Modification of natural analcime
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2022-06-19 09:16
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TSITSISHVILI, Vladimer, DOLABERIDZE, Nanuli, NIJARADZE, Manana, MIRDZVELI, Nato. Modification of natural analcime. In: Achievements and perspectives of modern chemistry, 9-11 octombrie 2019, Chişinău. Chisinau, Republic of Moldova: Tipografia Academiei de Ştiinţe a Moldovei, 2019, p. 28. ISBN 978-9975-62-428-2.
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Achievements and perspectives of modern chemistry 2019
Conferința "International Conference "Achievements and perspectives of modern chemistry""
Chişinău, Moldova, 9-11 octombrie 2019

Modification of natural analcime


Pag. 28-28

Tsitsishvili Vladimer1, Dolaberidze Nanuli2, Nijaradze Manana2, Mirdzveli Nato2
 
1 Petre Melikishvili Institute of Physical and Organic Chemistry at Ivane Javakhishvili Tbilisi State University,
2 Ivane Javakhishvili Tbilisi State University
 
Disponibil în IBN: 31 octombrie 2019


Rezumat

Analcime is usually referred among the commonly used natural zeolites, but its application is limited due to peculiarities of crystal structure. The possibilities of analcime modification are not well understood, and the purpose of our report is to demonstrate the new data on the results of the acid treatment of natural analcime samples from the Chachubeti (A-Cha) and Gelati (A-Gel) manifestations, Eastern and Western Georgia, respectively. Acid treatment of the grinded samples (0.063-0.1 mm) at a solid:liquid ratio of 1:10 was carried out in aqueous HCl solutions of different concentration at a controlled temperature. Fast and significant removal of aluminum from the analcime crystalline structure occurs at low concentration of the acid, but high degree of dealumination (Si/Al>7) is unattainable even after protracted treatment in high-concentrated acid solutions. Removal of aluminum at acid concentration over 0.5 N can be expressed in terms of the relative aluminum content C(N)=0.42(2)[1+1.38(7)exp(–0.20(2).N)]. The process of acid mediated dealumination in analcime is of a general nature, but removal of alkali and alkaline earth cations is specific for samples of different origin. X-ray diffraction patterns and IR-spectra of treated samples show partial decomposition of zeolite crystal structure, but the main peaks and IR-bands, especially structure-sensitive oscillations are remained even after treatment in 10N solution. The water adsorption capacity of micropores increases from ~2 to ~7 mmol/g for samples treated in diluted solutions (0.1-1.0 N), but decreases to 7 mmol/g at higher concentrations. Total benzene adsorption capacity after acidic treatment gradually increases with the increase of the acid concentration (from 0.4 to 1.3 mmol/g for A-Cha, and from 0.5 to 1.7 mmol/g for A-Gel). Pore size distribution curves of treated samples show a developed system of mesopores with sizes up to 200 nm and with total volume up to 0.05 cm3/g. Thus, acid treatment allows to obtain micromesoporous adsorbents with a fairly high capacity. Preliminary thermal treatment at 300-700oC makes analcime more resistant to acid, mesopores have low specific volume and narrow distribution of sizes up to 60-100 nm.