This study is devoted to studying the sorption of ¹³⁷Cs on mineral sorbents at a wide pH range, from 2 to 10, as well as to studying sorption mechanisms. In order to obtain the most reliable sorption characteristics, samples of high purity were examined as sorbents: bentonite, glauconite, zeolite, and diatomite. A detailed description of their mineral composition, cation exchange capacity and specific surface of sorbents is given. XRD, XRF, FTIR, SEM, and BET adsorption methods were used for assaying. The sorption and desorption values were identified for each sorbent. As a result of the conducted research, it can be concluded that ¹³⁷Cs sorption mainly occurs through the exchange reaction on zeolite, glauconite and bentonite. The highest cesium Kd was observed on zeolite due to its high CEC and amounted to 4.05 mg/L at pH 7. The higher sorption capacity of glauconite in comparison with bentonite is primarily due to the high layer charge which is mainly localized in tetrahedral sheets, and to the existence of highly selective sorption sites (frayed edge sites) on the glauconite surface. Diatomite showed the lowest sorption capacity provided by the presence of a small quantity of smectite and kaolinite in its composition. The values of desorption increase in the following order: zeolite < bentonite ~ diatomite < glauconite.

—Complex studies revealed transformations of composition, structure, and properties of bentonite clays of the Taganskoe (Kazakhstan) and Dahskovskoe (Moscow oblast) deposits under...

Bentonite clays have unique properties that determine their use as the main component of engineered barrier systems (EBS) for the isolation of radioactive waste. At present, the Russian Federation is elaborating the concept of deep geological disposal of radioactive waste in crystalline rocks of the Yeniseisky site, where bentonite clays play an important role in ensuring the safety of the repository for a long period of time. This work demonstrates the first results of short-term laboratory experiments (1 and 3 months) on the thermochemical interaction of bentonite and concrete in the presence of synthetic water at an elevated temperature. These experiments will help predict the effect of EBS materials on montmorillonite. Bentonite from the 10th Khutor deposit (Russia) and Portland cement were used in the experiments. At the first stage of the experiments, solutions were obtained after leaching the concrete with a synthetic groundwater solution for 1 month at 90 °C. At the second stage, the interactions of the obtained solutions with bentonite at 90 °C were studied. As a result of the experiments, the processes of concrete leaching were revealed, which changed the composition and acidity (an increase in the pH from 6.1 to 12.1) of the synthetic water and led to an increase in the porosity of the material in contact with the solution. However, no dissolution of montmorillonite was observed, and the changes were quite small. The research results show the high stability of bentonite from the 10th Khutor deposit under model conditions, which was confirmed by modeling. Thus, we can say that at pH ≈ 12 and at elevated temperatures, montmorillonite retains a stable structure for a long time, which is important for ensuring the safety of disposal in general.

Problems of studying the pore space of moraine clay soils are considered by analyzing SEM images of the surface of samples prepared using a special technique. A new algorithm for estimating the pore shape is described. The study of the microstructure of moraine clay soils showed that they are characterized by five pore types. Of particular interest is the existence of large micropores with specific anisometric crescent shape in such soils. These micropores are formed at the interface between the surface of large sand-dust quartz or feldspar grains and the finely divided unoriented clay matrix. Such pores can be ways of localized groundwater filtration through soils, significantly affecting the soil properties.

Using the Pauzhetka and Nizhnee Koshelevskoe geothermal deposits (South Kamchatka), we studied physical-chemical characteristics of hydrothermal clays that form thick (on average, 1.5–1.8 m) and spacious (up to few km² in area) subsurface horizon with peculiar petrophysical and mineralogical-geochemical properties. It was established that the properties of hydrothermal clays are determined by their micro- and nanostructure, which is made up of nanoparticles of aluminosilicates, sulfates, accessory and ore minerals (primarily, sulfides and iron oxides), and amorphous phases. The subsurface horizon of hydrothermal clays represents a long-lived (up to 10 ka and more) highly dynamic colloidal-dispersed mineralogical-geochemical system, which reflects the interaction of deep-seated metalliferous fluids with geological medium in the supergene zone of geothermal deposits.