The Studies Of Surface Properties Of Pure
THE STUDIES OF SURFACE PROPERTIES OF PURE
AND MODIFIED ZEOLITES
P. Staszczuk, M. Matyjewicz, M. Majdan
Faculty of Chemistry, Maria Curie-Sklodowska University,
Maria Curie-Sklodowska sq. 3, 20-031 Lublin, Poland
Zeolites history started in the 18th centuary but they were known and used in the archiecture in the acient. Time in 1756 the Swedish mineralogist, amateur, A. F. von Cronstedt observed that some minerals emit much water during the heating process. They looked as if they were in a "boiling" state. He called them zeolites which in Greek means "boiling" stones. In 1930 it was proved using the X-ray data that absorption of small molecules on the zeolite surface depends on the nature of the compound and sizes of "windows" in the zeolite inner structure (therefore later zeolites were called "molecular sieves"). Most dynamic development took place in Japan, USA and Europe in 1960-70 when zeolites began to be used as additives to fodders and to remove ammonium ions from water. Since that time industrial applications of natural zeolites has been developed. Till now there have been discovered over 40 types of natural zeolites and synthetic zeolites production exceeds 100 generations, but most of them do not have equivalents in nature.
The measurements of the programmed thermodesorption of polar (water, n-butanol) and nonpolar (benzene, n-octane) liquids from pure (natural from Ukraine and synthetic) and modified by Ni+2 adsorption of ions of AD 10N zeolite Na-A and CBV 10A zeolite mordnite samples (Zeolyst International Co., USA) were made. In the studies of liquids thermodesorption process the zeolite samples were wetted with liquid vapors in a vacuum dessicator where the relative vapor pressure p/po was 1. The quasi-isothermal technique using the simultaneous derivatograph Q-1500 D (MOM Hungary) had been adopted to charactrize properties of samples studied. The Q-TG mass loss and the first derivative Q-DTG mass loss with respect to temperature and time were registered. It was possible to obtain information concerning surface capacity (thickness and volume of adsorbed films) and wetting phenomena, nature of active centres, discontinuous change of adsorption layer properties,
mechanism of surface film destruction, kinetic thermodesorption of films and its stability. Moreover, porosity of samples were estimated by means of nitrogen adsorption at 77.4 K, with the BET and BHJ equations employed using a sorptomat apparatus of the type ASAP 2405 V1.01 (Micrometrics Inc., USA). On the basis of the obtained data specific surface area, pore volume and radius as well as pore-size distribution functions were calculated. From the experimental thermogravimetry results, adsorption and porosity parameters of the tested zeolite samples were compared with analogous ones obtained by the sorptometry technique and good correlations have been obtained.
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