Micrographic Evaluation of Water-in-Oil Emulsion Stability up to Critical Electric Field
- 1Federal Fluminense University , , ,
- 2Federal University of Rio de Janeiro , , ,
- 3Celso Suckow da Fonseca Federal Center for Technological Education − CEFET , ,
Abstract
Electrostatic demulsification is widely applied in the petroleum industry for the separation of water-in-oil emulsions; however, the relationship between microscopic droplet dynamics and the macroscopic electrical response remains insufficiently understood, particularly regarding the definition of the critical electric field (CEF). This work presents a quantitative investigation of electrocoalescence using optical microscopy coupled with electrical current monitoring under a direct current electric field. Water-in-oil (W/O) model emulsions were evaluated through a factorial experimental design comprising 81 experiments, in which the electrode gap (100–300 μm), water cut (5–15 wt %), and surfactant concentration (0.5–1.5 wt %) were systematically varied. Real-time observations enabled the identification of droplet polarization, chain formation, coalescence, and the development of conductive pathways. The CEF, ranging approximately from 0.7 to 4.0 kV/cm, was determined from the simultaneous occurrence of current spikes and the visual formation of coalesced droplets that establish conductive pathways within the emulsion. The results demonstrate that droplet alignment occurs at the initial stages of electric field application and does not correspond to a significant increase in current. Instead, the abrupt rise in current was associated with the growth of droplets that establish electrical conduction, indicating that the CEF corresponds to the final stage of the electrocoalescence process. Statistical analysis revealed a pronounced quadratic effect of water cut, while electrode spacing and surfactant concentration also exerted significant influences through linear, quadratic, and interaction effects. These findings provide mechanistic insight into electrocoalescence and support a revised interpretation of the critical electric field, contributing to the understanding and potential optimization of electrostatic separation processes.
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BibTeX
@article{assenheimer2026micrographic,
title = {{Micrographic Evaluation of Water-in-Oil Emulsion Stability up to Critical Electric Field}},
author = {Troner Assenheimer and Hyago Braga dos Santos and Thiago Americano do Brasil and Edson Watanabe and Frederico Wanderley Tavares and Márcio Nele},
journal = {ACS omega},
year = {2026},
month = oct,
doi = {10.1021/acsomega.6c02577},
url = {https://europepmc.org/article/PMC/PMC13670763},
note = {CC BY},
}
RIS
TY - JOUR
TI - Micrographic Evaluation of Water-in-Oil Emulsion Stability up to Critical Electric Field
AU - Troner Assenheimer
AU - Hyago Braga dos Santos
AU - Thiago Americano do Brasil
AU - Edson Watanabe
AU - Frederico Wanderley Tavares
AU - Márcio Nele
PY - 2026
DA - 2026/10/01
JO - ACS omega
DO - 10.1021/acsomega.6c02577
UR - https://europepmc.org/article/PMC/PMC13670763
AB - Electrostatic demulsification is widely applied in the petroleum industry for the separation of water-in-oil emulsions; however, the relationship between microscopic droplet dynamics and the macroscopic electrical response remains insufficiently understood, particularly regarding the definition of the critical electric field (CEF). This work presents a quantitative investigation of electrocoalescence using optical microscopy coupled with electrical current monitoring under a direct current electric field. Water-in-oil (W/O) model emulsions were evaluated through a factorial experimental design comprising 81 experiments, in which the electrode gap (100–300 μm), water cut (5–15 wt %), and surfactant concentration (0.5–1.5 wt %) were systematically varied. Real-time observations enabled the identification of droplet polarization, chain formation, coalescence, and the development of conductive pathways. The CEF, ranging approximately from 0.7 to 4.0 kV/cm, was determined from the simultaneous occurrence of current spikes and the visual formation of coalesced droplets that establish conductive pathways within the emulsion. The results demonstrate that droplet alignment occurs at the initial stages of electric field application and does not correspond to a significant increase in current. Instead, the abrupt rise in current was associated with the growth of droplets that establish electrical conduction, indicating that the CEF corresponds to the final stage of the electrocoalescence process. Statistical analysis revealed a pronounced quadratic effect of water cut, while electrode spacing and surfactant concentration also exerted significant influences through linear, quadratic, and interaction effects. These findings provide mechanistic insight into electrocoalescence and support a revised interpretation of the critical electric field, contributing to the understanding and potential optimization of electrostatic separation processes.
SN - 2470-1343
ER -