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Effects of Applied DC Electric Fields on Water-Oil Interfacial Properties

  • Author / Creator
    Zhang, Ye
  • Among all the competing methods to enhance the phase separation of water-in-oil emulsions in chemical industries, electric field is considered as one of the best treatment options. To better understand the mechanism by which electric field assists water droplets coalescence and the corresponding physics of skin formation, the interfacial properties of the water/oil interface in a water-in-model oil emulsion system, including interfacial tension, shape factor, crumpling ratio and dilatational rheology, are studied with a tensiometer. The pendant water drop deforms immediately at the onset of electric field application, into either a prolate shape or an oblate shape in the direction of electric field, depending on the properties of the continuous phase. The degree of drop deformation is of positive correlation with the experienced electric field strength and is also affected by the electric field direction and the drop position in between the electrodes. An external electric field is found to enhance the formation of interfacial asphaltene layer elucidated by a higher crumpling ratio, lower interfacial tension, higher shape factor and higher elasticity with increasing electric field strength. This could be due to the induced electrohydrodynamic flow, which triggers the interfacial convection and accelerates asphaltene movements and adsorption. The same trend holds true for measurements with various asphaltene concentration, aging time, water phase pH, and water salinity under electric field application. Although the electric-assisted formation of a stronger interfacial barrier is against drop-drop coalescence, a hypothesis is proposed that the electric-induced drop deformation may dominant, enlarging the interfacial area and generating a patchy film with weak spots for easier drop-drop coalescence.

  • Subjects / Keywords
  • Graduation date
    Spring 2019
  • Type of Item
    Thesis
  • Degree
    Master of Science
  • DOI
    https://doi.org/10.7939/r3-mzd8-jp85
  • License
    Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.