Sorption of CH3131I from Steam-Gas Phase on Modified Ag-Containing Zeolites

Sorption of CH₃ ¹³¹I from the steam-gas phase on Ag-containing zeolites modified with acetylene was studied. The radioiodine adsorption in a column depends on the silver concentration in the sorbent, humidity of the steam-gas flow, and the temperature. The modified sorbents AgX-m containing 30-57% silver efficiently localize CH3I at the humidity up to 80% and sorption temperature from 120 to 195°C. Under these conditions the decontamination factor of a gas flow with respect to CH₃ ¹³¹I at 7.5-cm height of the sorbent bed and a 0.2 s gas-sorbent contact time exceeds 99.99%. The sorption properties of the modified Ag-containing sorbents are better that those of the nonmodified sorbents and known Ag-substituted zeolites.     

Localization of U(VI) on nickel hydroxide from aqueous solution in the presence of complexing anions at 25°C

Sorption and coprecipitation of U(VI) from aqueous solution containing various complexing anions (CO₃^25-, SO₄²⁻, H₂EDTA²⁻) with the Ni(OH)₂ solid phase at 25°C was studied. Uranium(VI) is not noticeably sorbed on the Ni(OH)₂ solid phase from aqueous solutions containing CO₃²⁻ and SO₄²⁻. The distribution coefficients K _d are less than 1.0 ml g⁻¹ throughout the examined range of [U(VI)]: [L] ratios (L = CO₃²⁻, SO₄²⁻) at V/m ≥ 100 ml g⁻¹ and contact time of the solid and liquid phases of 60 min. In the presence and in the absence of H₂EDTA²⁻, the degree of the U(VI) sorption is essentially the same (K _d ∼90–140 ml g⁻¹ at V/m ≥ 100 ml g⁻¹). Uranium(VI) does not coprecipitate with Ni(OH)₂ from aqueous solutions containing SO₄²⁻ and H₂EDTA²⁻. The distribution coefficients K _d are less than 0.001 ml g⁻¹ at V/m ≥ 200 ml g⁻¹ and contact time of the solid and liquid phases of 60 min. In solutions containing CO₃²⁻, the U(VI) capture by the Ni(OH)₂ precipitate depends on the [CO₃²⁻]: [U(VI)] ratio. The higher the [CO₃²⁻]: [U(VI)] ratio, the more strongly U(VI) coprecipitates with Ni(OH)₂.     

Coprecipitation of 60Co from aqueous solutions with triethylenediamine complexes of d-element nitrates

Formation of complexes of Co²⁺ with triethylenediamine (CH₂-CH₂)₃N₂ (Q) in aqueous solution and coprecipitation of microamounts of ⁶⁰Co with triethylenediamine complexes of Cu²⁺, Ni²⁺, and Zn²⁺ nitrates were studied. Microamounts of ⁶⁰Co poorly coprecipitate with triethylenediamine complexes of Cu²⁺ and Zn²⁺ nitrates. At practically 100% precipitation of Cu²⁺ and Zn²⁺ from solutions in the form of the corresponding complexes, the degree of coprecipitation of ⁶⁰Co with these complexes does not exceed 15%. With the Ni²⁺ complexes formed from 10⁻¹ M aqueous solutions at the molar ratios Ni²⁺: Q = 1 : 1 and 1 : 2, the degree of coprecipitation of ⁶⁰Co is about 45 and 90%, respectively.     

Gas-Phase Conversion of Uranium Monocarbide in a Nitrating Atmosphere

Radiochemistry - Gas-phase conversion of UC in NOx-air, NOx-H20 (vapor)-air, and HN03 (vapor)-air atmospheres in the temperature interval from 298 to 673 K was studied. In the course of the...     

Sorption of 131I2 and CH3 131I from gas-water vapor medium with porous inorganic sorbents containing d elements

Sorption of ¹³¹I₂ and CH₃ ¹³¹I from gas-water vapor medium on porous inorganic sorbents based on silica gel of the MSKG type, containing d elements, was studied. Sorbents containing Zn, Ni, Cu, and Co ammoniates show a low degree of recovery of ¹³¹I₂ and CH₃ ¹³¹I from the gas-water vapor flow (less than 30%); their calcination at a temperature above 250°C does not noticeably affect the sorption power of the sorbent. The sorbents containing Zn, Ni, and Cu nitrates, both unmodified and modified, show a low degree of recovery of CH₃ ¹³¹I from the gas-water vapor medium (less than 1%). At the same time, whereas for unmodified sorbents the degree of recovery of ¹³¹I₂ from the gas-water vapor phase does not exceed 70%, their modified analogs have higher degree of absorption of ¹³¹I₂ (more than 99%), comparable with the similar data for Ag-containing sorbents based on silica gel of the MSKG type.     

Sorption of I2 and CH3 131I on ion-exchange materials from aqueous solutions at 20°C

Sorption of I₂ and CH₃ ¹³¹I from aqueous solutions at 20°C on the materials obtained by modification of KU-2 cation-exchange resin was studied. It was found that these materials are able to absorb I₂ both from distilled water and from a solution whose composition corresponds to the composition of aqueous coolant of the primary circuit of NPPs equipped with reactors of the WWER type, with the distribution coefficients K _d higher than 10³ ml g^?1 at the ratio V/m = 100 ml g^?1. Practically complete absorption of I₂ (>95%) is reached in 15 min. It was shown that AV-18 anion-exchange resin extracts CH₃ ¹³¹ I from aqueous solution with a distribution coefficient K _d exceeding 300 ml mg^?1 at the ratio V/m = 100 ml g^?1.     

Cocrystallization processes in physicochemical studies of radioactive elements in various media

Cocrystallization processes widely occur in the nature and are used in chemical technology. In radiochemistry, they came into use since the end of XIX-beginning of XX century owing to studies by M. Curie, O. Hahn, V.G. Khlopin, and his disciples. They formulated the laws of isomorphous cocrystallization involving microamounts of radioactive elements. However, the formation of anomalous mixed crystals remained poorly understood. Major contribution to the development of this problem was made by A.N. Kirgintsev. Thanks to his studies and the subsequent studies made by other researchers, it became possible to make substantiated conclusions on the charges of ions of the cocrystallizing microcomponents. The use of cocrystallization processes allowed determination of the main physicochemical properties of actinides that are inaccessible in weighable amounts.     

Sorption of 131I? and 131IO3? from Aqueous Solutions on Porous Inorganic Sorbents Modified with d-Element Ammoniates at 25°C

Sorption of ¹³¹I⁻ and ¹³¹IO ₃ ⁻ from aqueous solutions on porous inorganic sorbents modified with d elements is studied at 25°C. The sorbents modified with Ag, Zn, Ni, Cu, and Co ammoniates are characterized by low distribution coefficients of ¹³¹I⁻ and ¹³¹IO ₃ ⁻ (K _d <150 ml g⁻¹ at V/m = 1000). Calcination of the sorbents modified with Ag, Cu, and Zn ammoniates at a temperature above 250°C affects the chemical state of the metals in the sorbent matrix, which is accompanied by slight increase in K _d of ¹³¹I⁻ and ¹³¹IO ₃ ⁻ as compared to as-prepared samples. With the γ-Al₂O₃-based sorbents modified with Ni or Cu, K _d of ¹³¹I⁻ and ¹³¹IO ₃ ⁻ is well comparable with that for the Ag-modified sorbents based on MSKG silica gel.__________Translated from Radiokhimiya, Vol. 47, No. 3, 2005, pp. 265–268.Original Russian Text Copyright © 2005 by Kulyukhin, Mizina, Krasavina, Rumer, Konovalova, Tanashchuk, Bogachev.     

Interaction of radionuclides with some functional derivatives of chitosan in solutions

New derivatives of low- and high-molecular-weight chitosan (LMWC and HMWC), containing various functional groups, were prepared. The solubility of the compounds in aqueous solutions at pH 1–10 and the sorption and complexation of radionuclides with these compounds were studied. Water-insoluble preparations based on LMWC and HMWC efficiently sorbed ⁹⁰Y and ²³³UO₂²⁺ with the distribution coefficients K _d > 10³ ml g⁻¹ at a phase contact time of 1 h and V/m = 100. The water-soluble preparations based on LMWC showed high complexing power toward ²³³UO₂²⁺ and virtually completely retained hydrolyzed U(VI) species in solutions in a wide pH range. In the presence of N-sulfosuccinyl-LMWC (N-SSLMWC), ²³³UO₂SO₄ solutions with pH 8–9 and U(VI)/N-SSLMWC weight ratio of 0.5 remained stable for 200 days, with no precipitation of hydrolyzed ²³³UO₂²⁺ species.