N,N'-二(2-乙基己基)二甘酰胺酸对Dy(Ⅲ)的萃取

Extraction of Dy(Ⅲ) With N,N'-di(2-Ethylhexyl)-Diglycolamic Acid From Nitric Acid

以正十二烷作为稀释剂,研究了N,N'-二(2-乙基己基)二甘酰胺酸(HDEHDGA,简称HL)萃取剂对硝酸介质中Dy(Ⅲ)离子的萃取性能。结果表明:该萃取剂对Dy(Ⅲ)有良好的萃取性能,在硝酸浓度为0.3~4.0mol/L时,Dy(Ⅲ)的分配比(D(Dy))随水溶液中平衡酸度的增加先减小后增大,在HNO_3浓度大约为1.0mol/L时,分配比最小。萃取分配比随水相硝酸浓度变化的关系表明,HDEHDGA萃取Dy(Ⅲ)的机理随硝酸浓度变化而不同。从3.0mol/L HNO_3中萃取Dy(Ⅲ)的分配比与萃取剂浓度及硝酸根浓度的关系表明,萃取过程中HDEHDGA主要以中性萃取剂形式与Dy(Ⅲ)配位,萃取反应方程式可能为:Dy(Ⅲ)+2HL+3NO_3^-=Dy(Ⅲ))(HL)_2(NO_3)_3该反应为放热反应,反应的热焓为-63.38kJ/mol,降低萃取温度有利于HDEHDGA对Dy(Ⅲ)的萃取。

The extraction of Dy（Ⅲ） from nitric acid medium by using N,N＇-di（2-ethylhexyl）- diglycolamic acid （HDEHDGA, HL） in n-dodecane was studied. The results show that HDEHDGA extractant has good capability for the extraction Dy（Ⅲ） from nitric acid Solution. In the range of 0.3-4.0 mol/L HNO3, at first, the distribution ratio, D（Dy）, decreases and reaches the minimum at 1.0 mol/L HNO3, then increases with the increase of the acid concentration, indicating that the extraction mechanism varies with the concentration of nitric acid in aqueous phase. With 3.0 mol/L nitric acid as aqueous phase, the HDEHDGA molecules mainly coordinate to Dy（Ⅲ） as neutral extraction agent in the extracted complex, and the extraction equation is deduced from the dependency of D（Dy） on the concentrations of extractant in the organic phase and the concentrations of nitrate ion in the aqueous phase. The detailed extraction equation is as follows.Dy（Ⅲ）＋2HL＋3NO3--=Dy（Ⅲ））（HL）2（NO3）3 The extraction is an exothermic reaction, and the enthalpy is calculated to be --63.38 kJ/ mol with Van＇t Hoff equation, which shows that decreasing reaction temperature is good to the extraction of Dy（ Ⅲ ）.