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

Abstract

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: − dC(UO2 2+)/dt = kC 1.11(UO2 2+)C 1.42(N2H5 +)C −0.72(H+), and the reaction rate constant is 1.3 · 10 –3 (mol/L) –0.81/min when r S/L is 0.008 kg/L at 50 ℃. The theoretical reaction equation of unit volume is as follows: Q = aΔ f H m,1 Θ  + Δ f H m,2 Θ [C(N2H4) − C(UO2 2+)a/2 − β]/3. The comparison shows the coincidence in 1 h of theoretical value and practical value.