Transformation behaviour of zeolite A to hydroxysodalite in batch and semi-batch crystallizers

Tassopoulos, Menelaos; Thompson, Robert W.

doi:10.1016/0144-2449(87)90059-5

Cited by 31 publications

(22 citation statements)

References 4 publications

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“…Table 3 The molar ratio of cations in AMSHC samples. [15][16][17][18][19] is supplied, it may transform to sodalite spontaneously. The Ostwald's law of successive transformation demonstrated the mechanism that the less thermodynamically stable phase of sodium alumino-silicate may be kinetically disposed and precipitated firstly, and then transforms to the more stable phase under the conditions.…”

Section: Resultsmentioning

confidence: 99%

Mineral phases and properties of alkali-activated metakaolin-slag hydroceramics for a disposal of simulated highly-alkaline wastes

Chen

Zhang

2010

Journal of Nuclear Materials

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Section: Resultsmentioning

confidence: 99%

Mineral phases and properties of alkali-activated metakaolin-slag hydroceramics for a disposal of simulated highly-alkaline wastes

Chen

Zhang

2010

Journal of Nuclear Materials

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“…17,18 At supersatu- ing a process of re-dissolution and transformation into a lower energy phase such as hydroxysodalite. 19 A further consequence of undersaturation is also shown in Figure 9 whereby crystal imperfections act to prevent crystal dissolution. This has the effect of pinning terrace retreat and the creation of protrusions at the crystal surface with edges parallel to [100].…”

Section: Discussionmentioning

confidence: 99%

Atomic Force Microscopy and High Resolution Scanning Electron Microscopy Investigation of Zeolite A Crystal Growth. Part 2: In Presence of Organic Additives

et al. 2014

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The full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-pro t purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. AbstractThe nanoscopic details of the crystal growth of zeolite A in the presence of the organic modifiers diethanolmaine (DEA) and triethanolamine (TEA) has been determined using a combination of atomic force microscopy (AFM) and high-resolution scanning electron microscopy (HRSEM) coupled with Monte Carlo simulations. Crystallization of zeolite A in the presence of TEA was faster than when the growing solution contained DEA. In addition the morphology of the final zeolite A crystals depended on the type of organic molecule, with TEA producing crystals bound only by {100} facets and DEA leading to the formation of relatively large {110} faces. These features can be explained in terms of the relative Si/Al in the growing medium and its control due to the different affinity of the organic molecules toAl. In addition, synthesis performed at 90 °C showed the appearance of {211} facets. Careful review of the HRSEM and AFM images, in addition to comparison with the MC simulations reveal that these are in fact pseudo-facets, product of the slow dissolution of the metastable zeolite A crystals. This proves that the final habit of the LTA crystals can be governed by very small changes of saturation of the growing medium and a control of this paremeter can prove advantageous when designing crystals for industrial applications.

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“…The relative stability of the zeolites in increasing order is NaA < NaX < sodalite. [42,43] Therefore, the rapid heating achieved using microwaves can result in the production of less stable zeolite phases.…”

Section: Naa Zeolitementioning

confidence: 99%

In Situ SAXS/WAXS of Zeolite Microwave Synthesis: NaY, NaA, and Beta Zeolites

et al. 2007

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A custom waveguide apparatus is constructed to study the microwave synthesis of zeolites by in situ small-angle X-ray scattering (SAXS) and wide-angle X-ray scattering (WAXS). The WR-284 waveguide is used to heat precursor solutions using microwaves at a frequency of 2.45 GHz. The reaction vessels are designed to include sections of thin-walled glass, which permit X-rays to pass through the precursor solutions with minimal attenuation. Slots were machined into the waveguide to provide windows for X-ray energy to enter and scatter from solutions during microwave heating. The synthesis of zeolites with conventional heating is also studied using X-ray scattering in the same reactor. SAXS studies show that the crystallization of beta zeolite and NaY zeolite is preceded by a reorganization of nanosized particles in their precursor solutions or gels. The evolution of these particles during the nucleation and crystallization stages of zeolite formation depends on the properties of the precursor solution. The synthesis of NaA and NaX zeolites and sodalite from a single zeolite precursor is studied by microwave and conventional heating. Microwave heating shifts the selectivity of this synthesis in favor of NaA and NaX over sodalite; conventional heating leads to the formation of sodalite for synthesis from the same precursor. The use of microwave heating also led to a more rapid onset of NaA zeolite product crystallization compared to conventional heating. Pulsed and continuous microwave heating are compared for zeolite synthesis. The resulting rates of formation of the zeolite products, and the relative amounts of the products determined from the WAXS spectra, are similar when either pulsed or continuous microwave heating is applied in the reactor while maintaining the same synthesis temperature. The consequences of these results in terms of zeolite synthesis are discussed.

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Transformation behaviour of zeolite A to hydroxysodalite in batch and semi-batch crystallizers

Cited by 31 publications

References 4 publications

Mineral phases and properties of alkali-activated metakaolin-slag hydroceramics for a disposal of simulated highly-alkaline wastes

Mineral phases and properties of alkali-activated metakaolin-slag hydroceramics for a disposal of simulated highly-alkaline wastes

Atomic Force Microscopy and High Resolution Scanning Electron Microscopy Investigation of Zeolite A Crystal Growth. Part 2: In Presence of Organic Additives

In Situ SAXS/WAXS of Zeolite Microwave Synthesis: NaY, NaA, and Beta Zeolites

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