EXTRACTION OF Am(III) AND Ln(III) BY DIALKYLDITHIOPHOSPHINIC ACID WITH DIFFERENT ALKYL GROUPS

Abstract

As a part of the study on the separation of Am(III) from Ln(III) by using dialkyldithiophosphinic acid as extractant, the method of preparing and purifying several dialkyldithiophosphinic acids was studied and the effect of alkyl group structure of dialkyldithiophosphinic 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 dialkyldithiophosphinic acid(alkyl = octyl, 1-methylheptyl, 2-ethylhexyl, heptyl and hexyl) were synthesized. With four kinds of dialkyldithiophosphinic acids (HA) with different alkyl group of C₈(alkyl = n-octyl, 1-methylheptyl, 2-ethylhexyl, 2,4,4-trimethylpentyl) as extractants and toluene as diluent, the dependencies of extracting 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 NaNO₃, the pH_1/2 values of aqueous phase for extracting tracer amount of ²⁴¹Am and ^152+154Eu(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 × 10³, 1.0 × 10⁴, 1.0 × 10⁴, 9.8 × 10³, respectively.

Keywords:

• Dialkyldithiophosphinic acid
• Am(III
• Eu(III)
• Separation

ACKNOWLEDGMENT

This study was supported by the Science Fund of Tsinghua University, Beijing.