Absorption of Nitrous Oxide from Air by Aqueous and Organic Solutions

Theoretical Foundations of Chemical Engineering - Findings from a study of the N2O absorption from an air flow in various aqueous and organic solutions at 293–298 K were reported. The maximum...     

Sorption of CH<Subscript>3</Subscript><Superscript>131</Superscript>I from water vapor-air medium on porous inorganic sorbents containing triethylenediamine and <Emphasis Type="Italic">d</Emphasis> element nitrates

Sorption of CH₃ ¹³¹I from a water vapor-air medium on porous inorganic sorbents based on silica gel of KSKG grade and containing triethylenediamine (CH₂-CH₂)₃N₂ and d element nitrates was studied. The sorbents prepared by impregnation with (CH₂-CH₂)₃N₂ and Zn, Ni, and Cu nitrates from aqueous solution recover CH₃ ¹³¹I from a water vapor-air flow poorly (degree of recovery <10%). Calcination of the sorbents at temperatures exceeding 250°C does not noticeably affect their sorption power. Heating of the complex Ag(NO₃)(OH)·(CH₂-CH₂)₃N₂H to 160°C causes its exothermic decomposition with a large heat release and formation of metallic silver. Thermal decomposition of the complex of Cu²⁺ with (CH₂-CH₂)₃N₂, synthesized from an aqueous solution at the molar ratio Cu(NO₃)₂: (CH₂-CH₂)₃N₂ = 1: 2, occurs similarly.     

Removal of 131I and 137Cs from aqueous and aqueous-organic solutions with porous polyvinyl formal

The removal of ¹³¹I and ¹³⁷Cs from aqueous and aqueous-organic solutions with porous polyvinyl formal (PPVF) was studied. The degree of radionuclide removal from water with a PPVF sample is determined by the amount of water absorbed by the polymer and is not influenced by the concentration of salts in solution. Porous polyvinyl formal allows recovering ¹³⁷Cs from aqueous-organic solutions with 70 to 99% efficiency.     

Sorption of Radioactive Iodine and Fluoride Ion on Hydroxyapatite from the Aqueous Phase

Sorption of the ¹³¹I^-, ¹³¹IO₃ ^-, and F^- ions on various samples of hydroxyapatite (HAP) from aqueous solutions was studied. The HAP samples were prepared by the following reactions: Ca(OH)₂ + H₃PO₄ HAP, CACl₂ + Na₃PO₄ + NaOH HAP, and Ca(NO₃)₂ + HAP seed + (NH₄)₂HPO₄ + NH₃ HAP. None of the HAP samples sorb ionic species of radioactive iodine from aqueous solutions. As for F^-, the best sorption properties are exhibited by the HAP sample prepared by the second reaction. The degree of recovery of fluoride ion with the HAP precipitate in 5 min, 4 h, and 5 days of the contact of the solid and liquid phases is 54, 66, and >95% of the initial F^- amount, respectively. The distribution factor K _d of the fluoride ion between the HAP solid phase and solution decreases with increasing V/m ratio and pH of the initial solution.     

Temperature-dependent activation energy for silicon desorption processes

A theoretical analysis is presented of the temperature dependence of the activation energy for thermal desorption of silicon from textured tantalum tape. The curves derived from experimental data for the initial stages of desorption are in qualitative agreement with calculation results, which makes it possible to estimate lateral interaction forces and the adatom-substrate interaction energy as a function of surface coverage and to predict structural changes in the film.     

Thermal decomposition of CH3 131I in a gas flow

Thermal decomposition of a volatile organic compound of radioactive iodine, methyl iodide CH₃ ¹³¹I, in a gas flow in the presence of various modifications of granulated materials based on KSKG silica gel impregnated with d elements was studied. Under comparable experimental conditions, 97–99% decomposition of CH₃ ¹³¹I is achieved at 770 ± 15°C without sorbents and at 540 ± 10 and 465 ± 20°C in the presence of straight KSKG silica gel and of the material based on it, impregnated with compounds of Ni or its mixture with Cu (8–10 wt %), respectively.     

Removal of 60Co and 137Cs from simulated NPP trap waters

The possibility of removing ⁶⁰Co and ¹³⁷Cs from simulated NPP trap waters by sorption and precipitation methods was examined. The use of layered double hydroxides (LDHs) of Mg and Nd, containing CO ₃ ^2? in the interlayer space, for removing ⁶⁰Co from NPP trap waters is inefficient, especially in the presence of EDTA. After 2 h of contact of the solid and liquid phases, the degree of ⁶⁰Co sorption does not exceed 12% at V/m = 500 mL g^?1. Coprecipitation of ⁶⁰Co with a complex precipitate of Fe³⁺ and triethylenediamine (CH₂-CH₂)₃N₂ from simulated NPP trap waters containing 0.03 M Co²⁺ allows ～85% removal of the radionuclide. The ⁶⁰CO coprecipitation with KFe[Fe(CN)₆] from simulated NPP trap waters does not ensure its efficient removal. The degree of coprecipitation of ⁶⁰CO with KFe[Fe(CN)₆] varies from ～55 to ～85%. A procedure was suggested for removing ⁶⁰Co and ¹³⁷Cs from aqueous solutions by coprecipitation of the radionuclides with the solid phase of K⁺, Fe³⁺, and Ni²⁺ ferrocyanides formed by adding K₄[Fe(CN)₆], Fe(NO₃)₃, and Ni(NO₃)₂ in succession to the solution. The procedure ensures almost 100% removal of both radionuclides from simulated NPP trap waters.     

Synthesis of sorbents based on coarsely dispersed silica gel, containing nanoparticles of Ag compounds, for localization of volatile radioactive iodine compounds from the water vapor-air medium

The paper deals with the synthesis and physicochemical properties of sorbents based on coarsely dispersed silica gel, containing 1, 2, 4, and 8 wt % nanoparticles of Ag compounds, intended for localization of volatile radioactive iodine compounds from the water vapor-air medium.     

Effect of complexing anions on sorption of U(VI), <Superscript>90</Superscript>Sr,and <Superscript>90</Superscript>Y from aqueous solutions on layered double hydroxides of Mg,Al, and Nd

Sorption of ⁹⁰Sr and ⁹⁰Y from aqueous solutions on Mg-Al and Mg-Nd layered double hydroxides (LDHs) in various forms was studied. The distribution coefficients K _d of U(VI) and ⁹⁰Sr on LDH-Mg-Al-EDTA are 100–120 ml g⁻¹ in 15 min of contact of the solid and liquid phases at V/m = 50 ml g⁻¹. At the same time, under similar conditions, U(VI) and ⁹⁰Sr are not sorbed from aqueous solutions on LDH-Mg-Al-C₂O₄. The sorption of U(VI) from aqueous solutions containing H₂EDTA²⁻, C₂O₄²⁻, and CO₃²⁻ on LDH-Mg-Nd-CO₃ and LDH-Mg-Al-CO₃ strongly depends on the concentration of the complexing anions in the solution. In particular, for 10⁻³ M aqueous UO₂²⁺ solutions, with an increase in [C₂O₄²⁻] from 10⁻³ to 5 × 10⁻² M, K _d of U(VI) decreases from >5 × 10³ to 70 ml g⁻¹ for LDH-Mg-Al-CO₃ and from 170 to ∼0 ml g⁻¹ for LDH-Mg-Nd-CO₃. In the presence of 10⁻³ to 5 × 10⁻² M CO₃²⁻ in aqueous solution, U(VI) is not noticeably sorbed on LDH-Mg-Nd-CO₃ (K _d does not exceed 16 ml g⁻¹ at V/m = 50 ml g⁻¹), and on LDH-Mg-Al-CO₃ the sorption sharply decreases (K _d decreases from >5 × 10³ to ∼0 ml g⁻¹ at V/m = 50 ml g⁻¹). The presence of complexing anions in the solution does not appreciably affect the ⁹⁰Sr sorption, but noticeably affects the 90Y sorption. With an increase in their concentration, K _d of ⁹⁰Y appreciably decreases. The effect exerted by Sr²⁺ ions on the sorption of microamounts of U(VI) and by UO₂²⁺ ions on the sorption of microamounts of ⁹⁰Sr and ⁹⁰Y from aqueous solutions on LDH-Mg-Nd-CO₃ was also examined.     

Sorption of 85Sr, 137Cs, and 152Eu from solutions on mixed hexacyanoferrates of potassium and uranyl

Sorption of ⁸⁵Sr, ¹³⁷Cs, and ¹⁵²Eu from neutral and acidic solutions on mixed hexacyanoferrates of potassium and uranyl K₄(UO₂)₄[Fe(CN)₆]₃ · 4H₂O and K₂(UO₂)₅[Fe(CN)₆]₄ · 3H₂O is studied. The distribution coefficients of ⁸⁵Sr, ¹³⁷Cs, and ¹⁵²Eu between the solid phase of K₂(UO₂)₅[Fe(CN)₆]₄ · 3H₂O and the aqueous phase are determined to be 210±10, 3000±500, and 1100±250 ml g^?1, respectively, at a contacting time of 120 min. For solid K₄(UO₂)₄[Fe(CN)₆]₃ · 4H₂O, the respective values are 6670±900, 5600±300, and 3300±250 ml g^?1. The ⁸⁵Sr, ¹³⁷Cs, and ¹⁵²Eu distribution coefficients K _d between the solid K₄(UO₂)₄[Fe(CN)₆]₃ · 4H₂O and the aqueous phase decrease with decreasing pH.