Me-TODGA与TODGA萃取锶性能对比

以N,N,N′,N′-四辛基-2-甲基-3-氧戊二酰胺(Me-TODGA)或N,N,N′,N′-四辛基-3-氧戊二酰胺(TODGA)为萃取剂、磷酸三丁酯(TBP)为相改良剂、煤油为稀释剂，对比研究了水相酸度、萃取剂浓度、锶浓度、温度对Me-TODGA-TBP体系和TODGA-TBP体系萃取Sr²⁺的影响，并采用斜率法确定了萃合物的组成。结果表明，2种酰胺荚醚萃取Sr²⁺的分配比(D_Sr)随HNO₃浓度(c(HNO₃)=0.1～2.7 mol/L)、萃取剂浓度(c(萃取剂)=0.05～0.3 mol/L)的增加而增大，随Sr²⁺浓度的升高略有下降，随温度的升高而下降。2种萃取剂的萃合物组成分别为Sr(NO₃)2?3Me-TODGA和Sr(NO₃)2?2TODGA。萃取反应的ΔH分别为-69.46 kJ/mol和-51.39 kJ/mol，ΔS分别为-190.5 J/(mol?K)和-128.4 J/(mol?K)，ΔG分别为-12.68 kJ/mol和-13.12 kJ/mol。相比之下，Me-TODGA萃取Sr²⁺的分配比不到TODGA的1/5。

Comparison of Extraction Ability of Me-TODGA and TODGA for Sr

The extraction of Sr²⁺ from aqueous nitric acid solutions with Me-TODGA (N,N,N′,N′-tetraoctyl-2-methyl-3-oxapentanediamide) was studied to compare with that of TODGA (N,N,N′,N′-tetraoctyl-3-oxapentanediamide). The effect of acidity of aqueous phase, extractant concentration, Sr²⁺ concentration and temperature on distribution ratio was investigated. In order to prevent the formation of third phase, TBP was added as phase modifier and kerosene was used as diluent. A slope method was used to determine the compositions of the extracted species. The results show that the distribution ratio of Sr²⁺ (D_Sr) increases with nitric acid or the extractant concentration (c(HNO₃)=0.1-2.7 mol/L, c(extractant)=0.05-0.3 mol/L), and decreases with the increase of the concentration of Sr²⁺ or temperature. The extracted species are Sr(NO₃)₂?3Me-TODGA and Sr(NO₃)2?2TODGA. The ΔH is -69.46 kJ/mol and -51.39 kJ/mol, ΔS is -190.5 J/(mol?K) and -128.4 J/(mol?K), and ΔG is -12.68 kJ/mol and -13.12 kJ/mol for Me-TODGA and TODGA respectively. The D_Sr in Me TODGA is only one-fifth of that in TODGA.