共查询到20条相似文献,搜索用时 31 毫秒
1.
D. Axente M. Abrudean A. Bâldea 《Journal of Radioanalytical and Nuclear Chemistry》1996,207(1):163-170
The rate of nitrogen isotope exchange between NO and HNO3 has been measured as a function of nitric acid concentration of 1.5–4M·1–1. The exchange rate law is shown to beR=k[HNO3]2[N2O3] and the measured activation energy isE=67.78kJ ·M–1 (16.2 kcal·M–1). It is concluded that N2O3 participates in15N/14N exchange between NO and HNO3 at nitric acid concentrations higher than 1.5M·1–1. 相似文献
2.
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
3.
A new diamide N,N,N′,N′-tetrahexylmalonamide (THMA) was synthesized, characterized and used in the extraction of U(VI) from
nitric acid solutions. N,N,N′,N′-tetrabutylmalonamide (TBMA) was also studied to test the steric hindrance. Factors affecting
this extraction system, the concentration of the extractant, aqueous nitric acid and NaNO3 and the temperature were investigated. The IR spectral study was also made of the extracted species. 相似文献
4.
Nitrosoruthenium nitrite-nitrate complexes in aqueous and nitric acid solutions as probed by 15N NMR
E. V. Kabin V. A. Emel’yanov S. V. Tkachev 《Russian Journal of Inorganic Chemistry》2013,58(2):229-238
Aqueous and nitric acid solutions of Na2[Ru15NO(15NO2)4OH] in the concentration range $c_{H^{15} NO_3 }$ = 0–3.3 mol/L have been studied by 15N NMR, dominating complex species have been identified, and the equilibrium constants for the nitrate ion incorporation into the inner coordination sphere of nitrosoruthenium have been estimated. The equilibration time for such equilibria is no more than 2 h at room temperature. In addition to the nitro complexes, isomeric nitritonitronitrosoruthenium compounds have been identified in solutions. In weak acidic solutions at $c_{HNO_3 }$ < 0.25 mol/L, nitro and nitritonitro complexes containing four and three coordinated nitrite ions predominate. At the HNO3 concentration 0.4–1.7 mol/L, the vast majority of ruthenium presents in solution as fac-dinitronitrosoruthenium complexes containing coordinated water molecules and nitrate ions. In solutions with $c_{HNO_3 }$ > 1.5 mol/L, the fractions of dinitro- and mononitronitrosoruthenium complexes are comparable. In strong nitric acid solutions ( $c_{H^{15} NO_3 }$ = 10 mol/L) kept for three years in contact with air, nitro complexes are absent, and mononitrato- and dinitratoaquanitrosoruthenium complexes are dominating. 相似文献
5.
The oxidation of N,N-dimethylhydroxylamine (DMHAN) by nitrous acid is investigated in perchloric acid and nitric acid medium, respectively. The
effects of H+, DMHAN, ionic strength and temperature on the reaction are studied. The rate equation in perchloric acid medium has been
determined to be −d[HNO2]/dt = k[DMHAN][HNO2], where k = 12.8 ± 1.0 (mol/L)−1 min−1 when the temperature is 18.5 °C and the ionic strength is 0.73 mol/L with an activation energy about 41.5 kJ mol−1. The reaction becomes complicated when it is performed in nitric acid medium. When the molarity of HNO3 is higher than 1.0 mol/L, nitrous acid will be produced via the reaction between nitric acid and DMHAN. The reaction products
are analyzed and the reaction mechanism is discussed in this paper. 相似文献
6.
G. X. Sun Y. S. Wang S. X. Sun B. R. Bao 《Journal of Radioanalytical and Nuclear Chemistry》1997,221(1-2):219-220
The partition of uranium(VI) between nitric acid solutions and solutions of N,N-dibutyldodecanamide (DBDA) in kerosene has been investigated at varying concentrations of nitric acid, extractant, salting-out agent LiNO3 and at different temperatures. The mechanism of extraction is discussed in the light of the results obtained. 相似文献
7.
K. A. Venkatesan K. V. Shyamala M. P. Antony T. G. Srinivasan P. R. Vasudeva Rao 《Journal of Radioanalytical and Nuclear Chemistry》2008,275(3):563-570
Batch and dynamic extractions of uranium(VI) in 10−3–10−2M concentrations in 3–4M nitric acid medium have been investigated using a commercially available phosphinic acid resin (Tulsion
CH-96). The extraction of uranium(VI) has been studied as a function of time, batch factor (V/m), concentrations of nitric acid and uranium(VI) ion. Dual extraction mechanism unique to phosphinic acid resin has been established
for the extraction of uranium(VI). Distribution coefficient (K
d
) of uranium(VI) initially decreases with increasing concentration of nitric acid, reaches a minimum value at 1.3M, followed
by increases in K
d
. A maximum K
d
value of ∼2000 ml/g was obtained at 5.0M nitric acid. Batch extraction data has been fitted into the linearized Langmuir
adsorption isotherm. The performance of the resin under dynamic extraction conditions was assessed by following the breakthrough
behavior of the system. Effect of flow rate, concentrations of nitric acid and uranium ion in the feed on the breakthrough
behavior of the system was studied and the data was fitted using Thomas model. 相似文献
8.
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
9.
Y. -S. Wang X. -F. Tan C. -H. Shen B. -R. Bao 《Journal of Radioanalytical and Nuclear Chemistry》1999,240(2):683-686
N,N,N',N'-Tetrabutyladipicamide (TBAA) was used for the extraction of nitric acid and uranyl(II) ion from nitric acid media
into toluene. The effects of nitric acid, uranyl(II) ion, and extractant concentration, temperature and back extraction on
the distribution coefficient of uranyl(II) ion have been studied. The main adduct of TBAA and HNO3 is TBAA·HNO3 in 1.0 mol/l nitric acid solution. The 1:2:2 complex of uranyl(II) ion, nitrate ion and TBAA as extracted species is further
confirmed by IR spectra of the extraction of uranyl(II) ion with TBAA. The values of the thermodynamic parameters have also
been calculated. 相似文献
10.
D. Axente A. Bâldea C. Teacă M. Abrudean R. Horga 《Journal of Radioanalytical and Nuclear Chemistry》1999,240(3):987-989
The basic isotopic exchange reaction is responsible for the separation of15N in the Nitrox system that between gaseous nitrogen oxides and aqueous nitric acid with a single stage separation factor
α=1.055 for 10M nitric acid, at 25°C and atmospheric pressure takes place. In order to know what happens in15N separation at higher pressure, when the isotopic transport between two phases is improved, a stainless steel laboratory
experimental plant with a 1000 mm long × 18 mm i.d. column, packed with triangular wire springs 1.8×1.8×0.2 mm2, was utilised. At 1.5 atm (absolute), and 2.36 ml·cm−2·min−1 flow rate HETP was 7% smaller than at atmospheric pressure and 1.5 times smaller flow rate. HETP at 3.14 ml·cm−2·min−1 flow rate and 1.8 atm is practically equal with that obtained at atmospheric pressure and 2 times smaller flow rate. The
operation of the15N separation plant at 1.8 atm (absolute), instead of atmospheric pressure, will permit doubling of the 10M nitric acid flow
rate and of15N production of the given column. 相似文献
11.
Attempts to develop new technologies of NO
x
(NO + NO2) emission reduction are still carried out all around the world. One of the relatively new approaches is the application of
ozone injection into the exhaust gas stream followed by the absorption process. Ozone is used to transform NO
x
to higher nitrogen oxides which yield nitric acid with better effectiveness. The main objective of this paper was to study
the influence of mole ratio (MR) O3/NO used in the ozonation process of NO
x
on the effectiveness of NO
x
oxidation to higher oxides. The ozonation process was carried out in a flow reactor for concentrations of nitric oxide in
the range of 1.5 × 10−5−7.7 × 10−5 mol dm−3 and varying O3/NO mole ratios. Measurements were conducted with the use of a FTIR spectrometer. The results obtained prove that for MR higher
than 1, the oxidation effectiveness of nitric oxides generally reaches 95 %, whereas for MR higher than 2, oxidation of NO
x
to higher nitrogen oxides is completed. 相似文献
12.
Si-Xiu Sun 《Journal of Radioanalytical and Nuclear Chemistry》2001,249(3):625-628
By using stirred-cell method as experimental technique, the kinetictransfer mechanism of UO2
2++ with N,N,N',N'-tetrabutyladipicamide(TBAA) from nitric acid solutions into toluene was studied. The differentconditions effecting the extraction rate constants (k'f and k'b ) were investigated, such as UO2
2+ concentration,HNO3 concentration, TBAA concentration, temperature and agitationspeed. It was found that the extraction process was controlled by the diffusionof UO2 (NO3 )2 . 2TBAA from the liquid-liquidsurface into the organic phase in the range of the experimental concentrationof HNO3. The extraction rate was found to be of pseudo-first orderwith respect to the concentration of uranium(VI). 相似文献
13.
The dissolution of UO2 particles in 4 mol·L−1 nitric acid medium at temperatures of 90–110°C by microwave heating and conventional heating has been investigated, respectively.
It is found that the dissolution ratios of UO2 particles by microwave heating were 10%–40% higher than that by conventional heating. Kinetics research shows that the dissolution
of UO2 particles in 4 mol·L−1 nitric acid is controlled by the diffusion control model for microwave heating and by the surface reaction control model
for conventional heating. The diffusion control model for the dissolution of UO2 particles by microwave heating could be explained by the diffuseness on the surface of UO2 particles. 相似文献
14.
The state of ruthenium in nitric acid solutions treated with sodium nitrite has been studied by 14N, 15N, 17O, and 99Ru NMR. In the acidity range 2.7-0.12 mol/L, the dominating ruthenium species are the [RuNO(NO2)2(NO3)(H2O)2]0 and [RuNO(NO2)2(H2O)3]+ complexes. When the acidity is decreased to 0.06 mol/L, trinitro-and tetranitronitrosoruthenium(II) complexes predominate in solution. In an acidic medium, the trinitro-and tetranitronitrosoruthenium(II) complexes exhibit catalytic activity toward oxidation with air of nitrite to nitrate. 相似文献
15.
J. C. Veselsky 《Journal of Radioanalytical and Nuclear Chemistry》1978,46(2):247-253
The extraction of Pu(IV) and Th with tridodecylamine—xylene mixtures from about 6M nitric acid soil leach solutions was studied
as a function of the chemical composition of the aqueous phase (iron and calcium concentration, acidity) and the amine concentration
in the extractant. No correlation was found between the partition coefficients of Pu(IV) and Th and the composition parameters
mentioned above at any of the amine concentrations examined. The slope, in a bilogarithmic plot, of the partition coefficients
versus the amine concentrations was found to be close to 2 for Pu(IV) as well as Th in pure 6.5M nitric acid solution, thus
indicating the presence of the complexes Pu(NO3)
6
2−
and Th(NO3)
6
2−
in the extract. When the pure nitric acid solution was replaced by soil leach solutions of similar molarity in HNO3, the slope remained 2 for Pu(IV), but changed to 1.5 for Th. A possible reason for this slope yielded by Th may be the coexistence
of the complexes Th(NO3)
6
2−
and Th(NO3)
5
−
in the extraction phase.
Presented at the 4th SAC Conference on Analytical Chemistry, Birmingham 1977. 相似文献
16.
Using the recently detected intense UV absorption spectrum of it has been established that SiCl2 reacts with nitric oxide in the gas phase with a bimolecular rate constant, k(SiCl2+NO), of (1.6±0.1)×109 M−1s−1 at 25°C. 相似文献
17.
分别在高氯酸和硝酸介质中研究了N,N-二甲基羟胺(DMHAN)与HNO2的反应动力学,通过考察溶液酸度、还原剂浓度、离子强度和温度等因素对反应过程的影响,获得高氯酸介质中反应动力学速率方程为-d[HNO2]/dt=k[DMHAN][HNO2],在18.5 ℃,离子强度μ=0.73 mol/L时,反应速率常数k=(12.8±1.0) mol/(L·min),反应活化能Ea=41.5 kJ/mol。 在硝酸介质中DMHAN与HNO2的反应比较复杂,硝酸浓度较高时,硝酸将参与反应重新生成HNO2,且硝酸浓度越大,HNO2的生成速度越快,HNO2与DMHAN的反应是自催化氧化的。 对DMHAN与HNO2的反应产物进行了分析,并推导了硝酸体系中DMHAN与HNO2的反应机理。 相似文献
18.
É. É. Liepin'sh R. M. Zolotoyabko Ya. P. Stradyn' M. A. Trushule K. K. Venter 《Chemistry of Heterocyclic Compounds》1980,16(6):568-571
The14N and15N NMR spectra of a number of 2-substituted 5-nitrofurans were studied. On the basis of experimental data it was concluded
that there is considerable π-electron density on the nitrogen atom of the nitro group. A linear relationship between the chemical
shifts in the14N NMR spectra and the frequencies of the asymmetrical deformation vibrations of the nitro group in the IR spectra was found
for the series of investigated 5-nitrofurans. The observed15N-H spin-spin coupling constants showed that in the 5-nitrofuran molecule transmission of spin information through the ring
oxygen atom to the H2 nucleus is appreciably greater than through the carbon atom to the H4 nucleus. It was established by measurement of the15N NMR spectra that the crude adduct formed in the nitration of furfural diacetate with acetyl nitrate is a mixture of trans
and cis isomers of 5-nitro-2-acetoxy-2,5-dihydrofurfural diacetate in a ratio of 7∶1.
Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 741–743, June, 1980. 相似文献
19.
Yuezhong Xian Jian Xue Song Zhang Xiangyang Ying Litong Jin 《Fresenius' Journal of Analytical Chemistry》1999,365(7):587-591
The development of a simple, sensitive, selective, and stable amperometric nitric oxide microsensor is described. It is based
on Ni(chitin)2 mediators immobilized on a platinum, Nafion modified electrode. The detection of NO is based on the Ni(chitin)2 catalysis of NO oxidation at an anodic potential of +0.74 V (vs. SCE). The catalytic peak current is linear for a NO concentration
in the range of 8.5 × 10–8 mol/L to 1.5 × 10–5 mol/L, with a correlation coefficient of 0.9992. The detection limit of the microsensor is 5.0 × 10–8 mol/L. It is suitable for the direct measurement of NO in biological systems.
Received: 5 February 1999 / Revised: 15 June 1999 / Accepted: 17 June 1999 相似文献
20.
Kuang-Hua Hsueh Wei-Ting Chen Yung-Chuan Chu Lung-Chang Tsai Chi-Min Shu 《Journal of Thermal Analysis and Calorimetry》2012,109(3):1253-1260
With two active O?CO peroxide groups, 1,1-bis(tert-butylperoxy)cyclohexane (BTBPC) has a certain degree of thermal instability. It is usually used as an initiator in chemical processes, and therefore reckless operation may result in serious thermal accidents. This study focused on the runaway reactions of BTBPC alone and mixed with various concentrations of nitric acid (1, 2, 4, and 8?N). The essential thermokinetic parameters, such as exothermic onset temperature (T o), activation energy (E a), frequency factor (A), time to maximum rate under adiabatic condition (TMRad) and time to conversion limit (TCL), were evaluated by differential scanning calorimetry at the heating rate of 4?°C min?1, and a kinetics-based curve fitting method was used to assess the thermokinetic parameters. All the results indicated that BTBPC mixed with one more than 4?N nitric acid dramatically increased the degree of thermal hazard in the exothermic peak and became more dangerous. However, it was relatively safe for BTBPC mixed with less than 1?N nitric acid under 34.5?°C. 相似文献