The adsorption of tri-<i>N</i>-butylphosphate at the benzene–water interface

Sagert, Norman H.; Lee, Woon; Quinn, Michael J.

doi:10.1139/v82-183

“…Equation [3] gives the salting coefficient for each ion, and it is necessary to sum the ionic contributions to get the salting coefficient for a given electrolyte. Calculated…”

Section: Distribution Theoriesmentioning

confidence: 99%

“…We are studying interfacial properties relevant to these extraction systems (2,3), and need to know distribution coefficients for organic phosphates between hydrocarbons and various aqueous media (4), including aqueous media with added salt. Measuring such distribution coefficients is equivalent to measuring the salting coefficients (5).…”

Section: Introductionmentioning

confidence: 99%

Salting-out of triethylphosphate by inorganic electrolytes

Sagert¹,

Lau²

1984

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. Can. J. Chem. 62, 81 (1984). The salting-out of triethylphosphate (TEP) from water was measured at 25°C for twelve inorganic electrolytes. If salting out is taken as an additive property of ions, then the effectiveness for salting TEP out of water is I-< Br-< C1-< +SO:-< $0:-for anions and $La3+ < Na+ .= NH: < Cs+ < $aZ+ = $~g " < K' < i~a " for cations. The results were fitted to three theories. The distribution theory of Conway, Desnoyers, and Smith predicts the order of magnitude of the experimental results, but does not discriminate well between salts of the same valence type. The electrostriction theory of McDevit and Long discriminates well between ions but gives results three or five times larger than those observed. Scaled particle theory predicts the results reasonably well, but the predictions depend critically on the choice of ionic and molecular parameters. Thus, none of these theories is entirely satisfactory.

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“…Thus at TBP organic phase concentrations that are relevant to process conditions significant perturbation of the interface is observed. Note that the experimental value is 51.4 mN/m for the pure water/n-hexane system 45 and 8.8 for the TBP saturated water/n-hexane 46 interface and that the calculated values fall within these two limits. In the left panel, the average number of TBP at an interface for each simulation is plotted against the total number of TBP available to adsorb from the organic phase.…”

Section: Surfactant Adsorption Increases Interfacial Roughnessmentioning

confidence: 67%

Interfacial Heterogeneity is Essential to Water Extraction into Organic Solvents

Servis¹,

Clark²

2018

Preprint

0

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Liquid/liquid extraction (LLE) is one of the most industrially relevant separations methods, successfully leveraging the variable solubility of solutes (or their complexes) between two immiscible solvents. Independently from the relative solubilities of those solutes and complexes which determine their distribution between phases, the kinetics of phase transfer is impacted by the molecular interactions and structure of those species at the interface. A simple example includes the formation and extraction of water-extractant adducts observed in the ternary water/organic/tri-n-butyl phosphate (TBP) system. Despite its implications for LLE, a detailed description of the structural and dynamic mechanisms by which such adducts are formed at the interface is not established. Describing that process requires connecting the evolving interfacial molecular organization in the presence of surfactants to dynamic surface fluctuations and interfacial heterogeneity. Herein, molecular dynamics simulation is combined with state of the art network theory analysis to reveal features of interfacial structure and their relationship to the extraction of water in the water/n-hexane/TBP system. Surfactant adsorption enhances interfacial roughness which in turn causes directly interfacial water to become less connected through hydrogen bonding to subjacent layers, particularly upon formation of the water bridged TBP dimer adduct. Further, heterogeneity within the interface itself is enhanced by surfactant adsorption, and serves as the basis for the formation of protrusions of water into the organic phase at the extremes of surface fluctuations. These features disproportionately incorporate the water bridged TBP dimer and are the primary means by which water is transferred to the organic phase. This work presents for the first time a holistic understanding of how interfacial heterogeneity and spatial fluctuations become amplified in the presence of surfactants, enabling water extraction into the organic phase. It further affords the opportunity to study how solution conditions can control interfacial behavior to create more efficient solvent extraction systems.

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“…Thus at TBP organic phase concentrations that are relevant to process conditions significant perturbation of the interface is observed. Note that the experimental value is 51.4 mN/m for the pure water/n-hexane system 45 and 8.8 for the TBP saturated water/n-hexane 46 interface and that the calculated values fall within these two limits. In the left panel, the average number of TBP at an interface for each simulation is plotted against the total number of TBP available to adsorb from the organic phase.…”

Section: Surfactant Adsorption Increases Interfacial Roughnessmentioning

confidence: 67%

Interfacial Heterogeneity is Essential to Water Extraction into Organic Solvents

Servis

¹

,

Clark²

2018

Preprint

0

View full text Add to dashboard Cite

Liquid/liquid extraction (LLE) is one of the most industrially relevant separations methods, successfully leveraging the variable solubility of solutes (or their complexes) between two immiscible solvents. Independently from the relative solubilities of those solutes and complexes which determine their distribution between phases, the kinetics of phase transfer is impacted by the molecular interactions and structure of those species at the interface. A simple example includes the formation and extraction of water-extractant adducts observed in the ternary water/organic/tri-n-butyl phosphate (TBP) system. Despite its implications for LLE, a detailed description of the structural and dynamic mechanisms by which such adducts are formed at the interface is not established. Describing that process requires connecting the evolving interfacial molecular organization in the presence of surfactants to dynamic surface fluctuations and interfacial heterogeneity. Herein, molecular dynamics simulation is combined with state of the art network theory analysis to reveal features of interfacial structure and their relationship to the extraction of water in the water/n-hexane/TBP system. Surfactant adsorption enhances interfacial roughness which in turn causes directly interfacial water to become less connected through hydrogen bonding to subjacent layers, particularly upon formation of the water bridged TBP dimer adduct. Further, heterogeneity within the interface itself is enhanced by surfactant adsorption, and serves as the basis for the formation of protrusions of water into the organic phase at the extremes of surface fluctuations. These features disproportionately incorporate the water bridged TBP dimer and are the primary means by which water is transferred to the organic phase. This work presents for the first time a holistic understanding of how interfacial heterogeneity and spatial fluctuations become amplified in the presence of surfactants, enabling water extraction into the organic phase. It further affords the opportunity to study how solution conditions can control interfacial behavior to create more efficient solvent extraction systems.

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The adsorption of tri-N-butylphosphate at the benzene–water interface

Cited by 12 publications

References 3 publications

Salting-out of triethylphosphate by inorganic electrolytes

Salting-out of triethylphosphate by inorganic electrolytes

Interfacial Heterogeneity is Essential to Water Extraction into Organic Solvents

Interfacial Heterogeneity is Essential to Water Extraction into Organic Solvents

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