Kinetics for Catalytic Reduction of U(Ⅵ) by Hydrazine on Platinum Black in Nitric Acid Media

The catalytic reaction kinetics of U(Ⅵ) with hydrazine on platinum black in nitric acid media was studied. By investigating the influence of U(Ⅵ) concentration, hydrazine concentration, acidity and catalyst amounts(r_S/L) on the reaction, the reaction rate equation is obtained: -dc(UO²⁺₂)dt=kc^0.44(UO²⁺₂)c^0.19(N₂H⁺₅)c^-0.23(H⁺), and the rate constant is 2.6×10^-3 (mol/L) 0.6/min at 60 ℃ and r_S/L=2.0 g/L. The effect of temperature was also investigated. The results show that the temperature accelerates the reaction and the reaction process changes from kinetics-controlled process to diffusion-controlled process. Comparing nitric acid with perchloric acid, it is found that the reaction rate in nitric acid is obviously lower than that of perchloric acid.