双二苷酰胺从硝酸溶液中萃取Eu(Ⅲ)和Am(Ⅲ)

采用混合酸酐法合成了两种双二苷酰胺(bisdiglycolamide, BisDGA)萃取剂: N,N,N',N'-四正辛基-N',N″-乙二基-双二苷酰胺(TOE-BisDGA)和N,N,N',N'-四正辛基-N',N″-间苯二甲基-双二苷酰胺(TOX-BisDGA). 以磺化煤油和正辛醇混合溶液(体积比 90∶10)作稀释剂, 研究了它们在硝酸溶液中对Eu(Ⅲ)和Am(Ⅲ), 以及自身对HNO₃的萃取行为. 结果表明, 2种BisDGAs对HNO₃均有一定萃取, 当酸度不超过1.0 mol/L时, 二者形成1∶1型的萃合物. 随HNO₃浓度增加, Eu(Ⅲ)和Am(Ⅲ)的萃取分配比增加. 相同条件下, TOE-BisDGA对Eu(Ⅲ)和Am(Ⅲ)的萃取能力强于TOX-BisDGA. 斜率分析表明TOE-BisDGA和TOX-BisDGA与Eu(Ⅲ)和Am(Ⅲ)均形成2∶1型的萃合物. 温度升高, 萃取分配比下降, 萃取反应是放热反应. 2种BisDGAs对Eu(Ⅲ)的亲和力强于对Am(Ⅲ)的亲合力, 表明BisDGAs对Eu(Ⅲ)有一定的选择性. 同时, 研究了BisDGAs萃取Eu(Ⅲ)和Am(Ⅲ)的机理, 给出了表观萃取平衡常数和萃取反应热力学函数ΔH, ΔS和ΔG的值. 此外, 还对TOE-BisDGA和TOX-BisDGA与Eu(Ⅲ)形成的配合物进行了红外和紫外光谱分析.

Extraction of Eu(Ⅲ) and Am(Ⅲ) from Nitric Acid Solution with Bisdiglycolamides†

Two bisdiglycolamides, N,N,N',N'-tetraoctyl-N',N″- ethanediyl bisdiglycolamide(TOE-BisDGA) and N,N,N',N'-tetraoctyl-N',N″-m-xylylene bisdiglycolamide(TOX-BisDGA), were synthesized by a mixed anhydrides method. Their extraction behaviors of Eu(Ⅲ) and Am(Ⅲ), as well as the extraction of nitric acid were investigated from nitric acid solution using kerosene/n-octanol(volume ratio 90∶10) as diluent. Nitric acid was extracted as the form of HNO₃·BisDGAs by BisDGAs at less than 1.0 mol/L HNO₃. The distribution ratios of Eu(Ⅲ) and Am(Ⅲ) increased with the increase of nitric acid concentration. TOE-BisDGA had a stronger extraction power for Eu(Ⅲ) and Am(Ⅲ) than TOX-BisDGA. Slope analyses showed that Eu(Ⅲ) and Am(Ⅲ) were extracted as di-solvated species by BisDGAs. The distribution ratios of Eu(Ⅲ) and Am(Ⅲ) decreased with temperature rise, which suggested that the extraction reaction of Eu(Ⅲ) and Am(Ⅲ) is exothermic. The two BisDGAs displayed a higher affinity toward Eu(Ⅲ) than Am(Ⅲ). In the mean time, the extraction mechanism was described and the apparent extraction equilibrium constant as well as Gibbs free energy change, enthalpy change and entropy change were presented. In addition, their Eu(Ⅲ) complexes were analyzed by IR and UV spectra.