Order Cs Research Articles

Enrichment of cesium and rubidium in weathered micaceous materials at the Savannah River Site, South Carolina.

The enrichment of Cs and Rb relative to Ba, Sr, and K in three soils representing a range of soil maturities was determined to investigate the long-term sorption behavior of these elements in upland soils of the Savannah River Site (SRS). Elemental mass fractions normalized to upper continental crust (UCC) decreased in the order Cs > Rb > Ba > K > Sr in the soil fine fractions. Only the UCC-normalized amount of Cs was greater than unity. The UCC-normalized amounts in strong-acid extracts decreased as Cs > Rb > Ba > K ≈ Sr. In all three soil cores, the trends of the UCC-normalized amounts of acid-extractable metals were similar to trends of cation-exchange capacity (CEC) calculated from synchrotron-X-ray diffractometry measurements of soil mineralogy. Consequently, the relative enrichment of Cs and Rb is largely controlled by selective sorption to micaceous minerals, including hydroxy-interlayered vermiculite, that dominate the CEC. Where high clay content had caused retention of soil solution, amounts of acid extractable K, Sr, and Ba were enhanced. The retention of natural Cs by these three soils, which developed over many thousands of years, is a strong indicator that radiocesium will likewise be retained in SRS soils.

Sorption processes of radiocesium in soil and bedrock

Abstract Three recent studies on cesium sorption in soil and bedrock are reviewed. 137Cs, originating from fallouts of nuclear weapons tests and the Chernobyl accident was found to decrease in an exponential manner in forest soil, and the highest fraction in soil profiles was found in the organic layer. Also, the mineral layer below the organic layer contained a large fraction of cesium inventory but at depths below 20 cm only a very small fraction was observed. In the bedrock of Olkiluoto, where the final repository for spent nuclear fuel from the Finnish nuclear power plants will be constructed, mica mineral biotite plays the most important role in cesium sorption. The selectivity of biotite decreases in the order Cs > K > Na > Ca and the overall selectivity coefficient for Cs/Ca exchange was approximately five and seven orders of magnitude higher than those for Cs/Na and Cs/K exchange reactions, respectively. Ion exchange isotherms for Cs/Na and Cs/K exchange were modelled by assuming three different ion exchange sites: frayed edge sites (FES), basal plane sites and intermediate sites. The selectivity coefficients derived for these sites were successfully used to predict cesium sorption in a mica gneiss rock. Sorption of cesium in mineral soil layers from the Olkiluoto overburden were studied using three different approaches: model batch experiments, an in-situ method and calculations. All three approaches gave the same trend but the distribution coefficient values varied in range of one order of magnitude.

Weak protein-cationic co-ion interactions addressed by X-ray crystallography and mass spectrometry.

The adsorption of Rb(+), Cs(+), Mn(2+), Co(2+) and Yb(3+) onto the positively charged hen egg-white lysozyme (HEWL) has been investigated by solving 13 X-ray structures of HEWL crystallized with their chlorides and by applying electrospray ionization mass spectrometry (ESI-MS) first to dissolved protein crystals and then to the protein in buffered salt solutions. The number of bound cations follows the order Cs(+) < Mn(2+) ≃ Co(2+) < Yb(3+) at 293 K. HEWL binds less Rb(+) (qtot = 0.7) than Cs(+) (qtot = 3.9) at 100 K. Crystal flash-cooling drastically increases the binding of Cs(+), but poorly affects that of Yb(3+), suggesting different interactions. The addition of glycerol increases the number of bound Yb(3+) cations, but only slightly increases that of Rb(+). HEWL titrations with the same chlorides, followed by ESI-MS analysis, show that only about 10% of HEWL binds Cs(+) and about 40% binds 1-2 Yb(3+) cations, while the highest binding reaches 60-70% for protein binding 1-3 Mn(2+) or Co(2+) cations. The binding sites identified by X-ray crystallography show that the monovalent Rb(+) and Cs(+) preferentially bind to carbonyl groups, whereas the multivalent Mn(2+), Co(2+) and Yb(3+) interact with carboxylic groups. This work elucidates the basis of the effect of the Hofmeister cation series on protein solubility.

Synthesis and equilibrium studies of titanium vanadate and its use in the removal of some hazardous elements

Titanium vanadate was synthesized and characterized by X-ray diffraction, thermal analysis (TGA and DTA), X-ray fluorescence, and IR spectroscopy. The empirical formula of titanium vanadate is Ti2V2O9·2.5H2O. Titanium vanadate was tested as sorbent for removing some harmful ions such as Cs, Co, Cu, and Cd. The distribution coefficients (Kd) were determined. They decrease in the order Cs+ ≫ Cu2+ > Co2+ > Cd2+. The distribution coefficients increase with increasing pH and reaction temperature. The thermodynamic functions of sorption (ΔH0, ΔS0, ΔG0) were calculated. Negative values of ΔG0 and positive values of ΔH0 show that the sorption is a spontaneous endothermic reaction.

Interface Properties and Physicochemical Characterization of the Low-Temperature Molten Salt Li/K/Cs Acetate

The surface of macroscopic films of the ternary molten salt mixture Li0.2K0.275Cs0.525[OAc] has been investigated by angle-resolved X-ray photoelectron spectroscopy (XPS) as a function of temperature. With increasing temperature a preferential depletion of K+ is observed by ∼40%. From temperature programmed desorption we find that the onset for the cation desorption follows the order Cs+, K+, and Li+, with activation energies of 125, 148, and 157 kJ mol–1, respectively; the corresponding value for the [OAc] anion is 147 kJ mol–1, which is, within the margin of error, identical to the average of the value found for the cations. Ultrathin films of the molten salt deposited on a Au(111) surface by physical vapor deposition show preferential enrichment of Cs+, in line with the lower activation energy and thus higher desorption rate of Cs[OAc] from the ternary mixture. Angle-resolved XPS of the molten salt/gold interface demonstrates that the first molten salt monolayer grows in a layer-by-layer growth, follow...

Leaching of lanthanides from various weathered elution deposited ores

Lanthanides adsorbed on clay minerals were easily recovered by ion exchange leaching with inorganic monovalent salt solutions under ambient conditions. The leaching efficiency (as per cent extraction) of various salts at 0·5M and 25°C was investigated as a function of cation type and salt system (sulphates versus chlorides). The selected lixiviant concentration was based on a 3∶1 stoichiometric ratio between total lanthanide content and the exchange cation. Leaching efficiency decreased in the order Cs+>NH4+>Na+>Li+, from 90% to ∼60% respectively, with sulphates exhibiting ∼10% higher extraction than chlorides; differences in lanthanide desorption were explained in terms of differences in cation hydration energies. (NH4)2SO4 was identified as the optimum lixiviant and a procedure was established to investigate the influence of temperature, pH and agitation on desorption kinetics and lanthanide extraction levels. It was determined that maximum extraction required pH below 5 and moderate temperatures (<50°C).Les lanthanides adsorbés sur les minéraux d’argile ont été facilement récupérés par lessivage à échange d’ion avec des solutions de sel monovalent inorganique, en conditions ambiantes. On a examiné le rendement du lessivage (pourcentage d’extraction) de sels variés, à 0·5M et 25°C, en fonction du type de cation et du système de sel (sulfates ou chlorures). La concentration choisie de lixiviant était basée sur un rapport stœchiométrique de 3∶1 entre la teneur totale en lanthanide et le cation d’échange. Le rendement du lessivage diminuait dans l’ordre de Cs+>NH4+>Na+>Li+, de 90% à ∼60%, respectivement, les sulfates exhibant une extraction environ 10% plus élevée que celle des chlorures; on expliquait la différence dans la désorption de lanthanide en termes de différence d’énergie d’hydratation du cation. On a identifié (NH4)2SO4 comme lixiviant optimal et l’on a établi une procédure d’étude de l’influence de la température, du pH et de l’agitation sur la cinétique de désorption et sur les niveaux d’extraction de lanthanide. On a déterminé que l’extraction maximale nécessitait un pH au-dessous de 5 et des températures modérées (<50°C).

Alkali metals as promoters in Co–Mn–Al mixed oxide for N2O decomposition

Alkali promoted Co4MnAlOx mixed oxide (molar ratio of alkali metal/Co=0.037) were prepared by impregnation of calcined Co–Mn–Al hydrotalcite (molar ratio Co:Mn:Al=4:1:1) with an aqueous solution of Li, Na, K, Rb or Cs nitrate. The catalysts were characterized by AAS, SEM/EDX, N2 physisorption, XRPD, XPS, H2-TPR, TPD of CO2 and NH3 and tested for N2O decomposition in inert gas and simulated waste gas from HNO3 production. N2O conversion over alkali promoted Co4MnAlOx mixed oxide decreased in order Cs>Rb>K>Na=Co4MnAlOx>Li in inert gas and was shifted to the lower values in the presence of typical components (NOx, O2 and H2O) of flue gas. The addition of alkali promoters to the Co4MnAlOx mixed oxide resulted in a modification of both electronic properties of active metals and acid–base function of the catalyst surface. The promotional effect of alkali metals is connected with their ionization potential, the charge transfer to the catalyst and a decrease in binding energies of all catalyst components (Co, Mn, Al and O). Pilot plant verification of N2O decomposition over K-promoted Co4MnAlOx is shown.

Removal of Co, Sr and Cs from aqueous solution using self-assembled monolayers on mesoporous supports

Sorptive removal of Co, Sr and Cs from aqueous solution by SAMMS was investigated. The single-solute sorption data were well fitted by the Freundlich, Langmuir and Dubinin-Radushkevich models (R 2 >0.95). The maximum sorption capacities (qmL) of the Langmuir model were in the order of Cs (1.14 mmol/g)>Co (0.20 mmol/g)≈Sr (0.195 mmol/g). The bi-solute competitive sorption of the metals was analyzed by the Langmuir, competitive Langmuir, modified extended Langmuir and P-factor models. The sorption of one metal was suppressed by the presence of competing metals. Sorptions of Co and Sr were strongly dependent on the initial solution pH but that of Cs was not. The calculated ther- modynamic parameters such as ∆H 0 , ∆S 0 and ∆G 0 showed that sorption of Co onto SAMMS was endothermic, whereas those of Sr and Cs were exothermic. The negative ∆G 0 values indicated all the sorption processes were spontaneous in nature.

Recovery of rare earth elements adsorbed on clay minerals: I. Desorption mechanism

The ongoing development of new, advanced technologies created increasing demands for rare earth elements (REE) in the international markets, with emphasis on identifying new resources to ensure adequate supply and access. The present study investigates the use of clay minerals as a source for extracting rare earth metals by leaching with sulfate and chloride salts. It was found that REE adsorbed on clays can be easily recovered via an ion-exchange mechanism during leaching with monovalent salt solutions under ambient conditions. The leaching efficiency of various salts at 0.5M and 25°C was investigated as a function of monovalent cation type (i.e. Li+, Na+, Cs+ and NH4+) and salt system (sulfates vs. chlorides). The initial concentration was based on a 3:1 stoichiometric ratio between all trivalent lanthanides in the clay and the exchange monovalent cation. Leaching efficiency (in terms of % REE extracted) decreased in the order Cs+>NH4+>Na+>Li+, from 90% to ~60%, respectively, with sulfates exhibiting ~10% better extraction behavior than chlorides. Differences in rare earth metal desorption capability were explained in terms of differences in cation hydration energies: species with low hydration energy extract to a lesser degree compared to species with high hydration energy (i.e. higher affinity for water). Based on these findings, (NH4)2SO4 was identified as the lixiviant of choice for further studies.

Ion-specific counterion condensation on charged peptides: Poisson–Boltzmann vs. atomistic simulations

We investigate ion-specific effects in the counterion condensation on a charged polypeptide by explicit-water molecular dynamics (MD) computer simulations. The charged polypeptide is a 10mer of polyglutamic acid (PGA), E10, and is simulated in a stretched, rod-like configuration which enables us to neatly compare to mean-field cell models for charged cylinders. The latter predict a fraction of condensed counterions of xc = 53% for our system independent of cell size. Using the inflection point criterion on the MD simulation density profiles, we find larger values of 71%, 66%, and 60% for Na+, K+, and Cs+, respectively, due to ion-specific adsorption effects, while the threshold radius for condensation is roughly constant at 1.4 nm. However, the values of xc decrease for larger cell radii R indicating that the specific effect is concentration-dependent and may reach the mean-field limit at infinite dilution. A simple scaling law indeed predicts that the nonelectrostatic adsorption decays ∝R−1 within the condensation layer. We further demonstrate that the Poisson–Boltzmann (PB) model can still be a valid description for the distance-dependent fraction of counterions around the polypeptide if ion-specificity is introduced by an empirical, attractive potential in the PB equation. The modeling of ion-specific effects by inclusion of such potentials may be useful in coarse-grained (implicit-model) simulations of PGA chains. The PB performance worsens, however, with the inclusion of salt at physiological concentration. Finally, we show that the binding time distribution of the condensed ions shows anomalous diffusive behavior, with faster decay in the order Cs+ > K+ > Na+ in the nanosecond time regime.

Relating Clay Structural Factors to Dioxin Adsorption by Smectites: Molecular Dynamics Simulations

Dioxin adsorption by smectite clays can greatly exceed that by soil organic matter when compared on an equal mass basis. Bulk‐phase adsorption experiments demonstrated that sorption of dioxin by smectites depended strongly on (i) the hydration properties of the exchangeable cations, (ii) the surface charge density of the smectite clay, and (iii) the location (tetrahedral vs. octahedral) of isomorphous substitution in the clay mineral structure. Molecular dynamics simulations of saponites saturated with different exchangeable cations (Na+, K+, Cs+, and Ca2+) and one, two, or three layers of water in the interlayer regions were conducted to study the molecular environment of adsorbed dioxin in each system. The simulated radial distribution functions were computed to quantify the spatial correlations between O on dioxin (Odd) and interlayer cations as well as water molecules. The magnitudes of the Odd–cation coordination numbers followed the order Cs+ &gt; K+ &gt; Na+ &gt; Ca2+, which agrees with the observed trend of dioxin adsorption to the smectites from water. The estimated adsorption enthalpies follow the trend Cs+ &lt; K+ &lt; Na+ ∼ Ca2+, further supporting the hypothesis that Odd–cation complexation plays an important role in adsorption of dioxin in clay interlayers.

Thymine quintets and their higher order assemblies studied by electrospray ionization mass spectrometry and theoretical calculation

We previously reported that thymine molecules can specifically form a pentameric magic number cluster named as thymine quintet in the presence of K(+) , Rb(+) and Cs(+) . Actually, thymine decamer and doubly charged thymine 15-mer metaclusters can be observed along with thymine quintet in the ESI mass spectra of thymine with the addition of K(+) , Rb(+) and Cs(+) . The product ion spectra of these metaclusters, especially the 15-mer with hetero central ions, indicate that they are higher order assemblies of thymine quintets. The collision-induced dissociation experiments show that the gas-phase stabilities of these metaclusters depend on the size of the central ions, following the order Cs(+) > Rb(+) > K(+) , while K(+) leads to the highest dissociation energy of a thymine quintet. The optimized structures of thymine quintet and decamer were provided by density functional theory calculations, which showed that thymine quintet is bowl-shaped and its tilting angle increases with the size of the central ion. Furthermore, the chirality of thymine quintet was defined for the first time and the resulting different diastereoisomers of thymine decamers were also revealed by the calculation study. Copyright © 2011 John Wiley & Sons, Ltd.

RESISTIVITY-DRIVEN STATE CHANGES IN VERTICALLY STRATIFIED ACCRETION DISKS

We investigate the effect of shear viscosity and Ohmic resistivity on the magnetorotational instability (MRI) in vertically stratified accretion disks through a series of local simulations with the Athena code. First, we use a series of unstratified simulations to calibrate physical dissipation as a function of resolution and background field strength; the effect of the magnetic Prandtl number, Pm = viscosity/resistivity, on the turbulence is captured by ~32 grid zones per disk scale height, H. In agreement with previous results, our stratified disk calculations are characterized by a subthermal, predominately toroidal magnetic field that produces MRI-driven turbulence for |z| < 2 H. Above |z| = 2 H, magnetic pressure dominates and the field is buoyantly unstable. Large scale radial and toroidal fields are also generated near the mid-plane and subsequently rise through the disk. The polarity of this mean field switches on a roughly 10 orbit period in a process that is well-modeled by an alpha-omega dynamo. Turbulent stress increases with Pm but with a shallower dependence compared to unstratified simulations. For sufficiently large resistivity, on the order of cs H/1000, where cs is the sound speed, MRI turbulence within 2 H of the mid-plane undergoes periods of resistive decay followed by regrowth. This regrowth is caused by amplification of toroidal field via the dynamo. This process results in large amplitude variability in the stress on 10 to 100 orbital timescales, which may have relevance for partially ionized disks that are observed to have high and low accretion states.

Contribution to the Complexation of some Univalent Metal Cations with p-Tert-Butylcalix[4]arene-Tetrakis(N,N-Diethylacetamide) in Nitrobenzene Saturated with Water

Abstract From extraction experiments and γ-activity measurements, the exchange extraction constants corresponding to the general equilibrium M+(aq)+NaL+(nb)⇔ML+(nb)+Na+(aq) taking place in the two-phase water-nitrobenzene system (M+=Li+, Ag+, Rb+, Tl+, Cs+; L=p-tert-butylcalix[4]arene-tetrakis(N,N-diethylacetamide); aq=aqueous phase, nb=nitrobenzene phase) were determined. Moreover, the stability constants of the ML+ complexes in water-saturated nitrobenzene were calculated; they were found to increase in the cation order Cs+ &lt; Rb+ &lt; Tl+ &lt; Ag+ &lt; Li+.

Lithium, rubidium and cesium ion removal using potassium iron(III) hexacyanoferrate(II) supported on polymethylmethacrylate

Potassium iron(III) hexacyanoferrate(II) supported on poly methyl methacrylate, has been developed and investigated for the removal of lithium, rubidium and cesium ions. The material is capable of sorbing maximum quantities of these ions from 5.0, 2.5 and 4.5 M HNO3 solutions respectively. Sorption studies, conducted individually for each metal ion, under optimized conditions, demonstrated that it was predominantly physisorption in the case of lithium ion while shifting to chemisorption with increasing ionic size. Distribution coefficient (K d) values followed the order Cs+ > Rb+ > Li+ at low concentrations of metal ions. Following these findings Cs+ can preferably be removed from 1.5 to 5 M HNO3 nuclear waste solutions.

The effect of NO 3 − and OH− ions on the laser ablation of Cs+ ion on Type 304 stainless steel

Type 304 stainless steel specimens artificially contaminated with CsCl solution were treated with KOH solution and KNO3 solution, respectively. Cs ? ion removal tests by a Q-switched Nd:YAG laser at 1064 nm at a given fluence of 57.3 J/cm 2 were performed. The surface mor- phology and the relative atomic mole ratio of the specimen surface were investigated by SEM and EPMA. The order of Cs ? ion removal efficiency of laser was no-treatment \ KOH \ KNO3 during the 42 shots. From the investi- gation of XPS peaks around 532.7 and 292.9 eV, KNO3 on a surface of specimen was found to be fully decomposed during the laser irradiation. It was suggested that Cs2O particulates formed by the reaction between the reactive oxygen generated from the nitrate ion and Cs ? ion on the metal surface could be easily suspended. For the KOH system, FeOOH was formed during the laser irradiation and it changed into Fe2O3. It was also suggested that Cs2O particulates were formed by the reaction between the reactive oxygen generated from the decomposition of K2O and Cs ? ion on the metal surface..

Use of Nano Crystalline Silicotitanate for the Removal of Cs, Co and Sr from Low-Level Liquid Radioactive Waste

The uptakes of Cs, Co and Sr ions onto nano crystalline silicotitanate (IONSIV ® IE-911, UOP) were investigated by using batch sorbers. The nanostructured adsorbent has many advantages such as high active surface area, fast diffusion rates and lower amount needs. Equilibrium sorption characteristics of Cs, Co and Sr ions onto the sorbent were investigated. The Freundlich, Langmuir and Dubinin-Radushkevich (D-R) isotherm models were fitted to the experimental data. Using the Langmuir model, the predicted sorption capacity of Cs, Co and Sr onto the silicotitanate at pHs 5, 7 and 9 was in the order Cs > Sr > Co. The silicotitanate was highly selective for Cs due to the ion exchange with sodium and hydrogen ions. The Langmuir model fitted better than the Freundlich and D-R models to the experimental data for the metals (0.83 < R 2 < 0.97).

Diffusion mobility of alkali metals in perfluorinated sulfocationic and carboxylic membranes as probed by 1H, 7Li, 23Na, and 133Cs NMR spectroscopy

The hydration, state, and ion mobility of protons and alkali metal cations (Li+, Na+, and Cs+) in perfluorinated sulfocationic membranes (MF-4SK) and carboxylic membranes (F-4KF) were studied using NMR and impedance spectroscopy. The hydration numbers and translational mobilities of ions and the formation conditions for cation/ionogenic group tight ion pairs were ascertained proceeding from analysis of chemical shifts and 1H, 7Li, 23Na, and 133Cs NMR line widths. NMR data correlate with the results of ion conductivity measurements. The translational mobility of cations and ionic conductivity in the sulfocationic membranes are higher than in the carboxylic membranes and increase in the order Cs+-Na+-Li+.

Long-lived electron–hole pair formation through photoionization of diphenylacetylene occluded in medium pores of aluminum rich M 6.6ZSM-5 zeolite (M = Li +, Na +, K +, Rb +, Cs +) : Influence of the counterbalancing cations on the recombination rate

Diffuse reflectance UV–vis and Raman spectroscopies show complete sorption of neutral diphenylacetylene (DPA) in the void space of M 6.6ZSM-5 zeolites (M = Li +, Na +, K +, Rb +, Cs +) after several months of exposure of solid DPA to empty zeolite at room temperature. After a long organization period, the laser photolysis of DPA occluded in M 6.6ZSM-5 generates long-lived DPA + radical cation as primary phenomenon. Charge recombination occurs mainly through electron transfer and DPA@M 6.6ZSM-5 − + electron–hole pair formation. This subsequent electron transfer takes place between the electron deficient radical cation DPA + and the electron donor oxygen atom of zeolite framework. The multivariate curve resolution analysis of the DRUVv spectra recorded during the reaction sequence including charge separation, electron transfer and charge recombination provide the specific absorption spectra and respective spectral concentrations of all species as function of time. The DRUVv spectrum assigned to the long-lived DPA@M 6.6ZSM-5 − + electron–hole pair exhibits broad bands between 450 and 550 nm. The electron–hole pair recombination depends on M + and appears to be in relation with the electron donor properties of the framework. The charge recombination rate decreases in the order Cs + > Rb + ∼ K + > Na + > Li +. The electron–hole pair lifetime exceeds several hours at room temperature. The stabilization of DPA +-electron pair and DPA@M 6.6ZSM-5 − + electron–hole pair depends on the combined effects of confinement which dramatically reduces the DPA mobility in the zeolite void space and on the intrazeolithe electrostatic field of DPA@M n ZSM-5 (M = Li +, Na +, K +, Rb +, Cs +).

Stability Constants of Some Univalent Cation Complexes of 2,3-Naphtho-15-crown-5 in Nitrobenzene Saturated with Water

The extraction of micro amounts of cesium by nitrobenzene solutions of sodium, potassium and rubidium dicarbollylcobaltates (M+B−;M+=Na+,K+,Rb+) has been investigated in the presence of 2,3-naphtho-15-crown-5 (N15C5, L). The equilibrium data were explained by assuming that ML+ and ML 2 + complexes (M+=Na+,K+,Rb+, Cs+; L=N15C5) were present in the organic phase. The stability constants of the complex species ML+ and ML 2 + have been determined in nitrobenzene saturated with water. It was found that the stability of the complex cation ML+ (where M+=Na+,K+,Rb+, Cs+; L=N15C5) in water-saturated nitrobenzene solutions increases along the series Cs+<Rb+<K+<Na+, whereas that of the species ML 2 + in the same medium increases in the order Cs+<Rb+<Na+<K+.