Abstract
Analcime is a fairly widespread zeolite in the territory of Georgia and other countries, but its practical application is limited due to the peculiarities of its compact structure with small pores and irregular channels. This work describes a method developed by us for hydrothermal recrystallization of analcime into a widely used ion exchanger of the LTA type in the form of micrometric crystals or nanosized crystals, depending on the synthesis conditions. Silver-, copper-and zinc-containing analcimes and synthetic LTA zeolites with bacteriostatic activity were obtained by ion exchange. It has been shown that the highest bacteriostatic activity is possessed by a silver-containing synthetic zeolite, and analcimes enriched with relatively cheap copper and zinc exhibit activity sufficient for practical use in water treatment, paper production and other applications.
Highlights
The practical use of zeolites [1,2], alunimosilicates with the general formula MenSixAlnO2(n+x).mH2O (Me = Na, K, ... 1⁄2Ca, 1⁄2Mg, ...), is based on their molecular-sieve and other properties, especially on the ability of zeolites to enter into ion exchange reactions with the participation of Me+ ions compensating the negative charge of the crystal lattice constructed from alternating SiO4 and AlO4– tetrahedrons
Analcime is rather widespread among the zeolites known on the territory of Georgia [3]: an abundance of analcime connected with volcanic-sedimentary rocks is observable in the Middle-Eocene rock masses of the Achara-Trialeti folded system, beginning with Mtskheta district, including the Borjomi valley and westward in Bagdadi and Vani districts; analcime-containing stratified rocks are known in Western Georgia in the deposits of Jurassic carbonaceous and colored suites of Kutaisi area, as well as analcime from a basaltic geode, analcime crystallized in the chemical way, and analcime of diagenetic origin in volcanic-sedimentary rocks from the Akhaltsikhe deposit, along with other zeolites
The analcime framework (Figure 1, left) consists of singly-connected 4-rings, irregular channels are formed by highly distorted eight-membered rings (8mR, Figure 2, right) and have small entrance windows of approx. 2.6 Å, and regular channels are formed by six-membered rings (6mR) along the [111] direction of the cubic lattice
Summary
The goal of our study was to demonstrate possibility to carry out synthesis of zeolite with high ion-exchange capacity by hydrothermal recrystallization of natural analcime and production of materials with different sizes of crystallites and suitable system of pores and channels, as well as to use the high ion-exchange capacity of analcime to obtain its metal-containing forms endowed with bacteriostatic activity. Preparation of synthetic zeolite material was carried out using greenish-grey analcime-containing rock from the Chachubeti plot of the Tedzami deposit having high zeolite phase content (up to 95%) with chemical composition (Na9.25K2.25Ca1.25Mg0.95)Me0.30[Al16.2Si32.0O96].18.4H2O (Me – impurity metals such as Fe, Cu, etc.), characterized by the X-ray diffraction pattern, IR spectrum, thermal analysis data, and ion exchange properties [6].
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