화학공학소재연구정보센터
Langmuir, Vol.35, No.35, 11345-11350, 2019
Computational Prediction of Adsorption Equilibrium for Nonionic Surfactants at the Oil/Water Interface
The non-Bornian solvation model has been applied for predicting the adsorption equilibrium for nonionic surfactants at the oil (O)/water (W) interface. In the nonBornian model, the small contribution from the long-range electrostatic interaction is ignored, and the solvation or resolvation energy is formulated based on the short-range solute molecule (or ion)-solvent interactions-cavity formation, Coulomb, polarization, charge transfer, etc. These interaction energies are given by zero, first, and second-order functions of the local electric field (E-i) on the molecular surface, which can be estimated by density functional theory calculation. In the present study, we considered an adsorption process as "partial" transfer of a molecule across the O/W interface. Using a non-Bornian, semi-empirical equation for the Gibbs energy of transfer of nonionic molecules, the adsorption states of alkyl alcohols (1-dodecanol, 1-octanol, and 1-hexanol) at the 1,2-dichloroethane/W interface were successfully predicted. The orientation angle (theta), the rotation angle (omega), and the penetration depth into the O phase (d) of the alcohols in the adsorption state could be estimated. Furthermore, the energies for the adsorption from O and W (Delta G(ad)(o,O -> I) and Delta G(ad)(o,w -> I)) could be estimated theoretically. The values of Delta G(ad)(o,O -> I) for the alcohols studied were in good agreement with those determined experimentally by the drop-weight method.