Spreading of Multi-component Oils on Water

Abstract

The spreading of multi-component oils on water has been investigated by direct observations and predicted from measurements of the interfacial tensions and surface tensions of decane, toluene, heptane, and their mixtures. Pure decane does not naturally spread at ambient conditions, as indicated by its negative spreading coefficient. However, when decane is mixed with toluene and heptane, the mixture spreads on water over a wide range of compositions. The spreading coefficients are highly nonlinear with respect to concentration and feature a maximum. The spreading is ascribed to preferential accumulation of toluene at the oil/water interface and heptane at the oil/vapor interface. Molecular dynamics simulations corroborate the hypothesis of preferential accumulation. The accumulation of lighter alkanes at the oil/vapor interface reduces the surface tension, and the accumulation of aromatics at the oil/water interface decreases the interfacial tension. As a consequence, the oil mixture spreads over water.

Spreading and Retraction of Spilled Crude Oil on Seawater

“…For decane/toluene, nearly half of the reduction in the surface tension of toluene occurs with addition of only 0.28 weight fraction (0.20 mole fraction) of decane. These observations are consistent with preferential accumulation of alkanes at the oil/air surface against the aromatic as shown in Figure 5 and also discussed in Kunieda et al (2012). The interfacial tension of these binary mixtures was also measured against water at pH=6-7, and the spreading coefficient was calculated using equation (4).…”

Mechanisms for Enhanced Hydrophobicity by Atomic-Scale Roughness

“…3 ). The cylindrical droplet is chosen because the contact line is straight and the contact angle is not affected by the drop size as imposed by the line tension 52 53 54 . Figure 3(c) shows the contact angle determined at 0.1 ns steps during the simulation.…”

“…In contrast, the difference of the contact angle values for the CF 3 -terminated surface is only 6°. Here, we caution that these values should be read qualitatively as the contact angle of spherical droplet depends on the size of droplet because of the line tension effect 52 53 54 .…”

“…To evaluate the contact angle, a cylindrical droplet was chosen considering that the cylindrical droplets are not affected by line tension since the contact line in the y -direction is straight 52 53 . Also, it is easy to determine the contact angle in both aspects of fitting method and computational cost (as the size along the y -direction can be small) 54 . For the cylindrical droplet simulation, the silica substrates were used which have either no concave (flat surface) or 4 concaves within the 9.68 nm length.…”

Pore-scale simulation of wettability and interfacial tension effects on flooding process for enhanced oil recovery

“…Nano-scale multiphase modelling has also been conducted by molecular dynamic methods. 16 It mainly brings some significant results for the mechanism insights. However, the high cost of molecular dynamics simulation method leads to the difficulty of simulating the multiphase flow characteristics in realistic level due to both the length scale and time scale limitation.…”