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1.
Jia Yongfen Zhang Pilu Zhu Zhixuan Fu Yibei Wang Fangding 《Journal of Radioanalytical and Nuclear Chemistry》1998,229(1-2):173-177
The reduction kinetics of pertechnetate by thiocyanate in perchloric acid is studied by spectrophotometric method. The effect
of the concentrations of pertechnetate, hydrogen ion and thiocyanate on the reaction rate is investigated. The kinetic expression
at 25°C is: −dC
VII/dt=(2.2±0.4)·10−3 [TcO4
−]1.1 [H+]3.2 [SCN−]3.3 The effect of temperature on the reaction rate is studied. The activation energy is 91 kJ/mol. The possible mechanism of
the reaction is discussed. 相似文献
2.
R. Kopunec F. N. Abudeab S. Skraŝková 《Journal of Radioanalytical and Nuclear Chemistry》1998,230(1-2):51-61
Solvent extraction of pertechnetate anions from aqueous solutions of some mineral acids (HCl, HNO3, HClO4, H2SO4), (NaCl, NaNO3, NaClO4, K2CrO4, NaCO3), NaOH and NH4OH by tetraphenylphosphonium chloride in chloroform and nitrobenzene was studied. The results are presented in the form of
the dependencies of extraction characteristics of TcO
4
−
(distribution ratio, percentage of extraction) on the (C6H5)4PCl, H+ and competitive anion concentrations. The solvent extraction of sub-and super-stoichiometric ratio of TcO
4
−
: (C6H5)4P+ was performed. The extraction constant values of ion pairs TcO
4
−
−Cl−, TcO
4
−
−NO
3
−
, TcO
4
−
−ClO
4
−
and of individual anions TcO
4
−
, Cl−, NO
3
−
, ClO
4
−
were calculated. 相似文献
3.
Nancy J. Hess Odeta Qafoku Yuanxian Xia Dean A. Moore Andrew R. Felmy 《Journal of solution chemistry》2008,37(11):1471-1487
The room temperature solubility of amorphous, hydrous technetium(IV) oxide (TcO2⋅xH2O) was studied across a broad range of pH values extending from 1.5 to 12 and in oxalate concentrations from dilute (10−6 mol⋅kg−1) to complete saturation with respect to sodium bioxalate at lower pH values, and to saturation with respect to sodium oxalate
at higher pH values. The solubility was measured to very long equilibration times (i.e., as long a 1000 days or longer). The
thermodynamic modeling results show that the dominant species in solution must have at least one more hydroxyl moiety present
in the complex than proposed by previous investigators (e.g., TcO(OH)Ox− rather than TcO(Ox)(aq)). Inclusion of the single previously unidentified species TcO(OH)Ox− in our aqueous thermodynamic model explains a wider range of observed solubility data for TcO2⋅xH2O(am) in the presence of oxalate and over a broad range of pH values. Inclusion of this species is also supported by the recently
proposed thermodynamic data for the TcO(OH)+ hydrolysis species that indicates that this species is stable at pH values as low as one. 相似文献
4.
Experimental data that support the hypothesis on the determining role of •OH radicals in the emergence of luminescence during the oxidation of U(IV) with atmospheric oxygen in aqueous HClO4 solutions have been obtained using the H2O2-FeSO4 system as a source of OH radicals. It has been found that brighter chemiluminescence (CL) is observed in the presence of
10−5 mol/l Fe2+ in a 5 × 10−4 mol/l U(IV) solution in 0.1 mol/l HClO4 compared with the FeSO4-free solution. The CL yield in the presence of Fe2+ (ηCL = 3.9 × 10−8) is 2.8 times that in the solution without iron (ηCL = 1.4 × 10−8). These results can be regarded as a further piece of evidence for the idea that the elementary event of the formation of
a CL emitter—electronically excited uranyl ion *(UO22+)—in radical chain U(IV) oxidation reactions is electron transfer from the uranoyl ion (UO2+) to the oxidant, the •OH radical. Thus, one of the main prerequisites for light emission during U(IV) oxidation reactions is a high generation efficiency
of •OH radicals and their easy access to the uranoyl UO2+ ion. 相似文献
5.
C. Kremer D. Gambino A. León E. Kremer 《Journal of Radioanalytical and Nuclear Chemistry》1990,145(2):123-133
Electrolytic pertechnetate reduction at inert electrodes was studied as an alternative procedure for synthesizing Tc complexes. Pertechnetate reduction was carried out in aqueous media using different aminated ligands /en, dien, trien and 1,3-dap/ forming [TcO2/amine/2]+ type complexes. Simultaneously with synthesis of the desired Tc complex, TcO2 was electrodeposited onto the cathode. Conversion of TcO
4
–
to Tc complex and TcO2 was studied as a function of several variables /kind and concentration of supporting electrolyte, ligand concentration, pH, current and electrolysis time/. 相似文献
6.
G. Bidoglio A. Chatt A. De Plano F. Zorn 《Journal of Radioanalytical and Nuclear Chemistry》1983,79(1):153-164
Speciation of technetium in ground water has been studied for understanding the migration behaviour of this radionuclide in
deep geological formations. A combination of free-liquid electromigration, ion exchange, solvent extraction, coprecipitation
and dialysis methods has been applied. Both oxic and anoxic conditions have been employed. Systems studied include leaching
of sodium borosilicate glass spiked with99Tc and95mTc followed by its passage through glauconitic sand columns, and dialysis of TcO2 with ground water, sodium chloride, and humic acid solutions. Results indicate the presence of the pertechnetate, TcO
4
−
, ion as the dominating species. 相似文献
7.
M. Chakrabortty V. Chakravortty S. R. Mohanty 《Journal of Radioanalytical and Nuclear Chemistry》1979,53(1-2):131-143
The solvent extraction of zirconium from HCl solutions by dipentyl sulphoxide (DPSO), dioctyl sulphoxide (DOSO), tributyl
phosphate (TBP), and their mixtures in various solvents has been studied. At a given H+ strength, the extraction coefficient η of the metal increases with an increase in Cl− activity whereas it is almost independent of H+ at constant Cl−. Under otherwise identical conditions, η increases with an increase in the extractant concentration but is virtually independent
of the metal ion concentration over a wide range. The species extracted are ZrCl4·DPSO, ZrCl4·DOSO, and ZrCl4·2TBP. In the case of mixtures, the slope of the log η−log M extractant plot for one component decreases with an increase
in the concentration of the second component, the lines crossing at a common point. Extraction is favoured by solvents of
low dielectric constant. It is possible to separate zirconium from thorium and uranium by solvent extraction with sulphoxides. 相似文献
8.
J. Cabicar A. Gosman J. Plicka K. Štamberg 《Journal of Radioanalytical and Nuclear Chemistry》1983,80(1-2):71-80
The kinetics of isotope exchange in the238U(VI)-233U(VI)-strongly acidic cation exchanger Ostion KS system was studied in the temperature range 275–307K and for total uranium
concentration 2.94·10−4–1.75·10−2 mol·l−1 in UO2(NO3)2 solution. The experimental results were evaluated by means of the “two-film mass-transfer model” and by the use of Fick's
diffusion equations which have been proved more suitable for the system studied than McKay's equation. The influence of the
temperature was evaluated using the Arrhenius equation. The diffusion character of the process follows also from the value
of the activation energy (15.12 kJ·mol−1). In comparison with the UO
2
2+
↔H+ ion exchange6 the isotope exchange studied is faster and less dependent on temperature (the activation energy is substantially lower). 相似文献
9.
F. Poineau T. Hartmann G. W. Chinthaka Silva G. Jarvinen K. Czerwinski 《Journal of Radioanalytical and Nuclear Chemistry》2009,279(1):43-48
A new method for the preparation of Tc metal from pertechnetate is described. Metallic technetium was prepared from TcO4− by initial reduction in dry argon atmosphere at 300 °C followed by a wet argon atmosphere in the presence of carbon between
700 and 910 °C. The higher temperature conditions in the presence of H2O and carbon form H2 and CO, which can drive the reduction of TcO2. This method was applied to the recovery of pertechnetate sorbed on anion-exchange resins resulting in the formation of Tc
metal microspheres. The resulting Tc was characterized by XRD analysis and SEM. 相似文献
10.
E. Makrlík P. Vaňura P. Selucký 《Journal of Radioanalytical and Nuclear Chemistry》2008,275(1):229-232
Extraction of microamounts of cesium by nitrobenzene solutions of potassium dicarbollylcobaltate (K+B−) and rubidium dicarbollylcobaltate (Rb+B−) in the presence of benzo-15-crown-5 (B15C5, L) has been investigated. The equilibrium data have been explained assuming
that the complexes ML+ and ML2+ (M+ = K+, Rb+, Cs+) are present in the organic phase. The stability constants of the species ML+ and ML2+ (M+ = K+, Rb+) in nitrobenzene saturated with water have been determined. 相似文献
11.
Silvia Berto Francesco Crea Pier Giuseppe Daniele Concetta De Stefano Enrico Prenesti Silvio Sammartano 《Journal of solution chemistry》2009,38(10):1343-1356
The formation constants of dioxouranium(VI)-2,2′-oxydiacetic acid (diglycolic acid, ODA) and 3,6,9-trioxaundecanedioic acid
(diethylenetrioxydiacetic acid, TODA) complexes were determined in NaCl (0.1≤I≤1.0 mol⋅L−1) and KNO3 (I=0.1 mol⋅L−1) aqueous solutions at T=298.15 K by ISE-[H+] glass electrode potentiometry and visible spectrophotometry. Quite different speciation models were obtained for the systems
investigated, namely: ML0, MLOH−, ML22−, M2L2(OH)−, and M2L2(OH)22−, for the dioxouranium(VI)–ODA system, and ML0, MLH+, and MLOH− for the dioxouranium(VI)–TODA system (M=UO22+ and L = ODA or TODA), respectively. The dependence on ionic strength of the protonation constants of ODA and TODA and of
both metal-ligand complexes was investigated using the SIT (Specific Ion Interaction Theory) approach. Formation constants
at infinite dilution are [for the generic equilibrium pUO22++q(L2−)+rH+
⇌(UO22+)
p
(L)
q
H
r
(2p−2q+r);β
pqr
]: log 10
β
110=6.146, log 10
β
11−1=0.196, log 10
β
120=8.360, log 10
β
22−1=8.966, log 10
β
22−2=3.529, for the dioxouranium(VI)–ODA system and log β
110=3.636, log 10
β
111=6.650, log 10
β
11−1=−1.242 for dioxouranium(VI)–TODA system. The influence of etheric oxygen(s) on the interaction towards the metal ion was
discussed, and this effect was quantified by means of a sigmoid Boltzman type equation that allows definition of a quantitative
parameter (pL
50) that expresses the sequestering capacity of ODA and TODA towards UO22+; a comparison with other dicarboxylates was made. A visible absorption spectrum for each complex reaching a significant percentage
of formation in solution (KNO3 medium) has been calculated to better characterize the compounds found by pH-metric refinement. 相似文献
12.
ZHU Hongping ZHANG Zhaoxia ZHAO Hongwei WANG Wenfeng & YAO Side . Shanghai Institute of Applied Physics Chinese Academy of Sciences Shanghai China . Graduate University of the Chinese Academy of Sciences Beijing China 《中国科学B辑(英文版)》2006,49(4):308-314
Reactive oxygen species (ROS) are generated dur- ing radiation, respiratory burst, normal metabolic processes and so on. There are enzymatic and non-enzymatic antioxidants such as superoxide dis- mutase (SOD), glutathione peroxidase (GSH-Px), vi- tamin E (VE) and carotenoids that can either inhibit or repair the ROS-induced damage. ROS is essential to maintain physiological homeostasis. However, exces- sive ROS give rise to oxidative damage to proteins, lipids and DNA which related t… 相似文献
13.
V. G. Avakyan L. E. Gusel’nikov S. L. Gusel’nikov V. F. Sidorkin 《Russian Chemical Bulletin》2005,54(9):2013-2022
The effect of the nature of substituents at sp2-hybridized silicon atom in the R2Si=CH2 (R = SiH3, H, Me, OH, Cl, F) molecules on the structure and energy characteristics of complexes of these molecules with ammonia, trimethylamine,
and tetrahydrofuran was studied by the ab initio (MP4/6-311G(d)//MP2/6-31G(d)+ZPE) method. As the electronegativity, χ, of the substituent R increases, the coordination bond
energies, D(Si← N(O)), increase from 4.7 to 25.9 kcal mol−1 for the complexes of R2Si=CH2 with NH3, from 10.6 to 37.1 kcal mol−1 for the complexes with Me3N, and from 5.0 to 22.2 kcal mol−1 for the complexes with THF. The n-donor ability changes as follows: THF ≤ NH3 < Me3N. The calculated barrier to hindered internal rotation about the silicon—carbon double bond was used as a measure of the
Si=C π-bond energy. As χ increases, the rotational barriers decrease from 18.9 to 5.2 kcal mol−1 for the complexes with NH3 and from 16.9 to 5.7 kcal mol−1 for the complexes with Me3N. The lowering of rotational barriers occurs in parallel to the decrease in D
π(Si=C) we have established earlier for free silenes. On the average, the D
π(Si=C) energy decreases by ∼25 kcal mol−1 for NH3· R2Si=CH2 and Me3N·R2Si=CH2. The D(Si←N) values for the R2Si=CH2· 2Me3N complexes are 11.4 (R = H) and 24.3 kcal mol−1 (R = F). sp2-Hybridized silicon atom can form transannular coordination bonds in 1,1-bis[N-(dimethylamino)acetimidato]silene (6). The open form (I) of molecule 6 is 35.1 and 43.5 kcal mol−1 less stable than the cyclic (II, one transannular Si←N bond) and bicyclic (III, two transannular Si←N bonds) forms of this molecule, respectively. The D(Si←N) energy for structure III was estimated at 21.8 kcal mol−1.
Dedicated to Academician N. S. Zefirov on the occasion of his 70th birthday.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1952–1961, September, 2005. 相似文献
14.
E. Makrlík P. Vaňura P. Selucký V. A. Babain I. V. Smirnov 《Journal of Radioanalytical and Nuclear Chemistry》2009,279(3):743-747
Extraction of microamounts of europium and americium by a nitrobenzene solution of hydrogen dicarbollylcobaltate (H+B−) in the presence of N,N,N′,N′-tetraethyl-2,6-dipicolinamide (TEtDPA, L) has been investigated. The equilibrium data have
been explained assuming that the cations HL+, HL23+, ML23+ and ML33+ (M3+ = Eu3+, Am3+) are extracted into the organic phase. The values of extraction and stability constants of the species in nitrobenzene saturated
with water have been determined. It has been found that the stability constants of the corresponding complexes EuL
n,org3+ and AmL
n,org3+, where n = 2, 3 and L is TEtDPA, in the mentioned medium are comparable. 相似文献
15.
The development of an accurate aqueous thermodynamic model is described for oxalate species in the Na—Ba—Ca—Mn—Sr—Cl—NO3—PO4—SO4—H2O system at 25 °C. The model is valid to high ionic strength (as high as 10 mol·kg−1) and from very acid (10 mol·kg−1 H2SO4) to neutral and basic conditions. The model is based upon the equations of Pitzer and co-workers. The necessary ion-interaction
parameters are determined by comparison with experimental data taken from the literature or determined in this study. The
proposed aqueous activity and solubility model is valid for a range of applications from interpretation of studies on mineral
dissolution at circumneutral pH to the dissolution of high-level waste tank sludges under acidic conditions. 相似文献
16.
P. Rajec V. Švec V. Mikulaj R. Hanzel 《Journal of Radioanalytical and Nuclear Chemistry》1998,229(1-2):9-12
Lead as well as strontium form low solubility compounds of composition (ML2)2A·nH2O, (M=Pb2+, Sr2+), in the presence of 15-crown-5 (L) and tungstosilicic acid (H4A) in acid media as found by radiometric precipitation titration. “Sandwich” structure of crown-ether complexes of lead and
strontium could be expected due to the small size of cavity of 15-crown-5. Coprecipitation of PbL2/su2+ with crown complexes of strontium cation after adding tungstosilicic acid was studied in 0.01 mol·dm−3 HNO3. A significant influence of H+ cation in 1 mol·dm−3 HNO3 on coprecipitation of lead was observed. Formation of HL+ complexes by protonisation of 15-crown-5 competes to the formation of ML2
2+ complexes (approximately twenty percent of 15-crown-5 are used for creation of HL+ complexes). Formation of low solubility salts was utilised for separation of lead from strontium in 0.01 mol·dm−3 HNO3. The ratio of constant stability of lead and strontium β‘ with 15-crown-5 in 0.01 mol·dm−3 HNO3 was calculated. The separation factor S(Pb/Sr) depends on the ratio of stability constants βPbL2/βSrL2 The precipitation method can be used for separation of metals with high constant stability with crown ethers from solutions
containing other metals in the case of gradual addition of crown. 相似文献
17.
Qian Huang Wei-qiang Chen Xing Chen Xiao-bin Liu Jia-rong Zhou Hong-rong Zuo Lin-liang Yu Chun-lin Ni 《Transition Metal Chemistry》2009,34(7):765-771
Two new hybrid organic–inorganic salts, [BzDMAP]2[Cu(mnt)2](1) and [NO2BzDMAP]2[Cu(mnt)2] (2) ([BzDMAP]+ = 1-benzyl-4′-dimethylaminopyridinium, [NO2BzDMAP]+ = 1-(4′-nitrobenzyl)-4′-dimethylaminopyridinium, and mnt2− = maleonitriledithiolate) have been characterized structurally and magnetically. The [BzDMAP]+ or [NO2BzDMAP]+ cations (C) and the [Cu(mnt)2]2− anions (A) in 1 and 2 stack into a 1D alternating CC-A-CC-A-CC column. The Cu···N, π···π, C–H···N, C–H···O, and C–H···S weak interactions play
important roles in the molecular stacking and generate a 2D or 3D structure of 1 and 2. The magnetic susceptibilities of these salts measured in the temperature range 2.0–300 K show weak antiferromagnetic coupling
features with θ = −2.370 K for 1 and −0.222 K for 2. 相似文献
18.
Yong Hou Jiarong Zhou Xiaoping Liu Linliang Yu Chunlin Ni 《Transition Metal Chemistry》2008,33(4):411-416
Two new salts, [oClBzTPP]2+[Ni(mnt)2]2−(1) and [oClBzTPP]+[Ni(mnt)2]−(2) ([oClBzTPP]+ = 1-(2′-chlorobenzyl)triphenylphosphonium and mnt2− = maleonitriledithiolate) have been prepared and characterized by elemental analyses, UV, IR, MS spectra, single crystal
X-ray diffraction, and magnetic susceptibility. The Ni ions of the Ni(mnt)2 anions for 1 and 2 exhibit the square-planar coordination geometry. The Ni(III) ions of 2 form a 1D zigzag alternating magnetic chain within a Ni(mnt)2− column through Ni···S, S···S, or Ni···Ni interactions. The C–H···N, C–H···S, C–H···π hydrogen bonds or π···π stacking interactions
play important roles in the molecular stabilizing and stacking of 1 and 2. Magnetic susceptibility measurements in the temperature range 1.8−300 K show that 2 exhibits diamagnetic behavior. 相似文献
19.
Piotr Filipiak Gordon L. Hug Krzysztof Bobrowski Marek Pietrzak Jerzy Paczkowski Bronislaw Marciniak 《Research on Chemical Intermediates》2009,35(4):389-399
Pulse radiolysis of acetonitrile solutions of tetra-n-butyl ammonium salts of 2- and 4-carboxybenzophenones [BP-COO−···N+(C4H9)4] were performed in order to generate directly the reduced forms of the benzophenone moieties within pre-formed ion pairs.
In earlier studies on photochemical electron transfer reactions, ion pairs containing a tetraalkyl ammonium cation and a benzophenone
radical anion were formed in an electron transfer to the triplet BP from a quencher consisting of a tetraalkyl ammonium salt
of (phenylthio)acetic acid. In the current work, the [BP•−COO−···N+(C4H9)4] ion pairs were formed by direct reduction of the salts without the complication of a third moiety, i.e., the (phenylthio)acetic
anion. The spectra and kinetic parameters of the radiolytically-reduced salts were compared to the behavior of reduced forms
of the 2- and 4-COOH substituted benzophenones. The results from the pulse radiolysis and photochemistry were compared and
explained in terms of the different structures of the ion pairs. 相似文献
20.
G. A. Domrachev Yu. A. Shevelev V. K. Cherkasov G. K. Fukin G. V. Markin A. I. Kirillov 《Russian Chemical Bulletin》2006,55(2):225-229
The [60]fulleride of bis(η-hexamethylbenzene)chromium(I) [(η6-C6Me6)2Cr]⋅+[C60]⋅−, and the complexes C60·C6Me6 and C60·C6Et6 were synthesized. Thermal decomposition of [(η6-C6Me6)2Cr]⋅+[C60]⋅− was studied. The molecular structures of C60·C6Me6 and C60·C6Et6 were determined.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 220—224, February, 2006. 相似文献