Investigation of the dielectric properties of water adsorbed by zeolites Communication 3. Dielectric losses in the system of NaA zeolite crystals and water at medium degrees of filling
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In the temperature region from-40 to 20° in NaA zeolite containing water, there are dielectric losses at low frequencies. The dielectric adsorption isotherm has a break at a water content in the zeolite corresponding to approximately five to seven molecules per unit cell, which is evidently due to the strucuration of water when the adsorption increases and to the different sorbability on sodium ions, bonded to the eight-membered and six-membered oxygen rings.
In the region of losses considered, there is a distribution of relaxation times, which is probably associated with the energy heterogeneity of the active centers. The region of the distribution becomes narrower with increasing water content, which indicates a development of the structure.
The values of the activation energy and entropy of activation for the process of polarization in an electric field increase with increasing water content, and at a water content of more than 5% they become greater than for normal ice.
The zeolites NaA-I and NaA-II possess different values of ɛ′ and ɛ″ at the same temperatures and degrees of filling, which is evidently due to certain differences in the technology of their manufacture. However, all the phenomena enumerated above were observed for both samples.
KeywordsEntropy Activation Energy Zeolite Relaxation Time Adsorption Isotherm
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