Advanced TALSPEAK Separations Using a Malonate Buffer System

Abstract

The extraction behavior of lanthanides and americium has been evaluated under Advanced TALSPEAK (Trivalent Actinide Lanthanide Separation by Phosphorus-reagent Extraction from Aqueous Komplexes) conditions using malonic acid as the aqueous buffering agent. The extractant 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (HEH[EHP]) was used as an organic phase liquid cation exchanger in n-dodecane diluent, while N-(hydroxyethyl)-ethylenediaminetriacetic acid (HEDTA) served as a selective aqueous holdback reagent. Extractions conducted from malonate media exhibit a pH profile that flattens as the concentration of malonate is increased up to 1.0 M malonate. This relatively flat extraction behavior from pH 2.5–4.0 is reminiscent of previous studies on Advanced TALSPEAK in lactate media. The extraction kinetics with other carboxylic acid buffers as well as the effects of varying HEDTA, HEH[EHP], and malonate concentration are compared.

Keywords:

• lanthanide
• actinide
• Advanced TALSPEAK
• malonate
• HEH[EHP]
• HEDTA

Additional information

Funding

The work presented here was supported by the U.S. Department of Energy, Office of Nuclear Energy Research and Development program Sigma Team Minor Actinide Separations project and in part by the Nuclear Energy University Program Project 10-881 under contract INL 14002-20.