of Geology, Geography and Geoecology

. The efficient and complex use of resources of high quality bentonite clays, as well as the application of relatively low quality bentonite clays in accordance with their mineralogical and lithological properties are identified in the article. As Azerbaijan’s oil industry developed, interest in studying the geological structure of bentonite deposits increased. Prospects for ben-tonite production to reach 1-1.5 million tons of annual productivity in the next 40-50 years are related to the industrial development of the Daşsalakhli deposit, the largest in terms of resources (explored reserves are 180 million tons). The Dashsalakhli field is unique in terms of mineral quality and is one of the largest deposits in the world. Since the Dashsalakhli field has been researched and prepared for industrial development, and taking into account the demand of the world market, it is possible to increase the production and pro - cessing of bentonites by 1.5-2 times with the production of various commodity products in the republic. For this purpose, a unique and powerful “Azbentonite” processing enterprise equipped with modern equipment was established in Baku. One of the most important physical properties of bentonite clay which determines its industrial use is swelling. The swelling of clays is determined by their gran - ulometric and mineral composition, as well as the content of absorbed


Introduction
Bentonite is an important type of non-metallic mineral raw material that is widely used in many leading sectors of the economy.
Bentonite clay got its name from Fort Benton, where it was first discovered in the United States, and industrial production began in the late 19 th century. Later, interest in bentonite clay increased significantly, and their deposits were discovered in many countries around the world.
Bentonites are finely dispersed clays that contain at least 60-70% montmorillonite mineral and have high binding capacity, adsorption and catalytic activity. Montmorillonite is a three-layered clay mineral. Its crystal structure consists of two silicon-oxygen compounds surrounding an octahedral aluminohydroxyl layer. They, in turn, form a structural package. There is no connection between the structural packages of the cations. Therefore, dipole water molecules easily penetrate into the interpacket space, and this ensures the high swelling capacity of the mineral. At the same time, the initial volume of montmorillonite crystals can increase 100 times.
Bentonite deposits are known in the United States (Black Hills, Sanders -Defiance), Canada, Greece, Japan, Italy, Great Britain, CIS and other countries. The main mineral of bentonite clay, montmorillonite got its name from Montmorillon (France), where it was first found. In England, bentonites are called «fuller's earth». Different types of clay have been known to mankind since ancient times.
Two genetic types of montmorillonite clays are known -hydrothermal and volcanic-sedimentary. The second genetic type of industry is important.
Volcanic-sedimentary deposits of bentonites are formed in quiet areas of the sea basin, in underwater lagoons or empty areas of the sea. In seawater, dispersed acidic tuffs disintegrate under prolonged exposure and transform into montmorillonite under alkaline conditions.
The montmorillonite group, which is included in the class of mica silicates, actually belongs to the class of mica silicates, which includes hydromicas and vermiculite, which have a similar structure, and they are united by a general formula which applies to montmorillonite, beidellite, nontronite, saponite, hectorite, and sakonite.
The oil and gas industry is the oldest industry of bentonite clays that consumes most of its products. In this industry, bentonite clays are used in the preparation of high-quality drilling mud used for drilling deep exploration and production wells.
When drilling exploration and production wells for oil and other minerals, the preparation of drilling mud from bentonite clays becomes more important since the rocks have a complex cross-section. For this purpose, bentonite clays with a high content of sodium oxide are selected, which are better moistened with water and swell in a short time and break down into small colloidal particles.

Methodology
Bentonite clays, which contain high amounts of calcium oxide, are not suitable for use in the preparation of drilling mud naturally, as only large particles of them break down in water and do not form a colloidal solution. They are suitable for this purpose after the addition of calcium soda and other reagents in the amount of 3% by weight of bentonite clay.
Bentonite clays are used for drilling mud in the form of piece and powder. Naturally, the demand is put on bentonite clay with technical condition of TT39-044-74, and on powder bentonites with technical condition of TN-39-043-74. Bentonite clay used in the preparation of drilling mud should meet the following requirements: -clay should belong to group B and its yield should not be less than 14-16 m 3 / ton; -its moisture should not exceed 6-10%; -the amount of sand in its composition should not exceed 5%; -the residue in the sieve No 0.0071 should not exceed 10%; -the specific gravity of the clay suspension should not exceed 1.07.
Currently, bentonite clay is used in large quantities as the main component of drilling mud. The high quality of bentonite clay has a significant impact on both the efficiency and quality of drilling mud.
Bentonite powder produced at Khirdalan enterprise of «Azbentonite» Open Joint-Stock Company established in Azerbaijan is naturally suitable for use in the preparation of drilling mud without processing.
The main physico-chemical and technological parameters of bentonite powder prepared at this enterprise are presented in Table 1. PBMA, PBA, PBB bentonite powder is produced from the clay extracted from the deposit. The quality indicators of that product are given in Table 2. Bentonite powder is produced in accordance with the requirements of API 13A-specification. The characteristics of the suspension made from this powder are given in Table 3.
It is possible to improve the quality of bentonite powder produced in accordance with the requirements of consumers. As a result, powder consumption is reduced and the quality indicators of the solution are higher. Recent analysis of bentonite clay has shown that there are some «deviations» in the quality indicators of bentonite, oriented especially towards drilling, i.e., its non-compliance with the standard is observed, and it is very important to take measures to address this problem. Thus, there are cases when the amount of sand in bentonite clay is 17-23%, which is a very high proportion.
Bentonite clays are also successfully used in the production of gel-cement for well buffering (Eriksson, 2017). In addition, bentonite paste can also be used successfully to buffer small fractured rocks.
Adding a certain amount of Ca 2+ -Na + bentonite to gypsum increases its solidification time and increases the strength of the buffer mixture.
When bentonite clay is added to cement, a waterproof buffering material is obtained. In many cases, this buffering material is used to buffer large fractured rocks.
Bentonite clays are used in the casting industry to give plasticity and adhesion to the mold mixture during the casting of both ferrous and non-ferrous metals (Kaufhold and Dohrmann, 2016;Anirudhan, et al, 2012).

Results
As a result of our research on clays of the Central and Southern areas of «Dashsalahli» bentonite clay deposit, it was determined that these clays are suitable for use in the casting industry. Bentonite clay and bentonite clay powder are used for this purpose.
Requirements for bentonite clays in the process of preparation of form mixtures are determined by SS (State standard) 3226-7 and SS 28177. According to these conditions, the strength of moist clay should not be less than 0.1 MPa, and in dry conditions not less than 0.3 MPa. The compliance of the bentonite clays of Dashsalahli deposit with these requirements ensures their use in the process of casting both ferrous and non-ferrous metals.
The use of bentonite clays for such purposes in the industrial fields of the republic can bring significant benefits to our economy.
The quality indicators of bentonite clays used in the casting industry are presented in Table 4.
Comparing bentonite clays with other clays used in this field, it can be concluded that the casting mixture is distinguished by high strength in both moist and dry conditions, as well as significantly lower consumption. Thus, 10% of bentonite clay is added during moist molding and 5% during dry molding. When high-quality bentonite clay is used for this purpose, the required strength can be obtained by reducing the amount of clay. In addition, thanks to the residual adhesive properties of bentonite clay, it is possible to use the mold mixture for a long time after thermal treatment process.
In the oil refining industry, bentonite clays can be used to refine various oil products. Final refining of oil products with absorbents is considered important, as these products contain oxygen, organic, sulfur, nitrogen compounds, excessive hydrocarbons and many other harmful compounds.
Resin is released during storage of oil products, which significantly reduces the quality of oil products. Oil products are mainly refined by corrosive alkalis, sulfuric acid, furfural and other solvents. The refining process is completed by an adsorption process to remove harmful impurities from oil products. Only alkaline-earth bentonite clays extracted from Gumbrin deposit in the Republic of Georgia were used for this process.
Bentonite clays in our country, especially bentonite clays extracted from Dashsalahli deposit, have high water absorption properties (Afandiyeva, 2009) These bentonite clays can naturally remove mineralized water when crude oil is extracted.
In the oil refining industry, natural absorbents are replaced by acid-activated bentonite clay to ensure the refining of oil products.
Both activated and highly dispersed natural bentonite clays can be successfully used in the petrochemical industry.
Activated bentonite clays, along with sorption properties, have catalytic activity in the process of oil cracking and other processes. The main role in the production process of solid consistency oils belongs to highly dispersed alkaline-soil-alkaline (Ca 2+ -Na + ) bentonite clays.
When high-molecular amines are processed from bentonite clays, particles of a certain measure, a finely dispersed colloidal fraction are released. The obtained hydrophobic material is one of the main components of the consistency oil.
Bentonite clays produced from deposits in the country are suitable for use in the production of both sorbents and catalysts.
Based on the porous structural properties, 3 minerals of absorbents are separated: a) layered silicates with expanding structure ocellar; b) layered structures with solid structure ocellar; c) banded structural silicates.
Montmorillonite belongs to the first group as the main rock-forming mineral. Montmorillonite is a microporous sorbent that changes the size of micropores during the adsorption process (Qashgay and Sultanov, 1980;Belusov et al., 2017;Gorn and Dimitrev, 1965).
Due to the crystal structure, in addition to the primary micropores, the sorbent has secondary transition pores, which are pores formed between the particles in contact.
The transition pores of montmorillonite can be increased by treatment with hot mineral acids (Lin and Juang, 2002).
The optimal conditions for acid activation depend on the crystal structure of clay minerals and their composition. Most bentonite clays require a soft mode of acid treatment.
The conducted research shows that bentonite clays can be successfully applied both naturally and activated in various adsorption and catalytic processes in the field of petrochemical refining (Hamzaev et al., 1980;Dunyamaliyev et al., 2004;Afandiyeva, 2007;2018). The bleaching properties of bentonite clays were studied in comparison with other clays. In order to evaluate the bleaching properties of bentonite clay, a refined oil was taken with a standard gumbrin.
The results of these studies are given in Table  5. According to the data presented in the table, the bleaching properties of bentonite clays of Dashsalahli deposit are naturally the same as the ratio of SU machine oil, D-II diesel oil, MK-22 aviation oil to gumbrin used in industrial practice.
When activating bentonite clays of Dashsalahli deposit with acid, its bleaching properties are 3 times higher than bleaching method with gumbrin.
Based on the above-mentioned data, it can be concluded with confidence that the gumbrin obtained from the Republic of Georgia can be completely replaced in the natural clays of Dashsalahli bentonite clay deposit without implementing any activation work.
Bentonite clays and their processed products can be used in the production of polymeric materials, such as a coagulant in wastewater treatment, in the process of alcohols synthesis, in the production of synthetic rubber (Ahmed and Ahmaruzzman, 2016;El-Maghrabi and Mikhail, 2014). The high sorption properties of bentonite clays allow them to be used in the dilution of vegetable oil and fat, as well as in the process of purifying wine, juice, syrup, various types of water, beverage, etc.
Bentonite clay activated in the field of oil-fat production can be used in the process of purifying cotton and other vegetable oils.
Activated bentonite clays can be used as a metallic catalyst in the hydrogenation process of vegetable oils. As a result, fat mass is obtained for the production of margarine. It can also be used in the process of purifying low-quality technical oils.
Bentonite clays of industrial deposits in our country naturally have high adhesive properties. According to this, the wine industry of the Republic can use these clays with great success in filling sweet drinks, grape and fruit wine, wine materials, stabilizing wines instead of food gelatine.
Bentonite clays are highly dispersed and sensitive to exchange reactions. Bentonite clay, in an acidic environment in wine materials, exchanges the sodium cation for the hydrogen ion of the wine, resulting in coagulation, as well as the formation of lumps, and the lumps precipitate quickly, resulting in reduced turbidity and dilution of wine. In addition, bentonite clay also reduces the amount of iron, copper and oth-er harmful compounds in wine (Tomul and Basoglu, 2010).
Experts noted that the purification of wines with bentonite clay is considered promising. The use of these clays provides stability in wine, gives the wine a shine and eliminates other flavours without changing useful substances in it.
When sour wines are purified by means of bentonite clays of Dashsalahli deposit, they become crystal-clear.
Bentonite clay and its processed products can be used with high efficiency in the preparation of cleaning, bleaching powder, paste, emulsions, durable suspensions, anti-corrosion paints for cars, hand sanitizers.
In the process of paint preparation, finely dispersed bentonites can be used in the preparation of stable suspension and emulsions (Saeed et al., 2019).
Finely-dispersed, Ca-Na-bentonite clays can be used in the preparation of injection solutions (Karland, 1998). When the prepared suspension is injected into the pores and cavities of natural rocks, the water permeability of these rocks decreases sharply (Birgersson, et al., 2017). This feature of bentonite clays can be used in the construction of large hydraulic equipment, dams, mines, subway tunnels.
The measure of bentonite clay particles used for this purpose should be less than 0ç05 mm (up to 90%).
Bentonite clays are used in the construction works, preparation of waterproofing materials, construction of tunnels and pipes, as well as in the construction of hydropower plants, dams, artificial reservoirs, industrial facilities, residential buildings, etc. using their feature of trapping cracks and gaps (Zhu, 2012;Dixon et al, 1996). The quality indicators of bentonite clay used in construction works are given in Table .6.

Conclusions
The use of low-condition bentonite clays and opening rocks in various fields ensures the full use of this raw material and the complex development of the deposit.
-The need to use bentonite clays, their processed products and rocks extracted during the production of these clays in many industries has been justified. -The use of bentonite clays in oil, gas, chemical, food, household, oil refining, agriculture, construction and other industries has been studied and scientifically substantiated, taking into account the demand for this raw material. The research on physical and chemical properties of bentonite clay fully meets the requirements of many industries and will contribute to their widespread use in modern production. Water bearing (press-filter) cm 3 15-17.5