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Bentonite clay, its physical and chemical characteristics and application in the national economy.

Bentonite clay, its physical and chemical characteristics and application in the national economy.

The article presents information about bentonite clay, its types and deposits. The physicochemical characteristics of bentonite clay, as well as its use in the national economy, have been investigated..

ABSTRACT.

The article presents information about bentonite clay, types and its deposits. The physicochemical parameters of bentonite clay, as well as its use in the national economy, were investigated.

Key words: bentonite clay, types, physical and chemical indicators, deposits, national economy, application, fine clay.

Keywords: bentonite clay, types, physical and chemical indicators, deposits, national economy, use, fine clay.

Bentonite clays got their name from the port of Benton, located in the state of Wyoming (USA), where the first commercial mining of them began at the end of the 19th century. In the subsequent period, interest in bentonite clays increased significantly, and their deposits were discovered on almost all continents of our planet..

It is customary to call bentonite clays (bentonites) fine clays consisting of at least 60-70% of the minerals of the montmorillonite group, which have a high binding capacity, adsorption and catalytic activity. Mixed-layer minerals, hydromica, polygorskite, zeolites, kaolinite, etc. are found in bentonites..

Bentonite is a complex mineral, the composition of which is determined by the content of montmorillonite in the clay, having the formula Si 8 Al 4 O 20 (OH) 4 × nH 2 O, where silicon can be replaced by various cations (aluminum, iron, zinc, magnesium, calcium, sodium, potassium, etc.). Montmorillonite has a layered crystal structure, high dispersion and a pronounced ability to adsorption, exchange of cations and hydrophilicity. Its crystal structure (three-layer package) is characterized by the ability to isomorphic substitutions within the crystal lattice in the octahedral layer: Al 3+ → Mg 2+ → Fe 2+ → Zn 2+ → Li +. The gaps between the layers of the elemental stacks and the inter-stack gaps of the montmorillonite structure are considered as lamellar micropores. According to the features of the porous structure, montmorillonite belongs to layered silicates with an expanding structural cell. Consequently, the value of the inter-package distance, the intervals between the layers of the element packages are not constant and vary depending on the amount and type of absorbed substance. This determines the ability of mont-morillonite clays to swell.

There are two types of bentonite clays – calcium and sodium, which have a complex structure, and for both types it is different. Typical calcium bentonites have large pore space values ​​compared to sodium samples, therefore, the latter are characterized by a less pronounced ability to swell, and the process itself is slowed down. This means that the maximum swelling moisture in natural bentonites, containing mainly divalent ions in the exchange complex, is always higher than in sodium natural samples, which is in good agreement with the data on the hydrophilicity of cation-substituted bentonites. In addition, if bentonites contain more divalent exchangeable cations Ca 2+, Mg 2+, they have a greater number of active centers on the surface of particles, through which the dispersed phase is hydrogen bonded with the dispersed medium. If, however, monovalent metals, mainly Na-ions, prevail in the composition of exchangeable cations, then the sorption activity of the surface manifests itself to a lesser extent. In this regard, natural calcium bentonites are the best sorbents in comparison with sodium ones, and are distinguished by low catalytic activity and thermal stability..

The main world reserves of bentonite are in China, about 15% in the United States, 7% in Turkey. Other countries with bentonite reserves include Greece, Russia, France, India, Turkey, Azerbaijan, Georgia, Armenia. Most deposits in all countries contain alkaline earth bentonites, while high-quality alkaline bentonites are of limited distribution and are concentrated in deposits of volcanogenic-sedimentary and hydrothermal-metasomatic geological-industrial types.

A number of deposits of alkaline earth bentonite clays have been discovered in the Russian Federation: Lyubinskoe in Western Siberia, Podsinskoe in Eastern Siberia; Zyryanskoe in the Kurgan region, etc. All of them were formed in freshwater lakes, in a reducing weakly alkaline or neutral medium with a pH of 7-8. The bentonites of these deposits are characterized by a relatively low quality, a low content of montmorillonite (on average, 60–70%), and a relatively larger admixture of sandy-silty material than in bentonites of the marine subtype. In addition, they are sometimes distinguished by increased calcareousness..

On the territory of Uzbekistan, geologists have discovered more than 200 occurrences of bentonite and bentonite-like clays, the exploration reserves of which, according to preliminary data, amount to approximately more than 2 billion tons. Mass formation of high-quality clay formations took place in the Jurassic, Cretaceous and Paleogene periods. To date, only the Navbahor, Azkamar, Kattakurgan, Lagon and Shorsu fields are being developed on an industrial scale. The total amount of mined and processed bentonite clays from these deposits is still only 30-40 thousand tons per year..

Currently, montmorillonite clays are used mainly as a binder and sorbent material. As a binder, they are used for the preparation of casting molds, the manufacture of pellets (balls with a diameter of 15-17 mm) from enriched iron and other ores (clay plays the role of a binder and a desiccant), the production of ceramic products (a binder of a ceramic batch); the addition of montmorillonite can also reduce the iron content in porcelain and improve its quality. In insectofungicides, montmorillonite clay acts as a filler and adhesive, fixing pesticides on the surface of plants. The ability of Na-montmorillonite clays to give a thick suspension is used for preparing drilling fluids, filling plastics, rubbers, paper, paints and other products, and preparing various medical preparations. The high sorption capacity of Samont-morillonite clays is used in the manufacture of catalysts for the cracking of oil, for the purification of petroleum, vegetable and animal oils, waste water, purification (“pasting”) of sugar syrups and wines, for obtaining high-quality photographic gelatin, in the manufacture of various washing pastes.

In addition to these properties, bentonites have such qualities as hydrophilicity, ion exchange capacity, surface activity, which has a positive effect on the absorption of nutrients in the animal’s body. Animal studies have shown that bentonite reduces the stress at the fat-water interface and, like bile acids, improves the absorption of fatty acids and fat-soluble substances. In the gastrointestinal tract of animals, bentonite absorbs water and digestive juices, thereby increasing the surface exposed to bacteria, which enhances the utilization of nutrients in the feed. Due to all these properties, in recent years in European countries, bentonite clays have begun to be widely used in the diets of farm animals as a source of macro- and microelements, as well as to increase the digestibility of feed nutrients, amide-concentrate additives for binding urea nitrogen.

A great deal of experience has been accumulated in the use of bentonites in agriculture. Abroad, bentonites and preparations from them are used in agriculture: as fillers for pesticides to combat pests of agricultural plants; additives to sandy and other marginal soils to improve their agrochemical properties; diluents and accumulators of mineral fertilizers – to reduce their harmful effect on soil biocenoses, to prevent leaching of fertilizers from the soil and, as a consequence, to prevent contamination of groundwater with mineral salts; in the production of liquid complex fertilizers as suspending and stabilizing agents.

The use of bentonite increases the resistance of plants to fungal and viral diseases, reduces the susceptibility of cotton to wilt, and increases the productivity of vegetable crops, potatoes, sugar beets, wheat, and cotton. It should be noted that the greatest effect from the introduction of bentonite clays is manifested at low rates of traditional mineral fertilizers (up to 0.5 of the rate recommended for a given crop).

With the help of bentonite, the possibility of obtaining non-caking urea was revealed. The experience of using alkaline earth bentonites of Tatarstan together with organic and mineral fertilizers to increase the fertility of sod-podzolic soil is known. Thanks to bentonite, potato yield increased by one and a half times.

There are several known works on the use of bentonite to improve the quality of ammonium nitrate, mainly to eliminate its caking. So, in order to obtain ammonium nitrate suitable for bulk transportation and storage in bulk, the inventor’s certificate patented a method for producing granular ammonium nitrate, according to which ammonium nitrate melt with a temperature of 172 ° C and pre-dried to moisture content 1 is simultaneously fed into a mixer with a rotating stirrer before granulation. , 5% bentonite with a grinding fineness of 40 microns. Bentonite is introduced at the rate of its content in the finished product 2 wt. %. Granules of ammonium nitrate, cooled to a temperature of 45 ° C, are treated with an aqueous 40% NF dispersant solution, preheated to a temperature of 65 ° C, in a rotating drum in an amount of 0.03 wt. % (in terms of dry matter). After applying a film of surfactant, the granules are dusted with vermiculite in an amount of 1 wt. %.

The disadvantages of this method are: multistage (mixing, granulating, spraying, dusting), vermiculite shedding from the surface of the granules during storage and transportation, low strength of the granules (2.25 MPa), the tendency of nitrate to thermal decomposition.

The work investigated the effect of the addition of bentonite on the strength of granules and caking of ammonium nitrate. As an additive, we used bentonite powders obtained from bentonite clays of various deposits: Gumbrinsky and Askansky (Georgia), Kazakh and Azkamarsky (Uzbekistan), Cherkassky and Krivorozhsky (Ukraine). The clay was ground in a ball mill, ground in a porcelain mortar, dried at a temperature of 100-110 ° C and sieved through a sieve. The finished additive had particles less than 40 microns in size and a moisture content of 1-2%. Saltpeter was melted in a reactor, then bentonite powder was introduced into the melt at a temperature of 170-175 ° C and constant stirring. The suspension was granulated by prilling. The granules were cooled. Samples of granular ammonium nitrate with additives of 0.5-3.0% of various bentonites were obtained.

It has been established that the addition of bentonite in an amount of 1-3% can significantly increase the strength of ammonium nitrate granules and resistance to modification IIIDIV transformations, as well as reduce caking. The rate of moisture absorption in the presence of bentonite practically does not change. The most effective additive was found to be bentonite from the Cherkassk deposit. If the strength of nitrate granules without additive was 0.54 MPa, with 0.3% addition of this bentonite – 0.97 MPa, then with 3% addition – 2.2 MPa. The traceability of nitrate without additive was 5.6 kg / cm 2, and with a 3% additive – 2.53 kg / cm 2. At 20 transitions of modifications of IIIDIV nitrate, the granules of nitrate without additives were completely destroyed, and at 100 transitions, the granules of nitrate with a 3% addition were destroyed only by 20%..

The data obtained give reason to consider the bentonite additive very promising for the production of nitrate, suitable for bulk transportation and storage, as well as less explosive..

References: 1. Ammonium nitrate: properties, production, application / A.K. Chernyshev, B.V. Levin, A.V. Tugolukov, A.A. Ogarkov, V.A.Ilyin – Moscow: ZAO INFOCHIM “, 2009. – 544s. 2. Pak V.V., Pirmanov N.N., Namazov Sh.S., Reimov A.M., Beglov B.M. Nitrogen sulfur fertilizers based on ammonium nitrate and phosphogypsum melt // Chemistry and Chemical Technology. – 2011, No. 2, p. 21-24. 3. Pak V.V., Pirmanov N.N., Namazov Sh.S., Reimov A.M., Beglov B.M., Seitnazarov A.R. Nitrogen sulfur fertilizers based on ammonium nitrate melt and natural gypsum // Chemical technology. Control and management. – 2012, No. 3, p. 5-8. 4. Review of the world production of bentonite // Eurasian chemical market – international business journal. – Moscow, 2006. – No. 12. –46p. 5. Market overview of bentonite clays in the CIS Text: collection of articles. articles. – Moscow, 2006, 76 p. 6. Bulatov A.P., Lushnikov N.A., Karmatskikh Yu.A. The use of bentonite from the Zyryansk deposit in animal husbandry (Recommendations). FGOUVPO “Kurgan State Agricultural Academy named after T.S.Maltsev”, – 2010. -54s.

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