Том 59, № 3 (2017)

The α-ThSiO₄ phase, a synthetic analog of thorite mineral, was prepared by hydrothermal synthesis and converted to β-ThSiO₄, a synthetic analog of huttonite mineral. The temperature dependences of the unit cell parameters were studied by high-temperature X-ray diffraction, and the thermal expansion coefficients of the compounds were determined.

Decomposition of aqueous suspensions of uranium(IV) oxalate under the action of an ozone–oxygen mixture was studied. The process occurs in two steps. In the first step, the U(IV) oxidation with the formation of oxalic acid uranyl solutions prevails. The second step involves decomposition of oxalate ions and hydrolysis of uranyl ions. An increase in temperature accelerates the transformation of uranium(IV) oxalate into uranium(VI) hydroxide compounds. In solutions containing KBr or UO₂Br₂, the following reaction occurs: O₃ + Br^– → O₂ + BrO^–. The arising hypobromite ions and hypobromous acid oxidize uranium(IV) oxalate extremely efficiently. The possible mechanism of ozonation of aqueous uranium(IV) oxalate suspensions is discussed.

Gas-phase conversion of uranyl molybdates UO₂MoO₄, UMo_1.7O_7.2, and UMo_0.4O_3.4, of strontium molybdate SrMoO₄, and of strontium uranate SrUO4 into water-soluble compounds in the NO_x–H₂O (vapor)–air or HNO₃ (vapor)–air atmosphere (hereinafter, nitrating atmosphere) was studied. The conversion of UO₂MoO₄, UMo_1.7O_7.2, and UMo_0.4O_3.4 in nitrating atmosphere results in formation of water-soluble uranium compounds and of the water-insoluble phase MoO₃·2H₂O. Rapid separation of the solution from the precipitate in reaction of UO₂MoO₄, UMo_1.7O_7.2, and UMo_0.4O_3.4 conversion products with water allows efficient transfer of U into the solution, with Mo remaining in the form of an insoluble precipitate. The conversion of SrMoO4 depends on the composition of the nitrating atmosphere. In the NO_x–H₂O (vapor)–air atmosphere, there is no SrMoO₄ conversion, whereas in the HNO₃ (vapor)–air atmosphere it is possible to reach ~85% conversion of SrMoO₄ into water-soluble Sr compounds. Complete conversion of SrUO₄ into water-soluble U and Sr compounds is reached when performing the gas-phase conversion at 130°С in both nitrating atmospheres. In the case of the HNO₃ (vapor)–air atmosphere, increasing the process temperature to 150°С leads to a decrease in the amount of water-soluble U(VI) phases.

Sorption of stable and radioactive strontium ions onto mesoporous manganese oxide of OMS-2 type, prepared by the sol–gel method via reduction of potassium permanganate with polyvinyl alcohol in aqueous medium, was studied. The influence exerted by the pore structure parameters and by the phase and chemical composition of manganese oxide on its sorption properties and selectivity to Sr ions was examined. Manganese oxide samples prepared using a 0.1 wt % KMnO₄ solution exhibit the highest values of the sorption capacity for Sr, about 100–150 mg g^–1, and of the Sr distribution coefficient, K_d = (11.5–19.5) × 10³ cm³ g^–1. Introduction of 0.1 M NaCl into this solution considerably decreases the sorption of stable Sr ions, and for all the samples the sorption capacity is 25–35 mg g^–1. On the other hand, for the most active sorbents the distribution coefficient in the presence of 0.1 M NaCl increases by a factor of approximately 8–10 relative to distilled water and reaches (91–208) × 10³ cm³ g^–1. Introduction of 0.05 M CaCl₂ also decreases the Sr uptake, and the sorption capacity of the most active sorbents for stable Sr ions is 25–35 mg g^–1 at K_d (85Sr) equal to (0.14–0.35) × 10³ cm³ g^–1.

The absorption of N₂O from an air flow in various aqueous solutions at 293–298 K was studied. The maximal N₂O absorption under the experimental conditions is reached for water (~22–24%) and saturated solution of K₂Cr₂O₇ in concentrated H₂SO₄ in the presence of Al₂O₃ and without it (~34 and ~30%, respectively). In concentrated HNO₃ and NH₄OH solutions and in 1.0 M NaOH and N₂H₄·nH₂O solutions, the degree of the N₂O absorption varied from ~7.5 to ~11.5%. Similar degree of absorption was obtained with 0.5 M (NH₂)₂CO (~11%). In the other solutions tested, the degree of the N₂O absorption did not exceed ~4.0%.

The kinetics and isotherm of lysozyme adsorption and the strength of lysozyme binding to two carbon materials, activated charcoal and carbon foil, were studied using tritium-labeled lysozyme. Polyethylene films were used as a model nonporous material. The lysozyme adsorption resulted in modification of the surface of the materials, making it more hydrophilic, and the rate at which the adsorption equilibrium was attained depended on the capability of the lysozyme solution to penetrate into pores of carbon materials. The specific coverage of the surface of graphite foil, activated carbon, and polyethylene with lysozyme appeared to be virtually equal when taking into account only pores accessible to the protein. The lysozyme adsorption on the polyethylene surface is reversible, whereas on the surface of activated charcoal and graphite foil it is practically irreversible. The possibility of modification of the carbon foil surface with a lysozyme solution to increase the adsorption zone was confirmed by autoradiography.

3-Amino-2-quinoxalinecarbonitrile 1,4-dioxide (QN) was labeled with ¹²⁵I, and the biological distribution of the product was studied. ¹²⁵I-QN was prepared by direct electrophilic substitution reaction using N-bromosuccinimide (NBS) as an oxidizing agent. The radiochemical yield of 92% was reached under the following optimum conditions: pH 7, 15 min, 100 μg of QN, and 75 μg of NBS. The labeled QN was stable for up to 12 h post labeling. Biodistribution study of ¹²⁵I-QN in tumor-bearing mice reflected that it accumulated in tissues with high proliferation rate with preferential accumulation in tumor sites. ¹²⁵I-QN was incorporated rapidly in the tumor site (T/NT = 4 at 2 h post injection), and then its content slowly decreased, whereas in the other tissues it decreased rapidly. The results obtained encourage the use of ¹²³I-QN as a tumor imaging agent.

The kinetics of radionuclide sorption onto finely divided samples of rocks from the Nizhnekansky massif, taken from the level of the planned arrangement of deep radioactive waste repository, was studied, and the times in which the sorption equilibrium was attained at 20 and 90°С were determined. The distribution coefficients of actinides (²³³U, ²³⁹Pu, ²⁴¹Am) and fission products (¹³⁷Cs, ⁹⁰Sr) were determined. Increasing the temperature from 20 to 90°С intensifies the sorption of the radionuclides studied, except cesium for which the sorption slightly decreases.

The tritium concentration in water samples taken in Yakutsk, Udachnyi town, some rivers, and drainage brines of the Udachnaya diamond-bearing pipe was determined. The tritium concentration in drainage brines of the Udachnaya diamond-bearing pipe virtually coincides with the background values. The study performed shows that there is no tritium migration from the cavity of the Kristall underground nuclear explosion to drainage brines of the Udachnaya diamond-bearing pipe.