Small-angle neutron scattering study of specific interaction and coordination structure formed by mono-acetyl-substituted dibenzo-20-crown-6-ether and cesium ions

This study uses small-angle neutron scattering (SANS) to elucidate the coordination structure of the complex of mono-acetyl-substituted dibenzo-20-crown-6-ether (ace-DB20C6) with cesium ions (Cs⁺). SANS profiles obtained for the complex of ace-DB20C6 and Cs⁺ (ace-DB20C6/Cs) in deuterated dimethyl sulfoxide indicated that Cs⁺ coordination resulted in a more compact structure than the free ace-DB20C6. The data were fitted well with SANS profiles calculated using Debye function for scattering on an absolute scattering intensity scale. For this theoretical calculation of the scattering profiles, the coordination structure proposed based on density functional theory calculation was used. Consequently, we conclude that the SANS analysis experimentally supports the proposed coordination structure of ace-DB20C6/Cs and suggests the following: (1) the complex of ace-DB20C6 and Cs⁺ is formed with an ace-DB20C6/Cs molar ratio of 1/1 and (2) the two benzene rings of ace-DB20C6 fold around Cs⁺ above the center of the crown ether ring of ace-DB20C6.     

Preferential cesium ion trapping by 2-pyrone-4,6-dicarboxylic acid (PDC) obtained from a metabolic intermediate of lignin,a woody biomass resource

2-Pyrone-4,6-dicarboxylic acid (PDC), a chemically stable metabolic intermediate of lignin, showed preferential Cs⁺ sedimentation even from the aqueous solutions containing other alkali metal ions, such as Na⁺. From the crystal structure of the Cs⁺/PDC complex, Cs⁺ was revealed to be coordinated by 10 oxygen atoms of PDC and such multiple coordination was the reason of the preferential complex formation of Cs⁺ with PDC.     

Mass Spectrometric Study of Ions Formed from Cesium Metaborate Vapor under Electron Impact

An ionization behavior of cesium metaborate vapor under electron impact has been studied by a mass spectrometric method. Formations of Cs²⁺, CsB⁺, CsO⁺, Cs⁺ ₂, Cs₂O⁺, B⁺ and BO^? ₂ ions have been identified in addition to the well known ions of Cs⁺, CsBO⁺, CsBO⁺ ₂ and Cs₂BO⁺ ₂. Ionization processes and vapor precursors for these ions have been given from ionization efficiency curves, appearance energies, temperature dependence of ion intensities and energetics of the ionization processes as follows: the process for the formations of Cs⁺ with AE(Cs⁺)=3.9± 1.0 eV and BO^? ₂ ions is the ion pair formation from CsBO₂(g), that for CsBO⁺ ₂ ion is the simple ionization of CsBO₂(g), that for Cs⁺ with AE (Cs⁺) =9.1±0.5 eV, Cs²⁺, CsBO⁺, CsB⁺, CsO⁺ and B⁺ ions is the dissociative ionization from CsBO₂(g) and that for Cs⁺ ₂, Cs₂O⁺ and Cs₂BO⁺ ₂ ions is the dissociative ionization from Cs₂(BO₂)₂(g). The knowledge of the ionization behavior of cesium metaborate vapor under electron impact is very useful in the mass spectrometric study of vaporization behaviors of CsBO₂(s) and simulated radioactive waste borosilicate glasses.     

Alkali Hydrothermal Synthesis of Zeolites from Coal Fly Ash and Their Uptake Properties of Cesium Ion

Zeolites were synthesized from coal fly ash by hydrothermal treatment with KOH solutions. K-H zeolite (K₂Al₂Si₄O₁₂-nH₂O) was produced under optimum conditions of 160°C, 3 d, 1 M (=mol/dm³) KOH and liquid-solid ratio of 15cm³/g. The uptake behavior of radioactive cesium for the products was investigated by batch and column methods. The uptake equilibrium of Cs+ for the above product was attained within 2h yielding the distribution coefficient of above 10⁴ cm³/g. The uptake of Cs⁺ was followed by a Langmuir adsorption isotherm and the maximum uptake capacity was estimated to be 3.34 mmol/g. The successive removal of Cs⁺ was accomplished through the column packed with granular composites of product-alginate gel polymer.     

Selective Uptake of Cesium by Ammonium Molybdophosphate (AMP)-Calcium Alginate Composites

The uptake properties of Cs+ for ammonium molybdophosphate (AMP, (NH₄)₃PMo₁₂O₄₀.3H₂O) and its composite with alginate gel polymer have been studied by the batch and column methods. The free energy for the ion exchange ([NH⁺ ₄]_ad+Cs⁺NH⁺ ₄+[Cs⁺]_ad) was found to have a relatively low value of -9.7 kJ/mol compared to other inorganic ion exchangers, indicating high selectivity of AMP for Cs⁺ ions. The fine crystals of AMP exchanger were granulated with calcium alginate (CaALG) gel polymer as an immobilization matrices. The uptake rate of Cs+ for AMP-CaALG composite was fairly fast and the uptake attained equilibrium within 3 h; the uptake was above 96% even in the presence of 5M (=mol/dm³) NaNO₃. The distribution coefficient of Cs+, Kd-Cs, decreased in the order of coexisting ions, H⁺>Na⁺>K+>NH⁺. In a wide HNO₃ concentration region of 10^-2-5M, the K_d,cs value for the composite was around 10⁴cm³/g, while those for other elements, Na⁺, Sr²⁺, Co²⁺, Eu³⁺ and Am³⁺, were less than 10²cm³/g. The uptake of Cs⁺ followed a Langmuir adsorption isotherm, and the uptake capacity of Cs⁺ increased with the content of AMP immobilized in the composite. The trace amounts of Cs⁺ in the presence of HNO3 were selectively adsorbed on the composite column.     

聚丙烯腈-亚铁氰化钾钴/钛球形复合吸附剂制备及其对Cs+的吸附性能研究

本文合成了聚丙烯腈-亚铁氰化钾钴/钛球形复合吸附剂（PAN-KCoCF和PAN-KTiCF）,通过静态吸附实验,研究了接触时间、pH值、竞争离子、Cs⁺初始浓度等对PAN-KCoCF和PAN-KTiCF吸附Cs⁺效果的影响,分析了吸附过程的反应动力学和吸附等温线,并用扫描电镜（SEM）、傅里叶红外光谱（FT-IR）、X射线衍射仪（XRD）等对吸附剂进行了分析。结果表明,PAN-KCoCF和PAN-KTiCF对Cs⁺的吸附平衡时间均为16 h,随着pH值的增加,PAN-KTiCF对Cs⁺的吸附量先快速增大,随后趋于平缓,而PAN-KCoCF对Cs⁺的吸附量几乎不变,溶液中含K⁺、Na⁺、NH⁺₄、Ca²⁺或Mg²⁺等竞争离子时,PAN-KCoCF相比PAN-KTiCF对Cs⁺的选择性更高;PAN-KCoCF和PAN-KTiCF对Cs⁺的吸附动力学行为可用准二级动力学方程来描述,表面吸附为动力学控制的主要步骤;吸附过程符合Langmuir等温吸附模型,为单分子层吸附,PAN-KCoCF和PAN KTiCF对Cs⁺的饱和吸附量分别可达128.370、278.552 mg/g。     

Theoretical study of the adsorption of Cs,Cs+, I,I−, and CsI on C60 fullerene

Theoretical investigation for the adsorption of the cesium atom (Cs), the cesium iodide molecule (CsI), the iodine atom (I), the cesium cation (Cs⁺), and the iodide anion (I^?) onto the surface of a single fullerene molecule (C₆₀) are reported. A hybrid exchange–correlation functional using the Coulomb-attenuating method (CAM-B3LYP) is employed. The adsorption energies, i.e., the opposite of enthalpy change through adsorption, are calculated to be 143, 12, 9, 46, and 49 kJ mol^?1 for Cs, CsI, I, Cs⁺, and I^?, respectively. The equilibrium constant for Cs is calculated to be 7×10³ atm^?1 at the temperature of 1000 K and is seven orders of magnitude higher than that for CsI, indicating that the C₆₀ molecule adsorb the Cs atom highly selectively against the CsI molecule.     

Application of a Chemical ion Exchange Model to Transport Cask Surface Decontamination

Abstract

Radionuclide contamination of stainless steel surfaces occurs during submersion in a spent fuel storage pool. Subsequent release or desorption of these contaminants from a nuclear fuel transportation cask surface under varying environmental conditions occasionally results in the phenomenon known as contamination ‘weeping’. Experiments have been conducted to determine the applicability of a chemical ion exchange model to characterise the problem of cask contamination and release. Surface charge characteristics of Cr₂O₃ and stainless steel (304) powders have been measured to determine the potential for ion exchange at metal oxide-aqueous interfaces. The solubility of Co and Cs electrolytes at varying pH and the adsorption characteristics of these ions on Cr₂O₃ and stainless steel powders in aqueous slurries have been studied. Experiments show that Co ions do reversibly adsorb on these powder surfaces and, more specifically, that adsorption occurs in the nominal pH range (pH=4–6) of a boric acid moderated spent fuel pool. Desorption has been demonstrated to occur at pH≤3. Cs⁺ ions also have been shown to have an affinity for these surfaces although the reversibility of Cs⁺ bonding by H⁺ ion exchange has not been fully demonstrated. These results have significant implications for effective decontamination and coating processes used on nuclear fuel transportation casks.     

Analysis of Sorption Behavior of Cesium and Iodide Ions on Pumice Tuff

In the reliable safety assessment of radioactive waste disposal, the understanding and modeling of the sorption behavior onto the host rock under various groundwater conditions are indispensable. The influence of pH, ionic strength, and the initial concentrations of Cs and I on the sorption of Cs and I on tuff and pumice isolated from the original pumice tuff rock was investigated. For both rocks, the proton concentration has little effect on the K_d values forCs in the pH range 3–10. As the ionic strength of the solution increases in the presence of sodium perchlorate as a matrix ion, the K_d value of cesium apparently decreases, reflecting the competition of the electrolyte Na⁺ with thespecific sorption of Cs⁺ on the negatively charged sites. In contrast, no significant dependence of ionic strength on the K_d of anionic iodine was found. A simple surface complexation model without considering electrostatic works was applied to simulate the sorption of ions on rocks, and the model parameters were determined. The K_d values at the given chemical conditions were estimated using the parameters and compared with the ones in the literature.     

Sorptive Removal of Cesium-137 and Strontium-90 from Water by Unconventional Sorbents

It has been shown that coal fly ash is a good adsorbent for both radionuclides of ¹³⁷Cs and ⁹⁰Sr. Radiocesium adsorption is maximal around the neutral region whereas radiostrontium adsorption increases with pH, especially above pH 8. Cesium retention sharply drops with ionic strength while strontium adsorption increases sharply and steadily at low and moderate concentrations of the inert electrolyte, respectively. The suggested mechanisms of radionuclide retention by fly ash is specific adsorption of Cs⁺ and irreversible ion-exchange uptake of Sr²⁺. The isotherm of adsorption is a Langmuir approximation of the B.E.T. multi-layered sorption. Acid pretreatment of fly ash, though not increasing radionuclide sorption capacity, may be useful in preventing the leach-out of other contaminants from the sorbent into water during the adsorption process.     

Source for intense collimated beams of fast Cs+ and Cs0

The characteristics of a surface-ionization source for Cs⁺ of 20–55 keV are described. For applications requiring fast Cs⁰ atoms, the Cs⁺ beam is neutralized to 90% by passage through Cs vapor. The observed Cs⁰ beam intensity through a 1.1 cm diameter aperture 78 cm from the ionizer is 10 particle-mA.     

Selective separation and recovery of cesium by ammonium tungstophosphate-alginate microcapsules

A fine crystalline ammonium tungstophosphate (AWP) exchanger with high selectivity towards Cs⁺ was encapsulated in biopolymer matrices (calcium alginate, CaALG). The characterization of the AWP-CaALG microcapsule was examined using SEM/WDS, IR and DTA/TG analyses, and the selective separation and recovery of ¹³⁷Cs were examined by the batch and column methods using simulated (SHLLW) and real high-level liquid waste (HLLW). The free energy (ΔG°) of the ion exchange (NH₄⁺ ↔ Cs⁺) for fine AWP crystals was determined at −13.2 kJ/mol, indicating the high selectivity of AWP towards Cs⁺. Spherical and elastic AWP-CaALG microcapsules (∼700 μm in diameter) were obtained and fine AWP crystals were uniformly immobilized in alginate matrices. Relatively large K_d values of Cs⁺ above 10⁵ cm³/g were obtained in the presence of 10⁻³–1 M Ca(NO₃)₂, resulting in a separation factor of Cs/Rb exceeding 10². The irradiated samples (⁶⁰Co, 17.6 kGy) also exhibited large K_d values exceeding 10⁵ cm³/g in the presence of 2.5 M HNO₃. The K_d values in the presence of 0.1–9 M HNO₃ for 67 elements were determined and the order of K_d value was Cs⁺ ? Rb⁺ > Ag⁺. The breakthrough curve of Cs⁺ had an S-shaped profile, and the breakpoint increased with decreasing flow rate; the breakpoint and breakthrough capacity at a flow rate of 0.35 cm³/min for the column (0.7 g AWP-CaALG) were estimated at 25.2 cm³ and 0.068 mmol/g, respectively. Good breakthrough and elution properties were retained even after thrice-repeated runs. The uptake (%) of Cs⁺ in SHLLW (28 metal components-1.92 M HNO₃, SW-11, JAEA) was estimated at 97%, and the distribution of Cs⁺ and Zr/Ru into the AWP and alginate phases, respectively, were observed by WDS analysis. Further, the selective uptake of ¹³⁷Cs exceeding 99% was confirmed by using real HLLW (FBR “JOYO”, JAEA). AWP-CaALG microcapsules are thus effective for the selective separation and recovery of Cs⁺ from HLLWs.     

On the emission of MoCs molecular ions from Cs irradiated molybdenum surface

The present paper deals with the emission of atomic and molecular ions from elemental molybdenum surface under Cs⁺ bombardment to explore the MCs⁺ formation mechanism with changing Cs surface coverage. Integrated count of MoCs⁺ shows a monotonic increase with increasing primary ion energy (1-5 keV). Change in MoCs⁺ intensity is attributed to the variation of surface work function ? and cesium surface concentration c_Cs due to varying impact energies. Variation of c_Cs has been obtained from the expression, c_Cs ∝ 1/(1 + Y) where Y is the elemental sputtering yield estimated from TRIM calculations. Systematic study of the energy distributions of all species emerging from Mo target has been done to measure the changes in surface work function. Changing slopes of the leading parts of Cs⁺ energy distributions suggest a substantial depletion in surface work function ? with decreasing primary ion energies. Δ? shows a linear dependence on c_Cs. The maximum reduction in surface work function Δ?_max = 0.69 eV corresponds to the highest value of c_Cs = 0.5. A phenomenological model, based on the linear dependence of ? on c_Cs, has been employed to explain the MoCs⁺ data.     

Ionic Diffusion Coefficients of Cs+, Pb2+, Sm3+, Ni2+, SeO2- 4 and TcO− 4 in Free Water Determined from Conductivity Measurements

The ionic diffusion coefficients for Cs⁺, Pb²⁺, Sm³⁺, Ni²⁺, SeO^2- ₄ and TcO^? ₄, in free water (Do) were determined at room temperature by measuring conductivity. The Do values were derived based on the Nernst-Einstein equation. The limiting ionic equivalent conductivities (λ₀) for Cs⁺, Pb²⁺, Sm³⁺, Ni²⁺ and SeO^2- ₄ were derived based on Kolrausch's square-root law and that for TcO^? ₄ was derived from the relation between the concentration of TcO^? ₄ in the solution and the λ because of its weak electrolyte. The Do values were in a range of 1.4 to 2.2x10^?9 m²/s. The Do values for Cs⁺, Pb²⁺, Sm³⁺, Ni²⁺ and SeO^2- ₄ and those found in the literature showed good agreement. The Do for TcO^? ₄, which was previously unknown, was determined to be 1.95x10^?9 m²/s, which is similar to that for analogous chemical species. The variation in Do has been expected to be approximately one order of magnitude at constant temperature and all Do values determined in this work were in this range. The variation in activation energy for diffusion for some important ions was less than a factor of two and it is concluded that the temperature dependence of Do is approximately the same.     

Formation of Analcime Film under Hydrothermal Conditions

Polycrystalline analcime film was prepared from hydrogels under hydrothermal conditions. The analcime film of about 200 pm thickness built up on a porous alumina support at temperatures above 160°C, and the size and crystallinity of analcime increased with temperature. The thickness of analcime film increased with incubation time, and the growth rate at 180°C was faster than that at 160°C. The analcime film obtained was thermally stable at temperatures up to 700°C, and no structural changes were observed after treatment in nitric acid solutions below 0.01M. Analcime had an ion-sieve ability to large sized Cs⁺ ion, and Ag⁺ and Rb⁺ ions of small sizes were incorporated in analcime.     

On the understanding of positive and negative ionization processes during ToF-SIMS depth profiling by co-sputtering with cesium and xenon

In this paper, ionization processes of secondary ions during ToF-SIMS dual beam depth profiling were studied by co-sputtering with 500 eV cesium and xenon ions and analyzing with 25 keV Ga⁺ ions. The Cs/Xe technique consists in diluting the cesium sputtering/etching beam with xenon ions to control the cesium surface concentration during ToF-SIMS dual beam depth profiling. Several depth profiles of a H-terminated silicon wafer were performed with varying Cs beam concentration and the steady state Si, Xe and Cs surface concentrations were measured in situ by Auger electron spectroscopy. It was found that the implanted Cs surface concentration increases with the Cs fraction in the beam from 0% for the pure Xe beam to a maximum Cs surface concentration for the pure Cs beam. Secondly, the variation of the silicon work function, due to the Cs implantation, was measured in situ and during depth profiling as the shift of the secondary ion kinetic energy distributions. Finally, the positive and negative elemental ion yields generated by the Ga analysis beam were recorded and modeled with respect to varying Cs/Xe mixture. We found that the Si⁻ and the Cs⁻ yields increase exponentially with the decrease of the silicon’s work function while that of Cs⁺ and Si⁺ decrease exponentially, as expected by the electron tunneling model.     

Vaporization and deposition of cesium dimolybdate,Cs2Mo2O7

Vaporization and deposition of cesium dimolybdate (Cs₂Mo₂O₇) in argon were studied by thermogravimetry and transpiration methods. From Raman spectra and electron probe microanalysis of deposits and inductively coupled plasma mass spectroscopy of the aqueous trap of the exhaust, it was judged that the Cs₂Mo₂O₇ vaporizes as Cs₂Mo₂O₇ (g). The effect of water addition on Raman spectral of Cs₂Mo₂O₇ was also investigated. Comparing the high-temperature mass losses of Cs₂Mo₂O₇ by thermogravimetry with that of Cs₂MoO₄, the equilibrium vapor pressure of Cs₂Mo₂O₇ was estimated. The vapor pressure of Cs₂Mo₂O₇ (l) in its liquid state was calculated to be: log₁₀P (Cs₂Mo₂O₇)(l) = (8.95 ± 0.07) ? (1.03 ± 0.01) × 10⁴ /T (T = 1273?1573 K). The enthalpy of vaporization of Cs₂Mo₂O₇ (l) was estimated to be 197 ± 31 kJ·mol^?1.     

Adsorption Properties of Europium on Granulated α-Zirconium Phosphate

Adsorption behavior of Eu³⁺ on granulated α-zirconium phosphate (α-ZrP) has been studied by batch and column methods. The distribution coefficients (K _d) of Eu³⁺+ into α-ZrP increased with equilibrium pH, suggesting ion-exchange adsorption. The K _d values were in the order of Eu³⁺>Cs⁺>Sr²⁺>Co²+Na⁺. An expansion of interlayer distance of α-ZrP in the presence of Na⁺ enables the large hydrated Eu³⁺ ions to be adsorbed on this exchanger, and the adsorption isotherm of Eu³⁺ ions followed Freundlich's adsorption formula. The granulated α-ZrP has high thermal stability and acid resistance. The breakthrough capacity for Eu³⁺ linearly increased with pH of the effluent.     

Study of ionization processes during TOF-SIMS analysis by co-sputtering cesium and xenon

Because they are less sensitive to matrix effect than their homologues M⁺, the $\text{M}{\text{Cs}}_n^{+}$ clusters are used for semi-quantitative depth profiling with ToF-SIMS. Unfortunately, their useful yields are low, particularly when the cesium surface concentration is high, leading to the drastic decrease of the positive ionization probability. In this paper, ToF-SIMS depth profiles of a bare silicon wafer were performed and the significant positive ions yields (e.g. Si⁺, SiCs⁺, Cs⁺) were monitored with respect to the varying cesium surface concentration. This analysis has been performed in the dual beam mode by diluting the cesium sputtering beam with xenon ions. This approach allows ToF-SIMS depth profiling with cesium beam concentrations varying from 0% (for pure xenon) to 100% (for pure cesium). At first, it was found that the Si⁺ and the ${\text{Si}}_2^{+}$ signals decrease exponentially with the increasing cesium beam concentration. The presence of optimums for the Cs⁺ and the $\text{M}{\text{Cs}}_n^{+}$ signals was also observed. Finally, the tunneling model has been used to fit those maximums, which are a trade off between the increase of the cesium surface concentration and the decrease of the positive ionization probability.