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用分光光度法研究了ＨＮＯ３介质中ｃ（ＨＯＣ２Ｈ４Ｎ２Ｈ３）、ｃ（Ｈ＋）、ｃ（ＵＯ２＋２）、ｃ（Ｆｅ３＋）、ｃ（ＨＮＯ２）、离子强度和温度等因素对还原Ｎｐ（Ⅵ）反应速率的影响。测定了不同条件下的表观速率常数，确定了Ｎｐ（Ⅵ）还原反应速率方程式。２５℃时，还原反应的表观速率常数ｋ２＝３９１ｍｉｎ－１；反应活化能为５６．６ｋＪ·ｍｏｌ－１。提高２－羟基乙基肼浓度、降低ＨＮＯ３浓度或升高温度，Ｎｐ（Ⅵ）的还原加快；增加ＵＯ２＋２浓度和离子强度，还原速率稍有降低；当ｃ（Ｆｅ３＋）≥１．０ｍｍｏｌ·Ｌ－１时，Ｆｅ３＋对Ｎｐ（Ⅵ）的还原有一定的加速作用。
The effect of c (HOC2H4N2H3), c (H +), c (UO2 + 2), c (Fe3 +) and c (HNO2), ionic strength and temperature on the reaction rate of Np (Ⅵ) reduction in HNO3 media was studied by spectrophotometry . The apparent rate constants under different conditions were determined, and the equation of reduction rate of Np (Ⅵ) was established. At 25 ℃, the apparent rate constant k2 = 391min-1 for the reduction reaction and the activation energy for the reaction was 56.6kJ · mol-1. When the concentration of 2-hydroxyethylhydrazine, the concentration of HNO3 or the temperature was increased, the reduction of Np (Ⅵ) accelerated; the concentration of UO2 + 2 and the ionic strength decreased slightly, while the reduction rate of c (Fe3 +) ≥1.0mmol·L- 1, Fe3 + accelerated the reduction of Np (Ⅵ) to a certain extent.