Wyniki wyszukiwania - Biblioteka Nauki

1

Properties and Application of Georgian Natural Phillipsite

100%

Tsitsishvili V. , Dolaberidze N. , Mirdzveli N. , Nijaradze M. , Amiridze Z. , Khutsishvili B.

Inżynieria Mineralna

|

2024

|

tom Vol. 1, no. 1

493--501

EN

Oceanic and terrestrial sedimentary phillipsites make up very large reserves, but the use of this natural zeolite is not so wide comparing to clinoptilolite, and purpose of our study was to characterize the phillipsites of the Georgian deposits and highlight their possible application. It is shown that natural phillipsite can be used as a raw material for the synthesis of phase-pure zeolite NaX with Si/Al~1.5-1.7 in the form of octahedral crystallites with uniform micrometric (2-7 μm) dimensions, characterized by high specific surface area (590-770 m2 /g) and volume of pores (0.58 cm3 /g) including uniform zeolitic micropores and channels with an average diameter of 55 nm, which opens up the prospect of its use in catalysis. It has been established that natural phillipsite is a suitable carrier of bioactive metals: silver-, copper-, and zinc-containing micro-mesoporous materials have been prepared using ion-exchange reactions between zeolite and a salt of a transition metal; the products contain up to 235 mg/g of silver, 85 mg/g of copper, and 87 mg/g of zinc, and in the Kirby-Bauer disk-diffusion test show strong bacteriostatic activity against such microorganisms as gram-negative bacterium Escherichia coli, gram-positive bacteria Staphylococcus aureus and Bacillus subtilis, fungal pathogenic yeast Candida albicans and a fungus Aspergilus niger. The use of bactericidal materials obtained on the basis of natural phillipsite is possible both for water purification and disinfection, and as fillers in the production of polymeric materials, paper and cardboard.

2

Structure Stability of Georgian Natural Heulandite

100%

Tsitsishvili V. , Dolaberidze N. , Mirdzveli N. , Nijaradze M. , Amiridze Z. , Khutsishvili B.

Inżynieria Mineralna

|

2024

|

tom Vol. 1, no. 1

503--510

EN

Zeolites have a unique set of molecular-sieve, sorption, ion exchange and catalytic properties due to their framework microporous structure, and structural stability is an important characteristic and often a decisive factor in the application and performance of natural zeolites. The aim of our work was to study the processes occurring under the influence of heat, which determine the thermal stability of the zeolite-containing tuff of the Tedzami-Dzegvi deposit, with zeolite phase content up to 90%, consisting of heulandite and chabazite in a ratio of 8:1, and chemical composition |Na0.25K0.06Ca0.19Mg0.15|[AlSi3.6O9.2] .3H2O. It was found that as a result of exposure to heat, a slight dealumination of the surface of the calcined (400-500 °C) samples occurs, as well as dehydration and amorphization of the crystal structure are observed. Sample dehydration occurs in several stages: (i) most of the water (≈60% of the total water content) is continuously lost at temperatures below ≈250 °C, (ii) the part of the remainder (≈24%) is slowly dehydrated up to 650 °C, (iii) complete dehydration of the sample is achieved at ≈800 oC. Amorphization of the heulandite phase begins at temperatures above 200 °C, the transition to the metastable heulandite B phase at ≈340 oC is not fixed, but at high temperatures wairakite or another mineral of the 9.GB.05 group and quartz are formed; the chabazite phase is stable up to ≈1000 oC, and at temperatures above 1100 oC, leucite (K,Na)AlSi2O6 and cristobalite SiO2 are formed. The adsorption of water vapor and benzene on heat-treated samples decreases monotonically with an increase in the calcination temperature, following amorphization. Nitrogen adsorption-desorption isotherms show slight decrease of the absorbent surface area with an increase in the calcination temperature and nonmonotonic changes in average mesopore diameters. It is also shown that heat treatment improves the acid resistance of heulandite by reducing dealumination after sample treatment with hydrochloric acid.

3

Acid Modification of Georgian Natural Heulandite

100%

Tsitsishvili V. , Ebralidze K. , Dolaberidze N. , Mirdzveli N. , Nijaradze M. , Amiridze Z. , Khutsishvili B.

Inżynieria Mineralna

|

2024

|

tom Vol. 1, no. 1

483--491

EN

Acid treatment is a powerful tool for improving the performance of natural zeolites, and the purpose of our work was to study chemical composition, structure and properties of acid-treated heulandite from the Tedzami-Dzegvi deposit. Samples of heulandite-containing tuff from the Rkoni plot with zeolite phase content up to 90%, consisting of heulandite and chabazite in a ratio of 8:1, and having chemical composition described by empirical formula |Na0.25K0.06Ca0.19Mg0.15)|[AlSi3.6O9.2] .3H2O were treated with hydrochloric acid solutions with concentration up to 2.0 N. It was established that acid treatment leads to significant dealumination (the molar ratio of Si/Al increases from 3.6 to 9.5) and decationization (the total charge per aluminium atom decreases from 1 to 0.68), sodium and magnesium are mainly leached, calcium and potassium does not take part in the decationization process. Powder X-ray diffraction patterns show that hydrochloric acid solutions with a concentration up to 2.0 N do not lead to amorphization of the zeolite microporous crystal structure, but can gradually dissolve it. The adsorption of water vapor indicates the availability of micropores for the entry of small polar molecules, benzene adsorption shows a slight increase of hydrophobicity of the surface as a result of acid treatment. Nitrogen adsorption-desorption isotherms show acid-mediated sharp increase of adsorption in micropores and of the surface area, as well as changes in the mesoporous system, leading to the prevalence of pores with a diameter of 3 – 10 nm. The concentration of dilute solutions of hydrochloric acid is determined, which provides availability of micropores for large ions and nonpolar molecules, but at which dealumination is insignificant and ion-exchange capacity remains at a sufficient level. Materials obtained by acid treatment of heulandite can be used as adsorbents, ion exchangers, and carriers of biologically active substances and metal ions.