Kinetics of Reaction Between Np(Ⅵ) and Hydroxysemicarbazide in Nitric Acid Solution
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Graphical Abstract
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Abstract
The effects of c(HSC), c(H+), c(Fe3+), c(UO2+2), ionic strength and temperature on the reduction rate of Np(Ⅵ) by hydroxysemicarbazide (HSC) were investigated. The results show that Np(Ⅵ) can be rapidly reduced to Np(Ⅴ) by HSC. The reaction rate of Np(Ⅵ) with HSC can be accelerated by increasing concentration of HSC and temperature,decreasing concentration of HNO3 and ionic strength. The kinetic equation for the reduction of Np(Ⅵ) by hydroxysemicarbazide is: -dc(Np(Ⅵ))/dt=kc(Np(Ⅵ))c2.52(HSC)c-0.53(H+)•c-0.61(NO-3) where k=(1037±60) (mol/L)-1.40•s-1 at 400 ℃. The activation energy is Ea=(64.03±6.4) kJ/mol. No significant effect on the reduction of Np(Ⅵ) by hydroxysemicarbazide is observed when the concentration of Fe3+ is less than 1 × 10-3 mol/L or in the presence of UO2+2.
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