共查询到20条相似文献,搜索用时 15 毫秒
1.
《Journal of Inorganic and Nuclear Chemistry》1981,43(11):2929-2934
The polymerization of Pu(IV) in aqueous nitric acid solutions has been studied spectrophotometrically both to determine the effects of large UO2(NO3)2 concentrations on the polymerization rates and, more generally, to review the influence of other major parameters on the polymer reaction. Typically, experiments have been performed at 50°C and at 0.05M Pu in aqueous solutions of HNO3 at concentrations ranging from 0.07 to 0.4M. An induction period usually precedes the polymer growth stage, during which time it is believed that primary hydrolysis products form and begin to aggregate. Uranyl nitrate retards the polymerization reaction by approximately 35% despite the counteracting influence of the nitrate ions associated with this solute. The rate of polymer formation at 50°C has been shown to be third order in Pu(IV) concentration. 相似文献
2.
N. G. Yakovlev V. N. Kosyakov G. M. Kazakova 《Journal of Radioanalytical and Nuclear Chemistry》1982,75(1-2):113-120
Extraction of Bk(IV), Ce(IV), Pu(IV) and Zr by tributyl phosphate from 2M to 16M nitric acid solutions has been studied. Using the data on the effect of the extractant, nitric acid and nitrate ion concentrations on the distribution coefficients of Bk(IV) and Ce(IV), the mechanism of Bk(IV) extraction by tributyl phosphate from nitric acid solutions is considered. 相似文献
3.
S. L. Yarbro S. B. Schreiber E. M. Ortiz R. L. Ames 《Journal of Radioanalytical and Nuclear Chemistry》1998,235(1-2):21-25
Los Alamos National Laboratory (LANL) has evaluated different techniques to concentrate and remove plutonium from solutions
stored at the Rocky Flats Environmental Technology Site (RFETS). Pu(III) oxalate precipitation was chosen to treat nitric
acid solutions because it is a simple and efficient technique for removing plutonium. Reducing Pu(IV) to Pu(III) is a key
process step which affects the rest of the processing sequence. Because of differences in the literature1 over the kinetics of the reaction, additional data was obtained and compared with existing data to examine the kinetic relationship,
and determine an appropriate relationship for future engineering evaluations. The results and conclusions of this work, along
with new experimental data, are presented. 相似文献
4.
S.-Y. Kim T. Asakura Y. Morita 《Journal of Radioanalytical and Nuclear Chemistry》2013,295(2):937-942
Electrochemical and absorption spectroscopic properties of Pu(IV) and Pu(III) in nitric acid have been investigated by using cyclic voltammetry (CV) and UV–Visible spectroscopy. CV using a glassy carbon electrode suggested that the electrochemical reaction of Pu(IV) nitrate complexes were found to be a quasi-reversible reduction to Pu(III) species. The formal redox potentials (E 0) for Pu(IV)/Pu(III) couples were +0.721, +0.712, +0.706, +0.705, +0.704, 0.694, and +0.696 V (vs. Ag/AgCl) when nitric acid concentrations are 1–7 M nitric acid solutions, respectively. These results indicate that the reduction product of Pu(IV) is only Pu(III). Further details for reaction mechanism of Pu(IV) were discussed on the basis of digital simulation of the experimental cyclic voltammograms. The absorption spectroscopic properties of Pu(III) and Pu(IV) in nitric acid solutions were investigated with UV–Visible spectrophotometry. As a result, it was founds that the intensities of the characteristic absorption peaks of Pu(III) and Pu(IV) tend to decrease with increasing nitric acid concentration for 1–8 M, and the peaks positions shifted longer or shorter wavelengths depending on the complex-forming abilities of Pu(III) and Pu(IV) with an increase in the nitric acid concentration. 相似文献
5.
A. G. Rykov N. N. Andreychuk V. Ya. Vasilev V. A. Ermakov 《Journal of Radioanalytical and Nuclear Chemistry》1979,51(2):363-376
Plutonium(IV) oxidation has been studied in 1 to 20 mol/1 HNO3 under 1 to 14 W/1 internal alpha-irradiation and at plutonium concentrations from 2 to 100 mmol/1. Curium isotopes have been
used as the basic alpha-irradiation sources. It has been established that in the systems investigated both oxidation of plutonium(IV)
and reduction of plutonium(VI) take place, resulting with time in reaching the equilibrium between plutonium(IV) and plutonium(VI).
The presence of plutonium(IV) enhances the reduction of plutonium(VI). The rate constants for plutonium(IV) oxidation and
plutonium(VI) reduction have been estimated and their dependences upon the concentrations of nitric acid, plutonium(IV) and
plutonium(VI) as well as upon the dose rate investigated. An equation has been derived which permits to calculate the concentrations
of plutonium(IV) and plutonium(VI) at any desired time. 相似文献
6.
K. V. Lohitakshan P. D. Mithapara P. S. Nair S. A. Pai K. Raghuraman A. V. Jadhav H. C. Jain 《Journal of Radioanalytical and Nuclear Chemistry》1994,183(2):359-370
Extraction of trivalent (Pu3+, Am3+, actinides and Eu3+, a representative of lanthanides) and tetravalent (Np4+ and Pu4+) actinides has been studied with dihexyl N,N-di-ethylcarbamoylmethyl phosphonate (DHDECMP) in combination with TBP in benzene from 2M nitric acid. The stoichiometries of the species extracted were found to be M(NO3)3·(3–n) TBP·n DHDECMP (for trivalent ions) and M(NO3)4·(2–n) TBP·n DHDECMP (for tetravalent ions) by the slope ratio method. The extraction constants evaluated (from the distribution data) indicate that for tetravalent ions (with solvation number two) the extraction constant increases when TBP (Kh=0.17) molecules are successively replaced by more basic DHDECMP (Kh=0.34) molecules. However, for trivalent ions (with solvation number three) when TBP molecules are totally replaced by DHDECMP molecules stereochemical factors appear and instead of increase, a substantial decrease in extraction constants is observed for Eu3+ and Am3+, a lesser decrease being observed for Pu3+ (larger ion). 相似文献
7.
J. P. Shukla S. A. Pai M. S. Subramanian 《Journal of Radioanalytical and Nuclear Chemistry》1980,56(1-2):53-63
Studies have been performed on the liquid-liquid extraction of neptunium from nitric acid solutions by di-n-hexylsulphoxide
(DHSO) di-no-octylsulphoxide (DOSO) and di-iso-amylsulphoxide (DISO) and their mixtures over a wide range of conditions. At
a given strength of the extractant, extraction of Np(IV) increases initially rapidly with increase in the acid concentration;
at high acidities, above 8M HNO3, the extraction decreases. Under otherwise identical conditions, extraction increases with an increase in the extractant
concentration. The species extracted would appear to be Np(NO3)4·2(R2SO). A mixture of two extractants extracts more than the sum of the extractions due to the individual components at concentrations
corresponding to those of the mixture. After loading the organic phase with uranium(VI), extractability of Np(IV) becomes
considerably lower. The diminution in extraction with increase in temperature is small. A comparison of the extraction behaviour
of Np(IV) with those of Pu(IV), U(VI) and some associated fission products has been made. 相似文献
8.
D. Schumann A. F. Novgorodov V. A. Khalkin R. Dreyer 《Journal of Radioanalytical and Nuclear Chemistry》1991,155(6):419-425
The hydrolytic behavior of trace quantities of tetra- and pentavalent vanadium has been studied by the zone electrophoresis method in a wide pH range (2–12). For the first time, the mobilities of all hydrolytic vanadium forms were determined in dilute nitric acid solutions of ionic strength 0.1M at 298 K. 相似文献
9.
Zu-Ming Zhou Yong-Xia Sun Shao-Ning Yu Hui-Fang Du 《Journal of Radioanalytical and Nuclear Chemistry》1996,214(5):369-379
The kinetics of solvent extraction of U (IV), Th (IV) and U (VI) from nitric acid solution with tributyl phosphate (TBP) in kerosene and cyclohexane have been studied using the single drop technique. The effects of concentrations of U (IV), Th (IV), U (VI), nitric acid, nitrate, TBP and temperature on the extraction rates of U (IV), Th (IV) and U (VI) have been examined. The mechanisms for the three extraction processes are discussed. 相似文献
10.
I. C. Pius R. D. Bhanushali K. T. Pillai S. K. Mukerjee V. N. Vaidya 《Journal of Radioanalytical and Nuclear Chemistry》1999,240(3):981-985
Sorption of Pu(IV) on alumina microspheres prepared by the sol-gel procedure has been investigated for the recovery of plutonium
from nitric acid-oxalic acid solutions. Distribution ratio for Pu(IV) between alumina microspheres and nitric acid-oxalic
acid have been determined. The influence of the mode of preparation and heat treatment of these microspheres, on the sorption
of Pu(IV) have been investigated. Pu(IV) breakthrough capacities have been determined using a 5 ml bed of alumina with solutions
of Pu(IV) in 1M HNO3+0.05M H2C2O4 and 0.5M HNO3+0.05M H2C2O4. The elution behavior of Pu(IV) loaded on these microspheres were studied using nitric acid solutions containing different
oxidising and reducing agents. Investigations were also carried out to fix the activity in the alumina matrix by heat treatment. 相似文献
11.
G. M. Nair G. R. Mahajan D. R. Prabhu 《Journal of Radioanalytical and Nuclear Chemistry》1995,191(2):323-330
The extraction behavior of U(VI) and Pu(IV) with dioctyloctanamide (DOOA), dioctylethylhexanamide (DOEHA) and diisobutylethylhexanamide (DIBEHA) was investigated from nitric acid medium. With DOOA, U(VI) extraction is higher than that for Pu(IV) upto 5M HNO3 and the trend is reversed at higher acid concentrations. Extraction yield of U(VI) is higher than that for Pu(IV) in the case of DOEHA and DIBEHA. DIBEHA extraction of Pu(IV) is found to be very small. The lower value of the distribution ratio for Pu(IV) with branched amides was attributed to steric reasons. The possibility of using these amides for separation of U(VI) and Pu(IV) without valency adjustment was explored. Both U(VI) and Pu(IV) are extracted as their disolvates by DOOA and DOEHA. 相似文献
12.
13.
T. Mioduski Dong Anh Hao Hoang Hong Luan 《Journal of Radioanalytical and Nuclear Chemistry》1989,132(1):105-113
A simple operational method for separating cerium from other lanthanides in natural mixtures of cerium dioxide with lanthanide(III) hydroxides, obtained from Vietnamese parisite and Mongolian bastnasite, has been developed. The method is based on drying crude Ln(OH)3×H2O material in air at about 200°C within 6h, followed by leaching Ln(III) with concentrated nitric acid added carefully with stirring to the dried material/water 11.5 slurry. Under optimum conditions cerium (and Th, if present) virtually does not pass into solution while the yield of leaching and the sum of REE oxides (REO) concentration in the after-leach solution reach the maximum values of 97% (mass) and 0.18 kg·dm–3, respectively. Besides an expected decrease of the leaching yield, roasting the starting material at 600°C results in over 7% Ce content in the Ln leached. 相似文献
14.
N. N. Andreychuk A. A. Frolov K. V. Rotmanov V. Ya. Vasiliev 《Journal of Radioanalytical and Nuclear Chemistry》1990,143(2):427-432
Plutonium(III) oxidation under high energy α-irradiation in nitric acid solutions has been studied relative to concentrations of both nitric acid (0.12–2.9 mol/l) and plutonium (1.4–10 mmol/l) using spectrophotometric techniques. Curium-244 has been used as the basic alpha-irradiation source. It has been stated that in solutions with nitric acid concentrations lower than 0.5 mol/l plutonium(III) does not oxidize completely. In the course of the process the formation of a plutonium(IV) peroxide complex is observed. Increase in the nitric acid concentration results in that in both the rate and degree of plutonium(III) oxidation. When cHNO 3 is higher than 0.5 mol/l the peroxide complex does not form and the process assumes an autocatalytic character. It has also been shown that plutonium(III) oxidation kinetics is significantly affected by nitrous acid, one of the nitrate ion radiolysis products. To describe plutonium chemical transformations under irradiation in nitric acid solutions, a kinetic scheme is proposed. The calculations have been carried out on a BESM-6 computer; a satisfactory agreement between the calculated and experimental data has been obtained. 相似文献
15.
You-Shao Wang Chao-Hong Shen Yong-hui Yang Jian-Kang Zhu Bo-Rong Bao 《Journal of Radioanalytical and Nuclear Chemistry》1996,213(3):199-205
It was found that N,N,N,N-tetrabutylsuccinylamide (TBSA) in a diluent composed of 50% 1,2,3-trimethylbenzene (TMB) and 50% kerosene (OK) can extract thorium(IV) ion from a nitric acid solution. The results of the extraction study suggested the formation of a 141 thorium(IV) ion, nitrate ion and N,N,N,N-tetrabutylsuccinylamide complex as extracted species. The related thermodynamic functions were also calculated. 相似文献
16.
Toshiyuki Fujii Souichirou Egusa Akihiro Uehara Akira Kirishima Isao Yamagishi Yasuji Morita Hajimu Yamana 《Journal of Radioanalytical and Nuclear Chemistry》2011,290(2):475-478
Palladium complexation in concentrated nitric acid solutions was studied by UV/Vis absorption spectrophotometry. The ionic
strength of the solutions was fixed to I = 1, 3, or 5 mol dm−3 (M) by mixing of HNO3 and HClO4. The major palladium species were found to be Pd2+, PdNO3
+, and Pd(NO3)2. The formation constant of PdNO3
+ was determined to be β
1 = 1.32 (I = 1 M), 1.49 (I = 3 M), or 1.47 (I = 5 M), while that of Pd(NO3)2 to be β
2 = 0.45 (I = 3 M) or 0.14 (I = 5 M). 相似文献
17.
Shen Chao-Hong Bao Bo-Rong Wang Gao-Dong Qian Jun Bao Ya-Zhi Cao Zheng-Bai 《Journal of Radioanalytical and Nuclear Chemistry》1992,162(2):207-216
Extraction of uranium(VI), thorium(IV) from nitric acid has been studied with N-octylcaprolactam and N-(2-ethyl)hexylcaprolactam. Distribution coefficients of U(VI), Th(IV) and HNO3 as a function of aqueous NHO3 concentration, extractant concentration and temperature have been studied. The compositions of extracted species, thermodynamic parameters of extraction have been evaluated. Third phase formation in extraction of U(VI) has been studied. Back extraction behavior of U(VI) and Th(IV) from the organic phase has also been tested. The results obtained are compared with those obtained by using TBP under the same experimental conditions. 相似文献
18.
《Polyhedron》1987,6(5):1153-1155
The reactions of pentaammine(o-fluorobenzoato)-, pentaammine(o-bromo-benzoato)- and pentaammine(o-nitrobenzoato)chromium(III) cations in 0.01 M perchloric acid solution and water have been studied at 21dgC. It was found that the reaction in acid was the release of ammonia but in water it was aquation to the pentaammineaquachromium(III) cation. The aquation rates in water decrease in the order o-fluorobenzoate, o-bromobenzoate and o-nitrobenzoate complexes, suggesting an associative mechanism. 相似文献
19.
The process of sodium ethylenediaminetetraacetate (EDTA) mineralization by cerium(IV) in nitric acid medium was studied in
batch and continuous feeding modes. In the batch mode EDTA solution was fed into the reactor in one stroke and in the continuous
mode it was fed with a constant flow rate during a definite time interval. Cerium(IV) concentration was kept at high and constant
level by selecting correct relation between cerium(IV) production in the electrochemical cell and the EDTA added. During the
organic mineralization process cerium(IV) is reduced to cerium(III). The process was carried out at different temperatures,
concentrations of nitric acid and cerium(IV). To obtain the limiting factors in the batch mode reaction, the dependence of
CO2 evolution with time and carrier gas blowing rate was studied. Application of the model previously developed by us to the
continuous process gave us the possibility to calculate pseudo first order kinetic constant on the basis of CO2 evolution data of both EDTA destruction regimes during feeding mode and after stopping organic addition. The efficiency of
organic destruction estimated on the basis of CO2 evolved was in the range 75–95% and on the basis of liquid phase residual organic carbon analysis 95–99%. 相似文献
20.
Zu-Ming Zhou Ying-Jie Zhang Hui-Fang Du 《Journal of Radioanalytical and Nuclear Chemistry》1994,188(3):177-187
The kinetics of oxidation of U(IV) in nitric acid solution by nitrous acid and air oxygen have been studied. The effects of concentrations of U(IV), nitric acid, hydrogen ion and nitrous acid in aqueous solution or oxygen in gas on the oxidation rate have been examined. The oxidation rate increases with increasing temperature and the activation energies are 47 kJ mol–1 for nitrous acid and 91 kJ mol–1 for oxygen. The mechanisms for both oxidation reactions are discussed. 相似文献