Adsorption and surface tension reduction at the vapor-liquid interface

Generalized van der Waals Theory of Interfaces in Simple Fluid Mixtures

“…The fortunate applicability to surface tension found here for the GvdW theory is, in the main, shared also by the earlier mean-field theory of Telo da Gama and co-workers (31,(35)(36)(37). Clearly, the leading mechanism for the surface tension phenomenon is the cohesive binding energy arising from attractive interactions in the fluid.…”

“…Later work by Cornelisse et al (33) on hydrocarbon mixtures with carbon dioxide has confirmed the efficiency of this approach, at least where the temperature is not too low, and applications to other complex fluids continue to appear (34). Lee et al (35,36) have applied both a mean-field theory, similar to our GvdW treatment except for the lack of nonlocal entropy, and molecular dynamics (MD) simulation to the same type of LJ models of binary mixtures to obtain density profiles and surface tension. Further results were reported by Almeida and Telo da Gama (37), who used the same mean-field theory applied to a wider range of binary mixtures.…”

“…Instead of a multidimensional search governed by precision requirements, the free energy optimization now depends only on the single variational parameter α and is readily implemented with standard techniques (49). In contrast, restricting the partial number densities in a mixture to a monotonic form would prohibit any possibility of preferential adsorption or desorption at the interface, a phenomenon clearly shown by both simulations (36, 39, 40) and detailed mean-field theory calculations (35,36,38). This objection can be circumvented, however, by assigning Fermi profiles to the total number density and to the individual component number fractions, so that…”

Classical density functional theory for the prediction of the surface tension and interfacial properties of fluids mixtures of chain molecules based on the statistical associating fluid theory for potentials of variable range

“…This type of enhanced adsorption of one component relative to the other is seen in binary mixtures of spherical molecules when there are significant differences in the values of the unlike dispersion interactions (e.g., see references 62,66,67,73 )…”

“…This type of approach is commonly referred to as a MF-DFT 62,63 . Studies employing MF-DFTs of this type have been used in a beautifully thorough series of studies by Telo da Gama and co-workers [64][65][66][67][68][69][70][71][72][73][74][75][76][77][78][79] to describe the vapour-liquid and liquid-liquid interfacial tension, the surface absorption, and the wetting behaviour for a variety of mixtures of spherical particles. A quantitative assessment of the theory is made by comparison with the interfacial data for mixtures of halocarbons.…”