Recovery of <Superscript>137</Superscript>Cs and <Superscript>90</Superscript>Sr from wastewater by sorption on finely dispersed minerals under static conditions

The natural minerals clinoptilolite and tripoli were used for sorption treatment of liquid radioactive waste (LRW) to remove ¹³⁷Cs and ⁹⁰Sr. The efficiency of sorption recovery of these radionuclides with finely dispersed mineral sorbents under static conditions was studied in relation to the sorption time, pH, size of mineral granules, sorbent amount, salt content and chemical composition of solutions, and number of successive sorption steps. The distribution coefficient of radionuclides between the sorbent and aqueous phase and the sorption capacity of sorbents for radionuclides were determined. It was found that treatment of real salt-containing LRW from the Leipunskii Institute of Energy Physics, State Scientific Center of the Russian Federation, with the natural sorbents decreased their activity by 2–3 orders of magnitude owing to recovery of ¹³⁷Cs and ⁹⁰Sr.     

Application of FIBAN fibrous sorbents to concentrating <Superscript>90</Superscript>Sr from wastewater

Sorption of ⁹⁰Sr on FIBAN fibrous sorbents from wastewaters is studied. The performance of sorbents depends on pH: chelating sorbent FIBAN Kh-1 efficiently sorbs ⁹⁰Sr at pH 5–8, and strongly acidic sorbent FIBAN K-1, at pH 1–3. Strontium is readily desorbed from the sorbents with 2 M HCl. Conditions of sorption of strontium from various acidic wastewaters are optimized. FIBAN K-1 exhibits high sorption efficiency for ⁹⁰Sr and good kinetic characteristics. With this sorbent, about 90% of radiostrontium is recovered in a convenient form from wastewaters of various compositions. Original Russian Text A.A. Shunkevich, V.I. Grachek, I.I. Ugolev, S.V. Matveichuk, 2007, published in Radiokhimiya, 2007, Vol. 49, No. 6, pp. 554–556.     

Sorption of <Superscript>137</Superscript>Cs from seawater onto resorcinol–formaldehyde resin

Sorption of ¹³⁷Cs from seawater onto a selective cation exchanger based on resorcinol–formaldehyde resin was studied. The maximal distribution coefficient of ¹³⁷Cs at the ratio S: L = 1: 1000 is (4.1–4.5) × 10³ cm³ g^–1. The sorption-selective characteristics of the resin are negatively affected by alkaline earth meal ions. In the dynamic regime, the operation life of the resorcinol–formaldehyde resin exceeds 700 bed volumes with more than 95% efficiency of cesium sorption. More than 95% of ¹³⁷Cs is eluted with a 1–3 M HNO₃ solution. The eluate volume does not exceed 10 bed volumes.     

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.     

Doping of the perovskite M<Superscript>I</Superscript>M<Superscript>II</Superscript>O<Subscript>3</Subscript> with weighable amounts of Pu and Am

Matrices of the compositions 0.2La₂O₃·Al₂O₃ and 0.4La₂O₃·Fe₂O₃, containing weighable amounts of Pu (13 mg g^?1) and Am (0.336 mg g^?1), were prepared, and their leaching rates were studied. The leaching rates calculated from the surface area determined by low-temperature nitrogen adsorption (BET method) virtually coincide with those found previously for the matrices with tracer amounts of the radionuclides, which indicates that these parameters are intrinsic characteristics of the matrices. The leaching rates calculated from the geometric surface areas are considerably higher and depend on the material porosity and hence on the procedure of its synthesis. The rates of the matrix corrosion were calculated from the ¹⁴⁷Pm leaching rates. They show that the matrix will not disintegrate into small fragments for 100 thousand years even under the emergency conditions of repository flooding with water.     

Determination of the Parameters of Selective <Superscript>137</Superscript>Cs Sorption onto Natural and Ferrocyanide-Modified Glauconite and Clinoptilolite

The effect exerted by surface modification of natural aluminosilicates, glauconite and clinoptilolite, with ferrocyanides on the parameters of selective ¹³⁷Cs sorption was studied. The modification leads to an increase in the specific sorption and in the radiocesium interception potential in the presence of potassium, RIP(K). RIP(K) of the modified sorbents NPF-Gl and NPF-Cl was 6.1 × 10⁵ and 5.0 × 10⁶ mmol kg^–1, and the specific sorption capacity, 138 ± 14 and 136 ± 12 mg g^–1, respectively. The regular trends in variation of the ¹³⁷Cs distribution coefficients in sorption onto the natural and modified sorbents at K⁺ and Са²⁺ concentrations ranging from 10^–4 to 2.0 M were found. The modified sorbents exhibit high specificity to ¹³⁷Cs in a wide range of Ca and K concentrations in the solutions.     

Sorption of <Superscript>90</Superscript>Sr and <Superscript>90</Superscript>Y with stable and metastable modifications of calcium carbonate

A comparative study of sorption of ⁹⁰Sr²⁺ and ⁹⁰Y³⁺ cations from aqueous solutions saturated with respect to calcium carbonate on the metastable CaCO₃ modifications (aragonite and vaterite) and also on the stable CaCO₃ modification (calcite) was carried out at 20°C. The sorption of these radionuclides from the solutions containing Sr(NO₃)₂ carrier and without it was studied. Aragonite shows the highest sorption capacity for ⁹⁰Sr²⁺, and these parameters are the lowest for calcite. All the CaCO₃ metastable modifications irreversibly sorb ⁹⁰Sr²⁺ and ⁹⁰Y³⁺ cations and therefore show promise for sorptive decontamination of water from ⁹⁰Sr.     

Cocrystallization of microamounts of <Superscript>137</Superscript>Cs, <Superscript>90</Superscript>Sr,and <Superscript>90</Superscript>Y from aqueous solutions with the solid phase of mixed potassium neodymium ferrocyanide

Cocrystallization of microamounts of ¹³⁷Cs, ⁹⁰Sr, and ⁹⁰Y with the solid phase of mixed potassium neodymium ferrocyanide was studied in relation to the K₄[Fe(CN)₆]: Nd(NO₃)₃ ratio in aqueous solution. At the K₄[Fe(CN)₆]: Nd(NO₃)₃ ratio higher than 2, all the radionuclides studied virtually quantitatively (to 96–99%) cocrystallize with the KNd[Fe(CN)₆]·4H₂O solid matrix. The cocrystallization coefficients D calculated by the Henderson-Krechek equation exceed 10³. Leaching of ¹³⁷Cs and ¹⁵²Eu from the K(¹³⁷Cs)Nd(¹⁵²Eu)· [Fe(CN)₆]·4H₂O solid matrix with water and with aqueous solutions of HNO₃ (0.1 and 1.0 M) and KOH (4.0 M) was studied.     

Effect of complexing anions on sorption of U(VI), <Superscript>90</Superscript>Sr,and <Superscript>90</Superscript>Y from aqueous solutions on layered double hydroxides of Mg,Al, and Nd

Sorption of ⁹⁰Sr and ⁹⁰Y from aqueous solutions on Mg-Al and Mg-Nd layered double hydroxides (LDHs) in various forms was studied. The distribution coefficients K _d of U(VI) and ⁹⁰Sr on LDH-Mg-Al-EDTA are 100–120 ml g⁻¹ in 15 min of contact of the solid and liquid phases at V/m = 50 ml g⁻¹. At the same time, under similar conditions, U(VI) and ⁹⁰Sr are not sorbed from aqueous solutions on LDH-Mg-Al-C₂O₄. The sorption of U(VI) from aqueous solutions containing H₂EDTA²⁻, C₂O₄²⁻, and CO₃²⁻ on LDH-Mg-Nd-CO₃ and LDH-Mg-Al-CO₃ strongly depends on the concentration of the complexing anions in the solution. In particular, for 10⁻³ M aqueous UO₂²⁺ solutions, with an increase in [C₂O₄²⁻] from 10⁻³ to 5 × 10⁻² M, K _d of U(VI) decreases from >5 × 10³ to 70 ml g⁻¹ for LDH-Mg-Al-CO₃ and from 170 to ∼0 ml g⁻¹ for LDH-Mg-Nd-CO₃. In the presence of 10⁻³ to 5 × 10⁻² M CO₃²⁻ in aqueous solution, U(VI) is not noticeably sorbed on LDH-Mg-Nd-CO₃ (K _d does not exceed 16 ml g⁻¹ at V/m = 50 ml g⁻¹), and on LDH-Mg-Al-CO₃ the sorption sharply decreases (K _d decreases from >5 × 10³ to ∼0 ml g⁻¹ at V/m = 50 ml g⁻¹). The presence of complexing anions in the solution does not appreciably affect the ⁹⁰Sr sorption, but noticeably affects the 90Y sorption. With an increase in their concentration, K _d of ⁹⁰Y appreciably decreases. The effect exerted by Sr²⁺ ions on the sorption of microamounts of U(VI) and by UO₂²⁺ ions on the sorption of microamounts of ⁹⁰Sr and ⁹⁰Y from aqueous solutions on LDH-Mg-Nd-CO₃ was also examined.     

Choice of the Optimum Composition of the Solution Fuel for a Homogeneous Reactor and of Termoxid Sorbent for Recovering <Superscript>99</Superscript>Mo

T-52 sorbent was chosen for recovering ⁹⁹Mo from low-enriched uranium fuel of a homogeneous solution reactor, because this sorbent exhibits the maximal ⁹⁹Mo distribution coefficient in sorption from solutions containing 150–360 g L^–1 uranium. The use of sulfate and nitrate solutions for producing and recovering ⁹⁹Mo from the fuel of a homogeneous solution reactor was compared. The optimum composition of the solution fuel of a commercial reactor for ⁹⁹Mo production was suggested: nitric acid uranium solution (20% ²³⁵U, 100–200 g L^–1, 1 M HNO₃).     

Clinoptilolite/Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>: a magnetic sorbent for removing <Superscript>90</Superscript>Sr from aqueous media

The ability of a magnetic sorbent prepared by modification of clinoptilolite with magnetite to take up ⁹⁰Sr was studied. ⁹⁰Sr is sorbed most efficiently at pH in the range 6–9. At the sorbent dosage of 5 g dm^–3 and sorption time of 24 h, the degree of ⁹⁰Sr sorption from aqueous solution is as high as 99.8%.     

Coprecipitation of Trace Amounts of <Superscript>137</Superscript>Cs and <Superscript>85</Superscript>Sr with [Na(18-Crown-6]BPh<Subscript>4</Subscript> from Neutral and Alkaline Solutions

Coprecipitation of ¹³⁷Cs and ⁸⁵Sr with [Na(18-crown-6]BPh₄ solid phase from aqueous, aqueous-ethanolic, and alkaline solutions is studied. ¹³⁷Cs and ⁸⁵Sr cocrystallize with [Na(18-crown-6]BPh₄ from aqueous and aqueous-ethanolic solutions. The cocrystallization coefficients D of ¹³⁷Cs and ⁸⁵Sr from aqueous solutions are 2.6±0.5 and 3.3±0.3, respectively. For aqueous-ethanolic solutions, the corresponding values are 4.4±0.5 and 3.4±0.4. In the alkaline solutions (0.1 and 1 M NaOH), 54–74% of ¹³⁷Cs and 37–51% of ⁸⁵Sr pass into the [Na(18-crown-6]BPh₄ solid phase, depending on the crown ether concentration in the system.__________Translated from Radiokhimiya, Vol. 47, No. 3, 2005, pp. 257–260.Original Russian Text Copyright © 2005 by Kulyukhin, Konovalova, Rumer, Kamenskaya, Mikheev.     

Phase distribution of iodine in the course of production of <Superscript>99</Superscript>Mo concentrate

A novel procedure was suggested for studying the phase distribution of radioactive iodine in the liquid–gas system. Without redox reactions, the degree of iodine transfer into the gas phase is maximal for sulfuric and nitric acid solutions at pH ≤ 1.5. In weakly acidic, neutral, and alkaline solutions, the iodine transfer into the gas phase is insignificant (degree of transfer <0.05). Conditions for stabilization of iodine species (presence of redox reagents, solution acidity) were found. The most efficient purification of ⁹⁹Мо to remove iodine radionuclides is observed in sulfuric acid solutions, where the probability of formation of IО₃ ^– anions, exhibiting the highest affinity for titanium hydroxide, is minimal. Silver-modified Termoxid sorbents are suitable for selective sorption of iodine only from alkaline solutions (0.3–0.5 M NaOH), with the best result obtained for Т-5(Ag) (iodine distribution coefficient 2000–3000 mL g^–1). An additional step of purification of alkaline molybdenum concentrates to remove iodine on Т-5(Ag) sorbent was suggested; it allows the residual iodine content of the molybdenum concentrate to be decreased by a factor of 20.     

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.     

Electrochemical properties and dissolution of UPd<Subscript>3</Subscript> in nitric acid solutions

Electrochemical properties of the intermetallic compound UPd₃ in 0.5–8 M HNO₃ solutions were studied by linear voltammetry. In 0.5–2 M HNO₃ solutions, the UPd₃ surface is in the passive state. At HNO₃ concentrations exceeding 4 M, the alloy passivation was not observed. The previously unknown electrochemical characteristics of UPd₃ in nitric acid solutions were obtained using the Tafel equation. The values of Е(i = 0) and v_corr increased from 39 mV and 38 μg cm^–2 h^–1 in 0.5 M HNO₃ to 821 mV and 11 mg cm^–2 h^–1 in 8 M HNO₃, respectively. Dissolution experiments have shown that UPd₃ can dissolve in HNO₃ solutions of concentration exceeding 4 M at room temperature. In 8 M HNO₃, the dissolution rate can reach 17 mg cm^–2 h^–1 at 25°С, with the dissolution being virtually equimolar and accelerating with time.     

Concentration of Tc(VII) from Aqueous Solutions with Filled Fibrous Sorbents

Sorption of Tc(VII) on fibrous sorbents filled with finely dispersed anion exchangers (AV-17-n and AN-31-n) and on a chelating sorbent bearing 1,3(5)-dimethylpyrazole groups (POLYORGS-17-n) is studied. The Tc(VII) distribution coefficients (K_d, cm³ g^?1) are determined in sorption from simulated nitric acid, alkaline, and saline solutions. The highest distribution coefficients (K_d ～10³ ? 10⁵ cm₃ g^?1) were obtained in sorption of Tc from weakly acidic (≤0.1 M HNO₃) and alkaline (0.1–1.0 M NaOH) solutions. In sorption of Tc from alkaline and nitric acid solutions containing NaNO₃, POLYORGS-17-n demonstrated the highest efficiency. Tc is totally recovered with the sorbents studied in 10 min. Then it can be eluted with 1 M HNO₃. The sorbents AV-17 and POLYORGS-17-n can be used for Tc(VII) recovery from saline solutions like groundwater (pH ～8).     

Kinetics of Np(V) transformation in concentrated HNO<Subscript>3</Subscript> solutions containing potassium phosphotungstate K<Subscript>10</Subscript>P<Subscript>2</Subscript>W<Subscript>17</Subscript>O<Subscript>61</Subscript>

The behavior of Np(V) in concentrated HNO₃ solutions containing potassium phosphotungstate K₁₀P₂W₁₇O₆₁ (KPW) at various concentrations of HNO₃ (1.0–3.0 M) and KPW [(1–5) × 10^?3 M] was studied. Under the examined experimental conditions, the final products of Np(V) transformation are Np(IV) and Np(VI). The reaction follows a first-order rate equation with respect to the Np(V) concentration.     

Reactor production and purification of <Superscript>153</Superscript>Sm radioisotope via <Superscript>nat</Superscript>Sm target irradiation

Neutron irradiation of a natural Sm target is performed to produce ¹⁵³Sm. Ion-exchange chromatography is used to separate ¹⁵³Sm from Eu radionuclides produced in the process. To prepare a target, Sm₂O₃ powder is dissolved in 0.2 ml of HNO₃ in a quartz vial. Samarium is deposited onto the vial walls by passing nitrogen gas at 120°C. The prepared samarium target is encapsulated in aluminum foil and irradiated in a 5-MW reactor in 5 × 10¹³ n cm⁻² s⁻¹ flux. The irradiated target is dissolved in 1 M HCl, and the produced radioisotopes are determined with an HPGe nuclear detector. Finally ¹⁵³Sm is separated from Eu radionuclides with ¹⁵³Sm recovery yield of more than 66% and purity better than 99.8%.     

Production and radiochemical separation of no-carrier-added <Superscript>88</Superscript>Y by liquid-liquid extraction

A method was suggested for the cyclotron production of ⁸⁸Y with liquid-liquid extraction. The sedimented ^natSrCO₃ target was irradiated with 18-MeV protons at current of 20 μA for 10 h. The ⁸⁸Y yields of about 1.326 MBq μA⁻¹ h⁻¹ were experimentally obtained. Solvent extraction of no-carrier-added ⁸⁸Y from irradiated strontium carbonate target in the hydrochloric acid solution was studied using di(2-ethylhexyl) hydrogen phosphate (HDEHP). The optimum separation was achieved in the system n-hexane/10% HDEHP-0.1 M HCl. Yttrium radionuclides were recovered from the HDEHP phase by stripping with 60 ml of 9 M HC1. Also, excitation functions of the proton, deuteron, and α-particle induced reactions of ⁸⁹Y, ⁸⁸Sr, ^natSr, and natRb were determined using computer codes and compared to the existing data.     

Electrochemical properties and dissolution of URu<Subscript>3</Subscript> in nitric acid solutions

The electrochemical properties of URu₃ intermetallic compound (IMC) in 0.5–8 M HNO₃ solutions were studied by linear voltammetry and galvanostatic electrolysis. In 0.5–2 M HNO₃, URu₃ occurs in the passive state at potentials lower than +1.3 V (here and hereinafter, vs. SHE), and in 4–8 M HNO₃, an anodic oxidation peak is observed at potentials from +1.0 to +1.2 V. This process, however, leads to IMC passivation and not to its dissolution. At potentials higher than +1.4 V, URu₃ passes into the transpassive state and starts to actively dissolve. The principal possibility of electrochemical dissolution of IMC at potentials exceeding the transpassivation potential was demonstrated by galvanostatic electrolysis. The rate of uranium leaching during electrolysis depends to a greater extent on the current density than on the HNO₃ concentration and reaches 35 mg cm^–2 h^–1 in 6 M HNO₃ at a current density of 182 mA cm^–2.