TODGA-DOHyA: Physicochemical Insights into a Stable Solvent System for Nuclear Reprocessing

N,N,N′,N′-tetraoctyldiglycolamide (TODGA), in n-dodecane, effectively separates trivalent metal ions but triggers early third-phase formation in the presence of higher metal ion concentrations from nitric acid. To mitigate this, N,N-dioctyl-2-hydroxyacetamide (DOHyA), a phase modifier for TODGA, forms a combined solvent system composed of TODGA+DOHyA/n-DD (n-DD = n-dodecane), which efficiently separates trivalent metal ions from radioactive waste. However, understanding the physicochemical behavior and radiolytic stability of this solvent before industrial-scale application is crucial. Hence, this study investigates the density and viscosity of TODGA+DOHyA/n-DD and the results obtained were compared with the individual systems. The results revealed a decrease in viscosity and density with increasing temperatures at all doses, and the solvents follow the trend as 0.15 mol kg–1 of TODGA + 0.29 mol kg–1 of DOHyA/n-DD > TODGA/n-DD > DOHyA/n-DD. In addition, although the density and viscosity increases with the gamma dose in all systems, TODGA + DOHyA/n-DD displays minimal change, signifying exceptional stability under irradiation. Thermodynamic parameters revealed weak molecular interactions in TODGA + DOHyA/n-DD. In summary, this study highlights the stability of TODGA + DOHyA/n-DD, with minor density and viscosity changes under irradiation, spotlighting its potential for nuclear reprocessing.