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.     

Behavior of radioaerosols formed by evaporation of 137Cs131I and 137CsOH from the metal surface in an electrostatic field

The behavior of radioaerosols formed by condensation of supersaturated ¹³⁷Cs¹³¹I and/or ¹³⁷CsOH vapor in an electrostatic field was studied. Supersaturated ¹³⁷Cs¹³¹I and/or ¹³⁷CsOH vapor was generated by evaporation of salt crystals from a metal surface heated to high temperatures owing to ohmic resistance. By applying additional potential to the aerosol generator, it is possible to control the behavior of ¹³⁷Cs¹³¹I, ¹³⁷CsOH, or ¹³⁷Cs¹³¹I + ¹³⁷CsOH aerosols in an electrostatic field.     

Estimation of intakes of 131I, 137Cs and 134Cs after the Chernobyl accident

Activities of (131)I and (137)Cs excreted in urine from two healthy males during May 1986, when contaminated air masses from Chernobyl arrived on the territory of the Czech Republic, were determined by bioassay. The data were used to estimate the intakes and committed effective doses from these radionuclides. The results for inhalation intakes are of particular interest, in the absence of sufficient contemporary data for airborne activity. They are found to be higher than initial estimates based on air sampling.     

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.     

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.     

Electrospun polyurethane fibers for absorption of volatile organic compounds from air

Electrospun polyurethane fibers for removal of volatile organic compounds (VOC) from air with rapid VOC absorption and desorption have been developed. Polyurethanes based on 4,4-methylenebis(phenylisocyanate) (MDI) and aliphatic isophorone diisocyanate as the hard segments and butanediol and tetramethylene glycol as the soft segments were electrospun from their solutions in N,N-dimethylformamide to form micrometer-sized fibers. Although activated carbon possessed a many-fold higher surface area than the polyurethane fiber meshes, the sorption capacity of the polyurethane fibers was found to be similar to that of activated carbon specifically designed for vapor adsorption. Furthermore, in contrast to VOC sorption on activated carbon, where complete regeneration of the adsorbent was not possible, the polyurethane fibers demonstrated a completely reversible absorption and desorption, with desorption obtained by a simple purging with nitrogen at room temperature. The fibers possessed a high affinity toward toluene and chloroform, but aliphatic hexane lacked the necessary strong attractive interactions with the polyurethane chains and therefore was less strongly absorbed. The selectivity of the polyurethane fibers toward different vapors, along with the ease of regeneration, makes them attractive materials for VOC filtration.     

Cleaning air from multicomponent impurities of volatile organic compounds by pulsed corona discharge

The relative efficiency of the removal of impurities from airflow under the action of pulsed corona discharge has been studied by processing model mixtures of air with volatile organic compounds (VOCs). A method is proposed that allows the influence of the VOC structure on its reactivity to be directly determined. For this purpose, it is suggested to calculate a relative energy parameter characterizing the reactivity of a given impurity component in the framework of the method employed. This approach significantly intensifies the process of determination of the energy parameters of impurity removal and can be used as a criterion for comparative estimation of the efficiency of various methods employing nonequilibrium plasma for cleaning air from VOCs.     

室内空气中挥发性有机物测定的研究进展

本文对室内空气中挥发性有机物测定的研究进展包括室内空气中挥发性有机物的定义、来源、危害、限量标准、采样方法、分析方法、存在的问题及发展方向等作了较全面的介绍，重点介绍了国内外室内空气中挥发性有机物的分析测试技术，特别是光离子化检测器（PID）及其应用前景。     

Preservation of the charge of radioaerosols formed by condensation of supersaturated 137Cs131I vapor in the course of their bubbling through aqueous solution

Variation of the charge of radioaerosols formed by condensation of supersaturated ¹³⁷Cs¹³¹I vapor, observed when the gas flow passes through an aqueous solution, was studied. The supersaturated ¹³⁷Cs¹³¹I vapor was formed by evaporation of salt crystals from the metal surface heated to high temperatures owing to ohmic resistance. The radioactive aerosols preserve their charge even after bubbling through aqueous solutions, which allows using electric filters for localizing the aerosols.     

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.     

Removal of p-xylene from an air stream in a hybrid biofilter

Biofiltration of an air stream containing p-xylene has been studied in a laboratory hybrid biofilter packed with a mixture of mature pig compost, forest soil and the packing material which was made of polyethylene (PE) and used in the moving bed biological reactor (MBBR) in wastewater treatment. Three flow rates, 9.17, 19.87 and 40.66 m(3)m(-2)h(-1), were investigated for p-xylene inlet concentration ranging from 0.1 to 3.3 g m(-3). A high elimination capacity of 80 g m(-3)h(-1) corresponding to removal efficiency of 96% was obtained at a flow rate of 9.17 m(3)m(-2)h(-1) (empty bed residence time of 132 s). At a flow rate of 40.66 m(3)m(-2)h(-1) (empty bed residence time of 30s), the maximum elimination capacity for p-xylene was 40 g m(-3)h(-1) and removal efficiencies were in the range of 47-100%. The production of carbon dioxide (P(CO(2))) is proportional to elimination capacity (EC) and the linear relation was formulated as P(CO(2))=1.65EC+15.58. Stable pH values ranging from 6.3 to 7.6 and low pressure drop values less than 0.2 cm H(2)O (19.6 Pa) of packing media in compost-based biofilter of hybrid biofilter were observed, which avoided acidification and compaction of packing media and sustained the activity of microorganism populations.     

Removal of oxygenated volatile organic compounds by catalytic oxidation over Zr-Ce-Mn catalysts

The composition-activity relationship of Zr-Ce-Mn-O materials was investigated for the catalytic removal of Oxygenated Volatile Organic Compounds (OVOC) emitted by stationary sources. Using a sol-gel method, very high surface specific areas, small crystallite sizes and high redox properties were obtained for Zr(0.4)Ce(0.6-x)Mn(x)O(2) catalytic systems after calcination at 500°C. The textural and redox properties were improved when Mn content increased in the material, especially for x=0.36. As a result the most active and selective catalyst in the butanol (model of OVOC) oxidation was obtained for the nominal composition Zr(0.4)Ce(0.24)Mn(0.36)O(2) due to a high oxygen mobility and surface Mn(4+) concentration.     

Real-time quantification of traces of biogenic volatile selenium compounds in humid air by selected ion flow tube mass spectrometry

Biological volatilization of selenium, Se, in a contaminated area is an economical and environmentally friendly approach to phytoremediation techniques, but analytical methods for monitoring and studying volatile compounds released in the process of phytovolatilization are currently limited in their performance. Thus, a new method for real time quantification of trace amounts of the vapors of hydrogen selenide (H(2)Se), methylselenol (CH(3)SeH), dimethylselenide ((CH(3))(2)Se), and dimethyldiselenide ((CH(3))(2)Se(2)) present in ambient air adjacent to living plants has been developed. This involves the characterization of the mechanism and kinetics of the reaction of H(3)O(+), NO(+), and O(2)(+?) reagent ions with molecules of these compounds and then use of the rate constants so obtained to determine their absolute concentrations in air by selected ion flow tube mass spectrometry, SIFT-MS. The results of experiments demonstrating this method on emissions from maize (Zea mays) seedlings cultivated in Se rich medium are also presented.     

Seasonal and long-term variations in 137Cs among adults from Swedish hunter families

To study seasonal variations in 137Cs, whole-body content measurements of adults from Swedish hunter families have been performed in autumn 1997 and spring 1998. Measurements were performed in three locations, By, Harbo and G?vle, geographically close (within 100 km of each other) but with large differences in ground deposition levels. The hunter families at these three locations were previously measured in 1994. The measured persons were also asked for their frequency of intake of moose, roe-deer, reindeer, freshwater fish, mushrooms and berries. A statistically significant lower frequency of intake of mushrooms and berries in By, moose, roe deer and mushrooms in Harbo, and moose in G?vle was found in springtime compared to autumn. In one of the locations, there was a statistically significant lower average 137Cs whole-body content in spring 1998 than in autumn 1997 while in the other two locations no such effects could be seen. The 137Cs whole-body content has decreased by 37% from 1994 and to 1998 (including physical decay) correlated to an effective ecological half time of 6 years.     

Chelating scintillation fibers for measurements of 137Cs

Solid scintillating fibers, coated with a dual-mechanism bifunctional polymer shown to bind Cs(I) in alkaline solutions, were developed for measurement of 137Cs. The effect of the epoxy-polymer coating thickness on attenuation of the signal from 137Cs was evaluated. After optimal coating conditions were determined, both scintillation fiber and resin functions were retained, producing stable field-ready fibers. Temporal studies were performed to examine the kinetics of 137Cs uptake into the resin. Calibration curves of the fiber response were generated by beta-emission from solutions of 137Cs dissolved in 1 M sodium hydroxide. The plots exhibited a linear response over a range of 4-3200 nCi/mL (3.4 x 10(-10)-2.7 x 10(-7) M 137Cs), with a limit of detection of 3.65 nCi/mL (approximately 42 parts per trillion 137Cs). The distribution coefficient of Cs was determined to be 490 +/- 50 mL/g from these measurements. Selectivity studies of the resin were performed in the presence of 100 fold excess of Sr(II), Al(III), and nonradioactive Cs(I). Linear calibration plots were obtained in the presence of these potential interferences, but at a reduced sensitivity. The fibers were also used to evaluate the 137Cs content of a mock tank waste sample to show the potential of the fibers in complicated matrixes.