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211.
The interaction of UO
2
2+
ions with orthosilicic acid Si(OH)4 and polymeric silicic acids (PSAs) was studied spectrophotometrically. The equilibrium constant of the reaction UO
2
2+
+ Si(OH)4 = UO2OSi(OH)
3
+
+ H+ in solutions with the ionic strength I = 0.1–0.2 is log K = −2.56±0.09 (log K
0 = −2.29±0.09 recalculated to I = 0); the stability constant of the complex UO2OSi(OH)
3
+
(I = 0) is log β0 = 7.52±0.09. Formation of small oligomers (degree of polymerization n ≤ 4) has virtually no effect on the apparent constant K. When high polymers are formed (n > 100), the apparent equilibrium constant decreases by a factor of 2–3, and the “true” equilibrium constant recalculated to the actual concentration of silanol groups increases by a factor of 3–4. The absorption spectrum of the complex UO2OSi(OH)
3
+
was obtained by treatment of the experimental spectra; it has an absorption maximum in the visible range at 422.5 nm, ɛ422.5 = 35±2 l mol−1 cm− 1. At pH higher than 5–6, complexes of UO
2
2+
with PSAs of the composition UO2(≡SiO)2(≡ SiOH)
m − 2 are formed. The absorption spectrum of such a complex was obtained.__________Translated from Radiokhimiya, Vol. 47, No. 4, 2005, pp. 315–321.Original Russian Text Copyright © 2005 by Yusov, Fedoseev. 相似文献
212.
Radiochemistry - Spectroscopic method was used to examine the stoichiometry of the reaction of No(VI) with hexamethylenediaminetetraacetic acid (HMDTA, H4hmdta) in a 0.05 M HClO4 solution. At an... 相似文献
213.
Stoichiometry of the reaction of Np(VI) with N(CH2COOH)3 (NTA) in a 0.05 M HClO4 solution was studied by spectrophotometry. With excess Np(VI), 1 mol of NTA reduces 2 mol of Np(VI) to Np(V). In 0.05–0.98 M HClO4 solutions (the ionic strength I = 1.0 was maintained by adding LiClO4) containing 5–30 mmol of NTA, at 25–45°С Np(VI) at a concentration of 0.3–2 mM is consumed in accordance with a firstorder rate law until less than 1/3 of Np(VI) remains in the solution. After that, the reaction decelerates. The reaction is first-order with respect to NTA and has an order of–2 with respect to Н+ ions. The activated complex is formed with the loss of two Н+ ions. The activation energy of the reaction is 100 ± 2 kJ mol–1. 相似文献
214.
The stoichiometry of the reaction Np(VI) + H3hedta [hedta is N-(2-hydroxyethyl)ethylenediaminetriacetate, HEDTA, anion] in a 0.05 M HClO4 solution was studied by spectrophotometry. With Np(VI) in excess, 1 mol of HEDTA reduces 4 mol of Np(VI) to Np(V). In 0.125–1.0 M HClO4 solutions (the ionic strength of 1.0 was maintained constant by adding LiClO4), containing 3–29.2 mM HEDTA, at 20–45°С Np(VI) at a concentration of 0.4–3.5 mM is consumed in accordance with a first-order rate law until approximately 40% of Np(VI) remains. Then, the reaction decelerates. The reaction rate has first order with respect to [HEDTA] and the order of–1.6 with respect to [Н+]. The activated complex arises with the loss of one and two Н+ ions. The activation energy is 88.4 ± 5.3 kJ mol–1. 相似文献
215.
Reaction of Np(VI) with cyclohexanediaminetetraacetic acid in HClO<Subscript>4</Subscript> solutions
The stoichiometry of the reaction of Np(VI) with cis-cyclohexanediaminetetraacetic acid (CHDTA, H4chdta) in 0.05 M HClO4 solution was studied by spectrophotometry. With Np(VI) in excess, 1 mol of the complexone converts 4 mol of Np(VI) into Np(V). In 0.115–0.98 M HClO4 solutions (the ionic strength of 1.0 was supported with LiClO4) containing 3–29 mM CHDTA at 20–45°С, Np(VI) at a concentration of 0.2–3.3 mM is consumed in accordance with the first-order rate law until less than 40% of Np(VI) remains. After that, the reaction decelerates. The reaction rate has first order with respect to [CHDTA] and the order of–1.2 with respect to [H+]. The activated complex is formed with the loss of one and two Н+ ions. The activation energy is 82.3 ± 3.8 kJ mol–1. 相似文献
216.
Radiochemistry - Three new Np(VI) complexes with cyclobutanecarboxylic acid anions and single-charged outer-sphere anions: ammonium, [NH4][NpO2(cbc)3] (I), guanidinium, [C(NH2)3][NpO2(cbc)3] (II),... 相似文献
217.
M. P. Parkhomenko D. S. Kalenov N. A. Fedoseev I. S. Eremin V. M. Kolesnikova D. A. Kovtykov 《Journal of Communications Technology and Electronics》2017,62(7):759-764
An improved resonator method for determination of the complex permittivity of materials in a reflective resonator is presented. The method is specific in the following. In the obtained relationship, imaginary part ε2 of the permittivity of an investigated material is determined using the variation of the resonance frequency and coupling coefficient of the resonator observed when a specimen is introduced, which increases the measurement accuracy. The method is approbated in the investigations of high-resistance silicon specimens. 相似文献
218.
A. N. Turanov V. K. Karandashev A. N. Yarkevich Z. V. Safronova N. I. Rodygina A. M. Fedoseev 《Radiochemistry》2007,49(6):618-623
Extraction of microamounts of U(VI), Th(IV), Pu(IV), and Am(III) nitrates from aqueous HNO3 solutions with solutions of (diphenylphosphinylmethyl)phenylphosphinic, (di-p-tolylphosphinylmethyl)phenylphosphinic, and (dioctylphosphinylmethyl)phosphinic acids and of butyl hydrogen (diphenylphosphinylmethyl)phosphonate in organic diluents was studied. The metal: extractant stoichiometric ratio in the extractable complexes was determined, and the diluent effect on the extraction efficiency was examined. The possibility of using a macroporous polymeric sorbent impregnated with (dioctylphosphinylmethyl)phenylphosphinic acid for concentrating metal ions from HNO3 solutions was demonstrated. 相似文献
219.
The effect of experimental conditions on UVL2 (1–2 mM) disproportionation was studied spectrophotometrically through the UIVL2 accumulation (L = P2W17O 61 10? ). In 1 M NaNO3 solution containing 0.01 M HAc and 0.01 M NaAc, the rate of UVL2 disappearance is described by the equation V = k 1[UVL2]. The k 1 value is almost constant with pH decreasing from 4.5 to 1.7, but increases with increasing acetate concentration; the presence of 1 mM UIVL2, U(VI), or L does not affect k 1. In the solutions of 0.1–1.0 M HClO4 (ionic strength 1), the reaction rate is described by the equation V = 2k 2[H+]2.5[UVL2]2. Probable disproportionation mechanism is discussed. The first stage is substitution of L by water molecules in the UIVL2 complex and appearance of the reactive U(V) complex with mixed coordination sphere. 相似文献
220.
A. V. Gogolev V. P. Shilov V. F. Peretrukhin A. B. Yusov A. M. Fedoseev 《Radiochemistry》2008,50(4):349-353
containing U(IV) polymer start to form. With an increase in pH from 1.5 to 4 or in temperature, the induction period becomes shorter. Under anaerobic conditions, the colloidal solution is stable for more than a month. Centrifugation at 8000 rpm (5500g) allows separation of the colloidal particles from the liquid phase. The colloid slowly dissolves in mineral acids saturated with argon or in a K2CO3 solution, whereas precipitates of individual freshly prepared U(IV) and U(VI) hydroxides dissolve rapidly. Short UV irradia-of a UO2(ClO4)2 solution saturated with argon and containing ethanol (pH 2.5) results in the appearance of U(V) which then disproportionates, and U(IV) forms with U(VI) a black colloid similar to that arising on mixing U(IV) and U(VI) solutions. 相似文献