Effect of temperature on SuperLig® 644 cesium removal from simulated Hanford tank waste supernate

Batch kinetic and column experiments have been carried out at 25, 35, and 45 °C to examine the effect of temperature on SuperLig® 644 cesium (Cs) removal from simulated Hanford tank waste supernate. The simulated solution mimicked the composition of the low-activity waste supernate from tank 241-AN-105 in the U.S. DOE Hanford site. Small quantities of toxic metals, such as Cd, Cr, Fe, and Pb were spiked into the simulant to evaluate the metal's competitiveness with Cs for sorption on SuperLig® 644 resin. The results indicated that the temperature affects the removal of Cs and metal ions, although the effect was not the same for all metal ions. The extent of Cs removal decreased with an increase in temperature. The Cs capacity at breakthrough point was 0.015, 0.013, and 0.011-mmole/g dry resin at 25, 35 and 45 °C, respectively. The column was effectively eluted to less than 1% (0.1 C/C ₀) of the feed concentration with approximately 10 BVs of 0.5M nitric acid. The resin showed limited affinity for toxic metal ions (Cr, Cd, Fe, and Pb) as compared to Cs. Based on the batch kinetic data, the Cs uptake of the resin was not hampered by the presence of the toxic metals in solution.     

浮石负载壳聚糖吸附去除水中丙溴磷

通过浮石负载壳聚糖制备了吸附剂壳聚糖/浮石复合物,采用扫描电子显微镜(SEM)、热重分析(TGA)、元素分析、傅里叶红外光谱(FT-IR)、X射线衍射(XRD)和X射线荧光光谱(XRF)等技术手段表征了吸附剂性质,考察了吸附剂量、吸附时间、溶液pH值、离子强度和温度对该吸附剂吸附去除水中丙溴磷的影响,研究了再生吸附剂的吸附性能。结果表明,负载在浮石上的壳聚糖占吸附剂总量的8.69%;在p H值3.0~7.0内,壳聚糖/浮石对丙溴磷的吸附率大于90%;这种吸附剂对丙溴磷的吸附受溶液离子强度影响较小,随温度升高而稍微减小。在溶液温度25℃、pH=7.0、丙溴磷浓度40 mg/L、壳聚糖/浮石剂量为0.7 g/L和吸附平衡时间为90 min条件下,此吸附剂对丙溴磷最大吸附率为93.3%(最大吸附量为53.4 mg/g)。壳聚糖/浮石连续经过3次吸附/再生循环,每次循环对丙溴磷的吸附率下降约12%。可见壳聚糖/浮石通过吸附可有效地去除水中的农药丙溴磷。     

Development of a method for nuclide leaching from glass fiber in HEPA filter

For the disposal of the high efficiency particulate air (HEPA) glass filter to environment, the glass fiber should be leached to lower its radioactive concentration. To derive the optimum method for removal of Co and Cs from HEPA glass fiber, four methods were applied in this study. Results of electrochemical leaching of glass fiber by 4.0 M HNO₃–0.1 M Ce(IV) solution showed that the removal efficiency of ¹³⁴Cs, ¹³⁷Cs, and ⁶⁰Cs from glass fiber after 5 h was 96.4, 93.6, and 93.8%, respectively. Results by 5 wt% NaOH solution showed that the removal efficiency of ¹³⁴Cs, ¹³⁷Cs, and ⁶⁰Cs after 30 h was 81.7, 82.1, and 10.0%, respectively. Results by repeat 2.0 M HNO₃ solution showed that the removal efficiencies of ¹³⁴Cs, ¹³⁷Cs, and ⁶⁰Cs after 2 h of three repetitions were 96.2, 99.4, and 99.1%, respectively. Finally, results by repeat 4.0 M HNO₃ solution showed that the removal efficiencies of ¹³⁴Cs, ¹³⁷Cs, and ⁶⁰Cs after 4 h of three repetitions were 100, 99.9, and 99.9%, respectively, and their radioactivities were below 0.1 Bq/g. Therefore, the chemical leaching method by 4.0 M HNO₃ solution was considered as an optimum one for removal of cesium and cobalt from HEPA glass fiber for self disposal. Also the removal efficiencies of ⁶⁰Co, ¹³⁴Cs, and ¹³⁷Cs from the waste-solution after its precipitation-filtration treatment for reuse of 4.0 M HNO₃ waste-solution were 88.0, 95.0, and 99.8%.     

Highly Crystallized Nanometer‐Sized Zeolite A with Large Cs Adsorption Capability for the Decontamination of Water

Nanometer‐sized zeolite A with a large cesium (Cs) uptake capability is prepared through a simple post‐milling recrystallization method. This method is suitable for producing nanometer‐sized zeolite in large scale, as additional organic compounds are not needed to control zeolite nucleation and crystal growth. Herein, we perform a quartz crystal microbalance (QCM) study to evaluate the uptake ability of Cs ions by zeolite, to the best of our knowledge, for the first time. In comparison to micrometer‐sized zeolite A, nanometer‐sized zeolite A can rapidly accommodate a larger amount of Cs ions into the zeolite crystal structure, owing to its high external surface area. Nanometer‐sized zeolite is a promising candidate for the removal of radioactive Cs ions from polluted water. Our QCM study on Cs adsorption uptake behavior provides the information of adsorption kinetics (e.g., adsorption amounts and rates). This technique is applicable to other zeolites, which will be highly valuable for further consideration of radioactive Cs removal in the future.     

Role of ions on structure and stability of a synthetic gramicidin ion channel in solution. A molecular dynamics study

We performed a molecular dynamics (MD) simulation to the investigate structure and stability of a synthetic gramicidin-like peptide in solution with and without ions. The starting structures of the MD simulations were taken from two recently solved NMR structures of this peptide in isotropic solution, which forms stable monomers or dimers in the presence or absence of ions, respectively. The monomeric structure is channel-like and is assumed to be stabilized by the presence of two Cs(+) ions bound in the channel, each one close to one channel entrance. In our MD simulations, we observed how the Cs(+) ions bind in the channel formed by the monomeric gramicidin-like peptide using implicit solvent and explicit ions with a concentration of 2 M. MD simulations were performed with and without explicit ions but with an implicit solvent model defined by the generalized Born approximation, which was used to mimic the dielectric properties of the solvent and to speed up the computations.     

One-step synthesis of magnetic composite UiO-66/Fe3O4/GO for the removal of radioactive cesium ions

Journal of Radioanalytical and Nuclear Chemistry - In this study, the UiO-66/Fe3O4/GO composite was prepared by one step method for removal of cesium ions (Cs+) in water and exhibited excellent...     

Competitive transport of toxic metal ions by polymer inclusion membranes

The paper gives a short overview of application of polymer inclusion membranes (PIMs) for separation and removal of metal ions. Investigation of the selective removal of toxic metal ions, i.e. Cr(VI), Cd(II), Zn(II) from acidic chloride aqueous solutions, as well as trace radionuclides, i.e., ¹³⁷Cs, ⁹⁰Sr and ⁶⁰Co from wastewaters using transport across polymer inclusion membranes was studied. The carriers, i.e., tri-n-octylamine for anionic metal species, as well as dibenzo-21-crown-7, tertbutyl-dibenzo-21-crown-7, and dinonylnaphtalenesulfonic acid for metal cations were incorporated into polymer inclusion membranes composed of cellulose triacetate as a support and o-nitrophenyl pentyl ether as a plasticizer. Selective transport of chromium(VI) over zinc(II) and cadmium(II) chloride complexes through PIMs was observed. Competitive transport of trace radionuclide ions, i.e., ¹³⁷Cs, ⁹⁰Sr, and ⁶⁰Co from NaNO₃ aqueous solutions across polymer inclusion membranes containing a mixture of dinonylnaphtalenesulfonic acid, and dibenzo-21-crown-7 as the carrier provide the selectivity order Cs(I)>Sr(II)>Co(II).     

An anomalous x-ray diffraction study of the hydration structures of Cs+ and I- in concentrated solutions

Anomalous x-ray diffraction experiments were carried out on concentrated aqueous solutions of sodium iodide (6 molal) and cesium iodide (3 molal). Data were gathered at two energies below the absorption edges of the Cs+ and I- ions in order to avoid contributions from fluorescence. The statistics and quality of the raw data were improved by the use of a focusing analyzer crystal. Differences were taken between the data sets and used to calculate the hydration structures of Cs+ and I-. The structures found are more complex than anticipated for such large ions with relatively low charge densities and show evidence of ion-pair formation in both solutions. A two-Gaussian fit to the Cs+ data gives information about the Cs+-O and Cs+-I- correlations. The central position of the Gaussian representing the Cs+-O was fixed at 3.00 A, that is, the maximum of this contribution. The other parameters were allowed to vary freely, giving a Cs+-I- distance of 3.84+/-0.05 A and coordination numbers of 7.9 and 2.7, respectively, for the Cs+-O and Cs+-I- correlations. The results on the structure of I- in the 6 molal NaI aqueous solution were also fitted to a model based on Gaussians; this gives correlations for I- -O and I- -Na+ at 3.17+/-0.06 and 3.76+/-0.06 A with respective coordination numbers of 8.8 and 1.6. The structure of I- in the 3 molal CsI solution shows overlapping contributions due to I- -H, I- -O, and I- -Cs+. The best Gaussian fit gives two peaks centered at 3.00+/-0.08 and 3.82+/-0.04 A and shows that the latter two correlations are unresolved. The hydration structures are compared with those of other alkali and halide ions. The results are also found to be in good agreement with those obtained from standard x-ray diffraction and computer simulation.     

Performance of immobilized moss in the removal of 137Cs and 90Sr from actual low-level radioactive waste solutions

The efficiency of immobilized moss as a bio-sorbent for the removal of ¹³⁷Cs and ⁹⁰Sr radionuclides from actual low-level radioactive waste (LLW) solutions was investigated. Preliminary batch experiments with the moss (Funaria hygrometrica) for the sorption of Cs and Sr have shown a pH dependent binding trend from pH 1–13, with maximum binding between pH 5–10. Time dependence of the batch studies showed that a contact time of 30 minutes was sufficient to reach equilibrium. Column experiments for the sorption of Cs and Sr by moss after immobilizing in polymer silica matrix demonstrated that the sorbent is capable of removing considerable amounts of Cs and Sr from actual LLW solutions under constant flow conditions. The adsorption capacity was estimated to be 8.5 mg/g for Cs and 15 mg/g for Sr. These sorbed metal ions from the column could be leached out using 0.20M nitric acid. The regenerated sorbent exhibited relatively the same initial binding capacity of both Cs and Sr even after 3 cycles of reuse. This revised version was published online in July 2006 with corrections to the Cover Date.     

Selective removal of Cs and Re by precipitation in a Na<Subscript>2</Subscript>CO<Subscript>3</Subscript>–H<Subscript>2</Subscript>O<Subscript>2</Subscript> solution

The removal of Cs and Re (as a surrogate for Tc) by selective precipitation from the simulated fission products which were co-dissolved with uranium during the oxidative dissolution of spent fuel in a Na₂CO₃–H₂O₂ solution was investigated in this study. The precipitations of Cs and Re were examined by introducing sodium tetraphenylborate (NaTPB) and tetraphenylohosponium chloride (TPPCl), respectively. The precipitation of Cs by NaTPB and that of Re by TPPCl each took place within 5 min, and an increase in temperature up to 50 °C and a stirring speed up to 1000 rpm hardly affected their precipitation rates. The most important factor in the precipitation with NaTPB and TPPCl was found to be a pH of the solution after precipitation. Since Mo tends to co-precipitate with Cs or Re at a lower pH, an effective precipitation with NaTPB and TPPCl was done at pH of above 9 without the co-precipitation of Mo. More than 99% of Cs and Re were precipitated when the initial concentration ratio of NaTPB to Cs was above 1 and when that of TPPCl to Re was above 1. The precipitation of Cs and Re was never affected by the concentration of Na₂CO₃ and H₂O₂, even though they were raised up to 1.5 and 1.0 M, respectively. Precipitation yields of Cs and Re in a Na₂CO₃–H₂O₂ solution were found to be dependent on the concentration ratios of [NaTBP]/[Cs] and [TPPCl]/[Re].     

Specificity of Lichen Species in Respect to 137Cs Binding

Abstract

The aim of this work was to investigate the significance of species specificity on the efficiency of ¹³⁷Cs isolation from lichens. It was shown that a 5% solution of both ammonium oxalate and phosphoric acid was able to solubilize 77.5% of ¹³⁷Cs from Cetraria islandica, 47.6% from Cladonia fimbriata and 46.4% from Usnea barbata. Since the tested lichen species had similar specific radioactivities (i.e. amount of ¹³⁷Cs) the difference could be explained by the existence of different types of bonds between radiocesium and the corresponding binding sites. Crystals precipitated from these extracts incorporated most of the soluble ¹³⁷Cs. The amount and specific radioactivity of the crystals varied between lichen species which could also be interpreted as the presence of specific ions in each lichen that either participated in crystal formation or inhibited the process. The potential of a tested solution to extract and “concentrate” ¹³⁷Cs in crystalline form may be a tool to correlate mass and radioactivity of ¹³⁷Cs.     

Studies on new titanium hexacyanoferrate sorbents for radiocesium removal from primary coolant of pressurized water reactors

Recent work directed towards synthesizing and exploring new effective sorbents for radiocesium removal from primary coolants of pressurized water nuclear reactors of the WWER type is presented. Various sorbents synthesized on the basis of titanium hexacyanoferrate are compared with one another from the point of view of their sorption efficiency and stability. The uptake of¹³⁷Cs from solutions containing boric acid and millimolar quantities of ammonium and potassium ions was studied under conditions simulating the process of purification of the coolant bled from the primary circuit of the reactor. A composite-type sorbent was selected of good mechanical properties and negligible solubility, efficiently decontamining large amounts of the solution (considerably exceeding 10⁴ bed volumes) in the course of the column process.     

A study of the SiO<Subscript>2</Subscript>-aqueous electrolyte (NaCl,CsCl) interface by X-ray photoelectron spectroscopy

The surface of amorphous silicon dioxide in NaCl and CsCl solutions with various values of ionic strength and pH is studied by X-ray photoelectron spectroscopy. Samples are prepared through the fast freezing of wet pastes prepared by the centrifugation of suspensions. It is shown that the X-ray photoelectron spectra of such samples provide experimental information on the composition of the SiO₂-solution interface, the number of electrolyte ions near the solid phase surface, and its chemical modification. The sign of the charge of silicon dioxide particles can be judged from the dependence of a measured Na(Cs)/Cl atomic ratio; the controlled removal of water from the samples in the chamber of an electronic spectrometer makes it possible to directly estimate the surface potential and study the energy effects of counterion hydration using the shifts in the binding energies of the corresponding photoelectron levels. An analysis of the binding energies of Cs 3d^5/2 and Cl 2p_3/2 lines in the X-ray photoelectron spectra for the SiO₂-CsCl solution interface yields additional information on the structure of the formed electrical double layer, thus making it possible to distinguish between the ions adsorbed at the surface and the counterions compensating for its charge.     

Selectivity of calix[4]arene-bis(benzocrown-6) in the complexation and transport of francium ion

It is shown for the first time that a representative member of the "cesium-selective" calix[4]arene-crown-6 family exhibits a high affinity for Fr+ ion. In the investigation, the transport of 221Fr+ and Cs+ ions by calix[4]arene-bis(benzocrown-6) from an aqueous sodium nitrate solution into the water-immiscible diluent 1,2-dichloroethane was measured and compared to address the question of selectivity of the calix-crown-6 cavity toward alkali metal ions of increasing size. Selective separation of 221Fr+ from its parent 225Ac and from the matrix Na+ ions was demonstrated. Higher distribution ratios were obtained than those for the Cs+ ion. The extraction equilibria were determined for the case of the Cs+ ion, and the same equilibria were shown to be applicable to the case of Fr+ with inclusion of additional competitive effects.     

Gas phase, solution, and solid state alkali ion binding by the [NbE8](3-) (E = As, Sb) complexes: synthesis, structure, and spectroscopy

Toluene solutions of Nb(toluene)(2) react with ethylenediamine solutions of K(3)E(7) (E = As, Sb) in the presence of 2,2,2-crypt to give [NbAs(8)](3-) (2) and [NbSb(8)](3-) (3) ions, respectively, in low yields. The (133)Cs NMR spectroscopy, ESIMS results (negative ion mode), and single-crystal X-ray structures of the ions are reported. The complexes have S(8)-like E(8) rings with Nb atoms in the center. The 1:1 complex of 2 with Cs+ was observed in solution and also in the gas phase as the oxidized ion [CsNbAs(8)](1-). The anion 2 selectively binds to Cs(+) in solution even in the presence of excess Na(+). Other gas-phase ions formed include [Cs(2)(NbAs(8))](1-), [KCs(NbAs(8))](1-), [KCs(NbAs(8))(2)](1-), [KNbAs(8)](1-), and [K(2)NbAs(8)](1-).     

Investigation of Cs(I) adsorption on densely crosslinked poly(sodium methacrylate) from aqueous solutions

In this study, a crosslinked copolymer bearing sodium methacrylate functional groups has been proposed to remove Cs(I) ions from aqueous solutions. For this purpose, the crosslinked copolymer of ethylene glycol dimethacrylate (EGDM) and methacrylic acid (MA) containing 25% MA as weight percentage was synthesized by using benzoyl peroxide (BPO)-N,N-dimethyl aniline initiator system. The available carboxyl groups in copolymer were converted to the groups of sodium methacrylate using 2 N NaOH. The adsorption behavior of cesium ions on the densely crosslinked poly(sodium methacrylate) from aqueous solutions were investigated by the technique of ICP-MS measurements of cesium ions in solutions. Batch adsorption method was used to analyze the Cs(I) adsorption as a function of parameters such as the amount of adsorbent, contact time, pH of solution, initial Cs(I) concentration and temperature. The adsorption data were evaluated by the Freundlich, Langmuir and Dubinin–Radushkevich (D–R) isotherms. The adsorption capacity and free energy change were calculated by using D–R isotherm. The adsorption data obtained from experimental results have been tested by the fractional power, the Elovich, the pseudo-first order and the pseudo-second order kinetic models.     

Ion-exchange behaviour of copper ferricyanide

A new inorganic ion exchanger, copper ferricyanide prepared by adding copper nitrate to a potassium ferricyanide solution at 80°C has been found to be stable in acids and salt solutions. It has been characterized by chemical analysis, thermogravimetry. X-ray and infrared spectroscopy. Distribution coefficients determined for various metal ions show that the exchanger has a high affinity for heavy univalent cations. The variation of K_d for a number of metal ions as a function of nitric acid concentration and ammonium nitrate has been investigated to elucidate the probable exchange mechanism and to work out conditions for elution. Binary separations of Cs from a number of other metal ions were achieved on the column of exchanger. The exchanger is useful for the separation of¹³⁷Cs.     

亚铁氰化钛钾从模拟高放废液中去除Cs中试初步研究

本文研究了无机离子交换业铁氰化钛钾对模拟高放废液进行三柱串级的中试实验,结果表明：当模拟高放废液中Ｃｓ的浓度为１．１５ｇ／Ｌ,酸度为１．１ｍｏｌ／Ｌ,焖液流速为２．０ＢＶ／ｈｙ,交换柱穿透率为１％时,干交换剂的交换容量为０．３８ｍｍｏｌ／ｇ,９０％穿透时,交换容量可达０．７７ｍｍｏｌ／ｇ,交换后的废交换剂用０．１ｍｏｌ／Ｌ的硝酸洗涤,卸柱时树脂仍保持良好的球型,说明交换剂亚铁氰化钛钾有良好的机械稳     

The interaction mechanisms between aqueous solutions of137Cs and134Ba radionuclides and local natural zeolites for an deactivation scenario

¹³⁷Cs and¹³⁴Ba were removed from synthetic aqueous solutions by means of natural zeolites of Slovakian origin. The equilibrium sorption behavior of Cs and Ba ions onto clinoptilolite and mordenite were studied under static as well as dynamic experimental conditions. Both Freundlich and Langmuir isotherms describe satisfactory by Cs and Ba adsorption on the zeolites studied. The elution of Cs and Ba ions from zeolite columns after the loading cycle was undertaken additionaly, in order to compare column operating runs of various exchanged zeolite forms.     

Sorption properties of chemically treated clinoptilolites with respect to Cs and Co

The sorption ability of clinoptilolite treated by NaOH solution has been studied. The distribution coefficients of¹³⁷Cs and⁶⁰Co were studied by the radiochemical method. The variation of distribution coefficients with pH was studied. Also the influence of competitive ions on distribution coefficients were investigated. The total cation exchange capacity and XRD analysis were also measured.