Uranyl Nitrate Complex Extraction into TBP/Dodecane Organic Solution: A Molecular Dynamics Study

Abstract

Liquid–liquid extraction of uranyl is studied by conducting atomistic molecular dynamics simulation using quantum chemistry calibrated force fields via restrained electrostatic potential fitting of atomic forces. The simulations depict the migration of uranyl nitrate complexes from the aqueous–organic interface into the tri-n-butyl phosphate (TBP)/dodecane organic phase, in the form of UO2(NO3)2H2O2TBP and UO2(NO3)2*3TBP. The migration process is characterized by the gradual breaking of all the hydrogen bonds between the complex and the water molecules at the interface. Moreover, our simulation results suggest that the experimentally observed complex UO2(NO3)2*2TBP is formed after the migration of the aforementioned complexes into the organic phase by means of a reorganization of the nitrate binding mode from mono to bidentate which removes the excess oxygen atoms bound to uranyl.