Study of <Superscript>63</Superscript>Ni(II) sorption on CMC-bound bentonite from aqueous solutions

Bentonite was investigated to remove Ni(II) from aqueous solutions because of its strong sorption ability. Herein, bentonite was modified with sodium carboxymethylcellulose (CMC) and used as an adsorbent to remove Ni(II) from aqueous solutions. The results indicated that CMC-bentonite had higher sorption capacity than bare bentonite in the sorption of Ni(II) from aqueous solutions. Sorption of Ni(II) on CMC-bentonite was mainly dominated by ion exchange or outer-sphere surface complexation at low pH values, but by inner-sphere surface complexation or surface precipitation at high pH values. The thermodynamic data calculated from temperature dependent sorption isotherms indicated that the sorption of Ni(II) to CMC-bentonite hybrids was an spontaneous process and enhanced with increasing temperature.     

Investigation of solution chemistry effects on sorption behavior of radionuclide <Superscript>64</Superscript>Cu(II) on illite

In this work, a series of batch experiments were carried out to investigate the effect of various environmental factors such as contact time, pH, ionic strength, coexisting electrolyte ions, humic substances and temperature on the sorption behavior of illite towards ⁶⁴Cu(II). The results indicated that ⁶⁴Cu(II) sorption on illite achieved equilibrium quickly. The pH- and ionic strength-dependent sorption suggested that ⁶⁴Cu(II) sorption on illite was dominated by ion exchange or outer-sphere surface complexation at pH < 7, whereas the pH-dependent and ionic strength-independent sorption indicated that the sorption process was mainly attributed to inner-sphere surface complexation at pH > 7. A positive effect of humic substances on ⁶⁴Cu(II) sorption was found at pH < 6.5, whereas a negative effect was observed at pH > 6.5. The Langmuir and Freundlich models were used to simulate the sorption isotherms of ⁶⁴Cu(II) at three different temperatures of 293, 313, and 333 K. The thermodynamic parameters (ΔH ⁰, ΔS ⁰, and ΔG ⁰) of ⁶⁴Cu(II) sorption on illite were calculated from the temperature dependent sorption isotherms, and the results indicated that the sorption of ⁶⁴Cu(II) on illite was endothermic and spontaneous. From the experimental results, it is possible to conclude that illite has good potentialities for cost-effective treatments of ⁶⁴Cu(II)-contaminated wastewaters.     

Impact of environmental conditions on sorption of <Superscript>210</Superscript>Pb(II) to NKF-5 zeolite

The sorption of Pb(II) from aqueous solution using NKF-5 zeolite was investigated by batch technique under ambient conditions. The NKF-5 zeolite sample was characterized by using FTIR and X-ray powder diffraction in detail. The sorption of Pb(II) was investigated as a function of pH, ionic strength, foreign ions, and humic substances. The results indicated that the sorption of Pb(II) on NKF-5 zeolite was strongly dependent on pH. The sorption was dependent on ionic strength at low pH, but independent of ionic strength at high pH. At low pH, the sorption of Pb(II) was dominated by outer-sphere surface complexation and ion exchange with H⁺ on NKF-5 zeolite surfaces, whereas inner-sphere surface complexation was the main sorption mechanism at high pH. From the experimental results, one can conclude that NKF-5 zeolite has good potentialities for cost-effective preconcentration of Pb(II) from large volumes of aqueous solutions.     

Impact of environmental conditions on the sorption behavior of radionuclide <Superscript>60</Superscript>Co(II) on MnO<Subscript>2</Subscript>

The fate and transport of toxic metal ions and radionuclides in the environment is generally controlled by sorption reactions. The removal of ⁶⁰Co(II) from wastewaters by MnO₂ was studied as a function of various environmental parameters such as shaking time, pH, ionic strength, foreign ions, and humic substances under ambient conditions. The results indicated that the sorption of ⁶⁰Co(II) on MnO₂ was strongly dependent on pH and ionic strength. At low pH, the sorption of ⁶⁰Co(II) was dominated by outer-sphere surface complexation and ion exchange with Na⁺/H⁺ on MnO₂ surfaces, whereas inner-sphere surface complexation was the main sorption mechanism at high pH. The presence of HA/FA enhances ⁶⁰Co(II) sorption at low pH values, whereas reduces ⁶⁰Co(II) sorption at high pH values. The Langmuir and Freundlich models were used to simulate the sorption isotherms of ⁶⁰Co(II) at three different temperatures of 298.15, 318.15 and 338.15 K. The thermodynamic parameters (ΔH ⁰, ΔS ⁰ and ΔG ⁰) calculated from the temperature dependent sorption isotherms indicated that the sorption process of ⁶⁰Co(II) on MnO₂ was endothermic and spontaneous.     

<Superscript>63</Superscript>Ni schottky barrier nuclear battery of 4H-SiC

The design, fabrication, and testing of a 4H-SiC Schottky betavoltaic nuclear battery based on MEMS fabrication technology are presented in this paper. It uses a Schottky diode with an active area of 3.14 mm² to collect the charge from a 4 mCi/cm^{2 63}Ni source. Some of the critical steps in process integration for fabricating silicon carbide-based Schottky diode were addressed. A prototype of this battery was fabricated and tested under the illumination of the ⁶³Ni source with an activity of 0.12 mCi. An open circuit voltage (V _OC) of 0.27 V and a short circuit current density (J _SC) of 25.57 nA/cm² are measured. The maximum output power density (P _max) of 4.08 nW/cm² and power conversion efficiency (η) of 1.01% is obtained. The performance of this battery is expected to be significantly improved by using larger activity and optimizing the design and processing technology of the battery. By achieving comparable performance with previously constructed p–n or p–i–n junction energy conversion structures, the Schottky barrier diode proves to be a feasible approach to achieve practical betavoltaics.     

Effect of pH,ionic strength,foreign ions,humic acid and temperature on sorption of radionuclide <Superscript>60</Superscript>Co(II) on illite

In this article, a series of batch experiments were carried out to investigate the effect of various environmental factors such as contact time, solid content, pH, ionic strength, foreign ions, temperature and coexisting humic acid on the sorption behavior radionuclide ⁶⁰Co(II) on illite. The results indicated that the sorption of Co(II) was strongly dependent on pH, ionic strength and temperature. At low pH, the sorption was dominated by outer-sphere surface complexation and ion exchange on illite surfaces, whereas inner-sphere surface complexation was the main sorption mechanism at high pH. The Langmuir, Freundlich and Dubinin-Radushkevich (D-R) models were used to simulate the sorption isotherms at three different temperatures of 303.15, 323.15 and 343.15 K. The thermodynamic data (∆G ⁰, ∆S ⁰, ∆H ⁰) were calculated from the temperature dependent sorption isotherms and the results suggested that the sorption process of Co(II) on illite was an endothermic and spontaneous process. The sorption test revealed that the illite can be as a cost-effective adsorbent suitable for pre-concentration of Co(II) from large volumes of aqueous solutions.     

Sequential separation of <Superscript>99</Superscript>Tc, <Superscript>94</Superscript>Nb, <Superscript>55</Superscript>Fe, <Superscript>90</Superscript>Sr and <Superscript>59/63</Superscript>Ni from radioactive wastes

A sequential separation procedure has been developed for the determination of ⁹⁹Tc, ⁹⁴Nb, ⁵⁵Fe, ⁹⁰Sr and ^59/63Ni in various radioactive wastes generated from nuclear power plants. Ion exchange and extraction chromatography were adopted for individual separation of the radionuclides. Precipitation was supplementarily utilized for both purification of the individual radionuclides and preparation of the radionuclide sources for use in a radioactivity measurement. The chromatographic separation behavior of the radionuclides both from the sample matrix metals and from one another was investigated using stable metals, Re (as a surrogate of ⁹⁹Tc), Nb, Fe, Sr and Ni. The validity of the procedure for reliability and applicability was evaluated by measuring the recovery of the metal carriers added to synthetic radioactive waste solutions. The recoveries by the chromatographic separation were in the range of 84.8 to 102.2% with 2s of less than 8.6%, the recoveries by the precipitation being in the range of 84.3 to 97.3% with 2s of less than 10.9%.     

Investigation of sequestration mechanisms of radionuclide 63Ni(II) on kaolinite in aqueous solutions

To better understand the application of kaolinite as an adsorbent for the decontamination of Ni(II) from radionuclide contaminated aqueous systems, herein, the sorption behavior of radionuclide ⁶³Ni(II) on kaolinite as a function of contacting time, pH, coexistent electrolyte ions, adsorbent concentration, fulvic acid and humic acid was investigated using batch technique. At low pH values, ion exchange and/or outer-sphere surface complexation was the main mechanism of Ni(II) sorption on kaolinite, whereas, the sorption of Ni(II) was dominated by inner-sphere surface complexation at high pH values. The presence of different electrolyte ions can enhance or inhibit the sorption of Ni(II) on kaolinite to some extent. The Langmuir and Freundlich models were used to simulate the sorption isotherms of Ni(II) at three different temperatures of 288, 313 and 338 K. The thermodynamic parameters (i.e., ΔS°, ΔH°, and ΔG°) calculated from the temperature-dependent sorption isotherms indicated that the sorption reaction of Ni(II) on kaolinite was endothermic and spontaneous. The findings in this present study demonstrates that the kaolinite can be used as a cost-effective adsorbent for the solidification and pre-concentration of Ni(II) from large volumes of aqueous systems.     

Selective ion-exchange sorption of K<Superscript>+</Superscript> from aqueous solutions containing Na<Superscript>+</Superscript>-K<Superscript>+</Superscript> mixture on Sn(IV) hydrophosphate

Ion-exchange sorption of K⁺ and Na⁺ from their mixture on X-ray-amorphous and crystalline Sn(IV) hydrophosphates was studied. These sorbents exhibit a high selectivity for K⁺. Amorphous Sn(IV) hydrophosphate can be used for efficient purification of aqueous sodium salt solutions to remove potassium impurity.Translated from Zhurnal Prikladnoi Khimii, Vol. 77, No. 8, 2004, pp. 1275–1278.Original Russian Text Copyright © 2004 by Smirnov, Dimova, Redchenko.     

Measurement of <Superscript>63</Superscript>Ni produced in Cu samples by the Hiroshima atomic bomb

The ⁶³Ni in copper samples exposed by the Hiroshima atomic bomb was clearly measured for the first time by liquid scientillation method For the measurement, the chemical separation scheme previously developed was improved The obtained result was agreed with that estimated by the new dosimetry system for atomic bomb survivor studies, DS02.     

Measurements of fast neutron capture cross sections on <Superscript>63</Superscript>Cu and <Superscript>186</Superscript>W

Neutron capture cross sections on ⁶³Cu and ¹⁸⁶W were measured by fast neutron activation method at neutron energies from 1 to 2 MeV. Monoenergetic fast neutrons were produced by ³H(p,n)³He reaction. Neutron energy spread by target thickness, which was assumed to be the main factor of neutron energy spread, was estimated to be 1.5% at neutron energy of 2.077 MeV. Neutron capture cross sections on ⁶³Cu and ¹⁸⁶W were calculated by reference comparison method on those of ¹⁹⁷Au(n,γ). Not only statistical errors of gamma-counts from samples but also systematic errors in the counting efficiency for HP Ge detector and the uncertainty of areal density of samples were considered in calculating neutron capture cross section. Estimated neutron capture cross sections on ⁶³Cu and ¹⁸⁶W were also compared with ENDF-6 data.     

Investigation of radionuclide 63Ni(II) sequestration mechanisms on mordenite by batch and EXAFS spectroscopy study

The sorption behavior and microscopic sequestration mechanisms of radionuclide 63Ni(II) on mordenite as a function of aging time,ionic strength,initial 63Ni(Ⅱ) concentrations,solid content and coexistent electrolyte ions were investigated by the com-bination of batch and EXAFS techniques.Macroscopic experiment results show that the sorption of 63Ni(Ⅱ) is dependent on ionic strength at pH<7,and independent of ionic strength at pH>7.The sorption percentage of 63Ni(Ⅱ) on mordenite increases with increasing solid content,while the sorption capacity decreases as solid content increases.The presence of different elec-trolyte ions can enhance or inhibit the sorption of Ni(II) on mordenite in various degrees.EXAFS analysis results of the sam-ples under three different ionic strengths suggest that the retained 63Ni(Ⅱ) in these samples exists in an octahedral environment with six water ligands.In the initial period of rapid uptake,the sorption of 63Ni(Ⅱ) is dominated by the formation of in-ner-sphere surface complexes.As aging time increases,63Ni(Ⅱ) sequestration behavior tends to be mainly controlled by the formation of Ni phyllosilicate co-precipitates and/or Ni(OH)2(s) precipitates.Results for the second shell fit of the sample pre-pared at an initial 63Ni(Ⅱ) concentration of 100 mg/L indicate the possible formation of Ni polynuclear surface complexes.Both the macroscopic sorption data and the molecular level evidence of 63Ni(Ⅱ) surface speciation at the mordenite/water in-terfaces should be factored into better predictions of the mobility and bioavailability of 63Ni(Ⅱ) in environment mediums.     

Preparation of <Superscript>26</Superscript>Al, <Superscript>59</Superscript>Ni, <Superscript>44</Superscript>Ti, <Superscript>53</Superscript>Mn and <Superscript>60</Superscript>Fe from a proton irradiated copper beam dump

The station for pions cancer therapy was operated at PSI from 1980 to 1992. After a cooling time of 12 years it’s made of copper beam dump was cut and samples were taken for analytical purposes. The sampling collected about 500 g of high active copper chips that can be used for separation of exotic radionuclides. The analyses by gamma spectrometry, LSC and AMS showed main nuclides present to be ⁶⁰Co, ⁵⁴Mn, ²²Na, ⁶⁵Zn, ²⁶Al, ⁵³Mn, ⁵⁹Ni, ⁶³Ni, ⁵⁵Fe and ⁶⁰Fe and ⁴⁴Ti with a daughter nuclide ⁴⁴Sc. In the frame of ERAWAST project a procedure combining selective precipitation and ion exchange for the separation of the rare radionuclides from the copper beam dump was developed. The proposed separation procedure is easy for remote controlled implementation in a hot cell. The ion exchange separation of Ni, Al, Mg, Ti and Fe was complete and high decontamination factors for copper and cobalt were achieved. Based on the developed procedure a remotely controlled system for separation of exotic radionuclides from the copper chips was set up. The full scale system was installed in a hot cell where high activity levels can be handled. In order to evaluate the reliability and functionality of the system extensive tests have been done. During the test period 13.86 g in total of the proton irradiated copper beam dump were processed for separation of ²⁶Al, ⁵⁹Ni, ⁵³Mn, ⁴⁴Ti and ⁶⁰Fe. The results showed that the system was operational and the radionuclide separation was selective with high chemical yield. The procedure manages as well the generated liquid wastes containing high level of ⁶⁰Co activity.     

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⁺.     

Determination of <Superscript>59</Superscript>Ni in radioactive waste

Composite material PAN-DMG, containing chelating agent dimethylglyoxime (DMG) immobilized in porous matrix of binding polymer polyacrylonitrile (PAN), was used for nickel separation and concentration. Method for preparation of ⁵⁹Ni source for low energy photon spectrometry was developed using homogeneous precipitation of nickel with DMG. The proposed method was tested with two types of real radioactive waste (boric acid concentrate from nuclear power plant (NPP) evaporator and spent ion exchanger from NPP).     

An x-ray diffraction study of the reaction products of copper(II) chloride with N<Superscript>1</Superscript>,N<Superscript>2</Superscript>-bis(5-methylpyridin-2-yl)oxalamide

Polymeric complexes of [Cu₂Cl₂L₂]_∞ copper(I) chloride (1) (L = N¹,N²-bis(5-methylpyridin-2-yl)-oxalamide)) and {[Cu₂(C₂O₄)Cl₂L](L)·2H₂O}_∞ copper(II) chloride (2) are obtained. The complexes are studied by powder and single crystal XRD. It is found that during the reaction of L with copper(II) chloride in the formation of complex 1 copper(II) is reduced to copper(I), while the formation of complex 2 is accompanied by the hydrolysis of the ligand.     

Structural organization of mercury(II) and copper(II) dithiocarbamates from EPR and <Superscript>13</Superscript>C and <Superscript>15</Superscript>N MAS NMR spectra and X-ray diffraction analysis

The structures and spectroscopic properties of mononuclear and binuclear mercury(II) and copper(II) complexes with four dithiocarbamate ligands R₂NC(S)S^? (R = CH₃, C₂H₅, or iso-C₃H₇; R₂ = (CH₂)₆) were studied by solid-state ¹³C and ¹⁵N CP/MAS NMR and EPR spectroscopy. Mercury(II) N,N-cyclohexamethylenedithiocarbamate [Hg₂{S₂CN(CH₂)₆}₄] was obtained and characterized in detail by X-ray diffraction analysis at 299 K. The binuclear molecule of the complex is centrosymmetric; the central tricyclic fragment [Hg₂S₄C₂] is in the chair conformation. In the ¹³C and ¹⁵N NMR spectra, the signals were assigned to the dithiocarbamate ligands with different structural functions: bidentate chelating and combined (both chelating and bridging) ones. The differences between the isotropic ¹⁵N chemical shifts for the dialkyldithiocarbamate ligands were interpreted in terms of combination of the mesomeric effect of the =NC(S)S-groups and the inductive effect of the alkyl substituents. According to the EPR data, copper(II) in magnetically diluted systems is mainly found in heterobinuclear molecules [CuHg(S₂CNR₂)₄] and the geometry of the chromophores [CuS₅] approximates to a tetragonal pyramid.     

Migration and sorption of <Superscript>137</Superscript>Cs and <Superscript>152,154</Superscript>Eu in crushed crystalline rocks under dynamic conditions

In migration experiments, sorption of ¹³⁷Cs and ^152,154Eu in the columns of crushed crystalline rocks of 0.25–0.8 mm grain size under dynamic flow conditions from the synthetic groundwater (SGW) has been studied. Five samples of crystalline rocks from Cavernous Gas Reservoir near Příbram were taken. Plastic syringes of 8.8 cm length and 2.1 cm in diameter were used as columns. The water phase was pumped downward through the columns, using a multi-head peristaltic pump, with a seepage velocity of about 0.2 cm/min. The radioactive nuclides, containing chemical carriers, were added into the water stream individually in the form of a short pulse. Desorption experiments were carried out with 2:1 (v/v) mixture of H₂SO₄ and HNO₃. In the columns the longitudinal distribution of the residual ¹³⁷Cs and ^152,154Eu activities was also determined. By the evaluation of respective breakthrough and displacement curves, the experimental and theoretical retardation factors, distribution coefficients and hydrodynamic dispersion coefficients were determined using the integrated analytical form of a simple advection-dispersion equation (ADE). Dynamic sorption experiments were also compared with the results of static sorption experiments. The paper was presented in part as a poster No. PB1-1 at the 11th International Conference Migration’ 07, held in Munich, Germany, August 26–31, 2007, Abstracts, p. 212.