engleski

Synthesis of some iodides within zeolite A crystals

Zeolites are very interesting materials for research due to their unique three dimensional structure. They have cavities and channels of nanoscale dimensions whose shape, as well as the size, is precisely defined for each type of zeolite. The negative charge of the zeolite crystal framework is compensated by mobile cations which are placed on specific positions inside cavities and channels. Above mentioned opened zeolite structure enables introduction (even synthesis) of different molecules (particles) within zeolite crystals (framework). Interaction of guest molecules with mobile cations and/or zeolite framework may form a nanocomposite material of special properties. The focus of our research is iodine interactions with sodium, silver, zinc and copper form of zeolite A. Mentioned metal iodides, formed inside the zeolite matrix, may be used in many technological applications such as: photoconductors, materials for information storage, catalysts in chemical reactions and for medical purposes. We have prepared the nanoparticles of metal iodides within zeolite matrix by direct synthesis via gas phase, by following pathway: first comes classic ion exchange of starting zeolite (NaA) with silver, zinc or copper cation, than vacuum dehydratation of such ion exchanged zeolite at 270°C, and of introduction of iodine into zeolite by gas phase diffusion also in vacuum (less than 0.1 mm Hg in sealed glass cuvette) at 210°C for 24 h. Initial pressure of I2 vapor in cuvette at 210°C was 0.8 MPa. All samples were examined using differential thermo-gravimetry (DTG), X– ray diffraction (XRD) and vibrational spectroscopies (FT-IR and FT-Raman). According to the changes in color of samples, diffusion of iodine into zeolite start at room temperature. From the Raman spectra one can see that certain amount of elemental iodine is present in all samples. Also, the presence of Me-iodide within zeolite framework was detected by DTG.

Iodine; zeolite A; AgI

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