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1.
Cu-di-(2-ethylhexyl)phosphate was used as the cation exchange extractant from molten nitrate salt. IR absorption spectra of
di-(2-ethylhexyl)phosphoric acid and Cu-di-(2-ethylhexyl)phosphate were compared and it was proved that the acidic form of
the extractant is not Cu-di-(2-ethylhexyl)-phosphate. Using LiNO3−NH4NO3 eutectic melt, it was shown that the back-extraction of Cu2+ is a cation exchange reaction. Np(V) and Pa(V) were extracted by Cu-di-(2-ethylhexyl)phosphate from LiNO3−NaNO3−KNO3 eutectic melt. The distribution ratio of Np(V) was greater than that of Pa(V) on the contrary of their distribution ratios
in the aqueous extraction system. A possible cation exchange extraction reaction was proposed for the extraction of Np(V). 相似文献
2.
E. Corradini E. M. Teixeira P. D. Paladin J. A. Agnelli O. R. R. F. Silva L. H. C. Mattoso 《Journal of Thermal Analysis and Calorimetry》2009,97(2):415-419
Complexation of neptunium(V) with fluoride in aqueous solutions at elevated temperatures was studied by spectrophotometry
and microcalorimetry. Two successive complexes, NpO2F(aq) and NpO2F2−, were identified by spectrophotometry in the temperature range of 10–70°C. Thermodynamic parameters, including the equilibrium
constants and enthalpy of complexation between Np(V) and fluoride at 10–70°C were determined. Results show that the complexation
of Np(V) with fluoride is endothermic and that the complexation is enhanced by the increase in temperature — a two-fold increase
in the stability constants of NpO2F(aq) and more than five-fold increase in the stability constants of NpO2F2− as the temperature is increased from 10 to 70°C. 相似文献
3.
Y. Xia J. I. Friese D. A. Moore L. Rao 《Journal of Radioanalytical and Nuclear Chemistry》2006,268(3):445-451
Summary A solvent extraction method was used to determine the stability constants of Np(V) complexes with fluoride and sulfate in
1.0M NaClO4 from 25 to 60 °C. The distribution ratio of Np(V) between the organic and aqueous phases was found to decrease as the concentrations
of fluoride and sulfate were increased. Stability constants of the 1 : 1 Np(V)-fluoride complexes and the 1 : 1 Np(V)-sulfate
and 1 : 2 Np(V)-sulfate complexes, dominant in the aqueous phase under the experimental conditions, were calculated from the
effect of [F-] and [SO42-] on the distribution ratio. The enthalpy and entropy of complexation were calculated from the stability constants at different
temperatures by using the Van't Hoff equation. 相似文献
4.
Y. X. Xia J. I. Friese D. A. Moore P. P. Bachelor L. Rao 《Journal of Radioanalytical and Nuclear Chemistry》2007,274(1):79-86
The complexation of plutonium(IV) with sulfate at variable temperatures has been investigated by solvent extraction method.
A NaBrO3 solution was used as holding oxidant to maintain the plutonium(IV) oxidation state throughout the experiments. The distribution
ratio of Pu(IV) between the organic and aqueous phases was found to decrease as the concentrations of sulfate were increased.
Stability constants of the 1:1 and 1:2 Pu(IV)-HSO4
− complexes, dominant in the aqueous phase, were calculated from the effect of [HSO4
−] on the distribution ratio. The enthalpy and entropy of complexation were calculated from the stability constants at different
temperatures using the Van’t Hoff equation. 相似文献
5.
S. S. Kim M. H. Baik K. C. Kang 《Journal of Radioanalytical and Nuclear Chemistry》2009,281(3):577-583
The solubilities of NpO2(s) in the KURT (KAERI Underground Research Tunnel) granitic groundwater with low ionic strength were measured experimentally
and calculated by a geochemical code. Then these results were compared with each other as well as with foreign results. The
concentrations of neptunium were measured as 6·10−8−2·10−8 mol/L at a pH = 9.5–11.1 and Eh = −0.2 V, and less than 5·10−9 mol/L at a pH = 11.8–13.0 and Eh = −0.3–0.44 V. The dominant aqueous species were presumed as Np(OH)x(CO3)y
4−x−2y complexes and Np(OH)4(aq) at pH = 9.5–13 under the Eh<−0.2 V reducing condition. 相似文献
6.
P. N. Pathak Neelam Kumari D. R. Prabhu V. K. Manchanda 《Journal of solution chemistry》2012,41(3):410-421
Spectrophotometric investigations have been carried out on the disproportionation of Np(V) to form Np(IV) and Np(VI) in 1.1
mol⋅L−1 solutions of tributyl phosphate (TBP) and in N,N-dihexyl octanamide (DHOA) in n-dodecane medium. The Np(V) was found to coordinate with Np(IV) in 1.1 mol⋅L−1 TBP solution in n-dodecane to form a mixed valence “cation–cation” complex by bonding through an axial oxo group on Np(V). By contrast, this
interaction was less prominent in the case of 1.1 mol⋅L−1 DHOA solutions. The effect of 1-octanol, added as phase modifier, on the disproportionation behavior of Np(V) was also investigated.
An attempt was made to calculate the disproportionation/reduction rate constants for Np(V) under the conditions of these studies.
Absorbance measurements on the Np stripped from organic phases revealed the occurrence of Np(V) in the aqueous phase. 相似文献
7.
Linfeng Rao Guoxin Tian Thandankorai G. Srinivasan PierLuigi Zanonato Plinio Di Bernardo 《Journal of solution chemistry》2010,39(12):1888-1897
Spectrophotometric titrations were performed to identify the Np(V)/acetate complex and determine the equilibrium constants
at various temperatures (T=283 to 343 K) and at the ionic strength 1.05 mol⋅kg−1. The enthalpies of complexation at the corresponding temperatures were determined by microcalorimetric titrations. Results
show that the complexation of Np(V) with acetate is weak but strengthens as the temperature increases. The complexation reaction
is endothermic and entropy driven. The enhancement of complexation at higher temperatures is primarily due to the increasingly
larger entropy gain when the solvent molecules are released from the highly-ordered solvation spheres of NpO2+\mathrm{NpO}_{2}^{+} and acetate to the bulk solvent where the degree of disorder is higher at higher temperatures. 相似文献
8.
Tingsheng Yue Wenming Dong Yukun Wang 《Journal of Radioanalytical and Nuclear Chemistry》1999,241(3):647-650
The adsorption-exchange equilibrium time and the adsorption isotherms of UO2
2+,137Cs,169Yb and HPO4
2− on modified peat have been investigated by batch experiments. The effect of pH on the adsorption-exchange percentage (E) and the distribution coefficients (K
d) was also examined. It was found that the adsorption-exchange of UO2
2+ and169Yb on the modified peat was described well by Freundlich isotherm, whereas the adsorption-exchange of137Cs and HPO4
2− on modified peat corresponded to a Langmuir isotherm and the maximum adsorption capacities of the modified peat for137Cs and HPO4
2− ions were 4.4 and 4.1 μg/g respectively. The optimum pH for the adsorption-exchange of UO2
2+,137Cs,169Yb and HPO4
2− on the modified peat was 7.0 at 25°C. 相似文献
9.
Precise conductance measurements are reported on dilute aqueous solutions of the sodium and potassium salts of orthophosphoric
acid at 25 ∘C. Conductance measurements on solutions of electrolytes such as these phosphate salts that exist in solution as complicated
mixtures of ions have previously proved difficult to interpret. To overcome this, a mathematical method has been developed
to calculate the concentrations of all the species in the aqueous system M3PO4/M2HPO4/M2HPO4/H3PO4 (M = Na or K) over a continuous range of stoichiometries. The Lee–Wheaton conductance equation has been used to interpret
the conductance of these multicomponent solutions in terms of the limiting ionic conductances and concentrations of all the
ions in the solution. The limiting molar conductances of the ions H2PO4
− and HPO4
2− and the ion-pair formation constants of these ions with sodium and potassium ions were determine
This work has enabled the accurate determination of solution parameters for the important hydrogenphosphate ions in water
and provides an excellent example of the use of an advanced conductance theory in the analysis of the conductance of multicomponent
electrolyte systems. 相似文献
10.
The sorption of anions H2PO4
−, HPO4
2−, PO4
3−, [Fe(CN)6]3−, and [Fe(CN)6]4− from aqueous solutions on the surface of FeIII and ZrIV oxyhydroxide hydrogels freshly precipitated at pH 4–13 was studied. The region of sorbate concentrations was from 0.00025
to 0.06 mol L−1. The plots of the anion uptakes vs. their equilibrium concentrations are represented by isotherms of the first type, which are well described by the Langmuir
equation if the quantity of the amount adsorbed is expressed as mol-site g−1. The maximum uptakes and constants of the Langmuir equation were calculated. The phosphate anions occupy the same number
of sorption sites on the sorbents precipitated at different pH. The average specific content of sorption sites for the ferro-
and zirconogels in the metastability period is independent of the pH of their precipitation, being 3.1·10−3 and 3.2·10−3 mol-site g−1, respectively. The [Fe(CN)6]3− and [Fe(CN)6]4− anions are sorbed only on the positively charged sites of the hydrogels and occupy not more than 2·10 mol-site g−1 in the studied interval of pH of precipitation.
__________
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1736—1741, August, 2005. 相似文献
11.
Freya Da Costa Giuseppe Lubes Mildred Rodríguez Vito Lubes 《Journal of solution chemistry》2011,40(1):106-117
Ternary complex formation reactions were studied between vanadium(III), dipicolinic acid and small molecular weight blood
serum components: lactic, oxalic, citric and ortophosphoric acids. The electromotive force measurement permitted us to determine
the chemical speciation of the complexes formed. In the vanadium(III)–dipicolinic acid–lactic acid system the complexes detected
were: V(dipic)(lac), V(dipic)(lac)(OH)− and V(dipic)(lac)(OH)22-(\mathrm{OH})_{2}^{2-}. In the vanadium(III)–dipicolinic acid–oxalic acid system the observed complexes were: V(dipic)(ox)−, V(dipic)(ox)(Hox)2− and V(dipic)(ox)23-(\mathrm{ox})_{2}^{3-}. In the vanadium(III)–dipicolinic acid–citric acid system the complexes V(dipic)(Hcit)−, V(dipic)(cit)2−, V(dipic)(cit)(OH)3−, V(dipic)(cit)(OH)24-(\mathrm{OH})_{2}^{4-} and V(dipic)(cit)(OH)35-(\mathrm{OH})_{3}^{5-} were detected. Finally in the vanadium(III)–dipicolinic acid–phosphoric acid system the complexes V(dipic)(H2PO4) and V(dipic)(HPO4)− were observed. The UV-vis spectra allowed us to perform a qualitative characterization of the complexes formed in aqueous
solution. 相似文献
12.
V. R. Bhandiwad Rajendra Swarup S. K. Patil 《Journal of Radioanalytical and Nuclear Chemistry》1979,52(1):5-14
The extraction of Np(IV), Pu(IV) and U(VI) from aqueous hydrochloric acid into quaternary amines has been studied. The dependence
of the distribution coefficient on amine concentration suggests that the actinide ions extracted are NpCl
6
2−
PuCl
6
2−
and UO2Cl
4
2−
. This is further supported by the absorption spectra of the amine extracts of these actinide ions. Based on the extraction
data obtained, a simple method for the separation of typical metal ions such as Cs, lanthanides and Zr from U(VI) and Pu(IV)
is suggested. 相似文献
13.
Hydroxamic acids are salt free, organic compounds with affinities for cations such as Fe3+, Np4+ and Pu4+, and have been identified as suitable reagents for the control of Pu and Np in advanced nuclear fuel reprocessing. The results
of a UV-visible, near-IR spectrophotometric study of the 1:1 and 2:1 complexes formed between formo- and aceto-hydroxamic
acids (FHA, AHA) and Np(IV) ions are interpreted using speciation diagrams for the identification of the species present at
different pH and ligand to metal ratios. A kinetic model that describes the instability of the complex due to hydrolysis of
the hydroxamate moiety, previously developed for the Fe(III)-AHA complexes (Andrieux et al. in J. Solution Chem. 36:1201–1217,
[2007]), is tested here against experimental Np(IV)-FHA data. Consequently, the complexation constant for formation of the 1:1
Np(IV)-FHA complex in nitric acid is estimated at K
1=2715 and indications are that complexation protects the ligand against hydrolysis at 0.1>pH>−0.1. 相似文献
14.
Isaida Shiozawa Giuseppe Lubes Mildred Rodríguez Vito Lubes 《Journal of solution chemistry》2011,40(1):17-25
In this work we present results for the speciation of the ternary complexes formed in the aqueous vanadium(III)–dipicolinic
acid and the amino acids cysteine (H2cys), histidine (Hhis), aspartic acid (H2asp) and glutamic acid (H2glu) systems (25 °C; 3.0 mol⋅dm−3 KCl as ionic medium), determined by means of potentiometric measurements. The potentiometric data were analyzed with the
least-squares program LETAGROP, taking into account the hydrolysis of vanadium(III), the acid-base reactions of the ligands,
and the binary complexes formed. Under the experimental conditions (vanadium(III) concentration = 2–3 mmol⋅dm−3 and vanadium(III): dipicolinic acid: amino acid molar ratio 1:1:1, 1:1:2 and 1:2:1), the following species [V(dipic)(H2asp)]+, [V(dipic)(Hasp)], [V(dipic)(asp)]−, [V(dipic)(asp)(OH)]2−, and [V(dipic)(asp)(OH)2]3− were found in the vanadium(III)–dipicolinic acid–aspartic acid system. In the vanadium(III)–dipicolinic acid–glutamic acid
system [V(Hdipic)(H2glu)]2+, [V(dipic)(H2glu)]+, [V(dipic)(Hglu)], [V(dipic)(Hglu)(OH)]−, and [V(dipic)(Hglu)(OH)2]2− were observed. In the vanadium(III)–dipicolinic acid–cysteine system the complexes [V(dipic)(H2cys)]+, [V(dipic)(Hcys)], [V(dipic)(cys)]−, and [V(dipic)(cys)(OH)]2− were present. And finally, in the vanadium(III)–dipicolinic acid–histidine system the complexes [V(Hdipic)(Hhis)]2+, [V(dipic) (Hhis)]+[\mathrm{V}(\mathrm{dipic}) (\mathrm{Hhis})]^{+}, [V(dipic)(his)], [V(dipic)(his)(OH)]−, and [V(dipic)(his)(OH)2]2− were observed. The stability constants of these complexes were determined. The species distribution diagrams as a function
of pH are briefly discussed. 相似文献
15.
I. A. Lebedev B. F. Myasoedov P. N. Palei 《Journal of Radioanalytical and Nuclear Chemistry》1970,5(1):61-69
The extraction of Np(IV), Zr, Nb, Cs, Ce(III) and Am(III) from nitric acid solutions containing oxalate and phosphate ions
by solutions of 1-phenyl-3-methyl-4-benzoylpyrazolon-5 (PMBP) and tri-n-butyl phosphate (TBP) in benzene has been investigated.
A solution 0.1M in respect to PMBP and 0.25M in respect to TBP was found to extract 99% of neptunium from aqueous solutions 1M in respect to H3PO4 and 0.5M in respect to HNO3. Under these conditions, the extraction of the other investigated elements does not exceed 0.1%. Based on this finding, a
procedure was developed to determine243Am through its daughter product239Np in solutions containing large quantities of curium and its fission products. The sensitivity of the procedure is 1·10−7 mg of243Am in the sample. The243Am content is obtained by calculation from measurements of the γ-activity of the extracted239Np. The purification ratio of239Np is∼105 from Zr, Nb and Ru, ∼108 from Ce and Cm and >1012 from Cs. 相似文献
16.
Complexation constants of the Al3+/F− system were determined at different ionic strengths in a NaClO4 (1.0, 2.0 and 3.0 mol⋅dm−3) ionic medium by means of a potentiometry using two electrode systems: an ion fluoride selective electrode as well as a glass
electrode. All the experimentation was performed at 25 °C. The main species in the complexation equilibria were determined
as AlF2+, AlF2+, AlF30, AlF4−, AlF52− and AlF63−. The differences found in the complexation constants for the ionic strength considered were explained by the different behavior
of the interaction parameters for the AlF
n
3−n
species. These parameters were calculated using the Modified Bromley’s Methodology (MBM). The corresponding thermodynamic
quantities were also determined. From all the results obtained, it can be concluded that pH, fluoride concentration and ionic
strength influenced the distribution of the fluoride-aluminium complexes. 相似文献
17.
Wandee Rakrai Nongnit Morakot Somchai Keawwangchai Chatthai Kaewtong Banchob Wanno Vithaya Ruangpornvisuti 《Structural chemistry》2011,22(4):839-847
The structural geometries of three tripodal thiourea receptors, i.e. 1,3,5-triethyl-2,4,6-tris[(N′-methylthioureido)methyl]benzene (1), tris[N′-methyl-N-(2-aminoethyl)thiourea]methane (2), tris[N′-methyl-N-(2-aminoethyl)thiourea]amine (3), and their complexes with F−, Cl−, Br−, I−, NO3
−, CO3
2−, SO4
2−, HSO4
−, PO4
3−, HPO4
2− and H2PO4
− were obtained using the density functional theory calculations. Electronic and thermodynamic properties of anion binding
complexes of the receptors 1, 2 and 3 were investigated. Recognition abilities of all the receptors in terms of selectivity coefficients are reported. Intermolecular
interactions in all the studied complexes occurring via multi-point hydrogen bonding were found. The receptors 1, 2 and 3 were found to be excellent selectivity for phosphate ion and their binding free energy for the phosphate ion are −292.57,
−291.77 and −295.01 kcal/mol, respectively. 相似文献
18.
The systems CaHPO4−MHPO4−H2O (M=Sr, Ba) were studied at 50°C. ForM=Sr, the series of single phases, Ca1−xSrxHPO4 for 0.95<X<0.75 and CaxSr1−xHPO4 for 0.4<X<1 have been prepared.
These solid solution were caracterized by their infrared spectra and their crystallographic unit cell parameters.
ForM=Ba a new phase Ca2Ba(HPO4)3 has been determined. It was characterized by DRX, IR, ATD and chemical analyses.
Zusammenfassung Bei 50°C wurde das System CaHPO4−MHPO4−H2O (mitM=Sr, Ba) untersucht. FürM=Sr wurden Serien von Einzelphasen erhalten: Ca1−xSrxHPO4 für 0.95<X< 0.75 und CaxSr1−xHPO4 für 0.4<X<1. Diese Mischkristalle wurden anhand ihrer Infrarotspektren und ihrer kristallographischen Elementarzellenparameter charakterisiert. FürM=Ba wurde die neue Phase Ca2Ba(HPO4)3 ermittelt. Sie wurde mittels DRX, IR, ATD und chemischer Analyse charakterisiert.相似文献
19.
The decay kinetics of hydrated electron (eaq
−) formed upon photolysis of aqueous solutions of sodium pyrene-1,3,6,8-tetrasulfonate at λ = 337 nm in the presence of phosphate
anions (up to 2 mol L−1) was studied by nanosecond laser-pulse photolysis in a wide range of pH (3.5–10) and ionic strength (I, up to 2 mol L−1) values. At high pH values, where the HPO4
2− ions dominate, the eaq
− decay kinetics depends only slightly on phosphate concentration (rate constant for the reaction is at most 2·105 L mol−1 s−1). The H2PO4
− ions react with eaq
− at a rate constant of 2.8·106 L mol−1 s−1 (I = 0), which increases linearly with the parameter
in accordance with the Debye-Hückel theory. The rate constant for quenching of eaq
− by H3PO4 at pH ≤ 4 decreases linearly with the parameter
due to the secondary salt effect and equals 1.6·109 L mol−1 s−1 at I = 0. The logarithm of the rate constant for quenching of eaq
− by phosphates is linearly related to the number of the O-H bonds in the phosphate molecule.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1277–1280, July, 2007. 相似文献
20.
The complexation of As(V) in aqueous solutions in the presence of iron(III) was investigated spectrophotometrically with both
variable and constant ionic strengths. The determined thermodynamic and stoichiometric formation constants of the FeHAsO4+ species are log10∘β = 9.21± 0.01 and log10Iβ (1.0mol⋅dm−3 NaClO4) = 7.78 ± 0.01, respectively. The numerical treatment of the obtained spectral data was performed with the SPECA program. The analysis required the consideration
of the hydrolysis of Fe(III) and the protonation of As(V) in the pH range studied. No significant hydrolysis was observed
because of the low pH values (pH < 2.5) involved. The stabilities of the solid Fe(III) arsenates was established by solubility
experiments. All of the solubility experiments were performed in aqueous NaClO4 solutions at constant ionic strength (1.0mol⋅dm−3) and at 25∘C. The experimental data were consistent with FeAsO4⋅2H2O being the solid phase (log10 ∘ Kso = −24.30± 0.08). The corresponding thermodynamic constants were computed by means of the Modified Bromley's Methodology (MBM)
that describes the variation of the activity coefficients of all of the ions involved in the complexation and precipitation
equilibria with the medium and ionic strength. Finally, the solid phase obtained in this work was also characterized by FT-IR
and FT-Raman spectroscopies, and the hydration of the solid iron arsenate was confirmed by X-ray diffraction data. 相似文献