT spectra evidenced in all cases the presence of two doublets, attributed to iron in tetrahedral and octahedral coordination, respectively. The evolution of quadmpolar splitting of high-spin Fe during the amorphization and crystallization processes, which characterize hydrothermal transformations, indicates that octahedral sites are structure sensitive, while the tetrahedral ones fundamentally depend on the Si/Al ratio. Isomer shift values depend on the Si/Al ratio in both processes. 

Tricoli and Nanetti [17] prepared a novel zeolite-Naflon composite manbrane by embedding zeolite fillers in Nafion. The zeolites used in this study were chabazite and clinoptilolite. The presence of zeolites in the membranes caused notable changes in conductivity, methanol permeability, and selectivity with respect to pure Nafion. In another interesting study, Holmberg et al. synthesized and characterized zeolite-Y nanocrystals for Nafion-zeolite-Y composite proton exchange membranes. The composite membranes were found to be more hydrophilic and proton conductive than the base-unmodified membranes at high temperatures [18]. 

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