Bahri M A, Ruas A, Labbé E, Moisy P
CEA, Nuclear Energy Division, Radiochemistry and Processes Department, F-30207 Bagnols sur Cèze, France.
Dalton Trans. 2017 Apr 11;46(15):4943-4949. doi: 10.1039/c6dt04765c.
This work investigates the electrochemical behavior of Pu(iv) and Pu(vi) complexes in n-tributylphosphate (TBP) as an entry to the electrochemical characterization of these complexes in organic extractants related to nuclear fuel reprocessing. Glassy carbon electrodes were used to show that Pu(iv) and Pu(vi) complexes display a reversible electrochemical reduction wave in TBP previously equilibrated with aqueous nitric acid solution. We investigated the reduction of Pu(iv) and Pu(vi) nitrato complexes extracted into TBP, with the aim to get thermodynamic (formal potential) and kinetic (diffusion coefficient) information about Pu(iv)/Pu(iii) and Pu(vi)/Pu(v) redox couples in the TBP medium. The formal potentials of the two redox couples were respectively 0.510 ± 0.005 and 0.478 ± 0.005 V per SCE in TBP equilibrated with 3 mol L nitric acid at room temperature. The diffusion coefficient values of Pu(iv) and Pu(vi) species were estimated to be 0.72 × 10 and 0.77 × 10 cm s respectively. Also, the Pu(iv) reduction showed a Nernstian dependence on the logarithm of nitric acid concentration in the organic phase, featuring the exchange of nitrates upon reduction of Pu(iv).
这项工作研究了正三丁基磷酸酯（TBP）中Pu（IV）和Pu（VI）配合物的电化学行为，以此作为对与核燃料后处理相关的有机萃取剂中这些配合物进行电化学表征的切入点。使用玻碳电极表明，Pu（IV）和Pu（VI）配合物在先前与硝酸水溶液平衡的TBP中显示出可逆的电化学还原波。我们研究了萃取到TBP中的Pu（IV）和Pu（VI）硝酸根配合物的还原反应，目的是获取有关TBP介质中Pu（IV）/Pu（III）和Pu（VI）/Pu（V）氧化还原对的热力学（形式电位）和动力学（扩散系数）信息。在室温下，与3 mol/L硝酸平衡的TBP中，这两个氧化还原对的形式电位分别为相对于标准甘汞电极0.510±0.005和0.478±0.005 V。Pu（IV）和Pu（VI）物种的扩散系数值估计分别为0.72×10和0.77×10 cm²/s。此外，Pu（IV）的还原显示出对有机相中硝酸浓度对数的能斯特依赖性，其特征是Pu（IV）还原时硝酸盐的交换。
