Gismondine

In the X-ray powder diffraction patterns of the composites, the disappearance of the broad band centered at 22 °20, typical of amorphous silica, indicates that the zeolitisation of the mineral fraction of the parent composite was complete. In no diffraction pattern any sign of crystallised chitosan could be found. The two methods in which the silica-polymer beads were extracted from the aluminate solution after impregnation (methods A and C) allowed the formation of the expected zeolite X, with traces of gismondine in the case of the method C. The method B, in which excess aluminate solution was present during the hydrothermal treatment, resulted in the formation of zeolite A. 

The precipitation and solution phenomena depend on the relative concentrations of the organic and alkali cation and on pH. This would predict that zeolites will not crystallize from pure organic cation systems in the absence of alkali. The two exceptions to this appear to be Meier and Baerlocher s crystallization of TMA-gismondine zeolite (4) and the fels-pathoid TMA-sodalite (6). 

As a demonstration of the use of DSC in the characterization of zeolites and related materials, Figure 4.37 illustrates the DSC profile of the LECA zeolite [53], The LECA zeolite has a phase composition of 13 4 [%], in wt %, of gismondine and 87 4 [%] of quartz, anorthite, and glass. The DSC profile presented two endothermic peaks at 112°C and 195°C, and an exothermic peak at 312°C. As is very well known, zeolites evolve adsorbed water in the course of heating [97]. Consequently, the endothermic peaks in the DSC profile of LECA zeolite sample were clearly related to adsorbed water located in different sites of the LECA zeolite surface and the framework of the gismondine contained in the LECA zeolite [53],... 

It is well known that zeolites of type NaP co-crystallize with faujasites (15,16). The typical reaction sequence under the appropriate synthesis condition is (17) amorphous— faujasite — . gismondine type Na-P. However, in some cases, zeolite Na-P appears as the first crystalline phase when freshly prepared gel has been heated at the appropriate temperature (15,18) in these cases, faujasite can be crystallized either by adding the seed crystals into the freshly prepared gel (6,13.18) or by ageing the gel at ambient temperature prior to the crystallization at the... 

In phillipsite, S4R are linked to form chains resembling a double crankshaft (Figure 8). Gismondine has a related... 

It must be emphasized that both phiUipsite and gismondine have unique frameworks. Mineralogically speaking they both are members of different families (see Tables 11 and 13). 

Figure 8 The double crankshaft chain element of structure in gismondine (GIS) and related zeolites (U = up, D = down describes the configuration of linked parrs of Si,A104 tetrahedra)...

Figure 9 Linkage of chains in (a) piuUipsite (PHI) and Figure 11 Faujasite (FAU) structure emphasizing the linkage of (b) gismondine (GIS) truncated octahedra (/3-cages) via D6R units...

Gismondine Family. Four minerals are accepted with the gismondine framework, again based upon variation of cation content and Si/Al disorder. These are listed in Table 11. 

GIS Gismondine Ca4[Al8Si8032]16H20 Capo di Bova (Rome, Italy)... 

FCAPO-37, SAPO-37, XAPO-37, beryllophosphate X, zincophosphate X Beryllosilicate gismondine, MAPSO-43... 

Figure 2.1 The structure of the zeolite pauliitgite, cubic, with a lattice parameter of 35.1 A, composed of (different coloured) gismondine units.

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