Coordination of Actinide Single Ions to Deformed Graphdiyne: Strategy on Essential Separation Processes in Nuclear Fuel Cycle

The coordination of actinides and lanthanides, as well as strontium and cesium with graphdiyne (GDY) was studied experimentally and theoretically. On the basis of experimental results and/or theoretical calculations, it was suggested that Th⁴⁺, Pu⁴⁺, Am³⁺, Cm³⁺, and Cs⁺ exist in single‐ion states on the special triangular structure of GDY with various coordination patterns, wherein GDY itself is deformed in different ways. Both experiment and theoretical calculations strongly indicate that UO₂²⁺, La³⁺, Eu³⁺, Tm³⁺ and Sr²⁺ are not adsorbed by GDY at all. The distinguished adsorption behaviors of GDY afford an important strategy for highly selective separation of actinides and lanthanides, Th⁴⁺ and UO₂²⁺, and Cs⁺ and Sr²⁺, in the nuclear fuel cycle. Also, the present work sheds light on an approach to explore the unique functions and physicochemical properties of actinides in single‐ion states.     

Interaction of actinide ions with [NaP5W30O110]14- and [P2W18O62]6-

Stability constants (log b₁₀₁) of Th⁴⁺, UO₂ ²⁺, NpO₂ ⁺ and Am³⁺ with [NaP₅W₃₀O₁₁₀]^14- were determined by solvent extraction (m = 0.1M NaCl) and found to be 6.18±0.07, 3.80±0.06, 2.98±0.04, and 5.85±0.05, respectively. The order of stability constants: Th⁴⁺>Am³⁺>UO₂ ²⁺>NpO₂ ⁺ is due to electrostatic repulsion between the actinyl oxygens and oxygens on the polyoxometalate surface. The order of stability constants for metal complexes with [P₂W₁₈O₆₂]^6- is Th⁴⁺>UO₂ ²⁺>Eu³⁺>NpO₂ ⁺ because the steric repulsion between actinyl oxygens and oxygens on polyoxometalate are less important. Enthalpies of complexation were measured by calorimetric titration of Th⁴⁺, UO₂ ²⁺, Nd³⁺ with [NaP₅W₃₀O₁₁₀]^14- and [P₂W₁₈O₆₂]^6-. The results indicate that the conformation and charge distribution of the microscopic surface structures are important factors in the formation of pseudocolloids.     

Affinity and removal of radionuclides mixture from low-level liquid waste by synthetic ferrierites

The affinity and removal efficiency of ¹³⁷Cs⁺, ¹³³Ba²⁺, ⁸⁵Sr²⁺ and ²⁴¹Am³⁺ mixture from aqueous solutions using two synthetic ferrierites HSZ 700KOA and 700KOD commercially used as a catalyst in oil industry were investigated. The uptake of metal ions as a function of different parameters has been studied using batch equilibrium technique. Kinetic curves showed that the equilibrium was mostly reached within 45 min for Cs⁺ and Ba²⁺ and revealed to be longer for Sr²⁺ and Am³⁺. Using Freundlich and Langmuir adsorption isotherms, the results showed that the affinity and adsorption capacity of 700KOA and 700KOD follow the order: Cs⁺ > Ba²⁺ > Sr²⁺ > Am³⁺ with higher values for first material. Both adsorbents exhibited significant high capacity for Cs⁺ relative to other cations giving q _max 1.97 and 1.78 mmol g⁻¹ for 700KOA and 700KOD, respectively. All metals uptake found to be concentration dependant and independent of the pH over 2 to 10 range except Am³⁺; this reveals that the adsorption mechanism is controlled mainly by pure ion exchange reaction for Cs⁺, Ba²⁺, Sr²⁺ and by surface complexation mechanism for Am³⁺. These simple nontoxic materials are recommended to be used for radioactive waste treatment especially fission product ¹³⁷Cs and activation product ¹³³Ba.     

Uptake behavior of americium on alginic acid and alginate polymer gels

The uptake behavior of Am³⁺ was investigated by using alginic acid and alginate polymer gels. The affinity of radioactive nuclides for carboxyl groups in gel matrices increased in the order of Na⁺ < Cs⁺ < Co²⁺ < Pd²⁺, Sr²⁺, Fe³⁺ < Eu³⁺, Am³⁺. Among alginate gels, calcium alginate exhibited relatively higher uptake rate and distribution coefficient of Am³⁺. The column packed with calcium alginate beads was effective for the removal of trace amounts of Am³⁺ from acidic nitrate solutions.     

Extraction behaviors of Eu,Th, U and Am with diamides+thenoyltrifluoroacetone

N,N-dimethyl-N,N-dihexyl-3-oxapentanediamide, DMDHOPDA, N,N-dihexyl-3-thiopentanediamide, DHTPDA and N,N-dihexyl-3-oxapentanediamide, DHOPDA were synthesized and tested for the synergistic extraction of Eu³⁺, Th⁴⁺, UO ₂ ²⁺ , NpO ₂ ⁺ and Am³⁺ with thenoyltrifluoroacetone (HTTA). Although Eu³⁺, Th⁴⁺, UO ₂ ²⁺ and Am³⁺ were not extracted by DHTPDA or DHOPDA alone, they were extracted synergistically when combined with HTTA. Analysis of the dependency of extraction on pH and extractant concentration indicated that the dominant extracted species were Eu(TTA)₃(A), Th(TTA)₃(A)(X), UO₂(TTA)₂(A) and Am(TTA)₃(A) (where A is diamide, and X is chloroacetate or ClO ₄ ^– ).     

Adsorption of some hazardous radionuclides on cerium (IV) antimonate

Cerium(IV) antimonate was prepared by dropwise addition of 0.6M antimony pentachloride and 0.6M cerium ammonium nitrate solutions by a molar ratio of Ce/Sb 0.75. Exchange isotherms for H⁺/Co²⁺, H⁺/Cs⁺, H⁺/Zn²⁺, H⁺/Sr²⁺ and H⁺/Eu³⁺ were determined at 25, 40 and 60°C. Besides, it was proved that europium is physically adsorped, while zinc, strontium, cobalt and cesium are chemically adsorbed. Moreover, the heat of adsorption of zinc, strontium, cobalt and cesium on cerium (IV) antimonate was calculated and indicated that cerium(IV) antimonate is of endothermic behavior towards these ions. Also the distribution coefficients of these ions were determined and it was found that the selectivity is in the order: Eu³⁺>Sr²⁺>Cs⁺>Na⁺.     

Pore-functionalized polymer membranes for preconcentration of heavy metal ions

Functionalized membranes containing carboxylate, phosphate and sulfonate groups were prepared by UV-initiator induced graft polymerization of the functional monomer (acrylic acid, ethylene glycol methacrylate phosphate (EGMP) and 2-acrylamido-2-methyl-1-propane sulfonic acid) with a crosslinker (methylenebisacrylamide) in the pores of poly(propylene) host membranes. The functionalized membranes thus obtained were characterized by gravimetry, FTIR spectroscopy, radiotracers and scanning electron microscopy for the degree of grafting and water uptake, presence of functional groups, ion-exchange capacity, and physical structure of the membranes, respectively. The uptakes of Cs⁺, Ag⁺, Sr²⁺, Cd²⁺, Hg²⁺, Zn²⁺, Eu³⁺, Am³⁺, Hf⁴⁺ and Pu⁴⁺ ions in the functionalized membranes were studied as a function of acidity of the equilibrating aqueous solution. Among the functionalized membranes prepared in the present work, the EGMP-grafted membrane (with phosphate groups) showed acid concentration dependent selectivity towards multivalent metal ions like Eu³⁺, Am³⁺, Hf⁴⁺ and Pu⁴⁺. The solvent extraction studies of EGMP monomer in methyl isobutyl ketone (MIBK) solvent indicated that divalent and trivalent metal ions form complexes with EGMP in 1:2 proportion, but the distribution coefficients of trivalent metal ions were significantly higher that for the divalent ions. The uptakes of Eu³⁺ ions in monomeric EGMP (dissolved in MIBK) and polymeric EGMP (in the forms of crosslinked gel and membrane) were studied as a function of concentration of H⁺ ions in the equilibrating solution. This study indicated that polymeric EGMP has better binding ability towards Eu³⁺ as compared to monomeric EGMP. The variation of distribution coefficients of Eu³⁺/Am³⁺ in gel and membrane as a function of H⁺ ion concentration in the equilibrating aqueous solution indicated that ionic species held in the membrane and gel were not same. These results indicated that proximity of functional groups (phosphate) plays an important role in metal ion binding with polymeric EGMP.     

Kinetic aspects of the ion-exchange reactions of Cs<Superscript>+</Superscript>, Na<Superscript>+</Superscript>, Sr<Superscript>2+</Superscript>and Eu<Superscript>2+</Superscript> ions on the H<Superscript>+</Superscript> form of chromium hexacyanoferrate(II)

Summary This paper reports the radiochemical study of the ion-exchange of Cs⁺, Na⁺, Sr²⁺ and Eu³⁺ ions with H⁺ by chromium hexacyanoferrate(II) which was prepared in a granular form using a gel method. The slow steps which determine the rate of exchange of these ions are directly proportional to the particle diameter and this is confirmed from the linearity test of Bt vs. t plots at different particle diameters. Boyed’s equation and Reichenberg’s tables were used for evaluating all the kinetic parameters. The results reveal that the effective particle radii are unchanged for both chromium hexacyanoferrate(II) dried at 60 and 120 °C. The obtained data were analyzed using McKay plots and Arrhenius equation and the kinetic and thermodynamic parameters, e.g., effective diffusion coefficient, activation energies and entropies of activation have been evaluated. The mobility of these ions inside the particles of chromium hexacyanoferrate(II) decrease in the order of Eu³⁺>Sr²⁺>Na⁺⊃Cs⁺.     

Preparation of hybrid ion exchanger based on acrylamide for sorption of some toxic metal ions from aqueous waste solutions

Crystalline phases of polyacrylamide titanium tungstophosphate composite material has been synthesized via sol–gel method. The properties of its were determined using different technique. The ion-exchange capacities of the hybrid material for Cs⁺, Co²⁺ and Eu³⁺ ions it was found that 6.22, 2.76 and 1.38 mequiv. g^–1 respectively. The material was found that highly selective for Eu³⁺ and the selectivity sequence for sorption of Cs⁺, Co²⁺ and Eu³⁺ ions on polyacrylamide titanium tungstophosphate was found that; Eu³⁺ > Cs⁺ > Co²⁺. Thermodynamic parameters have been calculated for the studied ions showing that the overall adsorption process is spontaneous and endothermic. The experimental isotherm data were analyzed using the Langmuir and Freundlich models.     

Extraction separation of Cs+, Sr2+ and Ba2+ from a mixture of cations forming stable non-extractable complexes with ethylenediamine-N,N, N′,N′-tetraacetic acid in the water-nitrobenzene system

In the two-hase water-nitrobenzene extraction system, a method for gradual separation of Cs⁺, Sr²⁺ and Ba²⁺ from the mixture of cations forming stable non-extractable complexes with ethylenediamine-N, N, N,N-tetraacetic acid in the presence of the sodium salt of dicarbollylcobaltate anion {[-(3)-1, 2-B₉C₂H₁₁]₂ Co(III)}^– and polyethylene glycol ligand with a mean relative molecular mass of 400 (PEG 400), respectively, was developed. In the first extraction step, Cs⁺ was extracted into the organic phase while the other cations studied (Ca²⁺, Sr²⁺, Ba²⁺, Zn²⁺, Co²⁺, Ce³⁺) remained in the aqueous phase. In the second extraction step, Sr²⁺ and Ba²⁺ were extracted into the nitrobenzene phase. Finally, in the following reextraction step, Sr²⁺ was transferred into the aqueous phase while Ba²⁺ remained in the organic phase.     

Liquid-liquid extraction of uranium(VI) and thorium(IV) by two open-chain crown ethers with terminal quinolyl groups in chloroform

Two open-chain crown ethers 2,2'-(ethylenedioxy)bis[(8-quinolyloxymethyl)benzene], (L1), and 2,2'-(ethylenedioxy)bis[(8-quinaldyloxymethyl)benzene], (L2) have been prepared and characterized by using elemental analysis, IR spectra, ¹H NMR spectra and positive-ion FAB mass spectra. The extraction of UO₂ ²⁺ and Th⁴⁺ by both open-chain crown ethers, L1 and L2 in chloroform as a diluent was studied at 25 °C. Extraction distribution ratios (D) of UO₂ ²⁺ and Th⁴⁺ were investigated as a function of pH, lithium picrate concentration, and extractant concentration. Based on the expertimental results, it was found that 1 : 1 complexes were formed involving either UO₂ ²⁺ or Th⁴⁺ with L1, and Th⁴⁺ with L2. The extractability of L1 for Th⁴⁺ is significantly higher than that for UO₂ ²⁺, the extractabilities of L1 and L2 for Th⁴⁺ being almost identical. L1 and L2 used here are not feasible for industry because of their relatively low extractabilities for Th⁴⁺ at pH<2.0 and for UO₂ ²⁺ at the extraction conditions used in this work.     

Spectrophotometric studies of alkali and alkali earth metal ions complexes of mono amino derivative of calix[4]arene

The synthesis and complexive abilities of 5,11,17-tris(tert-butyl)-23 amino-25,26,27,28-tetra-propoxycalix[4]arene towards alkali cations Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺ and alkali earth cations Mg²⁺, Ca²⁺, Sr²⁺ and Ba²⁺ in methanol-chloroform mixture have been evaluated at 25°C, using UV-Vis spectrophotometric techniques. The results showed that the ligand is capable to complex with all the cations by 1: 1 metal to ligand ratios. The selectivity presented considering the calculated formation constants are in the order Li⁺ > Na⁺ > K⁺ > Rb⁺ > Cs⁺ and Mg²⁺ > Ca²⁺ > Sr²⁺ > Ba²⁺ with the ligand.     

An unusual extraction behavior of americium (III) and dioxouranium (VI) from picric acid medium using 18-crown-6 as neutral oxodonor

The extraction behavior of Am³⁺ and UO₂ ²⁺ is investigated employing chloroform solution of 18-crown-6 as the organic phase and picrate solution at pH 3.0 as the aqueous phase. In contrast to the commonly observed behavior, the extraction of Am³⁺ is preferred to that of UO₂ ²⁺. This unusual separation behavior is investigated as a function of several variable parameters such as crown ether concentration, picric acid concentration, inert electrolyte concentration, nature of diluent etc. Thermodynamic parameters are also evaluated.     

Thermodynamic modeling of actinide complexation with oxalate at high ionic strength

A geochemical model describing the solubility of actinides in underground water at the Waste Isolation Pilot Plant (WIPP) Project is under development. The database for this model consists of standard chemical potentials and Pitzer model parameters for hundreds of species that may be present in the WIPP disposal room. Organic ligands used in separation and decontamination processes may be present in the nuclear wastes placed in the WIPP site and could have a significant impact on mobile actinide concentrations. In this work the ₁ and ₂ stability constants of NpO₂ ⁺, UO₂ ²⁺, Am³⁺ and Th⁴⁺ with the oxalate anion have been measured in 0.3–5.0M NaCl media at 25 °C by a solvent extraction technique. For the 1:1 complexation, the values of the stability constants increased in the order: NpO₂ ⁺<Am³⁺<UO₂ ²⁺<Th⁴⁺, in accordance with the actinide charge density and reflecting the strongly ionic bonding of the complexes. The Pitzer ionic interaction model was used to model the data. Because the data were collected mainly in the high ionic strength region, values of ⁽¹⁾ were estimated from these plus literature values. The Pitzer model gives a good representation of the data using three interaction parameters ⁽⁰⁾, ⁽¹⁾, and c.     

A further understanding of the cation exchange mechanism for the extraction of Sr2+ and Cs+ by ionic liquid

The cation exchange mechanism was further investigated during the extraction of Sr 2+ and Cs+ using the extractant dicyclo- hexano-18-crown-6 (DCH18C6) in an ionic liquid (IL)1-ethyl-3-methyimidazolium bis[(trifluoromethyl)sulfonyl]imide (C2 mimNTf2 ). The concentrations of both the cation C2 mim + and the anion NTf2 in aqueous phase were detected. The con-centration of NTf2 in the aqueous phase decreased as Sr2+ or Cs+ exchanged into the IL phase. Addition of C2 mim + or NTf2 as well as the variation of the solubility of C2 mimNTf2 influenced the extraction efficiency of Sr2+ or Cs+ .     

Solvent Extraction of Calcium and Strontium into Nitrobenzene by Using Hydrogen Dicarbollylcobaltate in the Presence of Dibutyl Diethylcarbamoylmethylene Phosphonate

Extraction of micro amounts of calcium and strontium by a nitrobenzene solution of hydrogen dicarbollylcobaltate (H⁺B⁻) in the presence of dibutyl diethylcarbamoylmethylene phosphonate (DBDECMP, L) has been investigated. The equilibrium data have been explained assuming that the complexes HL⁺, HL₂⁺\mathrm{HL}_{2}^{+}, ML₂²⁺\mathrm{ML}_{2}^{2+} and ML₃²⁺\mathrm{ML}_{3}^{2+} (M²⁺=Ca²⁺,Sr²⁺) are extracted into the organic phase. The values of extraction and stability constants of the species in nitrobenzene saturated with water have been determined. It was found that the stability of the complex cations CaL₃²⁺\mathrm{CaL}_{3}^{2+}, SrL₃²⁺\mathrm{SrL}_{3}^{2+}, EuL₃³⁺\mathrm{EuL}_{3}^{3+} and AmL₃³⁺\mathrm{AmL}_{3}^{3+}, where L is DBDECMP, increases in the order Sr²⁺<Ca²⁺≪Eu³⁺≈Am³⁺.     

Preparation and ion-exchange properties of zirconium tungstoarsenate

A new inorganic ion-exchanger, zirconium tugnstoarsenate, has been synthesized which has been characterized by chemical analysis, thermogravimetry, X-ray and infrared spectroscopy. The ion exchanger has been found to be stable in acids and neutral salt solutions. The K_d values for 30 metal ions have been determined at pH 3–4 which show that the exchanger has high affinity for UO ₂ ²⁺ , ZrO²⁺, Cs⁺ and Tl⁺ ions. The variation of K_d for a number of metal ions as a function of concentration of nitric acid and ammonium nitrate has been investigated to elucidate the probable exchange mechanism and to work out conditions for elution. Some binary separations, viz. Sr²⁺−Cs⁺, Sr²⁺−Rb⁺, Sr²⁺−Y³⁺, Fe³⁺−Al³⁺, Fe³⁺−Zn²⁺ and Zn²⁺−Hg²⁺ in trace amounts have been carried out on the column of the exchanger which demonstrate the utility of the exchanger in radionalytical and analytical chemistry.     

Effect of Sr2+ doping on the luminescence properties of YVO4:Eu3+,Sr2+ particles prepared by a solvothermal method

Well-dispersed Eu³⁺ and Sr²⁺ co-doped YVO₄ luminescent particles (YVO₄:Eu³⁺,Sr²⁺) on the submicron scale were prepared by a facile solvothermal method at low temperature. The effect of Sr²⁺ doping on the luminescence of YVO₄:Eu³⁺,Sr²⁺ particles was investigated by fixing the Eu³⁺ doping concentration at 7 mol%. It was found that the luminescence intensity of the as-prepared YVO₄:Eu³⁺,Sr²⁺ particles increased with the Sr²⁺ doping concentration x to reach a two-fold enhancement when x = 5 %, and then decreased for higher x. We also investigated the effect of thermal annealing on the luminescence properties of the YVO₄:Eu³⁺ and YVO₄:Eu³⁺,Sr²⁺ particles. A remarkable enhancement in their luminescence properties was observed after annealing at 900 °C in air for 30 min. It was showed that the annealed YVO₄:Eu³⁺,Sr²⁺ particles exhibited a two-fold stronger emission than the annealed YVO₄:Eu³⁺. This work indicates that Sr²⁺ doping is beneficial to the luminescence enhancement for both the as-prepared and annealed YVO₄:Eu³⁺,Sr²⁺ particles.     

Synthesis, characterization and analytical application of a new inorganic cation exchanger—Titanium(IV) molybdophosphate

A novel polyoxometalate-cation exchanger, titanium(IV) molybdophosphate (TMP) has been synthesized under varying conditions. The material was characterized by X-ray diffraction, infrared spectroscopy, inductively coupled plasma and thermogravimetry techniques. Its stability was investigated in water, dilute acids, alkaline solutions, and high temperature up to 750 °C. Ion-exchange capacity and distribution coefficients (K_d) for twenty-nine radionuclides and metal ions have been determined. It was found that the TMP has high affinity for Cs⁺, Sr²⁺, UO₂²⁺, Ba²⁺, Pb²⁺, Tl⁺, Zn²⁺, Rb²⁺ and Zr⁴⁺ ions. The results of binary separation of metal ions showed that TMP can be potentially useful for analytical applications.     

Extraction of europium and cerium into nitrobenzene using synergistic mixture of hydrogen dicarbollylcobaltate and polyethylene glycol PEG 600

Solvent extraction of microamounts of europium and cerium by a nitrobenzene solution of hydrogen dicarbollylcobaltate (H⁺B⁻) in the presence of polyethylene glycol PEG 600 (L) has been investigated. The equilibrium data have been explained assuming that the complexes HL⁺, H₂L²⁺ and ML³⁺ (M³⁺ = Eu³⁺, Ce³⁺; L = PEG 600) are extracted into the organic phase. The values of extraction and stability constants of the species in nitrobenzene saturated with water have been determined. It was found that the stability constants of the EuL³⁺ and CeL³⁺ cationic complex species (L = PEG 600) in water-saturated nitrobenzene are the same.