Extraction of U(VI) from Aqueous Media with Layered Zn,Al and Mg,Al Double Hydroxides Intercalated with Citrate Ions and with Their Magnetic Nanocomposites

Radiochemistry - Synthesis methods and the phase composition of Zn,Al and Mg,Al double layered hydroxides intercalated with citrate ions and their magnetic nanocomposites are described. It is shown...     

Magnetic Sorbents for Removing U(VI) from Aqueous Media

Sorption of U(VI) onto magnetic sorbents from aqueous media was studied. The limiting value of the U(VI) adsorption onto magnetite and magnetic potassium zinc hexacyanoferrate(II) at pH 5.0, calculated from the Langmuir equation, is 125 and 102 μmol g^–1, respectively. Natural components of waters, namely, Na⁺ and Ca²⁺ ions and fulvic acids at concentrations of up to 200 mg dm^–3, do not noticeably influence the U(VI) sorption onto magnetic sorbents. Owing to high selectivity (degree of recovery 87–91%) and possibility of separating the solid phase by magnetic separation, these sorbents show promise for removing U(VI) from mineralized mine water.     

Recovery of 137Cs, 90Sr, 90Y, and d-element ions from aqueous solutions with sorbents containing triethylenediamine

The possibility of using sorbents based on KSKG coarsely porous silica gel and containing triethylenediamine N(CH₂-CH₂)₃N (TEDA) for recovering ¹³⁷Cs, ⁹⁰Sr, ⁹⁰Y, and d-element ions (Cu²⁺, Ni²⁺) from aqueous solutions was examined. Both ⁹⁰Sr, ⁹⁰Y radionuclides and Cu²⁺, Ni²⁺ ions are sorbed on KSKG containing 0.01–6.72 wt % TEDA. However, on sorbents based on KSKG and containing complexes of Cu²⁺, Ni²⁺, and Zn²⁺ nitrates with TEDA, the ¹³⁷Cs, ⁹⁰Sr, and ⁹⁰Y radionuclides are not sorbed. The equilibrium in the systems with these sorbents is attained within 3 h. The sorption capacity for Cu²⁺ and Ni²⁺ strongly depends on the conditions of the sorbent synthesis. The capacity of the sorbents for Cu²⁺ varies from 63 to 320 mg of metal per gram of sorbent. For Ni²⁺, the sorption capacity is considerably lower (no more than 130 mg of Ni²⁺ per gram of sorbent). The distribution coefficients of ⁹⁰Sr and ⁹⁰Y are 300–700 ml g^?1 at the contact time of the solid and liquid phases of 96 h and V/m = 100 ml g^?1.     

以水滑石为前体的Co-Mn-Al复合氧化物的制备及表征

采用共沉淀法制备了n(Co)∶n(Mn)∶n(Al)=4∶0∶2、4∶1∶1、4∶2∶0的CO32-离子插层层状双金属氢氧化物(LDHs),经500℃煅烧4h得到相应的Co-Mn-Al复合过渡金属氧化物。利用X射线衍射(XRD)、X射线荧光光谱分析(XRF)、N2吸附脱附、透射电镜(TEM)技术对样品进行了表征。研究结果表明,Co-Mn-Al复合氧化物具有含Co尖晶石氧化物的结构特征,属于中孔材料,与Co-Mn-Al LDHs相比,其比表面积增大,孔容增加,孔径尺寸变小,且随着Mn与Al原子比的增加,样品结晶度及有序性均下降。     

Sorption of 60Co, 90Sr, 90Y, and 137Cs from aqueous solutions onto Mg-Ln layered double hydroxides (Ln = Ce, Pr, Sm, Gd)

Sorption of ⁶⁰Co, ⁹⁰Sr, ⁹⁰Y, and ¹³⁷Cs from aqueous solutions onto Mg-Ln layered double hydroxides (LDHs) (Ln = Ce, Pr, Sm, Gd) was studied. All the synthesized LDH-Mg-Ln-CO₃ samples (Ln = Ce, Pr, Sm, Gd) sorb ¹³⁷Cs poorly. At a contact time of the solid and liquid phases of 15 min and V/m = 50 mL g^?1, K _d of ¹³⁷Cs is no higher than 1.0 mL g^?1. Despite similar composition of the LDH-Mg-Ln-CO₃ samples (Ln = Ce, Pr, Sm, Gd), they noticeably differ in the ability to sorb ⁹⁰Sr. At a contact time of the solid and liquid phases of 15 min and V/m = 50 mL g^?1, Kd of ⁹⁰Sr varies from 10 to >5 × 10³ mL g^?1. All the synthesized LDHs efficiently sorb ⁹⁰Y and ⁶⁰Co. At a contact time of the solid and liquid phases of 15 min and V/m = 50 mL g^?1, K _d of ⁹⁰Y and ⁶⁰Co from aqueous solutions with LDH-Mg-Ln-CO₃ (Ln = Ce, Pr, Sm, Gd) exceeds 5 × 10³ mL g^?1.     

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 U(VI) from aqueous solutions on layered double hydroxides of Mg,Al, and Nd

Sorption of U(VI) from aqueous solutions of various compositions on layered double hydroxides (LDHs) of Mg, Al, and Nd, and also on layered double oxides (LDOs) of Mg and Al was studied. Experiments on sorption of UO₂²⁺ carbonate complexes from aqueous solution on LDO-Mg-Al showed that [UO₂(CO₃)₃]⁴⁻ ions are weakly captured by LDH-Mg-Al formed by contact of LDO-Mg-Al with water. With an increase in the uranium concentration in solution, K _d of U(VI) decreases. For 3.3 × 10⁻³ M [UO₂(CO₃)₃]⁴⁻ solutions, after 24-h contact of the solid and liquid phases, the distribution coefficients do not exceed 1.0 ml g⁻¹ at V/m = 50 ml g⁻¹. From aqueous nitrate solutions, U(VI) is sorbed on LDH-Mg-Al-NO₃ poorly: K _d of U(VI) does not exceed 1.0 ml g⁻¹ at 24-h contact of the solid and liquid phases and V/m = 50 ml g⁻¹. At the same time, U(VI) is efficiently sorbed from aqueous 10⁻³ M UO₂(NO₃)₂ solutions on LDH-Mg-Al and LDH-Mg-Nd with CO₃²⁻ and OH⁻ ions in the interlayer space. After 15-min contact of the solid and liquid phases, K _d of U(VI) exceeds 5 × 10³ ml g⁻¹. With an increase in the UO₂²⁺ concentration to 10⁻¹ M, K _d of U(VI) decreases considerably, becoming lower than 25 ml g⁻¹, but increases to ∼150 ml g⁻¹ with an increase in the contact time of the solid and liquid phases to 24 h. The effect of the Na⁺, Ca²⁺, Cl⁻, and SO₄²⁻ ions and of pH of the initial solution on the U(VI) sorption from aqueous UO₂(NO₃)₂ solutions on LDH-Mg-Al-CO₃ was examined.     

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.     

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.     

The Synthesis and Characterization of Dodecylbenzenesulfonic Ion Intercalated Layered Double Hydroxides(Ldhs)

正Layered double hydroxides(LDHs)are aclass of layered inorganic materials that consist ofstructurally positively charged layers and exchange-able anions in the interlayer gallery for charge bal-ance.The delamination of LDHs is decided by syn-thesis method to some extent.In this work,LDHsare synthesized via three different routes and theirdelamination properties are characterized.Co-precipitation methodion-exchange meth-     

Extraction of U(VI) from Perchlorate Solutions with Diantipyrylmethane Derivatives

Extraction of U(VI) from perchlorate solutions with diantipyrylmethane derivatives in chloroform and dichloroethane is studied. The composition of extractable complexes is [UO₂L₂](ClO₄)₂. The extraction constants are estimated. The maximal extractive power is shown by diantipyrylmethane in dichloroethane. Introduction of substituents at the methylene carbon of the extractant molecule makes the extraction worse.     

Sorption of U(VI) onto layered double hydroxides and oxides of Mg and Al,prepared using microwave radiation

Layered double hydroxides of Mg and Al, containing CО₃^2– ions in the interlayer space (LDH-Mg-Al-CО₃), and layered double oxides of Mg and Al (LDO-Mg-Al) were prepared using microwave radiation (MWR). The use of MWR allows not only acceleration of the synthesis of both LDH and LDO, but also preparation of compounds with high kinetic characteristics of the U(VI) sorption. The degree of U(VI) sorption (α) from 10^–2 M aqueous U(VI) solutions at a sorption time of 4 h and V/m = 50 mL g^–1 exceeds 99.0%. In sorption from more concentrated (10^–1 M) aqueous U(VI) solutions under similar conditions, α on all the samples does not exceed 37.5%.     

L-(-)-苹果酸柱撑水滑石的合成及结构表征

用返混沉淀方法和共沉淀法实现了L-(-)-苹果酸柱撑水滑石(LDHs)超分子结构手性层柱材料的插层组装, 得到结晶度高、晶相单一,且L-(-)-苹果酸在层间垂直插层有序排列的超分子结构手性层柱材料.用X射线衍射、红外光谱及差热分析表征了超分子结构手性层柱材料的结构,并给出了L-(-)-苹果酸柱撑水滑石超分子结构模型.     

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.     

Nanostructured Magnetic Sorbents for Selective Recovery of Uranium(VI) from Aqueous Solutions

Direct sol-gel, novel template, and additional high-temperature reduction procedures for preparing iron oxides and their composites, showing promise for selective sorption of dissolved U(VI) from aqueous media of various acidities, are described. The sorption activity of the materials was studied, the kinetic curves of the sorption were obtained, and the efficiency of the selective recovery of U(VI) from aqueous solutions with different pH values using the new sorbents was compared. The probable mechanism of the U(VI) sorption onto the sorbents studied was suggested on the basis of SEM, XPS, emf, and BET data. The quantitative sorption of U(VI) is determined to a greater extent by the composition of the sorbent solid phase, rather then by the specific surface area of the sorbents, which ranges from 0.1 to 47.3 m² g^?1 depending on the synthesis procedure. The crystalline Fe⁰ phase in the sorbents prepared using additional high-temperature reduction plays the key role in the U(VI) sorption by the reducing deposition mechanism. The saturation magnetization for this type of sorbents can reach 133–140 emu g^?1, which is an additional advantage allowing magnetic separation of the spent sorbents from the treated solutions.

     

Desorption of 90Sr and 137Cs from Flood Plain Deposits of the Sozh River and Rocks of the Adjacent Catchment Areas

Desorption of ⁹⁰Sr and ¹³⁷Cs from flood plain warps, meadow sod, humus-containing sandy loam, peat, clays, limonite, meadow marl, and friable rocks of the adjacent catchment areas (moraine clay, loam, sandy loam) was studied. ¹³⁷Cs is sorbed the most strongly on clays by the mechanism of isomorphic ion-exchange incorporation into the crystal lattice of montmorillonite-type minerals. ¹³⁷Cs is also tightly fixed on buried and peaty soils due to association with the poorly mobile species of humic acids and humin. The strong fixation of ⁹⁰Sr on amorphous iron hydroxides is caused by its association with poorly soluble ferrite-type minerals. Sorption of ⁹⁰Sr on peaty soils can be attributed to their association with aluminum and iron-containing organomineral complexes. ¹³⁷Cs sorbed on flood plain warps, sandy loams, and loams exhibits increased mobility and is leached with all the tested desorbing solutions. These deposits apparently contribute maximally to the redistribution of radiocesium over flood plain and the adjacent catchment areas. The desorption efficiency of cations of the desorbing solutions decreases in the order Cs⁺ > K⁺ > Fe^{3 +} > NH₄ ⁺ > Ca^{2 +} > H⁺ for radiocesium and Fe^{3 +} > Sr^{2 +} > K⁺ > H⁺ > Ca^{2 +} > NH₄ ⁺ for radiostrontium.     

Extraction of REE(III), U(VI), and Th(IV) from Nitric Acid Solutions with Carbamoylmethylphosphine Oxides in the Presence of Dinonylnaphthalenesulfonic Acid

The extraction of REE(III), U(VI), and Th(IV) from nitric acid solutions with solutions of carbamoylmethylphosphine oxides (CMPOs) considerably increases in the presence of dinonylnaphthalenesulfonic acid. The stoichiometry of the extractable complexes was determined, and the influence of the aqueous phase composition, kind of organic diluent, and CMPO structure on the efficiency of the extraction of the metal ions was analyzed.     

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.     

Extraction of REE(III), U(VI), and Th(IV) from Nitric Acid Solutions with N-Akyl(aryl)carbamoylmethylphosphine Oxides in the Presence of an Ionic Liquid

Radiochemistry - It was found that the extraction of REE(III), U(VI), and Th(IV) from nitric acid solutions with N-alkyl(aryl)carbamoylmethyl phosphine oxides Ph2P(O)CH2C(O)NHR (R = C9H19, Ph,...