title: Quantifying Dimer and Trimer Formation by Tri-n-butyl Phosphates in n-Dodecane: Molecular Dynamics Simulations.
abstract: Tri-n-butyl phosphate (TBP), a representative of neutral organophosphorous ligands, is an important extractant used in the solvent extraction process for the recovery of uranium and plutonium from spent nuclear fuel. Microscopic pictures of TBP isomerism and its behavior in n-dodecane diluent were investigated utilizing MD simulations with previously optimized force field parameters for TBP and n-dodecane. Potential mean force (PMF) calculations on a single TBP molecule show seven probable TBP isomers. Radial distribution functions (RDFs) of TBP suggest the existence of TBP trimers at high TBP concentrations in addition to dimers. 2D PMF calculations were performed to determine the angle and distance criteria for TBP trimers. The dimerization and trimerization constants of TBP in n-dodecane were obtained and match our own experimental values using the FTIR technique. The new insights into the conformational behaviors of the TBP molecule as a monomer and as part of an aggregate could greatly aid in the understanding of the complexation between TBP and metal ions in a solvent extraction system.
authors.affiliation: Department of Chemical Engineering and Materials Science, University of California, Irvine , Irvine, California 92697, United States.
authors.forename: Quynh N
authors.initials: QN
authors.lastname: Vo
authors.affiliation: Physical Science Division, Pacific Northwest National Laboratory , Richland, Washington 93352, United States.
authors.forename: Liem X
authors.initials: LX
authors.lastname: Dang
authors.affiliation: Department of Chemical Engineering and Materials Science, University of California, Irvine , Irvine, California 92697, United States.
authors.forename: Mikael
authors.initials: M
authors.lastname: Nilsson
authors.affiliation: Department of Chemical Engineering and Materials Science, University of California, Irvine , Irvine, California 92697, United States.
authors.forename: Hung D
authors.initials: HD
authors.lastname: Nguyen