甲醛肟与Pu(Ⅳ)的还原动力学

Kinetics of Reaction Between Pu(Ⅳ) and Formoxime in Nitric Acid Solution

摘要: 研究了甲醛肟(FO)与Pu(Ⅳ)的还原反应动力学，其动力学方程式为-dc(Pu(Ⅳ))/dt ＝ kc(Pu(Ⅳ))c^1.61(FO)c^-0.88(H⁺)，在18.7 ℃时，反应速率常数k＝(110.39±7.70) (mol/L)^-0.73/s，活化能为(68.82±3.00) kJ/mol。研究了甲醛肟浓度、H⁺浓度、硝酸根浓度、Fe³⁺浓度、UO₂²⁺浓度以及温度对甲醛肟与Pu(Ⅳ)还原反应速率的影响。结果表明：增加甲醛肟浓度、降低UO₂²⁺和H⁺浓度、增加Fe³⁺浓度以及升高温度，均使Pu(Ⅳ)还原速度增加；硝酸根浓度对甲醛肟还原Pu(Ⅳ)的速率基本无影响。

Abstract: The kinetics of reaction between Pu(Ⅳ) and formoxime (FO) in nitric acid solution was determined. The rate equation is found to be -dc(Pu(Ⅳ))/dt ＝ kc(Pu(Ⅳ))c^1.61(FO)c^-0.88(H⁺) where k ＝(110.39±7.70) (mol/L)^-0.73/s at 18.7 ℃. The activation energy is found to be E_a＝ (68.82±3.00) kJ/mol. Effects of c(FO), c(H⁺), c(Fe³⁺),c(UO₂²⁺), c(NO₃^-) and temperature on reduction rate of Pu(Ⅳ) were investigated. Pu(Ⅳ) can be rapidly reduced to Pu(Ⅲ) by FO under normal conditions. The reaction rate can be accelerated by increasing concentration of formoxime, decreasing concentration of UO₂²⁺ and H⁺, increasing concentration of Fe³⁺ and rising temperature. The influence of NO₃^- on reaction rate is negligible.