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decade [ 11 – 13 ]. The reduction of nitrate by Fe 0 poses many challenges when compared to other metal such as Mg 0 including the need for a high dose, the possibility of Fe 2+ entering the water, blocking of the reaction by Fe(OH) 3 precipitation

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Reaction Kinetics, Mechanisms and Catalysis
Authors:
Alexander Khassin
,
Georgiy Filonenko
,
Tatyana Minyukova
,
Irina Molina
,
Lyudmila Plyasova
,
Tatyana Larina
, and
Vladimir Anufrienko

and reactivity. The present study aims to compare the kinetics of Cu 2+ reduction from the mixed CuMg oxide samples, which differ by their anionic composition. Experimental The sample of mixed Cu 0.15 Mg 0.85 oxide was

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Abstract  

Valency control of neptunium is an important issue in the partitioning of high level liquid waste (HLLW) from power-reactor spent fuel treatment. The redox behavior of neptunium in HLLW is quite different from that in nitric acid because of the effect of the large amount of ions in HLLW. In order to remove neptunium from HLLW, we studied the reduction of neptunium in synthetic HLLW (SHLLW) to maintain its valency at IV so that it can be extracted by TRPO extractant in the well developed Chinese TRPO process. Five different reductants were tested and the reduction behavior was investigated. The influence of some active elements in SHLLW was studied. The mechanism that the reductants react with neptunium through Fe element was supposed and proved by experiments. The reduction rate of Np(V) was highly enhanced by Fe element. Finally, a hybrid reductant was suggested and good reduction efficiency was obtained.

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Abstract  

The results concerning the reduction of U(VI) adsorbed on anion exchange resin as uranyl chloro complexes and sulfate complexes with V(III) in HCl and H2SO4 solution are presented. The reduction of uranyl sulfate adsorbed on anion exchange resin (UO2SO4(R)) in 0.05 M sulfuric acid was carried out, the reaction rate being first order with respect to both concentrations: [U(VI)(R)] and [V(III)]. From Arrhenius plot the activation parameters of the reaction between U(VI)(R) and V(III) in sulfuric acid solution were determined: E a = 34.9 ± 0.9 kJ/mol; ΔΗ  = 35.5 ± 0.9 kJ/mol and ΔS  = −165.7 ± 3 J/K mol. The reduction reaction rate makes possible the utilization of this reaction for displacement of the uranium adsorption band in a 235U separation column packed with anion exchange resin.

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Abstract  

A commercial Pd/activated carbon catalyst (10%) was treated using several redox processes: reduction with gaseous hydrogen at 140 °C, reduction by negative electrochemical polarization in acidic and basic environments, oxidation with aqueous hydrogen peroxide, and positive electrochemical polarization in acidic and basic environments. To establish the electrochemical reduction/oxidation conditions, the potentials of hydrogen and oxygen evolution at Pd/AC powder electrodes were determined from cyclic voltammetric (CV) measurements. The samples were examined for the presence of palladium oxide phases on dispersed metal particles using XRD, TPR, and TPD. The metal oxide phase disappeared following hydrogen and electrochemical reduction. Oxidative treatment of the commercial catalyst differentiated the palladium oxide layers on the metal particle surface. Changes in the surface chemistry of the Pd/PdO/AC system were confirmed by the electrochemical behavior of electrodes prepared from the carbon samples.

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Abstract  

The structure changes and the degree of reduction of U3O8 after mechanoactivation in agate and stainless steel vessels in different media are studied. Clearly expressed reduction of U(IV, VI) oxide, accompanied by oxygen release as a result of mechanochemical activation is observed. The highest degree of reduction is reached when mechanoactivation is performed in suspension with nonpolar organic solvents. The presence of acetaldehyde as a reducing agent did not cause valuable increase of the reduction process. Quantitative evaluation of the mechanochemically induced changes in the crystal structure of U3O8 is done. Decrease of the crystallite sizes of both the U3O8 and the reduced form, provoked by the mechanochemical treatment is observed for all the samples. No other uranium-contained compounds, formed during the mechanoactivation in the different media and mixtures were found.

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Abstact  

Nitrous acid is a key redox controlling factor, affecting the speciation of neptunium in the reprocessing of used nuclear fuel by solvent extraction. The kinetics of the reduction of neptunium(VI) by nitrous acid in solutions of nitric acid was investigated spectrophotometrically by the method of initial rates. The reaction is of first order with respect to Np(VI) while the order with respect to HNO2 is 1.20 ± 0.04. The reaction rate is almost inversely proportional to the hydrogen ion concentration (reaction order −0.92 ± 0.06), indicating that the reaction proceeds primarily through the reaction of neptunium(VI) with the nitrate anion. The experimental value of the rate constant k for the rate law −d[Np(VI)]/dt = k·[Np(VI)]·[HNO2]1.2/[H+] is of (0.159 ± 0.014) M−0.2 s−1 in I = 4 M and at 20 °C. The activation energy is (−57.3 ± 1.6) kJ/mol, which is in agreement with previous data on this reaction in perchloric acid.

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Journal of Thermal Analysis and Calorimetry
Authors:
J. Maul
,
A. S. Brito
,
A. L. M. de Oliveira
,
S. J. G. Lima
,
M. A. M. A. Maurera
,
D. Keyson
,
A. G. Souza
, and
I. M. G. Santos

indicating that organic compounds are still present on the material surface. A mass gain between the temperatures of 550 and 620 °C was also observed for all samples. This gain was attributed to the oxidation of the Cu(I) which indicated that a reduction

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Abstract  

A mode is an idempotent and entropic algebra. We show that each variety Rm of m-step left reductive Ω-modes is the Mal'cev product (relative to modes) of Rkand Rm-k. The dual result holds for varieties R n 1 of n-step right reductive Ω-modes. The main result says that the join Rm V R n 1 is independent and coincides with the Mal'cev product Rm ∘ R n 1 . We also give an equational characterization of this variety, and discuss the structure of such modes.

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Indian way of life and vision of the world, life in the reductions and a response to the critics . This last article is a transcript and French translation of the last seven chapters (6 to 12) of Book 3 of the Latin manuscript by the Jesuit F. X. Eder on the missions or reductions in the Amerindian nations of the Moxos and Baures. It is the continuation of the first eight articles on the Jesuit missions in the now Bolivian Amazon basin in the 18th century , entitled:

  1. 1. Lima, Peru, and their inhabitants in the 18th century.
  2. 2. Jesuit missions in the now Bolivian Amazon basin in the 18th century.
  3. 3. Quality of the soil and description of the Indians.
  4. 4. Constructive works, beliefs and superstitions of the Indians, and how to convince them to join a reduction.
  5. 5. Trees, fruits, plants and mammals.
  6. 6. Birds, hunting, crocodiles, dolphins, fishes and fishing.
  7. 7 Fauna (last part), poisons and antidote, arms used by Indians for hunting and fishing.
  8. 8. Choice of a spouse, feasts and games, meals, food and drink, handicraft and arts.

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