Effect of degradation products of TEHDGA on actinide partitioning process

• Actinide partitioning solvent TEHDGA was degraded by hydrolysis/radiolysis.
• Degradation products were isolated and investigated for their effects.
• Two degradation products, BEHGA and DGAMA affect the partitioning process.
• BEHGA affects the selectivity during extraction.
• DGAMA affects the stripping process causing insufficient stripping.

Degradation products of TEHDGA, obtained on γ-radiolysis of 0.2 M TEHDGA + 30% isodecyl alcohol/n-dodecane in the presence of nitric acid, were isolated and studied for their extraction behaviour with americium and other metal ions of high level waste. It was observed that two degradation products, N,N-bis(2-ethylhexyl)glycolamide (BEHGA) and diglycolic acid monoamide (DGAMA), considerably affect actinide partitioning process. BEHGA a neutral extractant, similar to TEHDGA, showed extraction for americium, lanthanides, Zr(IV) and Mo(VI) at higher (extraction) acidities, while, DGAMA an acidic extractant showed extraction at lower (stripping) acidities. BEHGA extract by solvation through a bidentate pre-organised five membered ring formed due to intramolecular hydrogen bonding between its α-OH and CO groups, and DGAMA having pKa of 1.8, extracts metal ions through cation exchange in pH medium. Their presence in the degraded solvent significantly affects the performance of the solvent with respect to loss of selectivity during extraction and insufficient stripping.