N,N-二甲基甲酰胺中铀(V)吸收光谱的研究

以中压汞灯为光源，采用吸收光谱法，观察了UO2（NO3）2•6H2O在DMF（N，N－二甲基甲酰胺）溶剂中光化还原时的吸收光谱随照射时间、铀浓度及溶液酸度的变化．经短时间光照后，在UO2（NO3）2－DMF溶液中有铀（Ⅴ）形成，其吸收峰在755和635nm处．结果表明，它们分别是UO2+－DMF和UOOH2＋－DMF的特征吸收，溶液中铀（Ⅴ）的岐化反应与H＋浓度密切相关，UOOH2＋是岐化反应的中间体．

Absorption Spectra of Uranium(V) Species in N,N-dimethylformamide

The absorption spectra of U(Ⅴ ) species in N, N-dimethylformamide (DMF) with a mercury lamp irradiation have been examined in the region of 500-800nm. In addition to the absorption of U(Ⅴ ) at 755nm a new absorption band at 635nm has been observed. When the solution was acidified with nitric acid both bands of U(Ⅳ)-DMF at 550 and 657nm appeared. These results indicate that the new band at 635nm as well as the 755nm band also belongs to U(Ⅴ ) species. When the irradiated solution was kept in the darkness both bands vanished and no absorption other that of U(Ⅳ) was observed, witch implies that a reversible process between U(Ⅳ) and U(Ⅴ) occurred. The relative intensities of the two bands depend on the acidity of the solution. While the acidity is lower than 9.0×10-3mol.dm-3, the absorption at 635nm increases with increasing the acidity, while that of the 755nm band decreases. When acidity reaches 9.0×10-3mol.dm-3 the absorption at 755nm band almost disappears, but that of the 635nm band still exists and U(Ⅳ) is formed. These results indicate that the absorption of U(Ⅴ) at 755nm and 635nm belong to two different U(Ⅴ) species, UO2+－DMF and UOOH2＋－DMF, respectively.