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Link for citation: Belousov P.E., Karelina N.D., Morozov I.A., Rudmin M.A., Milyutin V.V., Nekrasova N.A., Rumyantseva A.O., Zakusina O.V., Krupskaya V.V. Zeolite-containing tripoli of Khotynets deposit (Orel region): mineral composition, sorption properties and formation conditions. Bulletin of the Tomsk Polytechnic University. Geo Аssets Engineering, 2023, vol. 334, no. 5, рр.70-84.In Rus. The relevance of the work is caused by the need to develop the mineral resource base of high-quality sorption materials in Russia, as well as to study the properties of natural sorbents with a view to their further application in practice. The aim of the work is to study the features of the geological structure, conditions of formation, mineral composition and sorption properties of zeolite-containing tripoli from the Khotynets deposit. The object of the study is the Khotynets deposit of zeolite-containing tripoli, studied by the field team of the Institute of Geology of Ore Deposits, Petrography, Mineralogy and Geochemistry of Sciences RAS in 2019–2020. Methods: XRD, XRF, FTIR, optical and scanning electron microscopy, determination of SSA and pore size distribution, CEC, experiments on the sorption of cesium, strontium and copper. The paleotectonic reconstruction was carried out as well. Results. The productive strata of the Khotynets deposit consists of three benches, the main useful components of which are minerals of the zeolite, opal-cristobalite and smectite group. Their total content reaches 80 %. The formation of the deposit occurred in three stages and is associated with the primary accumulation of biochemogenic silica in coastal sea waters, the removal of terrigenous clay material from the nearby land, their further compaction, and processing of the accumulated material at the diagenesis stage. The formation of clinoptillolite is associated with an increase in pH and the dissolution of the opal-cristobalite and clay material as a result of the secondary impact of low-temperature deep solutions. The performed experiments showed that this mineral material has high sorption characteristics with respect to cesium and copper and can be used as a component of sorption mixtures for the purification of polluted waters.

The effect on the characteristics of the electrodialysis process of the acid activation of bentonite included in the cationexchange layer of an experimental bipolar membrane obtained by applying a liquid LF-4SK cation-exchange layer containing bentonite particles onto an anion-exchange membrane-substrate MA-41 was studied. Acid activation of bentonite was carried out with nitric acid (C = 1 and 4 mol/dm3) for 6 hours at temperatures of 20 and 90 °C. The conversion of sodium sulphate (C = 0.5 mol/dm3) was carried out in a six-section electrodialysis apparatus with experimental bipolar membranes containing bentonite in its original form and after acid activation. It has been shown that the addition of bentonite treated with nitric acid (C = 4 mol/dm3, t = 90 °C, t = 6 h) to the cation-exchange layer of a bipolar membrane leads to an increase in productivity, current efficiency and a decrease in energy costs compared to a membrane containing bentonite in its original form. Experimental bipolar membranes made on the basis of MA-41 and a liquid sulphonic cation exchanger containing acidactivated bentonite clays make it possible to obtain an acid and alkali performance omparable to that of the MB-3 bipolar membrane.

This article is devoted to the comparison of various methods for the quantitative determination of montmorillonite content in bentonite clays based on the adsorption of organic molecules and cations. The studies were conducted on samples of natural bentonite clays of the main Russian industrial deposits and the CIS: 10th Khutor (Republic of Khakassia), Zyryanskoe (Kurgan region), Dash-Salakhlinskoe (Republic of Azerbaijan), Dinozavrovoe (Republic of Kazakhstan). All samples selected for the study are characterized by a high content of montmorillonite (more than 70 %). As reference values ​​for the contents of montmorillonite, we used the data of X-ray diffraction analysis according to the Rietveld method. As the tested methods, the most common approaches were used both in the research and industrial sectors of Russia, based on the adsorption of a mixture of rhodamine 6zh and chrysoidine dyes (GOST 28177-89), adsorption of methylene blue dye and adsorption of copper (II) complex with triethylenetetramine (Cu-trien), as well as thermal characteristics after saturation with organic compounds. The best convergence of the montmorillonite content values ​​was shown by modified techniques based on the adsorption of methylene blue dye and the adsorption of the Cu-trien complex. Other methods are characterized by a large measurement error. A common problem with these methods is overs equivalent adsorption on highly charged alkaline bentonites and reduced adsorption on alkaline earth bentonites, as well as the presence of impurity minerals and amorphous phases capable of sorption in the composition of bentonite. The research results can be used to compare the results of the content of montmorillonite, cited by various authors in scientific publications and used in production.

In rural areas, research on the environment in native (untaught) soils is important to understand the rate of pedogenesis and to prevent the problems associated with hidden huger. In this article, original data on vegetation, chemical properties and elemental and mineralogical composition of Kastanozems (Protosalic, Siltic) and Hypersalic Solonetz (Siltic) of the small gully catchment (2 ha in total) located at the NE Ergeni Upland (Western Kalmykia, Russia) were presented. Vegetation was described and cut off (to characterize an aboveground biomass) at 13 key plots of 1 × 1 m. The list of species of the small gully catchment area amounts to 23 species (predominantly, perennial herbs) belonging to 13 families and 11 orders. The main dominants are Artemisia lerchiana, A. austriaca, Festuca valesiaca and Poa bulbosa. Soils were described and sampled in 11 cross-sections and two key plots (0 – 10 cm topsoil sampling). In soil water extracts (79 samples in total), electrical conductivity (EC) and pH were measured. In soil samples, particle size distribution, soil organic carbon and CaCO3 contents, total concentration of all the macro elements, some trace (Cl, Nb, Rb, Th, Y, Zr) and potentially toxic elements (As, Co, Cr, Cu, Ni, Pb, Sr, V, and Zn) were described. Moreover, the concentration of three mobile fractions of elements (Li, Be, B, Na, Mg, Al, Si, P, S, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Sr, Ba, Cd, Pb) measured using Inductively Coupled Plasma Atomic Emission Spectrometry (AES-ICP) was presented. Geochemical indexes of weathering (R – Silica/Alumina, CIW – Chemical Index of Weathering, CIA - Chemical Index of Alteration, WIP – Weathering Index of Parker, PWI –Product of Weathering Index, Vogt Ratio, PIA – Plagioclase Index of Alteration, STI – Silica-Titanium Index, B/A – Bases/Alumina, B/R – Bases/R2O3, Si/R - Silica/R2O3, Weathering indexes WI-1 and WI-2, Si/Ses – Silica/Sesquioxides, Si/Fe – Silica/Iron, a – Potassium/Sodium, ba-1 – (Potassium-Sodium)/Alumina, ba-2 – (Calcium-Magnesium)/Alumina, Ba – (Potassium-Sodium-Calcium)/Alumina) were calculated. In 12 bulk soil samples from Kastanozems and Solonetz, mineralogy (X-Ray diffractometry, the Rietveld full-pattern fitting method for quantitative analysis) was described. Data obtained can be used for more confident identification of pollution sources and pollutants’ migration routes, as well as for more effective land-use management, calculating the required doses of nutrients and for adaptation of land use.

Bentonite clay is an important natural material, widely used in many industries. The purpose of this article is to analyze the mineral resource base of bentonite clays in Russia. The data on reserves of deposits, the degree of their development and production volumes are given. The composition and uses of the main developed deposits of bentonite clay in Russia are characterized. A comparative analysis of the reserves and production growth of bentonite over the past decade is carried out. A brief description of the world situation is given, and the mineral resource base of the CIS countries is considered. Since the quality of raw materials, its properties and reserves directly depend on the conditions of origin, a characteristic of the geological and tectonic position and genesis of the bentonite clay deposits of Russia is given. Bentonite-bearing provinces with favorable conditions for the formation of bentonite deposits with volcanogenic-sedimentary genesis are considered. The most promising regions are proposed for the purposes of expanding the mineral resource base of bentonite materials. This work is the result of the authors’ own geological works at various deposits of bentonite clays in Russia, the near and far abroad, as well as the study and interpretation of published materials on this subject over the past decades.