Association of radionuclides with colloids in soil solutions

Association of Pu and Am with variously sized particles in soil extracts is studied by ultrafiltration. In aqueous extracts, the Pu and Am concentrations depend on the soil type and aqueous solution composition. In the aqueous extracts, from 60 to 100% of the radionuclides and organic carbon are associated with fine colloidal particles (<0.05 μm). The presence of humic acid increases the recovery of radionuclides by a factor of 4–8 depending on the soil type. The Pu and Am distribution among the groups and fractions of humus acids is studied. In the group of humic acids of chernozem, from 65 to 75% of the radionuclides are associated with the fraction with MW > 100 kDa; about 25%, with the fraction with MW 50–10 kDa; and 2–4%, with the low-molecular-weight fraction with MW < 3 kDa. In the group of fulvic acids, 44–49% of the radionuclides is found in the fraction with MW > 100 kDa, and 42–51%, in the fraction with MW < 3 kDa.     

Association of radionuclides with components of fulvic acids isolated from soils

The distribution of Pu and Am between specific and nonspecific components of various groups of the organic matter of soil was studied. For chernozem and soddy podzolic soil, 63 and 53% of Pu and only 1 and 8% of Am, respectively, are bound with fulvic acid purified to remove low-molecular-weight compounds by fractionation on BAU activated charcoal. Larger relative amount of Am, compared to Pu, in the form of low-molecular-weight nonspecific compounds is responsible for higher migration mobility of Am, compared to Pu, in the environment. The sorption of organic complexes of Pu and Am on carbon nanotubes was studied. The degree of Pu sorption only slightly depends on the nature of the organic substance, except solutions of humic acids from which the Pu sorption is appreciably higher. The degree of Am sorption regularly increases with a decrease in the molecular weight of the organic substances.     

Effect of Humic Substances on Plutonium and Americium Speciation in Soils and Soil Solutions

The molecular-weight distribution of humic substances (HSs) of the organic and mineral soils and corresponding soil solutions was studied by gel chromatography, and their distribution over fractions of humus acids was evaluated by the Ponomareva-Plotnikova chemical fractionation technique. Distribution of ^239,240Pu and ²⁴¹Am over HS fractions of different dispersity was studied. In these fractions, HSs are associated with different mineral components and have different solubility and mobility. Plutonium and americium are more strongly associated with humic substances of organic soils as compared to those of mineral soils. Therefore, in passing from mineral to organic soils, the migration ability of radionuclides decreases. These effects are caused by qualitative difference in the HS chemical composition of the HSs of organic and mineral soils. As compared to plutonium, americium enters the composition of poorly soluble organomineral complexes to a smaller extent, forming to a greater extent mobile anionic complexes in the soil solutions. This difference can be responsible for enhanced americium mobility and its easier availability to plants.     

Speciation and Migration Behavior of Pu and Am in Floodplain Soils and Bottom Sediments of the Yenisei River

Am and Pu speciation in floodplain soils and bottom sediments of the Yenisei River is studied. Pu is more tightly associated with amorphous hydroxides as compared to Am. Am associated with organic matter is potentially more mobile than Pu. Model experiments showed that fulvic acids decelerate Am sorption from water to floodplain soil.     

A novel malonamide grafted polystyrene-divinyl benzene resin for extraction, pre-concentration and separation of actinides

A new chelating polymeric extraction chromatographic resin was prepared by chemical anchoring of N,N'-dimethyl-N,N'-dibutyl malonamide (DMDBMA) with chloromethylated Merrifield resin((R)). The grafted resin exhibited stronger binding for hexavalent and tetravalent actinides such as U(VI), Th(IV) and Pu(IV) over trivalent actinides, viz. Am(III) and Pu(III). Batch studies on solid phase extraction performed over a wide range of acid solution (0.01-6M HNO(3)) revealed that ternary mixer of uranium, americium and plutonium or thorium, americium and plutonium could be separated from each other at 1M HNO(3). Desorption of U(VI), Pu(IV) and Am(III) from the loaded resin was efficiently carried out using 0.1M alpha-HIBA, 0.25M oxalic acid and 0.01M EDTA, respectively. Quantitative pre-concentration of actinide ions such as Th(IV) and U(VI) was possible from 3M HNO(3) solution. The practical utility of the grafted resin was evaluated by uranium sorption measurements in several successive cycles. The sorption efficiency of the resin with respect to uranyl ion remained unchanged even after 30 days of continuous use. The surface morphology of the resin was monitored with the help of scanning electron microscopy (SEM) technique.     

Model Assessment of the Migration Capability of Transuranium Radionuclides (<Superscript>241</Superscript>Am and Pu Isotopes) and <Superscript>152</Superscript>Eu in the System Bottom Sediments-Yenisei River Water by Chemical Fractionation Technique

Sorption of radiotracers ²⁴¹Am and ²⁴²Pu and weighable amounts of uranium and stable Eu on bottom sediments in the simulated system bottom sediments—Yenisei river water was studied. At a contact time of 40 min these metals are completely sorbed on the bottom sediments, presumably via association with organomineral complexes and hydrated gels. Along with sorption, these metals can form soluble complexes and stable colloids (pseudocolloids). The distribution factors of ²⁴¹Am and ²⁴²Pu, and stable Eu in the simulated system between bottom sediments and liquid phases were calculated from the results of sorption experiments. The introduced ²⁴¹Am and ¹⁵²Eu initially present in radioactively contaminated bottom sediments of the Yenisei river show similar pattern of distribution over differently mobile fractions. The distribution of weighable amounts of stable Eu significantly differs from that of initially present ¹⁵²Eu and tracer ²⁴¹Am due to decelerated sorption of stable Eu and its considerably higher concentration. A significant part of ²⁴²Pu, ²⁴¹Am, and ¹⁵²Eu is associated with mobile fractions of bottom sediments, which, under certain environmental conditions, can pass into river water as migrating species.__________Translated from Radiokhimiya, Vol. 47, No. 4, 2005, pp. 379–384.Original Russian Text Copyright © 2005 by Bondareva, Bolsunovskii, Sukhorukov, Kazbanov, Makarova, Legler.     

Extraction and sorption preconcentration of U(VI), Am(III), and Pu(IV) from nitric acid solutions with alkylenediphosphine dioxides

The extraction of U(VI), Am(III), and Pu(VI) from nitric acid solutions in the form of complexes with alkylenebis(diphenylphosphine) dioxides and their sorption with POLIORGS F-6 sorbent prepared by noncovalent immobilization of methylenebis(diphenylphosphine) dioxide (MDPPD) on a KhAD-7M? polymeric matrix were studied. The preconcentration conditions and distribution coefficients of U(VI), Am(III), and Pu(IV) in their sorption from 3 M HNO₃ were determined. The possibility of concentrating actinides from multicomponent solutions was demonstrated. The composition and nature of complexes of U(VI) with MDPPD were determined from the ³¹P NMR data.     

Sorption-barrier properties of granitoids and andesite-basaltic metavolcanites with respect to Am(III) and Pu(IV): 1. Absorption of Am and Pu from groundwater on monolithic samples of granitoids and andesite-basaltic metavolcanites

A model study is made of the sorption-barrier properties of intact monolithic samples of granitoids and andesite-basaltic metavolcanites with respect to Am(III) and Pu(IV). In sorption from simulated groundwater (pH 8.3), the surface distribution coefficient in surface sorption K _a was determined to be 8–37 and 4–80 cm for Am and Pu, respectively. The mineral components of the rocks responsible for the radionuclide sorption were identified by autoradiography. The rocks tested are characterized by high retention capacity for Am and Pu.     

Dependence of the migration ability of plutonium and americium in soils on additions of natural and modified organic compounds

The nature and content of modified humic acid derivatives influence the intensity of the recovery of Pu, Am, and C_org from soddy podzolic soil with distilled water. Under the dynamic conditions, these radionuclides are recovered more intensely in the presence of carboxylated humic acids, compared to the hydroxymethylated derivatives. When soils with the introduced modified humic acid derivatives are subjected to prolonged washing with distilled water, the radionuclides undergo redistribution within the columns, suggesting their migration. Under the action of dissolved organic substances isolated from soils (low-molecular-weight nonspecific organic compounds and fulvic acids), the radionuclide migration in soils occurs still more intensely. In the course of soil column washing with an aqueous phase containing the dissolved organic matter, Pu and Am pass into the mobile state to a greater extent than in washing the soils with distilled water.     

Comparison of Methods for Assessing Plutonium Speciation in Environmental Objects

Several methods for Pu speciation study are compared using the same sample of bottom sediment. Data on Pu distribution among different soil fractions (water-soluble, exchangeable and readily soluble, mobile, associated with organic matter, including humic and fulvic acids, and also with amorphous hydroxides, primarily of iron and manganese) are reported. The major fraction of plutonium is associated with the organic matter. The experimental results on the Pu speciation, obtained by different methods, show satisfactory agreement.     

Effect of colloidal component in solutions on adsorption of actinides [Am(III), Pu(IV)] from simulated groundwater by glass and granodiorite

The effect of the colloidal component in solutions on Am(III) and Pu(IV) adsorption from simulated groundwater on glass and monolithic granitoid samples was examined. For the systems under consideration, the presence of colloids in solutions affects the initial step of Am(III) sorption on glass and rocks, decelerating it. As the system approaches the equilibrium state, the role of the colloidal component becomes less significant. When forecasting conditions of underground isolation of transuranium elements, their colloidal form exhibiting increased migration ability in aqueous solutions should be taken into account.     

Association of 90xSr, 137Cs, 239,240Pu, 241Am,and 244Cm with Soil Absorbing Complex in Soils Typical of the Vicinity of the Chernobyl NPP

Association of the main long-lived radionuclides ¹³⁷Cs, ⁹⁰Sr, ^239,240Pu, ²⁴¹Am, and ²⁴⁴Cm with various components of the soil absorbing complexes from soil samples collected along the western, northwestern, and northern tracks of radioactive fallout in the vicinity of the Chernobyl NPP was studied by the sequential leaching. In the samples of the sandy soil collected in the floodplain of the Pripyat river along the northwestern radioactive track, more than 85% of ⁹⁰Sr, 55% of ^239,240Pu, and 75% of ²⁴¹Am and ²⁴⁴Cm are associated with various components of the soil absorbing complex and are potentially mobile species. In the soil samples collected along the narrow western track, 80-85% of ¹³⁷Cs, ⁹⁰Sr, ^239,240Pu, ²⁴¹Am, and ²⁴⁴Cm are incorporated in hot particles. The degree of ¹³⁷Cs, ⁹⁰Sr, ^239,240Pu, ²⁴¹Am, and ²⁴⁴Cm association with different components of the soil absorbing complex is a function of the radionuclide type and physicochemical features of soil.     

Production and characterization of plutonium dioxide particles as a quality control material for safeguards purposes

Plutonium (Pu) dioxide particles were produced from certified reference material (CRM) 136 solution (CRM 136-plutonium isotopic standard, New Brunswick Laboratory, Argonne, IL, U.S.A., 1987) using an atomizer system on December 3, 2009 after chemical separation of americium (Am) on October 27, 2009. The highest density of the size distribution of the particles obtained from 312 particles on a selected impactor stage was in the range of 0.7-0.8 μm. The flattening degree of 312 particles was also estimated. The isotopic composition of Pu and uranium (U) and the amount of Am were estimated by thermal ionization mass spectrometry (TIMS), inductively coupled plasma mass spectrometry (ICPMS), and α-spectrometry. Within uncertainties the isotopic composition of the produced particles is in agreement with the expected values, which were derived from the decay correction of the Pu isotopes in the CRM 136. The elemental ratio of Am to Pu in the produced particles was determined on the 317th and 674th day after Am separation, and the residual amount of Am in the solution was estimated. The analytical results of single particles by micro-Raman-scanning electron microscopy (SEM)-energy-dispersive X-ray spectrometry (EDX) indicate that the produced particles are Pu dioxide. Our initial attempts to measure the density of two single particles gave results with a spread value accompanied by a large uncertainty.     

Distribution of <Superscript>137</Superscript>Cs, <Superscript>90</Superscript>Sr, <Superscript>239 + 240</Superscript>Pu, <Superscript>241</Superscript>Am,and <Superscript>244</Superscript>Cm among Components of Organic Matter of Soils in Near Exclusion Zone of the Chernobyl NPP

Distribution of Chernobyl-derived ¹³⁷Cs, ⁹⁰Sr, ^{239 + 240}Pu, ²⁴¹Am, and ²⁴⁴Cm among organic fractions of soddy-podzolic, sandy, soddy-meadow, and peat soils collected from the Chernobyl Exclusion Zone along the North-Western radioactive fallout track was determined. Regardless of the soil type, 80–85% of ¹³⁷Cs is tightly fixed on the mineral fraction of the soil. Depending on the soil type, 50–70% of ⁹⁰Sr and 15– 45% of ²⁴¹Am are associated with fulvic acid fractions. ²⁴¹Am and ²⁴⁴Cu are similarly distributed among the organic acid fractions. In all the soil types studied, ^{239 + 240}Pu is associated essentially with humic acid fractions. Natural ^{230, 232}Th and technogenic ^{239 + 240}Pu are similarly distributed among the organic fractions.__________Translated from Radiokhimiya, Vol. 47, No. 1, 2005, pp. 91–96.Original Russian Text Copyright © 2005 by Odintsov, Pazukhin, Sazhenyuk.     

Formation of polymeric Pu(IV) hydroxide structures in aqueous solutions

Forms of occurrence of polymeric Pu(IV) in simulated groundwater (SGW) were studied spectrophotometrically and by the method of centrifugal ultrafiltration through filtering inserts permeable to polymeric Pu species with different molecular weights. The dependences of the fractions of definite Pu(IV) forms on the total Pu content in the solution were found. The possibility of formation of Pu(IV) quasipolymeric structures in aqueous solutions was considered in relation to the problem of the transfer of radioactive contaminants with underground water. Equilibrium distribution of Pu(IV) polymers depending on the total Pu(IV) concentration in the solution was analyzed theoretically. From the experimental data obtained, the parameter allowing determination of the weight distribution of the polymeric particles in relation to the total Pu(IV) concentration was theoretically calculated, and their equilibrium distributions depending on the total Pu(IV) concentration were found.     

Sorption preconcentration of radionuclides on Taunit carbon nanostructural material

The possibility of using Taunit carbon nanostructural material for sorption recovery of radionuclides from aqueous solutions was examined. Taunit efficiently recovers Am, Pu, Eu, U, and Tc from weakly acidic and neutral solutions. Taunit is a suitable support for preparing solid extractants based on a phosphonium ionic liquid and diphenyl(dibutylcarbamoylmethyl)phosphine oxide for recovery of actinides from nitric acid solutions.     

Chromium speciation in environmental samples by solid phase extraction on Chromosorb 108

In the present work, a solid phase extraction system has been proposed for speciation of Cr(III) and Cr(VI) in the real samples. The procedure based on the adsorption of chromium(III) as dithizonate chelate on the Chromosorb 108 resin. After reduction of Cr(VI) by concentrated H2SO4 and ethanol, the system was applied to the total chromium. Cr(VI) was calculated as the difference between the total Cr content and the Cr(III) content. The influences of the analytical parameters including pH of the aqueous solution, amounts of dithizone, eluent type, sample volume and flow rates of the sample and eluent solution were investigated. No considerable interferences have been observed from other investigated anions and cations on the chromium speciation. The adsorption capacity of sorbent was 4.50 mg/g Cr(III). The detection limit of Cr(III) is 0.75 microg/L. The proposed method was applied to the speciation of chromium in environmental samples including natural waters and total chromium preconcentration in microwave digested Turkish tobacco, coffee and soil samples with satisfactory results. In order to verify the accuracy of the method, two certified reference materials (NIST SRM 1573a Tomato Leaves and RTC-CRM 025-050 Metals on Soil) were analyzed and the results obtained were in good agreement with the certified values. The relative errors and relative standard deviations were below 5% and 9%, respectively.     

Interaction of plutonium with iron- and chromium-containing precipitates under the conditions of reservoir bed for liquid radioactive waste

The behavior of Pu under the conditions of liquid radioactive waste (LRW) disposal in a reservoir bed was studied. The pH dependence of the Pu sorption is the same in the cases when the radionuclide is introduced together with the simulated LRW solution or after the precipitate formation. The composition and morphology of Fe,Cr-containing precipitates formed under the conditions simulating the radioactive waste disposal were determined. The solid phase was characterized by X-ray diffraction analysis and by transmission and scanning electron microscopy. The phase composition of the precipitates was determined in relation to the presence of acetate ions, Fe concentration in the solution, and storage time and temperature. The main phases formed are ferrihydrite, goethite, hematite, and grimaldiite.     

Interaction of Pu(VI) with Aluminosilicate in Alkaline Solution

Behavior of Pu(VI) in the course of crystallization of aluminosilicate in 2 and 3 M NaOH was studied. Plutonium(VI) inhibits aluminosilicate crystallization. At the Al : Si : Pu molar ratio of 10 : 40 : 2 in the initial mixture, only a minor amount of the X-ray amorphous phase is formed. Partial sorption of Pu(VI) on the aluminosilicate precipitate depends on the alkali concentration in the solution. As determined by spectrophotometry, only neutral and low-charged Pu(VI) hydroxo complexes are sorbed on the aluminosilicate; anionic complexes like [PuO₂(OH)₄]^{2 -} formed in more alkaline solutions are not sorbed. Plutonium(IV) formed by reduction of Pu(VI) is sorbed on aluminosilicate from 3 M NaOH.     

Preparation, Properties, and Application of Modified Mikoton Sorbents

To improve the performance of chitin-containing Mikoton-Ch sorbent, it was modified with K2Cu[Fe(CN)6] or Fe2O3. The sorbents modified with a mixture of these agents were also prepared. The modifying agents are strongly fixed on the Mikoton surface. The techniques for preparing the modified Mikoton are described. The sorption of Cs, Sr, Pu, and Am on modified Mikoton sorbents was studied in relation to the modifier content. Mikoton modified with K2Cu[Fe(CN)6] efficiently sorbs ¹³⁷Cs with the distribution factor K _d of up to 10⁴ ml/g but exhibits low sorption power for Sr, Pu, and Am. Mikoton modified with Fe3O4 is a ferromagnetic material. This sorbent exhibits increased sorption power for Pu and Am (K _d = 10⁴-10⁵ ml/g) but poorly sorbs ¹³⁷Cs. The feasibility of practical application of different kinds of modified Mikoton sorbents is demonstrated.