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1.
Ashok Kumar Ashoke Chandra Deb S. K. Mukerjee V. N. Vaidya D. D. Sood 《Journal of Radioanalytical and Nuclear Chemistry》1999,240(1):375-377
Solvent extraction of plutonium(VI) from nitric acid (1 to 5M) into 20% and 30% TBP in dodecane saturated with uranium(VI)
(0% to 80%) has been studied. For a particular nitric acid concentration, the distribution coefficient (K
d
) is found to decrease with the increase in saturation of organic phase with uranium(VI). At a fixed organic phase the saturationK
d
increased with increase in nitric acid concentration, however, the magnitude of this increase inK
d
decreased with the increase in saturation. 相似文献
2.
Nitrous acid is a key redox controlling factor, affecting the speciation of neptunium in the reprocessing of used nuclear
fuel by solvent extraction. The kinetics of the reduction of neptunium(VI) by nitrous acid in solutions of nitric acid was
investigated spectrophotometrically by the method of initial rates. The reaction is of first order with respect to Np(VI)
while the order with respect to HNO2 is 1.20 ± 0.04. The reaction rate is almost inversely proportional to the hydrogen ion concentration (reaction order −0.92 ± 0.06),
indicating that the reaction proceeds primarily through the reaction of neptunium(VI) with the nitrate anion. The experimental
value of the rate constant k for the rate law −d[Np(VI)]/dt = k·[Np(VI)]·[HNO2]1.2/[H+] is of (0.159 ± 0.014) M−0.2 s−1 in I = 4 M and at 20 °C. The activation energy is (−57.3 ± 1.6) kJ/mol, which is in agreement with previous data on this reaction
in perchloric acid. 相似文献
3.
K. A. Venkatesan B. Robert Selvan M. P. Antony T. G. Srinivasan P. R. Vasudeva Rao 《Journal of Radioanalytical and Nuclear Chemistry》2005,266(3):431-440
Summary Commercially available polystyrene-divinylbenzene (PS-DVB) resins functionalized with isothiouronium (Tulsion CH-95), phosphinic
acid (Tulsion CH-96) and methylene thiol (Tulsion CH-97) moieties have been used for separating palladium from nitric acid
medium. Extraction of palladium has been studied as a function of time, concentration of nitric acid and palladium. The distribution
coefficients (Kd, ml/g) of palladium on sulfur based resins (Tulsion CH-95 and Tulsion CH-97) are higher (5000-104ml/g in 0.1M nitric acid) than on Tulsion CH-96 resin and decrease with increasing concentration of nitric acid. The initial
rate of extraction of palladium by Tulsion CH-95 and Tulsion CH-97 resins was very rapid and the time required for the establishment
of equilibrium was a function of palladium concentration in the aqueous phase. The rate data could be fitted by a second order
rate equation and the magnitude of rate constant for the extraction of palladium by these resins (~102M-1. min-1) decreased in the order of: Tulsion CH-95 > Tulsion CH-97 > Tulsion CH-96. The extraction isotherms of Tulsion CH-95 were
fitted by Langmuir adsorption model and the coefficients were obtained by regression. The extraction capacity of palladium
on Tulsion CH-95 was found to be ~20 mg/g at 3M nitric acid. Column experiments have been conducted and the data were fitted
using Thomas model. A column utilization of 75% was achieved for the extraction of palladium by Tulsion CH-95 resin. 相似文献
4.
The extraction of chromium(VI) from aqueous hydrochloric, nitric and sulfuric acid solutions by diphenyl-2-pyridylmethane(DPPM)
dissolved in chloroform has been studied. Chromium(VI) is quantitatively extracted from hydrochloric acid solutions in the
range 0.1–1M. With increasing acid concentration, the extraction of chromium diminishes and in concentrated acid solutions
practically all the chromium remains in the aqueous phase. The quantitative back-extraction of chromium from the organic phase
is possible with HCl or HNO3 at concentrations higher than 5M through the use of reducing agents. The composition of the extracted chromium(VI) species
was studied in solution. The complexes (DPPMH)+HCrO
4
−
and (DPPMH)2Cr2O
7
−
are extracted for tracer and macro amounts of chromium(VI) respectively. The data have been utilized for the separation of
chromium(VI) from base metal ions. 相似文献
5.
Sujoy Biswas D. K. Singh K. N. Hareendran J. N. Sharma S. B. Roy 《Journal of Radioanalytical and Nuclear Chemistry》2010,284(1):201-205
Solvent extraction of U(VI) with di-isodecyl phosphoric acid (DIDPA)/dodecane from nitric acid medium has been investigated
for a wide range of experimental conditions. Effect of various parameters including nitric acid concentration, DIDPA concentration,
temperature, stripping agents, and other impurities like rear earths, transition metal ion, boron, aluminum ion on U(VI) extraction
has been studied. The species extracted in the organic phase is found to be UO2(NO3)(HA2)·H2A2 at lower acidity (<3.0 M HNO3). Increase in temperature lead to the decrease in extraction with the enthalpy change by ∆H = −16.27 kJ/mol. Enhancement in extraction of U(VI) from nitric acid medium was observed with the mixture of DIDPA and tri
butyl phosphate (TBP). The stripping of U(VI) from organic phase (DIDPA–U(VI)/dodecane) with various reagents followed the
order: 4 M H2SO4 > 5% (NH4)2CO3 > 8 M HCl > 8 M HNO3 > Water. High separation factors between U(VI) and impurities suggested that the use of DIDPA for purification of uranium
from multi elements bearing solution. 相似文献
6.
Yang Yan-Zhao Zeng Shan Bao Li-Ping Liu Wen-Tao Sun Si-Xiu 《Journal of Radioanalytical and Nuclear Chemistry》2003,258(2):403-408
The synergistic extraction of uranium(VI) from aqueous nitric acid solution with mixtures of bis(hexylsulfinyl)ethane (BHxSE) and petroleum sulfoxides (PSO) in 1,1,2,2-tetrachloroethane was studied. It has been found that the maximum synergistic extraction effect occurs when the molar ratio of PSO to BHxSE is close to 1. The composition of the complex of synergistic extraction was estimated as UO2(NO3)2
.BHxSE.PSO. The formation constant of the complex was equal to KBP = 4.23±0.03. The effects of extractant, nitric acid, salting-out agent, and complex anion concentrations and temperature on the extraction equilibrium of uranium(VI) were also studied. 相似文献
7.
P. B. Ruikar M. S. Nagar M. S. Subramanian 《Journal of Radioanalytical and Nuclear Chemistry》1992,159(1):167-173
The extraction behavior of uranium(VI), plutonium(IV) and fission products like zirconium, ruthenium and europium from 3.5M nitric acid medium with gamma-irradiated dibutyl derivatives of hexanamide (DBHA), octanamide (DBOA) and decanamide (DBDA) in dodecane has been investigated as a function of absorbed dose up to 184 MRads. The results indicate that the Kd value for extraction of uranium(VI) decreases gradually, while Kd for extraction of plutonium(IV) decreases rapidly with dose up to 35 MRads, increasing thereafter with dose, indicating synergistic effects of radiolytic products at higher doses. Ruthenium and europium are not extracted in the entire dose range up to 184 MRads, while extraction of zirconium(IV) increases steadily up to 50 MRads and increases radiply thereafter, indicating synergistic effect of radiolytic products similar to that of plutonium(IV) beyond a dose of 50 MRads. The extractability of uranium(VI) and plutonium(IV) with 1M dibutyl decanamide (DBDA) in dodecane was studied for uranium loading up to 75 mg/ml and plutonium loading up to 3 mg/ml. The percent extraction was found to vary from 91 to 71 for uranium and 95 to 89 for plutonium, respectively. Quantitative stripping of uranium can be achieved with 0.01M nitric acid and plutonium with 0.5M nitric acid and 0.05M hydroxylamine soluton in two steps from an organic phase loaded with 53.2 mg/ml of uranium. 相似文献
8.
P. Giridhar K. A. Venkatesan T. G. Srinivasan P. R. Vasudeva Rao 《Journal of Radioanalytical and Nuclear Chemistry》2005,265(1):31-38
Summary A systematic study on the extraction of U(VI) from nitric acid medium by tri-n-butylphosphate (TBP) dissolved in a non-traditional diluent namely 1-butyl-3-methylimidazolium hexafluorophosphate (bmimPF6) ionic liquid (IL) is reported. The results are compared with those obtained using TBP/n-dodecane (DD). The distribution ratio for the extraction of U(VI) from nitric acid by 1.1M TBP/bmimPF6 increases with increasing nitric acid concentration. The U(VI) distribution ratios are comparable in the nitric acid concentration range of 0.01M to 4M, to the ratios measured using 1.1M TBP/DD. In contrast to the extraction behavior of TBP/DD, the D values continued to increase with the increase in the concentration of nitric acid above 4.0M. The stoichiometry of uranyl solvate extracted by 1.1M TBP/IL is similar to that of TBP/DD system, wherein two molecules of TBP are associated with one molecule of uranyl nitrate in the organic phase. Ionic liquid alone also extracts uranium from nitric acid, albeit to a small extent. The exothermic enthalpy accompanying the extraction of U(VI) in TBP/bmimPF6 decreases with increasing nitric acid and with TBP concentrations. 相似文献
9.
S. Biswas P. N. Pathak D. K. Singh S. B. Roy V. K. Manchanda 《Journal of Radioanalytical and Nuclear Chemistry》2011,289(2):557-564
The extraction of U(VI) from sulphate medium with 2-ethylhexyl phosphonic acid-mono-2-ethylhexyl ester (PC88A, H2A2 in dimeric form) in n-dodecane has been investigated under varying concentrations of sulphuric acid and uranium. Slope analysis of uranium (VI)
distribution data as a function of PC88A concentration suggests the formation of monomeric species, viz. UO2(HA2)2. This observation was further supported by the mathematical expression obtained during non-linear least square regression
analysis of U(VI) distribution data correlating the percentage extraction (%E) and the acidity (H
i). A mathematical model correlating the experimental distribution ratio values of U(VI) (D
U) with initial acidity (H
i) and initial uranium concentrations (C
i) was developed:
D\textU = 12.98( ±0.90)/{ C\texti - 0.75( ±0.05) ×[ H\texti ]2 } D_{\text{U}} = 12.98( \pm 0.90)/\left\{ {C_{\text{i}}^{ - 0.75( \pm 0.05)} \times \left[ {H_{\text{i}} } \right]^{2} } \right\} . This expression can be used to predict the concentration of uranium in organic as well as in aqueous phase at any C
i and H
i. The extraction data were used to calculate the conditional extraction constant (K
ex) values at different acidities (2–7 M H+), uranium (0.02–0.1 M) and PC88A (0.2–0.6 M) concentrations. These studies were also extended for the extraction of U(VI)
using synergistic mixtures of PC88A and TOPO from sulphate medium. 相似文献
10.
E. Metwally A. Sh. Saleh S. M. Abdel-Wahaab H. A. El-Naggar 《Journal of Radioanalytical and Nuclear Chemistry》2010,286(1):217-221
The diamide N,N,N′,N′-tetraoctyldiglycolamide (TODGA) was synthesized and characterized. The prepared TODGA was applied for extraction of Ce(III)
from nitric acid solutions. The equilibrium studies included the dependencies of cerium distribution ratio on nitric acid,
TODGA, nitrate ion, hydrogen ion and cerous ion concentrations. Analysis of the results indicates that the main extracted
species is Ce(TODGA)2(NO3)3HNO3. The capacity of Ce loading is approximately 45 mmol/L for 0.1 M solution of TODGA in n-hexane. Finally, the thermodynamic parameters were calculated: K (25 °C) = 3.8 × 103, ΔH = −36.7 ± 1.0 kJ/mol, ΔS = −54.6 ± 3.0 J/K mol, and ΔG = −20.4 ± 0.1 kJ/mol. 相似文献
11.
Extraction of molybdenum and technetium with diamides of dipicolinic acid from nitric acid solutions
J. L. Lapka A. Paulenova M. Yu. Alyapyshev V. A. Babain R. S. Herbst J. D. Law 《Journal of Radioanalytical and Nuclear Chemistry》2009,280(2):307-313
The concentration of molybdenum(VI) in dissolved spent nuclear fuel is comparable with the concentrations of Tc, and the minor
actinides (Np, Am). Therefore it is of great interest to understand its behavior under conditions imposed by separation processes.
The simultaneous extraction ability of ortho, meta, and para isomers of N,N′-diethyl-N,N′-ditolyl-dipicolinamide (EtTDPA) for molybdenum and technetium were investigated in a large range of nitric and hydrochloric
acid conditions. Molybdenum shows no increase in extraction at higher concentrations of nitric acid giving a solvate number
n=0 with all isomers of EtTDPA, while Mo shows great extractability from HCl. Technetium distribution ratios decrease with
increasing concentrations of nitrate showing indication of ion exchange occurring between TcO4
− and NO3
− anions. Et(m)TDPA and Et(p)TDPA show the greatest extractability, with 60% of the total technetium extracted into the organic
phase at 1M HNO3. 相似文献
12.
Efficient uranium(VI) biosorption on grapefruit peel: kinetic study and thermodynamic parameters 总被引:3,自引:0,他引:3
The uranium(VI) biosorption by grapefruit peel was studied from aqueous solutions. Batch experiments was conducted to evaluate
the effect of contact time, initial uranium(VI) concentration, initial pH, adsorbent dose, salt concentration and temperature.
The equilibrium process was well described by the Langmuir, Redlich–Peterson and Koble–Corrigan isotherm models, with maximum
sorption capacity of 140.79 mg g−1 at 298 K. The pseudo second order model and Elovish model adequately describe the kinetic data in comparison to the pseudo
first order model and the process involving rate-controlling step is much complex involving both boundary layer and intra-particle
diffusion processes. The effective diffusion parameter D
i and D
f values were estimated at different initial concentration and the average values were determined to be 1.167 × 10−7 and 4.078 × 10−8 cm2 s−1. Thermodynamic parameters showed that the biosorption of uranium(VI) onto grapefruit peel biomass was feasible, spontaneous
and endothermic under studied conditions. The physical and chemical properties of the adsorbent were determined by SEM, TG-DSC,
XRD and elemental analysis and the nature of biomass–uranium (VI) interactions was evaluated by FTIR analysis, which showed
the participation of COOH, OH and NH2 groups in the biosorption process. Adsorbents could be regenerated using 0.05 mol L−1 HCl solution at least three cycles, with up to 80% recovery. Thus, the biomass used in this work proved to be effective materials
for the treatment of uranium (VI) bearing aqueous solutions. 相似文献
13.
Retention of U(VI) by laumontite, a fracture-filling material of granite was investigated by conducting dynamic and batch
sorption experiments in a glove-box using a granite core with a natural fracture. The hydrodynamic properties of the granite
core were obtained from the elution curve of a non-sorbing tracer, Br−. The elution curve of U(VI) showed a similar behavior to Br−. This reveals that the retention of U(VI) by the fracture-filling material was not significant when migrating through the
fracture at a given condition. From the dynamic sorption experiment, the retardation factor R
a
and the distribution coefficient K
a
of U(VI) were obtained as about 2.9 and 0.16 cm, respectively. The distribution coefficient (K
d
) of U(VI) onto laumontite obtained by conducting a batch sorption experiment resulted in a small value of 2.3±0.5 mL/g. This
low K
d
value agreed with the result of the dynamic sorption experiment. For the distribution of uranium on the granite surface investigated
by an X-ray image mapping, the fracture region filled with laumontite showed a relatively lower content of uranium compared
to the surrounding granite surface. Thus, the low retention of U(VI) by the fracture-filling material can be explained by
following two mechanisms. One is that U(VI) exists as anionic uranyl hydroxides or uranyl carbonates at a given groundwater
condition and the other is the remarkably low sorption capacity of the laumontite for U(VI). 相似文献
14.
A. Bhattacharyya P. K. Mohapatra P. N. Pathak V. K. Manchanda 《Journal of Radioanalytical and Nuclear Chemistry》2006,268(2):323-328
Summary Sorption
behavior of Th and U on cation-exchange resins was investigated from nitric
acid medium by both batch and column methods. The cation-exchange studies
involved the sorption of UO22+ and Th4+ and
their cationic complexes onto Dowex 50Wx8 and Dowex 50Wx4 resins (50-100 mesh).
The batch data yielded a separation factor (Kd,Th/Kd,U)
value of >100 for the cation-exchanger, Dowex 50Wx4 at 1-2M HNO3.
Separation of uranium from thorium was also carried out by column method in
nitric acid medium using cation-exchangers, Dowex 50Wx4 as well as Dowex 50Wx8.
While uranium elution was possible at 1M HNO3, Th could be eluted
only at higher concentration of nitric acid (>6M). The stripped solution
emanating from a mixer settler employing di-2-ethyl hexyl isobutyramide as
extractant and feed solution similar to THOREX process comprising 350 mg/l U
and 380 mg/l Th in 0.75M HNO3 was loaded on the column and the
decontamination factor value for U in the product was >1000.</p>
</p> 相似文献
15.
R. Kumaresan K. A. Venkatesan R. Sajimol M. P. Antony T. G. Srinivasan P. R. Vasudeva Rao 《Journal of Radioanalytical and Nuclear Chemistry》2009,281(3):625-631
Imidazolium nitrate anchored on poly(styrene-divinylbenzene) co-polymer, Im-NO3, has been synthesized and evaluated for plutonium purification. The results are compared with those obtained using Dowex
1 × 4 anion exchange resin. The distribution coefficient (Kd) of Pu(IV) increased with increase in concentration of nitric acid, reached a maximum at 8 M, followed by decrease in Kd values. Rapid ion exchange of Pu(IV) followed by the establishment of equilibrium occurred within 100 min of equilibration
and the data was fitted in to first order rate equation. Variation of distribution coefficient of Pu(IV) as a function of
exchange capacity and nitrate ion concentration suggest the involvement of anion exchange mechanism is responsible for extraction.
The apparent ion exchange capacity was 310 mg/g at 8 M nitric acid. The performance of the Im-NO3 under dynamic condition was assessed by column breakthrough experiments. Radiolytic degradation of Im-NO3 resin in presence and absence of nitric acid (8 M) was studied and the results are reported in this paper. 相似文献
16.
A selective and effective column chromatographic separation method has been developed for uranium(VI) using poly[dibenzo-18-crown-6].
The separation was carried out in L-valine medium. The adsorption of uranium(VI) was quantitative from 1.0 × 10−4 to 1 × 10−1 M of L-valine. Amongst various eluents 2.0–8.0 M hydrochloric acid, 1.0–4.0 M sulfuric acid, 1.0–5.0 M perchloric acid, 6.0–8.0
M hydrobromic acid and 5.0–6.0 M acetic acid were found to be efficient eluents for uranium(Vl). The capacity of poly[dibenzo-18-crown-6]
for uranium(VI) was 0.25 ± 0.01 mmol/g of crown polymer. Uranium(VI) was separated from number of cations and anions in binary
mixtures in which most of the cations and anions show a very high tolerance limit. The selective separation of uranium(VI)
was carried out from multicomponent mixtures. The method was extended to determination of uranium(VI) in geological samples.
The method is simple, rapid and selective with good reproducibility (approximately ∼2%). 相似文献
17.
H. B. Ortiz-Oliveros E. Ordoñez-Regil S. M. Fernández-Valverde 《Journal of Radioanalytical and Nuclear Chemistry》2009,279(2):601-610
The sorption of uranium(VI) on the perovskite structure of strontium titanate in a 0.5M KNO3 solution is studied. SrTiO3 commercial material was characterized by XRD showing a tausonite face, with a specific area of 2.42 m2.g−1. The electrical surface characterization of the compound was performed by mass and potentiometric titrations. pHpzc in water was 8.5±0.3 and 9.1±0.2 in 0.5M KNO3 solution, showing a positively charged surface. FITEQL 4.0 program was used to calculate the sorption curves and the surface
acidity constants by the constant capacitance model obtaining: log K
1 = 8.67 and log K
2 = −9.43. The sorption edge was fitted with two different uranium(VI) species sorbed, corresponding to bidentate complexes
of UO22+ and UO2(OH)2H2O on the surface of strontium titanate. 相似文献
18.
In this paper, the crosslinked polyester resin containing acrylic acid functional groups was used for the adsorption of uranium
ions from aqueous solutions. For this purpose, the crosslinked polyester resin of unsaturated polyester in styrene monomer
(Polipol 353, Poliya) and acrylic acid as weight percentage at 80 and 20%, respectively was synthesized by using methyl ethyl
ketone peroxide (MEKp, Butanox M60, Azo Nobel)-cobalt octoate initiator system. The adsorption of uranium ions on the sample (0.05 g copolymer
and 5 mL of U(VI) solution were mixed) of the crosslinked polyester resin functionalized with acrylic acid was carried out
in a batch reactor. The effects of adsorption parameters of the contact time, temperature, pH of solution and initial uranium(VI)
concentration for U(VI) adsorption on the crosslinked polyester resin functionalized with acrylic acid were investigated.
The adsorption data obtained from experimental results depending on the initial U(VI) concentration were analyzed by the Freundlich,
Langmuir and Dubinin–Radushkevich (D–R) adsorption isotherms. The adsorption capacity and free energy change were determined
by using D–R isotherm. The obtained experimental adsorption data depending on temperature were evaluated to calculate the
thermodynamic parameters of enthalpy (ΔH°), entropy (ΔS°) and free energy change (ΔG°) for the U(VI) adsorption on the crosslinked polyester resin functionalized with acrylic acid from aqueous solutions. The
obtained adsorption data depending on contact time were analyzed by using adsorption models such as the modified Freundlich,
Elovich, pseudo-first order and pseudo-second-order kinetic models. 相似文献
19.
P. Behera Ms. S. Mishra Ms. I. Mohanty V. Chakravortty 《Journal of Radioanalytical and Nuclear Chemistry》1994,178(1):179-192
Extraction studies of uranium(VI) and molybdenum(VI) with organophosphoric, phosphinic acid and its thiosubstituted derivatives have been carried out from 0.1–1.0M HCl solutions. The extracted species are proposed to be UO2R2 and MoO2 CIR on the basis of slope analysis for uranium(VI) and molybdenum(VI), respectively. The extraction efficiencies of PC-88A, Cyanex 272, Cyanex 301 and Cyanex 302 in the extraction of molybdenum(VI) and uranium(VI) are compared. Synergistic effects have been studied with binary mixtures of extractants. Separation of molybdenum(VI) from uranium(VI) is feasible by Cyanex 301 from 1M HCl, the separation factor log being 2.3. 相似文献
20.
S. Biswas P. N. Pathak D. K. Singh S. B. Roy V. K. Manchanda 《Journal of Radioanalytical and Nuclear Chemistry》2010,284(1):13-19
The extraction of uranium(VI) from nitric acid medium is investigated using 2-ethylhexyl phosphonic acid-mono-2-ethylhexyl
ester (PC88A in dimeric form, H2A2) as extractant either alone or in combination with neutral extractants such as tri-n-butyl phosphate (TBP), trioctyl phosphine oxide (TOPO), and dioctyl sulfoxide (DOSO). The effects of different experimental
parameters such as aqueous phase acidity (up to 10 M HNO3), nature of diluent [xylene, carbon tetrachloride (CCl4), n-dodecane and methyl iso-butyl ketone (MIBK)] and of temperature (303–333 K) on the extraction behavior of uranium were investigated. Synergistic
extraction of uranium was observed between 0.5 and 6 M HNO3. Use of MIBK as diluent was also studied. Temperature variation studies using PC88A as extractant showed exothermic nature
of extraction process. Studies were carried out to optimize the conditions for the recovery of uranium from the raffinate
generated during the purification of uranium from nitric acid medium. Inductively Couple Plasma Atomic Emission Spectroscopy
(ICP-AES) and Energy Dispersive X-Ray Fluorescence (EDXRF) techniques were employed for analysis of uranium in equilibrated
samples. 相似文献