Sorption of CH3 131I from a water vapor-air flow onto inorganic sorbents containing Ag and nonferrous metals (Cu,Ni, Zn)

Sorption of CH₃ ¹³¹I from a water vapor-air medium onto Fizkhimin inorganic sorbents containing Ag and nonferrous metals (Cu, Ni, Zn) was studied. Ag-free Fizkhimin inorganic sorbents exhibit poor ability to take up CH₃ ¹³¹I. No more than 51% of the initial 10-mg portion of CH₃ ¹³¹I is taken up by the sorbents heated to 350°C. The sorbents containing 1.4–2 wt % Ag and 5.6–8 wt % nonferrous metal (Cu, Ni, Zn) show high ability to take up CH₃ ¹³¹I (>99.8% uptake), with the performance of the Ni-containing sorbents remaining very high (>99.9%) with variation of various parameters of both the sorbents and the medium. The Cu- and Zn-containing analogs do not exhibit such properties.     

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.     

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.     

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.     

Behavior of 131I and 137Cs in the oil-water and oil-gas phase systems

The behavior of ¹³¹I and ¹³⁷Cs in various chemical forms in the oil-water and oil-gas phase systems and the sorption of these radionuclides from radioactive transformer oil onto various inorganic and organic sorbents was studied. The degree of the ¹³⁷Cs extraction depends neither on the time of contact of the oil with aqueous solutions nor on the ¹³⁷CsI concentration in the solution. Under all the experimental conditions, the degree of extraction of ¹³⁷Cs did not exceed 5%. The degree of ¹³¹I extraction from water by the oil depends on the chemical form of the radionuclide: ¹³¹I^?, ³¹IO ₃ ^? , or ¹³¹I₂. The maximal extraction (～70%) is observed for K¹³¹IO₃, and the minimal (～25%), for ¹³¹I₂. Granulated nanocomposites containing particles of carbon or NaX zeolite and Fizkhimin sorbents based on coarsely porous silica gel and containing Ag and Ni in 1: 4 ratio allow efficient removal of ¹³⁷Cs and ¹³¹I from spent transformer oil of GK grade.     

Recovery of <Superscript>131</Superscript>I and <Superscript>137</Superscript>Cs from a solution simulating NPP trap waters

Sorption of ¹³¹I and ¹³⁷Cs from a solution simulating NPP trap waters on various inorganic and organic sorbents was studied. The highest degree of ¹³¹I recovery (>99%) can be attained with Fizkhimin granulated sorbents based on coarsely porous silica gel containing Ag and Ni in 1: 4 ratio, with K _d for ¹³¹I exceeding 10⁵ ml g⁻¹ at V/m = 10³ ml g⁻¹ and contract time of the solid and liquid phases of 120 min. Elevation of the solution temperature to 40°C does not affect the degree of ¹³¹I and ¹³⁷Cs recovery. The degree of ¹³⁷Cs recovery in all the experiments did not exceed 35%. The degree of ¹³¹I recovery by coprecipitation with AgCl and Ag₄[Fe(CN)₆] was about ∼96% and only 65%, respectively.     

Interaction of aqueous UO<Stack><Subscript>2</Subscript><Superscript>2+</Superscript></Stack> solutions with sorbents based on modified silica gel containing Cu,Ni, and Zn

Interaction of aqueous UO ₂ ²⁺ solutions with modified sorbents based on coarsely porous silica gel MSKG, containing Cu, Ni, and Zn ions, was studied. Uranyl ions are sorbed on all the sorbents. The decontamination factors of 10^?2 M aqueous UO ₂ ²⁺ solutions on straight MSKG and on MSKG modified with Cu, Ni, and Zn are of the same order of magnitude and do not exceed 100. In the case of 1.1 × 10^?1 M UO ₂ ²⁺ solutions, the decontamination factors on straight MSKG and on MSKG modified with Cu, Ni, and Zn are also of the same order of magnitude but do not exceed 10. Interaction of the modified Ni-containing sorbent with a UO ₂ ²⁺ solution results in formation of a swamp-green precipitate of the composition NiU(OH)₆·4N₂H₅OH, i.e., UO ₂ ²⁺ is reduced to U⁴⁺.     

Localization of CH<Subscript>3</Subscript><Superscript>131</Superscript>I from Water vapor–Air flow on granulated sorbents containing nanoparticles of Ag and Ni compounds

Sorption of CH₃ ¹³¹I from the water vapor–air medium onto Fizkhimin inorganic sorbents containing nanoparticles of Ag and Ni compounds was studied. The developed solvents containing 2 wt % Ag and 4–10 wt % Ni exhibit high performance in CH₃ ¹³¹I sorption (>99.9% uptake). The sorption efficiency remains very high (>99.9%) as characteristics of the sorbents and the medium are varied.     

Sorption of radioactive iodine from aqueous medium at 25°C on granulated sorbents containing nitrates of <Emphasis Type="Italic">d</Emphasis> elements

Sorption of various species of radioactive iodine from aqueous phase at 25°C with granulated sorbents based on silica gel of the MSKG type, containing nitrates of d elements, was studied. Sorbents containing Zn, Ni, Cu, and Co, both nonmodified and modified, have low distribution coefficients K _d for ¹³¹I^? and ¹³¹IO ₃ ^? (at V/m = 1000, K _d < 120 ml g^?1). Whereas nonmodified sorbents do not noticeably sorb I₂ from the aqueous phase (at V/m = 1000, K _d < 10 ml g^?1), their modified analogs adsorb molecular iodine species and have K _d ～ 170–250 ml g^?1 at V/m = 1000. The study of sorption of radioactive iodine species with granulated sorbents containing silver nitrate showed that nonmodified sorbents have relatively low distribution coefficients K _d for all species of radioactive iodine (at V/m = 1000, K _d < 100 ml g^?1). At the same time, the modified sorbents containing Ni and Ag sorb not only I₂ (at V/m = 1000, K _d ～ 270 ml g^?1) but also ¹³¹I^? and ¹³¹IO ₃ ^? ions from aqueous solutions (at V/m = 1000, K _d ～ 3100 and 1500 ml g^?1, respectively).     

Sorption of CH3 131I from the water vapor-air medium onto nanocomposite materials

Sorption of CH₃ ¹³¹I from the water vapor-air medium onto inorganic nanocomposite materials containing 1, 2, 4, and 8 wt % Ag in various chemical forms was studied. Despite high ability of the synthesized nanocomposite materials containing 1, 2, and 4 wt % Ag in various chemical forms to take up ¹³¹I₂ (>99%), they cannot be used for localizing CH₃ ¹³¹I from the gas flow. The material containing 8 wt % Ag, namely, the SiO₂-8% Ag nanocomposite prepared by treatment of the precursor with a 0.01 M hydroxylamine solution, is the most suitable for this purpose.     

Removal of volatile radioactive iodine compounds from water vapor–air medium

Sorption of CH₃ ¹³¹I and ¹³¹I₂ from water vapor–air medium onto SiO₂–C (2 wt %) composite material and a mixture of SKT-3I with SiO₂–Cu⁰ (10 wt %) was studied. SKT-3I shows high performance in sorption of ¹³¹I₂ and CH₃ ¹³¹I. The degree of localization of ¹³¹I₂ and CH₃ ¹³¹I exceeds 99.99% at ~60°С and gas phase–sorbent contact time τ of ~0.45 s. The degree of sorption of ¹³¹I₂ and CH₃ ¹³¹I onto the SiO₂–C (2 wt %) composite material under similar conditions does not exceed ~87 and ~8%, respectively. Experiments on ¹³¹I₂ and CH₃ ¹³¹I sorption onto mechanical mixtures of SiO₂–Cu⁰ and SKT-3I in the weight ratio varied from 1: 4 to 1: 1 showed that the degree of the ¹³¹I₂ and CH₃ ¹³¹I sorption at ~60°С and τ ~0.45 s exceeded 99.95 and 99.0%, respectively. The scheme of layer-by-layer arrangement of SiO₂–Cu⁰ and SKT-3I in the column was examined. It shows promise for use in AUI-1500VM filters in ventilation systems of nuclear power plants.     

Removal of volatile 137Cs and 131I compounds from an air flow

The removal of volatile ¹³⁷Cs and ¹³¹I compounds from an air flow on various filtering elements was studied. ¹³¹I₂ and ¹³⁷CsOH are sorbed on basalt wool, but the degree of their recovery is low: ～86 and 90–93%, respectively, at the basalt wool bed height of 15–18 cm. The use of a cascade of bubblers in combination with a column packed with basalt wool allows virtually complete (>99.9%) removal of ¹³¹I and ¹³⁷Cs in the form of ¹³¹I₂, ¹³⁷Cs¹³¹I, and ¹³⁷CsOH from an air flow.     

Sorbents for treatment of water vapor-air flows to remove volatile organic compounds of radioactive iodine

Sorption of CH₃ ¹³¹I from water vapor-air medium on Fizkhimin and Siloksid inorganic sorbents and on SKT-3I activated carbon was studied. The sorption power of Fizkhimin, Siloksid, and SKT-3I sorbents toward CH₃ ¹³¹I was examined (1) after their 20-h contract with water, followed by removal of the liquid phase and drying at 110°C; (2) after 4-h treatment with steam (95–98°C), followed by drying at 25°C; (3) after keeping for 9 months in 100% humid air at ambient temperature of 10 to 45°C; and (4) after treatment with a water vapor-air flow (95–98°C, 60–80 vol % water vapor) for 2 h. In most cases, Fizkhimin sorbent and SKT-3I activated carbon preserve high sorption efficiency toward CH₃ ¹³¹I from water vapor-air flow.     

Sorption of 131I2 and CH3 131I from Water Vapor-Air Phase on Polysorb-1

Sorption of ¹³¹I₂ and CH₃ ¹³¹I from water vapor-air phase on Polysorb-1 polymeric sorbent was studied. The efficiency of radioiodine sorption depends on the humidity and flow rate of the vapor-air stream, column temperature, and the amount of volatile radioiodine compounds. Polysorb-1 effectively removes molecular iodine at the relative humidity of up to 100% and the sorption temperature from 20 to 125°C. Under these conditions, more than 99.9% of ¹³¹I₂ is removed from a gas flow at the height of the sorbent bed of 22.0 cm and time of gas-sorbent contact of 3.4 s. Polysorb-1 does not sorb methyl iodide from a water vapor-gas flow.     

Gas-Phase UV Photolysis of CH<Subscript>3</Subscript><Superscript>131</Superscript>I

Gas-phase UV photolysis of ¹³¹I-labeled CH₃I was studied. CH₃ ¹³¹I (228 mg) is completely photolyzed within 5 min under the static conditions at room temperature in an argon atmosphere. The final radioiodine compound formed under these conditions is ¹³¹I₂. The chemical composition of the final products of CH₃I photolysis in air is more complex. Agglomeration corcystallization of the CH₃I photolysis products with NH₄Cl in the gas phase was studied. The results of this study suggest that the main final product of CH₃I photolysis in air is a fine I_xO_y aerosol. In the presence of NH₄Cl, formation of NH₄ ¹³¹I aerosols is possible.__________Translated from Radiokhimiya, Vol. 47, No. 3, 2005, pp. 269–273.Original Russian Text Copyright © 2005 by Kulyukhin, Kulemin, Rumer, Konovalova.     

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.     

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.     

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.     

The Effect of Hydrophobization of Ag-Containing Zeolites on Absorption of CH3131I from the Water Vapor-Air Phase

The effect of hydrophobization of Ag-containing nonmodified and acetylene-modified zeolites with poly(vinyl chloride) (PVC) on sorption characteristics of sorbents with respect to CH₃ ¹³¹I was studied. The PVC coating on the sorbent results in increased absorbtion of CH₃ ¹³¹I from a water vapor-air flow at a humidity of up to approximately 70 vol %; the decontamination factor of approximately 10⁵ is reached. The sorbent modified with PVC retains radioiodine at heating to 300°C and can be proposed for practical purposes.     

Recovery of iodine and cesium radionuclides localized on granulated sorbent Fizkhimin from air-vapor phase

A procedure for recovery of ¹³¹I and ¹³⁷Cs radionuclides from Fizkhimin sorbent containing ¹³⁷Cs¹³¹I and ¹³⁷CsOH radioaerosols and also of Ag¹³¹I formed in the sorbent matrix during chemisorption of gaseous ¹³¹I₂ and CH₃ ¹³¹I was developed. Sequential treatment of the sorbent with 6.0 M HNO₃ and then 10.0 M N₂H₄·nH₂O allows practically complete (more than 99%) removal of ¹³⁷Cs and noticeable decrease of the ¹³¹I content in the sorbent matrix (in some cases, by a factor of more than 10).