Molecular Chemical Engineering-Aided Design and Assessment of an Alternate Ligand-Solvent System for PUREX Process

Nuclear power has become inevitable to mitigate the global energy demand, which necessitates efficient and safe nuclear fuel reprocessing. Liquid-liquid extraction (LLE) is the heart of spent fuel reprocessing, for which the search for an efficient ligand-solvent system is a continuous endeavor. Thermophysical data for a complex chemical mixture often are of high value for chemical engineers in the synthesis and design of chemical processes and plants since they often face the situation that no experimental data are available, neither from databases nor from measurement, at affordable costs. Molecular dynamics simulations in conjunction with density functional theory and a conductor-like screening model can be employed to achieve this goal. Therefore, extensive molecular simulations have been conducted to mimic the LLE process considering tri-iso amyl phosphate (TiAP) as a potential alternative of TBP and octanol as an alternative to dodecane for metal ion transport. The partition coefficients of TiAP in octanol and dodecane were comparable. It was observed that the diffusivity of TiAP is improved in the presence of octanol and thus might provide faster kinetics. The total interface thickness was significantly high for the water-octanol interface and thus, it offers better interfacial ion transfer. Again, the total interface thickness was found to be increased with increased acid molarities. The surface roughness as well as the water finger formation is enhanced with acid molarity. Moreover, a significant improvement has been observed for back extraction of uranyl ions from the oil phase when octanol is used as the solvent. The present findings demonstrate that a polar solvent like octanol can be introduced along with dodecane to enhance the efficiency of the interfacial ion transfer process.