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.     

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.     

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.     

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.     

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.     

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.     

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.     

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 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.     

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.     

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.     

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.     

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.     

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).     

Selective removal of cesium ions from aqueous solutions using different inorganic metal hexacyanoferrate-prepared sorbents

Mg-Fe–hexacyanoferrate (MgFeCF) and Ni-Fe–hexacyanoferrate (NiFeCF) were prepared and characterized using X-ray diffraction, Fourier-transform infrared spectroscopy spectra, and thermal analysis. The isotherm study showed that the sorption data fit with the Langmuir and Freundlich isotherms at 25?±?1°C. The sorption capacities of the prepared sorbents for MgFeCF and NiFeCF were found to be 154.32 and 180.83?mg?g^?1, respectively. The adsorption of cesium by MgFeCF and NiFeCF is exothermic and spontaneous processes. Kinetic study indicated that the adsorption of cesium on MgFeCF and NiFeCF fits with the pseudo-second-order kinetic model. Desorption tests indicated that the sorption process is relatively stable. The new sorbents are promising efficient materials for cesium removal from aqueous solutions and sea water. The possibility of reusing the sorbents after stripping the metal ions was studied using 0.5?M HCl, and its efficiency for cesium removal was found to be 98% after five runs.     

Sorption of strontium ions onto mesoporous manganese oxide of OMS-2 type

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.     

Absorption of molecular radioiodine from the water vapor-air flow

Sorption of ¹³¹I₂ from the water vapor-air medium on inorganic nanocomposite materials was studied. All the nanocomposite materials synthesized, containing 1, 2, 4, and 8 wt % Ag in various chemical forms, remove ¹³¹I₂ from the water vapor-air flow with more than 99% efficiency.     

Sorption of actinide ions onto mesoporous phosphorus-containing silicas

Equilibrium and kinetic characteristics of template mesoporous silicas containing phosphonic acid residues in sorption of various actinide ions were studied. The sorption equilibrium involving these sorbents is attained within 20 min after introducing the sorbent into the solution. The calculated values of the internal diffusion coefficient \((\bar D)\) and half-exchange time (τ_0.5) in sorption of uranium were ～3.5 × 10^?16 m² s^?1 and ～390 s, respectively. Mesoporous phosphorus-containing silicas efficiently sorb from acid solutions uranyl ions, Th(IV), and Pu(IV). In sorption of uranium from sulfuric acid solutions, the capacity of the sorbents is 125–132 mg g^?1, and in sorption from nitric acid solutions (0.5–3.0 M HNO₃), 276–299 mg g^?1. In sorption of Th(IV) from nitric acid solutions, the capacity of the sorbents is 60–66 mg g^?1. In sorption of microamounts of ²³⁹Pu(IV), the distribution coefficient reaches 4500 cm³ g^?1. Phosphorus-containing silicas in nitric acid solutions do not noticeably sorb ²⁴¹Am, which allows using them for efficient separation of the Pu/Am pair with the separation factor of no less than 2 × 10₃.     

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.     

Evaluation of the effects of treatment factors on the properties of bio-apatite materials

Animal bones have been studied as a resource of low-crystalline apatite for immobilization of toxic heavy metals. Chemical and thermal treatments can be applied for selective removal of bone organic constituents. In this study, the impact of different treatment factors was determined by experimental design methodology, and comparison of the estimated effects was performed in order to optimize the treatment conditions. Fractional factorial design with five variables at two levels was applied for factors screening. The type of chemical reagent (H₂O₂ or NaOH), its concentration (0.1 or 2 mol/L), reaction temperature (20 or 60 °C), contact time (1 or 3 h) and sample annealing (without or at 400 °C) were considered as process variables. Structural properties of bone sorbents, loss of ignition, point of zero charge, surface functional groups, specific surface area, chemical composition, and Cd²⁺ sorption efficiency, were selected as system responses. Samples significantly differed in respect to the organic phase content and composition, thus mechanisms of Cd²⁺ sorption were complex. Statistical analysis has revealed that, between all studied factors, temperature treatment was the most important for sorbents increased specific surface area, porosity and cation sorption. Furthermore, NaOH was more effective than H₂O₂, while the effects produced by variation of other factors were less pronounced. The highest proportion of bio-apatite with desired low crystallinity and high specific surface area was achieved by synergetic effects of chemical treatment with NaOH and thermal treatment at 400 °C.