title: Initial partition and aggregation of uncharged polyaromatic molecules at the oil-water interface: a molecular dynamics simulation study.
abstract: Initial partitioning and aggregation of several uncharged polyaromatic (PA) molecules with the same polyaromatic core but different terminal moieties at oil-water interfaces from the bulk oil phase were studied by molecular dynamics simulation. The partition of the PA molecules between the bulk organic phase and oil-water interface was highly dependent on the terminal moiety structure of the PA molecules and aromaticity of the organic phase. The polarity ratio between the oil and water phases showed a significant influence on adsorption of the PA molecules at the oil-water interface. The presence of hydrophobic aromatic moieties in PA molecules hindered the adsorption process. Larger aromatic rings in PA molecules lowered the interfacial activity due to strong intermolecular π-π interactions and molecular aggregation in the bulk oil phase. The presence of a terminal carboxylic functional group on the side chain enhanced the adsorption of the PA molecules at the oil-water interface. The fused ring plane of the uncharged PA molecules was found to preferentially adsorb at the oil-water interface in a head-on or side-on orientation with the polyaromatic core staying in the nonaqueous phase (i.e., the principal plane of the molecule perpendicular to the oil-water interface). The results obtained from this study could provide a scientific direction for the design of proper chemical demulsifiers for PA molecule-mediated emulsions formed under specific process conditions of temperature, pressure, and pH.
authors.affiliation: Department of Chemical and Materials Engineering and ‡Department of Mechanical Engineering, University of Alberta , Edmonton, Alberta T6G 2G6, Canada.
authors.forename: Robel B
authors.initials: RB
authors.lastname: Teklebrhan
authors.forename: Lingling
authors.initials: L
authors.lastname: Ge
authors.forename: Subir
authors.initials: S
authors.lastname: Bhattacharjee
authors.forename: Zhenghe
authors.initials: Z
authors.lastname: Xu
authors.forename: Johan
authors.initials: J
authors.lastname: Sjöblom
mesh_terms: D000327:Adsorption; D006863:Hydrogen-Ion Concentration; D056004:Molecular Dynamics Simulation; D009821:Oils / Q000737:chemistry*; D010316:Particle Size; D011084:Polycyclic Aromatic Hydrocarbons / Q000737:chemistry*; D011312:Pressure; D013499:Surface Properties; D013696:Temperature; D014867:Water / Q000737:chemistry*
chemical_list: D009821:Oils; D011084:Polycyclic Aromatic Hydrocarbons; D014867:Water