Assessment of the Applicability of an Iron-Containing Composite for the Purification of Transformer Oils

Theoretical Foundations of Chemical Engineering - The possibility of using a composite material (hereinafter referred to as composite) based on silica gel modified with particles of Fe(III)...     

X-ray photoelectron study of complexation between uranyl group and chitosan

The interaction of U with chitosan in sorption of U(VI) from sulfate solutions was examined by X-ray photoelectron spectroscopy. It was found that uranyl complexes are formed on the chitosan surface. They contain in the equatorial plane the nitrogen atom of the amino group, as well as, probably, oxygen atoms from the chitosan ring and free hydroxy groups. Prolonged exposure of the chitosan-U(VI) complex in a vacuum chamber of the spectrometer results in cleavage of the bonds linking the uranyl groups with amino and hydroxy groups, which is responsible for formation of U(IV) compounds on the surface with surface depletion in OH groups.     

Localization of cesium radioaerosols on granulated materials from the water vapor-air medium

The paper deals with localization of ¹³⁷Cs¹³¹I radioaerosols and products of their oxidative hydrolysis from the water vapor-air medium with various filtering elements: granulated sorbents based on silica gel and their combination with a helical filtering element (HFE) and TRUMEM metallic membrane filter (pore size ～2.0 μm). The degree of localization of ¹³⁷Cs¹³¹I aerosols was studied in relation to the air flow temperature, water vapor content, linear flow velocity in the sorption column, and amount of ¹³⁷Cs¹³¹I aerosols delivered to the filtration system. Localization of ¹³⁷Cs₂MoO₄ radioaerosols on the granulated sorbents was also studied.     

Gaseous Products of the Interaction of CH3I with Ag-Containing Sorbents Based on Silica Gel and Aluminum Oxide

Radiochemistry - The IR spectra of the gas phase formed during the interaction of gaseous CH3I with granular sorbents based on SiO2 and γ-Al2O3 containing various Ag and Ni compounds were...     

Sorption of U(VI) from aqueous solutions on layered double hydroxides of Mg,Al, and Nd

Sorption of U(VI) from aqueous solutions of various compositions on layered double hydroxides (LDHs) of Mg, Al, and Nd, and also on layered double oxides (LDOs) of Mg and Al was studied. Experiments on sorption of UO₂²⁺ carbonate complexes from aqueous solution on LDO-Mg-Al showed that [UO₂(CO₃)₃]⁴⁻ ions are weakly captured by LDH-Mg-Al formed by contact of LDO-Mg-Al with water. With an increase in the uranium concentration in solution, K _d of U(VI) decreases. For 3.3 × 10⁻³ M [UO₂(CO₃)₃]⁴⁻ solutions, after 24-h contact of the solid and liquid phases, the distribution coefficients do not exceed 1.0 ml g⁻¹ at V/m = 50 ml g⁻¹. From aqueous nitrate solutions, U(VI) is sorbed on LDH-Mg-Al-NO₃ poorly: K _d of U(VI) does not exceed 1.0 ml g⁻¹ at 24-h contact of the solid and liquid phases and V/m = 50 ml g⁻¹. At the same time, U(VI) is efficiently sorbed from aqueous 10⁻³ M UO₂(NO₃)₂ solutions on LDH-Mg-Al and LDH-Mg-Nd with CO₃²⁻ and OH⁻ ions in the interlayer space. After 15-min contact of the solid and liquid phases, K _d of U(VI) exceeds 5 × 10³ ml g⁻¹. With an increase in the UO₂²⁺ concentration to 10⁻¹ M, K _d of U(VI) decreases considerably, becoming lower than 25 ml g⁻¹, but increases to ∼150 ml g⁻¹ with an increase in the contact time of the solid and liquid phases to 24 h. The effect of the Na⁺, Ca²⁺, Cl⁻, and SO₄²⁻ ions and of pH of the initial solution on the U(VI) sorption from aqueous UO₂(NO₃)₂ solutions on LDH-Mg-Al-CO₃ was examined.     

Coprecipitation of <Superscript>137</Superscript>Cs, <Superscript>90</Superscript>Sr,and <Superscript>90</Superscript>Y from aqueous and organic solutions with triethylenediamine complexes of <Emphasis Type="Italic">d</Emphasis>-element nitrates

Coprecipitation of ¹³⁷Cs, ⁹⁰Sr, and ⁹⁰Y with low-soluble complexes of nitrates of d elements (Cu²⁺, Ni²⁺, Zn²⁺) with triethylenediamine [(CH₂-CH₂)₃N₂] from aqueous and aqueous-organic solutions was studied. ¹³⁷Cs and ⁹⁰Sr do not noticeably coprecipitate with precipitates of complexes of Cu²⁺, Ni²⁺, and Zn²⁺ with (CH₂-CH₂)₃N₂ in water; in the process, the radionuclide recovery into the precipitate phase does not exceed 10%. At the same time, the degree of recovery of ⁹⁰Y reaches 65% depending on the experimental conditions. In C₂H₅OH and CH₃CN containing 9 and 5% H₂O, respectively, ¹³⁷Cs, ⁹⁰Sr, and ⁹⁰Y coprecipitate with the complexes to a greater extent, with the degree of recovery varying from 30 to 97% at the molar ratio M²⁺: (CH₂-CH₂)₃N₂ = 1 : 1.     

Recovery of 137Cs, 90Sr, 90Y, and d-element ions from aqueous solutions with sorbents containing triethylenediamine

The possibility of using sorbents based on KSKG coarsely porous silica gel and containing triethylenediamine N(CH₂-CH₂)₃N (TEDA) for recovering ¹³⁷Cs, ⁹⁰Sr, ⁹⁰Y, and d-element ions (Cu²⁺, Ni²⁺) from aqueous solutions was examined. Both ⁹⁰Sr, ⁹⁰Y radionuclides and Cu²⁺, Ni²⁺ ions are sorbed on KSKG containing 0.01–6.72 wt % TEDA. However, on sorbents based on KSKG and containing complexes of Cu²⁺, Ni²⁺, and Zn²⁺ nitrates with TEDA, the ¹³⁷Cs, ⁹⁰Sr, and ⁹⁰Y radionuclides are not sorbed. The equilibrium in the systems with these sorbents is attained within 3 h. The sorption capacity for Cu²⁺ and Ni²⁺ strongly depends on the conditions of the sorbent synthesis. The capacity of the sorbents for Cu²⁺ varies from 63 to 320 mg of metal per gram of sorbent. For Ni²⁺, the sorption capacity is considerably lower (no more than 130 mg of Ni²⁺ per gram of sorbent). The distribution coefficients of ⁹⁰Sr and ⁹⁰Y are 300–700 ml g^?1 at the contact time of the solid and liquid phases of 96 h and V/m = 100 ml g^?1.     

Mechanism of UO<Subscript>2</Subscript>(NO<Subscript>3</Subscript>)<Subscript>2</Subscript>·6H<Subscript>2</Subscript>O decomposition under the action of microwave radiation: Part 2

Products of UO₂(NO₃)₂·6H₂O decomposition under the action of microwave radiation (MWR) were studied by thermal gravimetric analysis, X-ray phase analysis, IR spectroscopy, and electron microscopy. The results of physicochemical studies of these decomposition products were compared to the published data for various uranium compounds, including UO₂(NO₃)₂·6H₂O. Apart from gaseous products, the final products of decomposition of 2–10 g of UO₂(NO₃)₂·6H₂O under the action of MWR for 35 min (the maximal process temperature, 170–320°C, is attained in the first 2–5 min of irradiation) are uranyl hydroxonitrate UO₂(OH)NO₃ and uranium trioxide UO₃ or their hydrates. The results obtained are consistent with the mechanism suggested in our previous paper and involving the reactions (1) UO₂(NO₃)₂·6H₂O → UO₂(OH)NO₃ + 5H₂O + HNO₃ and (2) UO₂(OH)NO₃ → UO₃ + HNO_3. The physicochemical study confirms the conclusions on the composition of products of UO₂(NO₃)₂·6H₂O decomposition under the action of MWR, made previously on the basis of chemical studies. The only precursor of UO₃ in microwave treatment of UO₂(NO₃)₂·6H₂O is UO₂(OH)NO₃ (or its hydrates). This is the main difference between the courses of uranyl nitrate decomposition under the conditions of microwave and convection heating. In the latter case, uranyl nitrate and its hydrates also participate in the formation of UO₃.     

Sorption of Cs,Sr, and Y radionuclides on mixed layered double hydroxides of Mg,Al, and Nd from the aqueous phase

Sorption of ¹³⁷Cs, ⁹⁰Sr, and ⁹⁰Y radionuclides from aqueous solutions on the solid phase of layered double hydroxides (LDHs) of Mg, Al, and Nd was studied. Sorption of ¹³⁷Cs from 10⁻⁵ M aqueous CsNO₃ solutions on the LDH-Mg-Al-Nd solid phase is extremely weak. At the same time, ⁹⁰Sr and ⁹⁰Y are efficiently sorbed on the LDH-Mg-Al-Nd solid phase from 10⁻⁵ M aqueous Sr(NO₃)₂ solutions. After 5-min contact of the solid and liquid phases, K _d of ⁹⁰Sr and ⁹⁰Y exceeds 10³ ml g⁻¹. With an increase in the Nd content in LDHs of mixed composition, their sorption properties toward ⁹⁰Sr and ⁹⁰Y are enhanced.