Multi-stage extraction and separation of Ln and An using TODGA and DTBA or DTPA accompanying pH adjustment with lactic acid and ethylenediamine

Abstract

ABSTRACT The mutual separation of actinides (An) from lanthanides (Ln), using diethylenetriamine- N,N′,N″-pentaacetic acid (DTPA) or diethylenetriamine- N,N′,N″-triacetic acid-N,N″-bis(diethylacetamide) (DTBA) masking agents in the aqueous phase via diglycolamide (DGA) extraction is focused on the basis of Trivalent Actinide-Lanthanide Separations by Phosphorus-reagent Extraction from Aqueous Complexes (TALSPEAK) method. We also obtained the same separation performance using the commercially available DTPA using DTBA. In this work, we selected lactic acid (LA) of pH buffer from 10 organic acids and ethylenediamine (ED) for the pH adjustment based on the salt-free system. Approximately same D and SF values are obtained in the following conditions: TODGA-DTPA-LA-NaOH, TODGA-DTPA-LA-ED, and TODGA-DTBA-LA, except for different pH conditions (DTPA: pH 1.7–1.71, DTBA: pH 1.15). Experimental results using batchwise multi-stage extractions showed average yields of Ln (La to Gd) and Am to be 3.73% and 98.1% in the aqueous phase using DGA-DTPA-LA-ED, 3.1% and 97.0% using DGA-DTPA-LA-NaOH, and 1.61% and 98.7% using DGA-DTBA-LA. The suitable pH condition for the multi-stage extraction, using DTBA to extract over 95% Am with under 5% coextraction of Ln was limited to 1.14–1.16 throughout this work.