Research of thermodynamic and kinetics in preparing U(IV) by reducing and catalyzing U(VI) with hydrazine

Abstract

The effect of concentration of U(VI), hydrazine, nitric acid and the amount of catalyst, and the thermodynamics and kinetics of the reaction in preparing U(IV) by catalyzing and reducing U(VI) are studied in catalytic reduction of U(VI) with hydrazine as reductant and Pt as catalyst. The comparison of calculated theoretical reaction heat value and practical value is also given. The result shows that with the increase of density of U(VI) and hydrazine, increase of amount of catalyst and decrease of nitric acid, reaction rate slows down. The reaction kinetic rate equation is as follow: −d (UO 2 2+ )/d = 1.11 (UO 2 2+ ) 1.42 (N 2 H 5 + ) −0.72 (H + ), and the reaction rate constant is 1.3 × 10 −3 (mol/L) −0.81 /min when S/L is 0.008 kg/L at 50 ∘ C. The theoretical reaction equation of unit volume is as follows: = Δ f m,1 + Δ f m,2 [ (N 2 H 4 ) − (UO 2 2+ ) /2 − ]/3. The comparison shows the coincidence in 1 h of theoretical value and practical value.

Optimization of Process Variables for the Catalytic Reduction of U(VI) over Pt/SiO2 using Hydrazine as Reducing Agent – Design of Experiments Approach

“…It was reported that formic acid reduced U(VI) to U(IV) much faster than hydrazine. Xia et al .reported kinetic and thermodynamics of U(VI) reduction with N 2 H 4 over platinum black catalyst material [28] . In this study Xia et al .…”

“…The rate of U(VI) reduction by hydrazine over Pt/SiO 2 can be described by the reaction shown in equation 9. [28] …”

“…Previously we studied the reduction behavior of U(VI) as a function of temperature. [28,32] It was reported that the rate of U(VI) reduction increased with increase of temperature in the lower temperature region followed by a marginal variation in the kinetics of reduction at higher temperature. The apparent activation energy of 66 kJ.mol À 1 was reported at lower temperature region (313 to 343 K), and 20 kJ.mol À 1 was obtained in higher temperature region.…”

“…Xia et alreported kinetic and thermodynamics of U(VI) reduction with N 2 H 4 over platinum black catalyst material. [28] In this study Xia et al derived the rate expression using power law model and reported the heat of the reaction at various temperatures. Sahoo et alstudied the reduction of U(VI) using H 2 as a reducing agent over Pt/Al 2 O 3 and Pt/SiO 2 catalyst materials and reported that the platinum leaches from alumina support over a period of time.…”

Recent Advance in Ionic‐Liquid‐Based Electrolytes for Rechargeable Metal‐Ion Batteries

“…Their electrochemical characteristics can be modulated through changing the combinations of anions and cations without upsetting the balance. [ 20,21 ] They are widely considered as one of the most promising green solvents [ 22,23 ] for various applications such as catalysis, [ 24,25 ] separation science, [ 26–28 ] synthesis (or reaction medium), [ 29–34 ] electrochemistry, [ 35–37 ] and energy storage. [ 38–42 ] The wide liquid phase range, high heat resistance, low vapor pressure, wide electrochemical windows, and high ionic conductivity make them highly desirable as electrolytes in various battery systems (i.e., LIBs, sodium‐ion batteries (SIBs), potassium‐ion batteries (PIBs), magnesium‐ion batteries (MIBs), zinc‐ion batteries (ZIBs), aluminum‐ion batteries (AIBs), metal–air, [ 43–45 ] metal–sulfur, [ 46–49 ] and metal–oxygen [ 50 ] ).…”