Vol 69, No 7 (2024)

The pyrochlore solid solution region in the Bi₂O₃–CoO–Sb₂O₅ system is determined. A previously unknown ternary oxide Bi₃Co_2/3Sb_7/3O₁₁ with cubic KSbO₃ structure (sp. gr. Pn-3, a = 9.5801(1) Å, wR =0.0132) is found. An isothermal section of the system is constructed in the region of CoO-Bi₃SbO₇-CoSb₂O₆-BiSbO₄ at 650°C. It is shown that cobalt state in pyrochlore crystal lattice is Co²⁺. For pyrochlore composition Bi_1.5CoSb_1.5O₇, the synthetic methods under hydrothermal conditions of both without microwave-assisted treatment and with it have been developed. Based on the data of X-ray diffraction analysis, local energy-dispersive X-ray analysis, scanning microscopy and IR spectroscopy, a mechanism for the pyrochlore phase formation under hydrothermal condition is proposed. The dispersed Bi_1.5CoSb_1.5O₇ samples (SCD = 30 nm) are synthesized and the prospects of their use as catalysts for CO oxidation are shown.

Polyoxotungstophosphate complex Li₇[γ-PW₁₀O₃₆] · 7H₂O was synthesized. Structure was studied by the X-ray method. Rhombic crystals, space group P21212, a = 12.401(3) b = 18.948(4), c = 9.636(2) Å, V = 2265 ų, Z = 2 (the heteropolyanion sits on a crystallographic twofold axis), λ = 0.71069 Å. The complex is thermostable. The interaction of Li₇W₁₀PO₃₆ with Co(NO₃)₂ forms a tetranuclear complex Co(II) Li₇[Co₄(H₂O)₂(γ-PW₁₀O₃₆)₂] · 36H₂O – an effective catalyst for the water oxidation to O₂. The number of turns of the catalyst is TON = 330, the quantum yield of photogenerated oxygen is Ф_O₂ = 0.46.

To maintain the single-phase nature of the cubic solid solution Ba₂(Y,Cu,Mo)₂O₆, which is prone to polymorphism, titanium oxide was used. As a result of the synthesis by burning the gel, annealing at 1000°C and subsequent cooling in an inertial thermal mode, the cubic modification F3m without an admixture of perovskite Fm3m for the composition Ba₅Y₂CuMoTiO₁₄ was obtained for the first time. A comparative study of samples Ba₄Y₂CuMoO₁₁ and Ba₅Y₂CuMoTiO₁₄ was carried out using the methods of X-ray phase analysis, X-ray fluorescence spectrometry, infrared spectroscopy and diffuse reflectance spectroscopy.

Two novel bismuth(III) iodide complexes – (1,3,4-MePy){[BiI₄]} (1) и (3-Br-1-MePy){[BiI₄]} (2)) – were synthesized by the reaction of iodides of corresponding cations with BiI₃ in organic solvents. Crystal structure of the compounds was determined by X-ray diffraction; For both complexes, the thermal stability was studied, and the optical band gap values were experimentally estimated.

[Zn₂(2-I-bdc)₂bpen]_n (1) and [Zn(I-ipa)bpen]_n (2) are two new metal-organic frameworks based on zinc, 2-iodoterephthalate (2-I-bdc), 5-iodisophthalate (5-I-ipa), and 1,2-bis(4-pyridyl)ethylene (bpen). Using single-crystal X-ray diffraction, crystal structures of 1 and 2 were determined.

The results of the synthesis and identification of complex compounds of hexamethylenetetramine (CH₂)₆N₄ (HMTA) with tungstenphosphatemetallates are presented. The processes and crystalline products of thermal decomposition of compounds with the general formula: Cat₅[PW₁₁O₃₉Z(HMTA)] ∙ nH₂O, Cat=Na⁺, NH₄⁺; Z=Co²⁺, Ni²⁺, Zn²⁺; n = 10–13 and the schemes for their thermolysis were established. It has been shown that ammonium salts during thermolysis form phases of the composition ZO ∙ 0.5P₂O₅ ∙ 11WO₃ or Z_6/73P_6/73W_66/73O₃ with the structure of phosphotungsten bronze. The decomposition products of sodium salts are a mixture of phases with the structures of sodium tungstates Na₂W₂O₇ and Na₂W₄O₁₃. The research results can be used to predict thermal transformations and the composition of thermolysis products of similar complexes of HMTA and tungstenphosphatemetallates of other 3d-elements.

The processes of co-crystallization of neodymium and strontium sulfates have been studied using X-ray phase, X-ray spectral analyses and microscopy. For the first time, high absorption activity of crystal matrices of trigonal modification SrSO₄ · 0.5H₂O and its dehydrated monoclinic modification SrSO₄ to isomorphic heterovalent inclusion of Nd³⁺ ions with the formation of moisture-resistant solid solutions were established. The parameters of the elementary cells of solid solutions and their structural proximity are determined. In a humid environment, solid solutions decompose within 6–10 hours to form stable poorly soluble individual compounds Nd₂(SO₄)₃ · 8H₂O and rhombic modification SrSO₄.

The phase equilibria in the quasi-quaternary GdCoO₃–SrCoO_3–δ–SrFeO_3–δ–GdFeO₃ system have been studied at 1373 K in air. The homogeneity ranges and crystal structure of solid solutions of general composition Gd_1–xSr_xCo_1–yFe_yO_3–δ have been determined. Depending on the concentration of introduced strontium and iron, the Gd_1–xSr_xCo_1–yFe_yO_3–δ oxides crystallize in orthorhombic (x = 0.1 and 0.4 ≤ y ≤ 1.0; x = 0.2 and y = 0.9, sp. gr. Pbnm), tetragonal (0.6 ≤ x ≤ 0.8 and 0.1 ≤ y ≤ 0.5, sp. gr. I4/mmm) or cubic (x = 0.9 and 0.1 ≤ y ≤ 0.9; 0.6 ≤ x ≤ 0.8 and 0.6 ≤ y ≤ 0.9, sp. gr. Pm-3m) perovskite structure. Structural parameters were determined for all single-phase samples. An increase in the concentration of strontium and iron leads to an increase in the unit cell parameters of the Gd_1–xSr_xCo_1–yFe_yO_3–δ oxides. It has been shown that the oxygen content in Gd_1–xSr_xCo_1–yFe_yO_3–δ cobaltites, determined by thermogravimetric analysis, decreases with increasing temperature and strontium content in the samples. An isobaric-isothermal phase diagram of the GdCoO₃ – SrCoO_3–δ–SrFeO_3–δ–GdFeO₃ system at 1373 K in air was constructed.

For the first time, the possibility of synthesizing zinc oxide nanoparticles during the processing of galvanic sludge using microemulsion leaching and subsequent precipitation of nanoparticles in this microemulsion has been demonstrated. Using model systems with ZnO and Zn(OH)₂, the leaching of zinc into reverse microemulsions is studied in the system sodium dodecyl sulfate – butanol-1 – kerosene – water, containing extractants di-(2-ethylhexyl)phosphoric acid, caproic acid or a mixture of tributyl phosphate and acetic acid. The best leaching results are observed for microemulsion with di-(2-ethylhexyl)phosphoric acid. Using the model system “zinc hydroxide contaminated with iron (III) hydroxide,” the possibility of selective extraction of zinc into a microemulsion is shown. A method for the synthesis of nanoparticles has been developed, which includes microemulsion leaching of zinc, separation of unreacted solid phase, precipitation of ZnO nanoparticles from the microemulsion with an aqueous NaOH solution, separation of the precipitate, washing and drying. Using a model system with ZnO, spherical nanoparticles with a diameter of 34 ± 9 nm (according to transmission electron microscopy) were synthesized by this method; X-ray diffraction analysis showed that ZnO was obtained.

Co-leaching of the cathode and anode materials of lithium iron phosphate (LFP) batteries was studied. It was determined that the nature of mineral acid (nitric, sulfuric, hydrochloric) affects the degree of leaching of Li, Fe, Al, and Cu. Hydrochloric acid was chosen as the most suitable leaching agent. The effect of the following parameters of the leaching of active materials was investigated: process duration, temperature, hydrochloric acid concentration, and solid : liquid ratio. For complete leaching of copper, hydrogen peroxide was used as an oxidizing agent. The conditions for the most complete extraction of target elements were found to be 25°C, 2 h, 2 M hydrochloric acid solution, 0.05 M H₂O₂ solution, solid : liquid ratio 1 : 50. The possibility of sufficiently complete leaching of the main elements from spent LFP batteries at room temperature was demonstrated.