共查询到20条相似文献,搜索用时 15 毫秒
1.
K. Sriramam Ch. Ramakrishna J. Sreelakshmi 《Reaction Kinetics and Catalysis Letters》1997,61(1):209-215
The reaction under study is first order in the complex ion over the entire composition range of the mixed solvent. A minimum
amount of mineral acid is needed for completion of the reaction (formation of colorless products), but the rate is practically
acid-independent. The influence of solvent composition and some common ions on the reaction rate have been examined. A reaction
mechanism consistent with the rate behavior is proposed where water is shown as an active participant in the dissociation
process. A plausible explanation for the retardation effect of HSO4
− as against the accelerating effect of Cl− under water-scarce conditions is provided. 相似文献
2.
《Journal of Inorganic and Nuclear Chemistry》1979,41(10):1465-1474
The forward and reverse extraction rate of Fe3+ at time zero between aqueous nitrate solutions and toluene solutions of tri-n-butylacetohydroxamic acid, HX, has been studied as function of the composition of the system and the stirring speed of the two phases. Experimental information has been also obtained on the degree of aggregation of HX, its surface active properties, its solubility in the aqueous phase as well as on the equilibrium distribution of Fe(III). Rate equations have been derived. The rate determining step of the extraction reaction has been shown to be the reaction of the free and hydrolyzed iron ions, Fe3+ (hydrated) and FeOH+ (hydrated), with the HX undissociated molecules. The reactions occur simultaneously in the aqueous phase (homogeneous path) and at the interface (heterogeneous path). A correlation between the rate constants and the equilibrium constant of the extraction reaction of Fe(III) has been established. 相似文献
3.
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
4.
Kambhampati Sriramam Brahmandam S. R. Sarma Konidena Kalidas Janapati Sreelakshmi Chintalapudi Ramakrishna 《Transition Metal Chemistry》1993,18(2):231-237
Summary The natural decay of Fe(phen)
f3
p3+
, where no CeIV is employed for scavenging the side reaction product, Fe(phen)
f3
p2+
, is now treated as a complex reaction involving two parallel processes, and the experimental kinetics are consistent with the rate laws derived from a mechanism that simultaneously explains the composition of the products as a function of acidity. In terms of the proposed mechanism the dissociation rate of the complex ion in acid solutions containing CeIV as scavenging agent is to be regarded as a CeIV retarded aquation rate, and OH– is to be assigned a catalytic role in the kinetics of basic reduction. 相似文献
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E. V. Timakova L. I. Afonina N. V. Bulina S. S. Shatskaya Yu. M. Yukhin V. A. Volodin 《Russian Journal of Applied Chemistry》2017,90(7):1040-1046
Conditions were determined in which basic bismuth oxalate of composition BiC2O4(OH) can be obtained by direct precipitation upon addition of oxalic acid from nitrate solutions used in production of bismuth compounds. The composition of the compound was confirmed by X-ray phase and chemical analyses, IR and Raman spectroscopy, and thermogravimetry. Electron microscopy was used to examine the effect of the composition of the reaction medium and temperature on the morphology of the product being obtained. It was shown that β-Bi2O3 can be obtained in oxidative thermolysis of basic bismuth oxalate, depending on its morphology. 相似文献
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Absorption at the excitation wavelength recovers in a sub-nanosecond, two stage process following bleaching of tris(1,10-phenanthroline) iron(II) by a single picosecond pulse at 530 nm. Absorption coefficients and decay times suggest that a CT and a dd excited state are consecutively occupied before ground state repopulation. 相似文献
12.
I. P. Pozdnyakov F. Wu A. A. Melnikov V. P. Grivin N. M. Bazhin S. V. Chekalin V. F. Plyusnin 《Russian Chemical Bulletin》2013,62(7):1579-1585
Photochemistry of a 1: 1 FeIII-lactic acid complex, [Fe(Lact)]+, in aqueous solutions was studied by stationary photolysis, nanosecond laser flash photolysis (355 nm, 6 ns), and femtosecond pump-probe spectroscopy (400 nm, 200 fs). The quantum yield of photolysis of [Fe(Lact)]+ upon excitation at 355 nm is 0.4 and 0.22 in the deoxygenated and air-saturated solutions, respectively. Weak transient absorption in the range 500–750 nm was observed in the nanosecond experiments. It was assigned to a [FeII...-O-CH(Me)-COO·]+ radical complex. The spectral properties of the ligand-to-metal charge transfer excited state and the characteristic time of formation of the radical complex (1.5 ps) were determined in the femtosecond spectroscopy experiments. A reaction mechanism was proposed, which involves inner-sphere electron transfer in the excited complex with the formation of a radical complex [FeII...-O-CH(Me)-COO·]+ and its subsequent transformation to the end product of the photochemical reaction. 相似文献
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X. Zhang Y. Gong F. Wu N. Deng I. P. Pozdnyakov E. M. Glebov V. P. Grivin V. F. Plyusnin N. M. Bazhinb 《Russian Chemical Bulletin》2009,58(9):1828-1836
Photochemistry of the 1: 1 FepIII complex with pyruvic acid (PyrH) in aqueous solutions was studied by stationary photolysis and nanosecond laser flash photolysis
with the excitation by the 3rd harmonics of an Nd:YAG laser. The quantum yield of [FeIIIPyr]2+ under the excitation at 355
nm is 1.0±0.1 and 0.46±0.05 in the absence and in the presence of dissolved oxygen, respectively. In experiments on laser
flash photolysis, a weak intermediate absorption in the region 580–720 nm was found. The absorption was ascribed to the [FeII…MeC(O)COO•]p2+ radical complex. Laser flash photolysis of [FePyr]p2+ in the presence of methyl viologen dications (MVp2+) resulted in the formation of the MV•+ radical cations. The proposed reaction mechanism includes the inner-sphere electron
transfer in the light-excited complex accompanied by the formation of the [FepII…MeC(O)COO•]p2+ radical complex followed by its transformation into the reaction products. 相似文献
16.
D. E. Chirkst T. E. Litvinova V. S. Starshinova G. S. Roshchin 《Russian Journal of Applied Chemistry》2007,80(2):185-188
Cerium(III) extraction with oleic acid in o-xylene from nitrate solutions was studied. The extraction mechanism and the dependence of the distribution ratio on pH and composition of the organic and aqueous phases were examined. The thermodynamic characteristics of extraction were calculated. 相似文献
17.
H. Bao S. Navaratnam B. J. Parsons G. O. Phillips 《Radiation Physics and Chemistry》1993,42(4-6):989-992
One-electron oxidation of the ferrous tris-PQ complex, a model for lipoxygenase, was attempted using oxidants such as •OH, N•3, Br•-2, Tl2+ and TlOH+. •OH was found to react with the complex with a bimolecular rate constant of (3.9±0.6)x109dm3mol-1s-1, a rate which is not very dissimilar to that for the reaction with the ligand PQ. However the product of the reaction was found to be a OH-adduct rather than a cation radical. No reaction was found to occur with N•3 or Br•-2. Both Tl2+ and TlOH+ reacted with the complex to form its oxidised species with rate constants of (7.0±1)x108dm3mol-1s-1 and (4.0±0.8)x108dm3mol-1s-1, respectively. From a comparison of the rate constants and the transient spectra it was concluded that the centre of oxidation is the ligand rather than the metal. 相似文献
18.
G. R. Khabibullina T. M. Buslaeva E. S. Fedotova V. R. Akhmetova A. G. Ibragimov 《Russian Journal of General Chemistry》2017,87(5):963-968
Bis(1,5,3-dithiazepanes) have been synthesized via cyclocondensation of aliphatic α,ω-diamines and hydrazine with formaldehyde and ethane-1,2-dithiol. Palladium(II) sorption with bis(1,5,3-dithiazepanes) from nitric acid solutions has been studied via a static method. Bis(1,5,3-dithiazepanes) efficiently extract palladium(II) from 0.1?4 mol/L nitric acid solutions at room temperature. 相似文献
19.
A heat-induced refractive index change is used to increase the sensitivity of the spectrophotometric determination of iron(II) in a dual-beam system. An argon ion laser (514.5 nm) is used as the heating source and the intensity variation of a helium—neon laser (632.8 nm) is measured. The sensitivity is increased 7.3 times compared with spectrophotometry; the detection limit is 3 × 10-7 M. 相似文献
20.
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