In order to enhance the efficiency of heavy metal ion extraction from aqueous medium, new nanocomposite magnetic sorbents were synthesized on the base of natural zeolite (Zt) and nanoparticles of ZnFe₂O₄ (F). The composition, structure and physical–chemical properties of new composites with 2% (Zt-2F), 8% (Zt-8F) and 16% (Zt-16F) of zinc ferrite were characterized by XRD, BET adsorption–desorption of nitrogen, SEM with elemental mapping, TEM and magnetometry. The sorption capacity of materials was assessed towards Cu²⁺ ions in aqueous solutions, for which kinetic and equilibrium features of sorption were established. The maximal sorption capacity (a_max, mg/g) of the studied materials increased in the order: Zt (19.4) < Zt-2F (27.3) < Zt-8F (30.2) < Zt-16F (32.8) < ZnFe₂O₄ (161.3). The kinetics of the sorption process followed a pseudo-second order kinetic model. The sorption equilibrium at zinc ferrite was successfully described by the Langmuir model, while the Freundlich model better fitted the sorption equilibrium on zeolite and composites. The efficiency of Cu²⁺ ion extraction from 320 mg/dm³ aqueous solution was 63% for composite Zt-16F and 100% for a sample of ZnFe₂O₄. It was established that the proposed composite sorbents provide the operation of several cycles without regeneration, they can be easily recycled with 0.1 N HCl solution and are capable of magnetic separation. The advantages of new composites and the proposed method of synthesis allow recommending these materials as effective sorbents of heavy metals from wastewater.

During the development of the disposal concept in a crystalline massif of the Russian Federation, a question arose regarding the selection of the most suitable types of bentonite for a buffer layer. Data on the composition, structure, surface, and adsorption properties of four promising deposits have been obtained. The correlations between genesis and specific surface area (SSA) revealed in this study indicate that bentonites of volcanogenic-sedimentary origin have lower SSA in comparison with those of sedimentary and hydrothermal origin. The main contribution to the charge of the 2:1 layer is made by isomorphic substitutions in the tetrahedral sheet, which directly affects the sorption properties of bentonites. The influence of smectite structure on adsorption properties have been described. In particular, the dependencies between the layer charge and cation exchange capacity (CEC) have been analyzed. At the same time, the research indicates that, unlike the CEC, the specific surface area of a deposit is determined by its geological history. Special attention is being paid to refining methodological approaches for deriving crystal chemical formulae of smectites, which will be needed in the future for modelling changes in bentonite over a long-term perspective.

New magnetic nanocomposite sorbents were obtained by doping natural bentonite with nanosized CoFe₂O₄ spinel (10 and 20 wt.%). Nanocrystals of cobalt ferrite were synthesized by a citrate burning method. The structure and physical-chemical properties of the composites were characterized by XRD, XRF, TEM, BET, FTIR and Faraday balance magnetometry. During the formation of nanocomposites, 10–30 nm particles of cobalt ferrite occupied mainly the interparticle space of Fe-aluminosilicate that significantly changed the particle morphology and composite porosity, but at the same time retained the structure of the 2:1 smectite layer. A combination of two functional properties of composites, adsorption and magnetism has been found. The adsorption capacity of magnetic nanosorbents exceeded this parameter for bentonite and spinel. Despite the decrease in the adsorption volume, pore size and specific surface area of the composite material relative to bentonite, the sorption activity of the composite increases by 12%, which indicated the influence of the magnetic component on the sorption process. FTIR data confirmed the mechanism of formaldehyde sorption by the composite sorbent. The production of a magnetic nanosorbent opens up new possibilities for controlling the sorption processes and makes it possible to selectively separate the sorbent from the adsorption medium by the action of a magnetic field.

Synthetic alumosilicates are used in many industrial applications, and the synthesis of clay minerals under different conditions allows us to understand the conditions of their formation. This study examined the impact of varying silica precursors, pH conditions and synthesis durations. Synthetic kaolinite group mineral analogues were investigated by X-ray diffraction, scanning electron microscopy and infrared spectroscopy. Additionally, the crystallinity index was calculated. The impact of using different silica sources on the structural features of synthetic kaolinite group analogues was revealed. The use of a Nanosil precursor resulted in the formation of highly crystalline kaolinite. The most significant alterations in the course of synthesis were observed at different pH values. The formation of various synthetic analogues of minerals from the kaolinite group was observed: at a high pH, the formation of halloysite with a small admixture of kaolinite was observed. Conversely, the synthesis resulted in the formation of ordered kaolinite at a low pH. The crystallinity index of the resulting synthesized kaolinite analogues rises as the synthesis duration increases, while the quantity of non-crystallized material decreases. The changes in the crystallinity of kaolinite when using different silica precursors are related to the different homogenization of the material that occurs at the stage of alumosilica gel formation.

This work is based on a detailed study of samples from three industrial bentonite deposits in Russia (10th Khutor, Zyryanskoe) and Kazakhstan (Taganskoe). The samples of the listed bentonites were undergoing stage-by-stage purification from carbonates, organic matter, and non-clay iron-bearing phase procedures. The conducted research revealed changes in the composition of bentonites already at the first stage of purification, which, however, were not noted for all bentonites, as well as a change in the forms of Fe in smectite structure. The latter is probably associated with changes in cis- and trans-vacant positions. Sorption characteristics with respect to ¹³⁷Cs are determined using the localization and charges in the smectite layer and the slight changes during purification, along with the specific surface area indicators.

This work is devoted to the study of the effect of acid treatment on the structural and textural properties of natural zeolite and its sorption activity with respect to radioiodide. To carry out the experiments, natural zeolite was treated with nitric acid of various concentrations at 20 and 90 degrees. The following methods were used to study the samples: XRD, SEM, DTA, XRF, FTIR, BET, and CEC analyses. Experiments on the sorption and desorption of radioiodide were carried out. The obtained results indicate that acid treatment results in the gradual leaching of aluminum from the crystal lattice and a significant increase in the specific surface area and microporosity of the zeolite. At the same time, the morphology of clinoptilolite is not significantly changed. Additional studies have shown that acid treatment leads to the hydrophobization of zeolite channels and the formation of an amorphous aluminosilicate phase, which makes a significant contribution to the increase in the specific surface area and microporosity. It was found that, with an increase in the degree of dealumination of the zeolite, there is an increase in the sorption properties with respect to radioiodide. The maximum values of sorption capacity were obtained after treating the zeolite with a 1 M nitric acid solution at 90 °C. With a further increase in the concentration of acid, critical changes in the structure of the zeolite occur, leading to a sharp decrease in the sorption capacity. Iodide sorption is not associated with physical adsorption in the micropores of the zeolite and the newly formed amorphous phase. The main mechanism of the sorption appears to be the interaction with silanol and bridging hydroxyl groups on the surface of the zeolite and the amorphous aluminosilicate phase.