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.     

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.     

Behavior of Microamounts of <Superscript>22</Superscript>Na, <Superscript>85</Superscript>Sr, <Superscript>137</Superscript>Cs,and <Superscript>152</Superscript>Eu in Sorption and Coprecipitation on Mixed Potassium Neodymium Ferrocyanide from Solutions

Sorption of ⁸⁵Sr, ¹³⁷Cs, ²²Na, and ¹⁵²Eu on solid mixed potassium neodymium ferrocyanide KNd[Fe(CN)₆]·4H₂O from neutral, acidic, and alkaline media and also coprecipitation of these radionuclides with KNd[Fe(CN)₆]·4H₂O in its formation from a homogeneous solution were studied. It was found that ⁸⁵Sr and ²²Na do not noticeably coprecipitate with solid KNd[Fe(CN)₆]·4H₂O and are not sorbed by this substance. In aqueous medium, depending on the cesium concentration in solution, from 80 to 98% of ¹³⁷Cs coprecipitates with solid KNd[Fe(CN)₆]·4H₂O. In this case, the distribution coefficient K_d depends on both the cesium concentration in solution and solution pH. Within 30 min of contact of the solid and liquid phases, the degree of recovery of ¹³⁷Cs from aqueous solution with KNd[Fe(CN)₆]·4H₂O is approximately 95.0% of the initial amount. ¹⁵²Eu coprecipitates with solid KNd[Fe(CN)₆]·4H₂O during its formation from a homogeneous solution to 98–99.9%. The degree of recovery of ¹⁵²Eu from aqueous solution with KNd[Fe(CN)₆]·4H₂O precipitate within 60 min of contact of the solid and liquid phases is 70.3% of the initial amount.     

Removal of 60Co and 137Cs from simulated NPP bottom residues on the solid phase of K+, Ni2+, and Fe3+ ferrocyanides

The possibility of simultaneous removal of ⁶⁰Co and ¹³⁷Cs from simulated NPP bottom residues by coprecipitation with the solid phase of K, Fe, and Ni ferrocyanides was examined. In coprecipitation of ⁶⁰Co and ¹³⁷Cs with the KFe[Fe(CN)₆] solid phase, the degree of removal of the radionuclides from simulated bottom residue containing 300 g L^?1 NaNO₃ and 3.4 × 10^?5 M EDTA does not exceed 80% for ⁶⁰Co and 99% for ¹³⁷Cs. The scheme based on coprecipitation of the radionuclides with the solid phase of K⁺, Fe³⁺, and Ni²⁺ ferrocyanides, formed by successive addition of K₄[Fe(CN)₆], Fe(NO₃)₃, and Ni(NO₃)₂ to the solution, ensures efficient removal of ⁶⁰Co and ¹³⁷Cs from simulated bottom residue containing simultaneously up to 400 g·L^?1 NaNO₃ and 3.4 × 10^?5 M EDTA. The radionuclides are removed to more than 99%.     

Coprecipitation of 137Cs and 85,90Sr radionuclides from aqueous solutions with the solid phases of CsBPh4 and [M(18-crown-6)]BPh4 (M = Na+, Cs+)

The possibility of joint recovery of cesium and strontium radionuclides from their aqueous solutions with the solid phase of CsBPh₄ or [M(18-crown-6)]BPh₄ (M = Na⁺, Cs⁺) was examined. Depending on the solid phase composition, the degree of coprecipitation of ^85,90Sr and ¹³⁷Cs varies from 40 to 95%. The degree of coprecipitation of ^85,90Sr and ¹³⁷Cs from solutions with the solid phase of the complex compounds is 1.5–3 times higher than with the CsBPh₄ phase. The kind of the anion (NO₃⁻ or Cl⁻) affects the coprecipitation of^85,90Sr and ¹³⁷Cs with the solid phase of the complex compounds [M(18-crown-6)]BPh₄.     

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.     

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.     

Investigation of the Prussian Blue Analog Co3[Co(CN)6]2 as an Anode Material for Nonaqueous Potassium‐Ion Batteries

Nonaqueous potassium‐ion batteries (KIBs) are attracting increasing attention as a potential low‐cost energy‐storage system due to the abundance of potassium resources. Here, cobalt hexacyanocobaltate (Co₃[Co(CN)₆]₂), a typical Prussian blue analog (PBA), is reported as an anode material for nonaqueous KIBs. The as‐prepared Co₃[Co(CN)₆]₂ exhibits a highly reversible capacity of 324.5 mAh g^?1 at a current density of 0.1 A g^?1, a superior rate capability (221 mAh g^?1 at 1 A g^?1), and a favorable long‐term cycling stability (200 cycles with 82% capacity retention). Based on a series of characterizations, it is found that potassiation/depotassiation in Co₃[Co(CN)₆]₂ proceeds via solid‐state diffusion‐limited K‐ion insertion/extraction process, in which both carbon‐ and nitrogen‐coordinated cobalt are electrochemically active toward K‐ion storage. Finally, the reaction pathway between potassium and Co₃[Co(CN)₆]₂ is proposed. The present study provides new insights on further exploration of PBAs as high‐performance electrode materials for KIBs.     

Complexation in Binary Systems Uranyl(VI)-8-Quinolinethiol in Gelatin-immobilized (UO2)2[Fe(CN)6] Matrices

Complexation processes occurring in gelatin-immobilized uranyl(VI) hexacyanoferrate(II) matrixsystems on contact with aqueous alkaline (pH 12.0) solutions of 8-quinolinethiol, its 5-chloro, 5-bromo' and 5-methylthio derivatives were studied. Incorporation of the ligand into the inner coordination sphere ofUO₂ ^{2 +} is preceded by alkali transformation of gelatin-immobilized (UO₂)₂[Fe(CN)₆] to uranic acid (H₂UO₄). In the course of complexation in each of the uranyl(VI)-ligand systems studied, only coordination compounds UO₂L₂ (L^- is the deprotonated form of the ligand) are formed.     

Effect of salts on oxidation of Np(VI) with Fe(CN)<Stack><Subscript>6</Subscript><Superscript>3−</Superscript></Stack> Ions in 0.1–1 M alkali solutions

The potential of the Fe(CN)₆³⁻/Fe(CN)₆⁴⁻ couple in solutions containing 0.5–1 M alkali and high concentrations of Li, Na, and K salts was estimated potentiometrically. The reactions of Fe(CN)₆³⁻ with Np(VI) in such media were studied by spectrophotometry. In 0.5–1 M KOH + 7 M KF or 0.5–1 M KOH + 8 solutions, Np(VI) is oxidized to the heptavalent state with a small excess of Fe(CN)₆³⁻. In the presence of lithium or sodium salts, a larger excess of the oxidant is required for complete oxidation of Np(VI). Carbonate ions in concentrations exceeding 2 M prevent the Np(VI) oxidation.     

Mesolamellar phases containing [Fe(CN)6]3? anion

The mesostructured lamellar phases with the general formula [C _n H_2n+1N(CH₃)₃]₃[Fe(CN)₆] (n = 14, 16, 18) were prepared by ion-exchange/precipitation reaction of alkyltrimethylammonium surfactants and K₃[Fe(CN)₆] complex in aqueous medium. The phases were characterized using powder X-ray diffraction, high-resolution transmission electron microscopy, IR spectroscopy, thermogravimetric, and differential scanning calorimetry means. The results obtained all support a proposed model of crystal structure for these materials, in which the layers are constructed by monolayer of the discrete complex molecules, and the surfactants tails of opposite head groups deeply penetrate and arrange with a tilt angle of 63°.     

Electrochemical behaviors of iron-based layered double hydroxide thin-films

The ordered ultrathin films based on the fabrication of Mg/Fe-LDHs ([Mg₆Fe₂(OH)₁₆CO₃·(H₂O)_4.5]_0.375) nanosheets and hexacyanoferrate(III) anions via the self-assembly procedure were prepared. The electrodes modified by the films demonstrated a couple of well-defined reversible redox peaks attributed to [Fe(CN)₆]^3?/4? and Fe^2+/3+ couples. The effects of cycle number, scan rate and Mg/Fe molar ratio on the CV performance of the thin-film electrodes were observed in K₃[Fe(CN)₆] electrolyte. The [Fe(CN)₆]^3? pillared Mg/Fe-LDHs with Mg/Fe molar ratio of 3 (LDH-(CN)-3) demonstrated an excellent electrochemical behavior with a potential window between ??0.2 and 1.0 V, high specific capacitance and sensitivity, indicating that the high crystallinity, large specific surface area and plentiful [Fe(CN)₆]^3? anions in interlayer spaces were necessary. Especially, the interlayer [Fe(CN)₆]^3? anions significantly affected the electrochemical behavior of the electrode, where the electrode reaction was controlled by the diffusion of [Fe(CN)₆]^3?/4? and Fe^2+/3+ couples. Under current density of 2.5 A g^?1, the optimized LDH-(CN)-3 electrode exhibited high specific capacitance of 250.81 F g^?1 with good cycling stability. This facile synthesis strategy and the good electrochemical properties indicated that the LDH-(CN)-3 was a potential economical alternative material for supercapacitor application.     

Sorption of 60Co from aqueous solutions on layered double hydroxides of Mg, Al, and Nd

Sorption of ⁶⁰Co from aqueous solutions of various compositions on layered double hydroxides (LDHs) of Mg, Al, and Nd in carbonate and hydroxide forms and on layered double oxides (LDOs) of Mg and Al was studied. ⁶⁰Co is poorly sorbed from aqueous nitrate solutions onto LDH-Mg-Al-OH. The ⁶⁰Co distribution coefficient K _d does not exceed 50 ml g^?1 at a phase contact time of 15 min and V/m = 50 ml g^?1. At the same time, ⁶⁰Co is efficiently sorbed from 10^?3?C10^?5 M aqueous Co(NO₃)₂ solutions onto LDH-Mg-Al and LDH-Mg-Nd with CO ₃ ^2? in the interlayer space. At a phase contact time of 15 min and V/m = 50 ml g^?1, K _d exceeds 2 × 10⁴ ml g^?1 for LDH-Mg-Nd and does not exceed 5 × 10³ ml g^?1 for LDH-Mg-Al. The ⁶⁰Co desorption from LDH-Mg-Nd-CO₃ into 0.05?C0.2 M solutions of Na₂CO₃, NaNO₃, (NH₄)₂C₂O₄, and Na₂H₂EDTA and into distilled water was studied. Na₂H₂EDTA is the most efficient desorbing agent. After 15-min contact of LDHMg(⁶⁰Co)-Nd-CO₃ with 0.1 and 0.05 M Na₂H₂EDTA solutions, the degree of desorption of ⁶⁰Co is ??100 and ??99%, respectively.     

Oxidation of Np(V) and Np(IV) with Fe(CN) 6 3− ions in carbonate solutions

The formal potential of the Fe(CN) ₆ ^3? /Fe(CN) ₆ ^4? couple in 1 M NaHCO₃ and 1–2 M Na₂CO₃ solutions was determined. It is equal to 505 and 510 mV, respectively, exceeding the potentials of the Np(VI)/(V) and Np(V)/(IV) couples in carbonate solutions. The equilibrium of the reaction Np(V) + Fe(CN) ₆ ^3? = Np(VI) + Fe(CN) ₆ ^4? was studied. Fe(CN) ₆ ^3? ions oxidize Np(IV) to Np(V) and then to Np(VI). The arising Np(VI) oxidizes Np(IV). The Np(IV) oxidation accelerates in going from NaHCO₃ to Na₂CO₃. An increase in [Na₂CO₃] or in the ionic strength (by adding neutral salts) decelerates the oxidation. Np(IV) introduced in an HCl solution reacts with Fe(CN) ₆ ^3? or with Np(VI) faster than Np(IV) introduced in a Na₂CO₃ solution. The activation energy of the reaction of Np(IV) with Fe(CN) ₆ ^4? in the range 20–45°C is 107 kJ mol^?1. The reaction mechanism involves formation of the activated complex from ions of Np(IV) hydroxocarbonate and oxidant.     

Silvering of magnesium by contact deposition in aqueous solutions and DMFA medium

We study the deposition of thin silver films onto a magnesium surface in aqueous solutions of silver complexes and in organic aprotic solvents. We show that compact silver films with good adhesion are deposited in aqueous solutions of [Ag(CN)₂]⁻ cyanocomplex under hydrodynamic conditions. In solutions of less stable complexes {thiocyanate [Ag(CNS)₄]³⁻ and thiocarbamide [Ag(thio)₄]⁺}, the contact deposition of only disperse silver is observed. In dimethylformamide solutions of [Ag(CNS)₄]³⁻ complexes, thin silver films with good adhesion to a magnesium surface are formed. We also describe some specific features of the morphology of silver deposits, formed on a magnesium surface. __________ Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 42, No. 5, pp. 95–97, September–October, 2006.     

Giant Incident Photon‐to‐Current Conversion with Photoconductivity Gain on Nanostructured Bismuth Oxysulfide Photoelectrodes under Visible‐Light Illumination

Nanostructured layered bismuth oxysulfide films synthesized by chemical bath deposition reveal a giant incident photon‐to‐current conversion efficiency (IPCE). This study shows that surprisingly for the cathodic photocurrent in the photoreduction process, the IPCE reaches ≈2500% in aqueous solutions containing [Fe(CN)₆]^3?. The giant IPCE is observed starting from a certain minimal oxidizer concentration (c > 10^?3m for [Fe(CN)₆]^3?) and decreases nonlinearly with an increase of illumination intensity. Giant IPCE is determined by the decrease in resistivity of the bismuth oxysulfide film under illumination with photoconductivity gain, which provides the possibility of charge carriers from an external circuit to participate in the photoreduction process. Giant IPCE is observed not only in [Fe(CN)₆]^3? solutions, but also in electrolytes containing other photoelectron acceptors: Fe³⁺, I₃^?, quinone, H₂O₂. In all, solution‐processed layered bismuth oxysulfide films offer large‐area coverage, nontoxicity, low cost, and compatibility with a wide range of substrates. Abnormally high photoelectrochemical activity, as well as a band gap energy value favorable for efficient conversion of solar light (1.38 eV, direct optical transitions), proves the potential of bismuth oxysulfide photoelectrodes for a new generation of high‐performance photoconverters.     

The reaction Pu(VI) + Fe(CN)<Stack><Subscript>6</Subscript><Superscript>3−</Superscript></Stack> ⇄ Pu(VII) + Fe(CN)<Stack><Subscript>6</Subscript><Superscript>4−</Superscript></Stack> in NaOH solutions

A spectrophotometric study showed that, in 5 M NaOH, Pu(VII) prepared by ozonation of Pu(VI) is reduced with excess K₄Fe(CN)₆. The Pu(VII) content can be estimated from the amount of the Fe(CN)₆³⁻ formed. In NaOH solutions of concentration exceeding 8 M, the Fe(CN)₆³⁻ ion oxidizes Pu(VI). In 10.3 M NaOH, the tenfold excess of K₃Fe(CN)₆ fully converts 1 mM Pu(VI) to the heptavalent state within 4 min (rate constant 1.3 l mol⁻¹ s⁻¹ at 20°C). With an increase in the NaOH concentration, the oxidation rate increases, and smaller excess of K₃Fe(CN)₆ is required. This oxidant is consumed not only for Pu(VI) oxidation but also in reactions with H₂O and OH⁻ ions. Pu(VII) is unstable and is slowly reduced with water and with products of decomposition of iron complexes.     

Structure of M(18-crown-6)+ (M=T1, NH4) oximate complexes: effective control of the molecular geometry employing a crystal engineering approach

The synthesis and structural characterization of one-dimensional coordination/H-bonded polymers M(18-crown-6) [H{ONC(CN)C(O)C₆H₅}₂] (M=NH₄, Tl) is reported. The hydrogen oximate anion is formed by means of strong hydrogen bonding O-H-O between two nitroso groups, it possesses a centrosymmetric structure and bridges two macrocyclic fragments. In both the structures these fragments M(18-crown-6) adopt unusual geometry with the large cations being situated exactly in the center of the crown ether cavity.     

Synthesis and characterization of Co-Fe Prussian blue nanoparticles within MCM-41

A Prussian blue analogue, K_0.84Co_1.08[Fe(CN)₆] is prepared by reaction between [Fe(CN)₆]³⁻ in aqueous solution and ion-exchanged Co²⁺ in the channels of MCM-41. Powder X-ray diffraction, transmission electron microscopy, thermogravimetric analysis, nitrogen adsorption/desorption isotherms, diffuse reflectance UV-vis absorption spectroscopy and magnetic measurements were employed to characterize the product. The results show that the Prussian blue analogue is in nanoparticles within the channels and the hexagonal phase of MCM-41 remains intact during the reactions. A particle size effect on optical and magnetic properties of the nanoparticles was observed.     

State of uranophosphates MII(PUO6)2·nH2O (MII = Mn2+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+, Pb2+) in aqueous solutions

The stability of uranophosphates M^II(PUO₆)₂·nH₂O(M^II = Mn, Co, Ni, Cu, Zn, Cd, Pb) in water and aqueous HClO₄ and NaOH solutions was studied. The acid-base limits of the existence of these compounds were determined, the products of their conversion into phases of other compositions and structures were identified and studied, and the solubility of M^II(PUO₆)₂·nH₂O was determined. From the data obtained, the solubility products and Gibbs functions of formation of uranophosphates and the solubility curves were calculated, and the speciation diagrams of U(VI), P(V), and M(II) in solutions and equilibrium solid phases were plotted.