Sorption of Cs,Sr, and Y radionuclides on mixed layered double hydroxides of Mg,Al, and Nd from the aqueous phase

Sorption of ¹³⁷Cs, ⁹⁰Sr, and ⁹⁰Y radionuclides from aqueous solutions on the solid phase of layered double hydroxides (LDHs) of Mg, Al, and Nd was studied. Sorption of ¹³⁷Cs from 10⁻⁵ M aqueous CsNO₃ solutions on the LDH-Mg-Al-Nd solid phase is extremely weak. At the same time, ⁹⁰Sr and ⁹⁰Y are efficiently sorbed on the LDH-Mg-Al-Nd solid phase from 10⁻⁵ M aqueous Sr(NO₃)₂ solutions. After 5-min contact of the solid and liquid phases, K _d of ⁹⁰Sr and ⁹⁰Y exceeds 10³ ml g⁻¹. With an increase in the Nd content in LDHs of mixed composition, their sorption properties toward ⁹⁰Sr and ⁹⁰Y are enhanced.     

Sorption of 137Cs and 90Sr by potassium production wastes, clay-salt slimes

Sorption of ¹³⁷Cs and ⁹⁰Sr by clay-salt slimes from model aqueous salt solutions (4.0–40.0 g l^?1 NaCl + KCl) was studied under static conditions. The influence of the sorption parameters (time, specific consumption, salt content) on the efficiency of the ¹³⁷Cs and ⁹⁰Sr recovery with finely dispersed sorbents was studied. The activity of the aqueous salt solution decreases by two orders of magnitude owing to the recovery of ¹³⁷Cs.     

Sorption of 137Cs and 90Sr Ionic Species on Soil of Various Types

Sorption of ¹³⁷Cs and ⁹⁰Sr ionic species on soils with different agrochemical features was studied. The dependence of ¹³⁷Cs sorption on peaty-bog soil on the ratio of the solid and liquid phases shows that sorption occurs by the ion-exchange mechanism. The correlation between the potassium content in soils and     

Sorption of 137Cs and 90Sr by Chemically Modified Humic Acids

Radiochemistry - The sorption characteristics of modified humic acid-based sorbents obtained from peat from the Gurovskoye deposit are studied. The functional and elemental composition of the...     

Sorption of 90Sr and 137Cs on Natural Sorbents in Model Environmental Systems

Sorption of ⁹⁰Sr and ¹³⁷Cs from both tap drinking water and water of Beloyarsk storage basin on samples of natural ion exchangers, glauconite concentrate and white alluvial clay, was studied under static conditions. The distribution coefficients of ⁹⁰Sr and ¹³⁷Cs between these sorbents and water were studied as influenced by the equilibration time and water type. With white alluvial clay and glauconite concentrate the sorption equilibrium is reached within 90 and 270 days, respectively. Sorption characteristics of these natural sorbents allow them to be recommended for water decontamination from ⁹⁰Sr and ¹³⁷Cs.     

Sorption Recovery of 137Cs and 90Sr with Carbonate-Containing Natural Mineral Tripolite

The sorption characteristics of a carbonate-containing mineral (tripolite) were studied on model aqueous solutions and real wastewaters in a wide range of pH in the presence of isotopic and nonisotopic carriers and organic impurities. The sorption of ¹³⁷Cs and ⁹⁰Sr is adequately described by a power function. Analysis of ¹³⁷Cs sorption isotherms suggests that radiocesium is adsorbed by the ion-exchange mechanism, during which Cs⁺ ions from the solution exchange mainly with bivalent ions of the sorbent, whereas in ⁹⁰Sr sorption trivalent ions of the sorbent also participate in the process. The saturation capacities of tripolite with respect to cesium and strontium were evaluated to be 0.3 and 1.0 mg-equiv g^{- 1}, respectively.     

Sorption of 85Sr, 137Cs, and 152Eu from solutions on mixed hexacyanoferrates of potassium and uranyl

Sorption of ⁸⁵Sr, ¹³⁷Cs, and ¹⁵²Eu from neutral and acidic solutions on mixed hexacyanoferrates of potassium and uranyl K₄(UO₂)₄[Fe(CN)₆]₃ · 4H₂O and K₂(UO₂)₅[Fe(CN)₆]₄ · 3H₂O is studied. The distribution coefficients of ⁸⁵Sr, ¹³⁷Cs, and ¹⁵²Eu between the solid phase of K₂(UO₂)₅[Fe(CN)₆]₄ · 3H₂O and the aqueous phase are determined to be 210±10, 3000±500, and 1100±250 ml g^?1, respectively, at a contacting time of 120 min. For solid K₄(UO₂)₄[Fe(CN)₆]₃ · 4H₂O, the respective values are 6670±900, 5600±300, and 3300±250 ml g^?1. The ⁸⁵Sr, ¹³⁷Cs, and ¹⁵²Eu distribution coefficients K _d between the solid K₄(UO₂)₄[Fe(CN)₆]₃ · 4H₂O and the aqueous phase decrease with decreasing pH.     

Sorption of radionuclides from solutions with composite materials based on Mikoton natural biopolymer

Composite sorbents based on Mikoton natural biopolymer, selective to ⁹⁰Sr, were prepared, and features of ⁹⁰Sr sorption with these sorbents were discussed. The inorganic compound used as modifier is deposited on the surface of fibers of Mikoton biopolymer in the form of single crystals and polycrystals. Certain physicochemical parameters of the sorption were determined: static exchange capacity, constants of sorption equilibrium, etc. Deposition of BaSO₄ on the surface of biopolymer fibers increases the sorption capacity toward ⁹⁰Sr in solutions containing sulfate ions, and deposition of MnO₂ enhances the sorption of ⁹⁰Sr from solutions with high concentrations of salts. The influence of the chemical composition and pH of solution was studied in detail. The calculated low value of ΔG ⁰ of radionuclide sorption is attributed to the simultaneous occurrence of several parallel processes in the system, some of which are energy-consuming. The Mikoton-Cs sorbent {composite of Mikoton biopolymer with K₂Cu[Fe(CN)₆]} appeared to be only weakly sensitive to variation of the chemical composition of the solution in a wide range of salt concentrations.     

Sorption of Sr on clay minerals modified with ferrocyanides and hydroxides of transition metals

The sorption properties toward strontium of bentonitic clays modified with Fe(II) and Cu(II) ferrocyanides and Ti(IV), Sn(IV), and Sb(V) hydroxides were studied. The sorption properties of modified bentonites significantly surpass those of the natural mineral. The sorption equilibrium is attained in 2 h. The most efficient sorbent is the bentonitic clay modified with titanium hydroxide, with which K _d reaches 3.2 × 10⁴.     

Sorption study of an acid dye from an aqueous solutions using modified clays

The removal of the pollutant Supranol Yellow 4GL (S.Y.4GL) was studied by using different clays: clay exchanged with sodium (BNa+) and hydroxyaluminic polycation pillared clays in the presence or absence of non-ionic surfactant. While decomposing the surfactant at 500 degrees C, the surface of the clay changed significantly. The study of the behaviour of the three clays with respect to coloring solutions, allowed to determine the equilibrium time and the rate-determining step of the dye S.Y.4GL adsorption. Two simplified kinetic models, were tested to investigate the adsorption mechanisms in terms of pseudo-first order and pseudo-second order equations. Besides, the adsorption capacity data were fitted to Langmuir and Freundlich equations as well. A better fixation was obtained with an acidic pH. The effect of temperature on the adsorption of dye has been also studied and the thermodynamic parameters DeltaG degrees , DeltaH degrees and DeltaS degrees were determined.     

Joint determination of 238Pu, 239, 240Pu, 241Pu, and 90Sr in soil

A procedure for determination of ²³⁸Pu, ^{239, 240}Pu, ²⁴¹Pu, and ⁹⁰Sr in soil is reported. ²⁴¹Pu was determined by liquid scintillation counting in the same Pu sample that was obtained from the initial soil sample by coprecipitation with neodymium fluoride and used for α-spectrometric measurements. ⁹⁰Sr was determined by the carbonate method after ion-exchange separation of plutonium. The ⁹⁰Sr activity in the sample was estimated using two measurements of the Cherenkov radiation of ⁹⁰Y, the first made just after separation of ⁹⁰Sr from ⁹⁰Y. This technique allows monitoring of ⁹⁰Y accumulation, excluding contributions from foreign radionuclides. Original Russian Text & V.N. Zabrodskii, Yu.I. Bondar’, A.S. Komarovskaya, V.N. Kalinin, 2006, published in Radiokhimiya, 2006, Vol. 48, No. 1, pp. 87–91.     

Ionic Composition of Hot Particles Containing U,Cs, and Sr,Evaluated from the Parameters of X-ray Photoelectron Spectra of Outer U5f and Inner U4f,Cs3d, 4d,and Sr 3d Electrons

The elemental and ionic composition of pellets produced from reactor fuel (UO₂) containing 0.1 wt % Cs and 0.5 wt % Sr relative to U and also of hot particles generated by heating of the fuel to 2000°C and then subjected to additional heating to 900°C in air or argon and condensed on aluminum support was analyzed by the X-ray photoelectron spectroscopy. It was shown that within the first 20 s of heating U and Cs sublime predominantly. In the subsequent 300 s of heating U, Cs, and Sr sublime. For example, it was found that hot particles collected in the first 20 s of heating and subjected to additional heating at 900°C in air flow contain 68% U and 32% Cs, whereas particles collected in the subsequent 360 s and subjected to the same additional heating contain 51% U, 13% Cs, and 36% Sr. It is assumed that these hot particles incorporate uranyl compounds of the following types: UO₂CO₃, Cs₂UO₄, Cs₄UO₂(CO₃)₃, CsUO₂(OH)₃, SrUO₄, Sr₃UO₆, and SrUO₂CO₃(OH)₂. Treatment of the surface of hot particles with Ar⁺ ions produces changes in their composition.     

Anisotropy of clays in diffusion transport of radionuclides

Comprehensive analysis of physicochemical and mineralogical properties of clays as surrounding rocks for radioactive waste repositories is performed with emphasis on the clay anisotropy. The results of a long-term experiment on diffusion transport of radionuclides in an experimental sample, a Cambrian clay monolith, are reported, and the anisotropy of the clay monolith with respect to diffusion properties along and perpendicular to the stratification plane is considered in detail.     

Sorption of endrin to montmorillonite and kaolinite clays

It has been discovered previously that clay minerals may have a greater potential for sorption of pesticides. In this paper, the sorption of endrin, a nonionic persistent organochlorine pesticide, to montmorillonite and kaolinite was investigated. The effect of pH, ionic strength on the sorption was studied. The effect of intercalation of hydroxyl aluminium species on sorption of endrin to montmorillonite was also investigated. The results show that, the sorption isotherm of endrin to montmorillonite and kaolinite was linear. The sorption increases with the increase in ionic strength. pH has effect on the sorption and the sorption on both montmorillonite and kaolinite has obvious troughs at pH about 7.2 and 5.4, respectively. The intercalation of hydroxyl aluminium species decreases the sorption. Sorption mechanism of endrin to montmorillonite and kaolinite was suggested to be a combination of hydrophobic interaction and charge–dipole interaction and troughs in the effect of pH on sorption was attributed to the proton shift reaction of the broken bonds at the clay edges.     

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.     

Sorption of Th,U, and Am on phosphorus-containing ion-exchange materials

Sorption of Th, uranyl, Am, Fe, and Al ions from nitric acid solutions on various phosphorus-containing ion-exchange materials (organic ion-exchange resins, SE-UPO solid extractant) was studied. The highest selectivity to quadruple-charged metal cations is exhibited by S-957 cation exchanger (Purolite) with phosphonic and sulfonic acid groups. The capacity of this resin for Th is essentially independent of the HNO₃ concentration in the range 1–7 M and amounts to 80–95 mg ml⁻¹. The uranyl, Am, Fe, and Al ions are sorbed on S-957 resin considerably worse than Th. The internal diffusion coefficient of Th⁴⁺ ions in S-957 resin from 3 M HNO₃ was determined to be (5.3 ± 0.5) × 10⁻¹³ m² s⁻¹. The IR spectra of S-957 resin in the hydrogen and thorium forms were recorded. S-957 resin shows promise for selective recovery of tetravalent actinides from multicomponent nitric acid-salt solutions.     

Determination of 90Sr, 238Pu, 239,240Pu, 241Pu, and 241Am in soils of chernobyl region using various sample preparation techniques

Radiochemical analysis is made of soddy-podzolic sandy and peaty gley soils collected from the Chernobyl zone. Radionuclides were separated by extraction chromatography or ion exchange, and then determined using an α-ray spectrometer and liquid scintillation and proportional gas counters. Leaching from the preliminarily calcined sample with 8 M HNO₃ does not ensure 100% recovery of radionuclides from peaty gley soil.     

Behavior of Cs, Np(V), Pu(IV), and U(VI) in pore water of bentonite

Sorption of Cs, Pu(IV), Np(V), and U(VI) with bentonite from solutions was studied. Physicochemical species of radionuclides in the liquid phase were determined, the sorption mechanisms were established, and the influence of bentonite colloids on the behavior of radionuclides was studied. It was shown that Cs is sorbed by the ion-exchange mechanism, whereas the sorption of actinides at pH > 5 is governed by the reaction with surface hydroxy groups of betonite, and at pH < 5 the competing processes are ion exchange and complex formation. Reduction of Np(V) and U(VI) to Np(IV) and U(IV) in the solution with Fe(II) compounds present in the system was proved by the extraction method. Various methods of separating the solid phase were used in studying the dependence of the distribution coefficients of Np and Pu on the ratio of pore water and bentonite; it was shown that Np and Pu are sorbed on bentonite colloids.     

Effect of Contact Time of Liquid Radioactive Waste with Bed Rock of Underground Repository on Migration Behavior of 90Sr, 137Cs, 239Pu,and 241Am

Behavior of radionuclides caused by interaction of acidic waste with sandy bedrock in deep underground repositories is studied, including sorption-desorption of ⁹⁰Sr, ¹³⁷Cs, ²³⁹Pu, and ²⁴¹Am. The amount of mobile forms of radionuclides decreases with increasing contact time with bedrock, thus decreasing the migration rate of the radionuclides in the collector bed.