Extraction of Am(III) and Ln(III) by Dialkyldithiophosphinic Acid with Different Alkyl Groups

摘要

As a part of the study on the separation of Am(III) from Ln(III) by using dialkyldithiophosphinic acid as extractant, the method of preparating and purifying several dialkyldithiophinic acids was studied and the effect of alkyl group structure of dialkyl-dithiophosphinic acid on separating Am(III) from Ln(III) was investigated. A three-step process under mild conditions which can be easily performed in the laboratory was developed. By the method with diethyl phosphite and alkylhalide as starting materials, five kinds of dialkyldithiophinic acid(alkyl = octyl, 1-methylheptyl, 2-ethylhexyl, heptyl and hexyl) were synthesized. With four kinds of dialkyldithiophosphinic acids (HA) with different alkyl gorup of C_8(alkyl n-octyl, 1-methylheptyl, 2-ethylhexyl, 2,4,4-trimethylpentyl) as extractans and toluene as diluene, the dependencies of extarcting Am(III) and Ln(III) on pH and extractant concentration were determined, The slopes of lgD/pH dependencies are close to 3 and the slopes of lgD/lg[HA] are close to 2. While the organic phases were 0.2 mol/L extractants in toluene and aqueous phase was 1 mol/L NaNO_3, the pH_(1/2) values of aqueous phase for extracting tracer amount of ~(241)Am and ~(152 + 154)Eu(III) by HA with R = n-octyl, 1-methylheptyl, 2-ethylhexyl, 2,4,4-trimethylpentyl are 2.58, 2.63, 2.67, 3.19, and 3.94, 3.99, 4.06, 4.52, respectively; the calculated separation factor (SF_(Am(III)/Eu(III)) was 9.7 X 10~3, 1.0 X 10~4, 1.0 X 10~4, 9.8 X 10~3, respectively.