A closer look at water/oil emulsions in energy and environment: modeling strategy

Goodarzi, Fatemeh (2019) A closer look at water/oil emulsions in energy and environment: modeling strategy. Masters thesis, Memorial University of Newfoundland.

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Abstract

The formation and presence of water/oil emulsion is an important phenomena in the oil and gas sector, drug delivery systems and food emulsion industry. In this work, mesoscale simulation is employed to investigate the structural and interfacial behaviour of the system. Both aliphatic and cyclic structures of the oil molecules were considered. A non-ionic surfactant was introduced to the system and the interfacial tension at the interface was measured at varying surfactant concentration. The effect of brine is also investigated on its ability to modify the electrostatic forces between the particles in the system. Flory-Huggins chi parameter were measured using molecular dynamics simulation and Monte Carlo method and implemented as an input in dissipative particle dynamics simulation. This parameter acted as a bridge between microscale and mesoscale simulation. The effect of temperature is studied on the solubility parameter and energy of mixing which are the parameters used to calculate the chi parameter. Water/oil ratio turned out to be an influencing factor in determining the type of emulsion formed in the system. According to the results of the MD simulations, the presence of salt improves the interfacial efficiency of the surfactant by decreasing the interfacial tension, which is in a good agreement with the literature data. . Comparing the snapshots taken at different simulation time steps, concertation profiles and radius of gyration values, it was observed that in the case of aliphatic hydrocarbons, surfactant molecules will stretch more due to the linear structure of oil molecules, however, for cyclic hydrocarbons, radius of gyration values reported to be smaller since less space is available for the interaction of surfactant tail groups with oil molecules — however, interfacial tension obtained to be a function of molecular weight of hydrocarbon, as it calculated to be the highest for Dodecane(43.62mN/m) and smallest for Benzene(29.68mN/m), regardless of their structure and polarity of the molecule. Based on the parameter considered to affect the properties of the system, an ideal case was introduced to have the lowest interfacial tension.

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