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.