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Li N, Pang Y, Sun Z, Sun X, Li W, Sun Y, Zhu L, Li B, Wang Z, Zeng H. Unraveling Partial Coalescence Between Droplet and Oil-Water Interface in Water-in-Oil Emulsions under a Direct-Current Electric Field via Molecular Dynamics Simulation. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2024; 40:5992-6003. [PMID: 38445586 DOI: 10.1021/acs.langmuir.3c04024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/07/2024]
Abstract
When the electric field strength (E) surpasses a certain threshold, secondary droplets are generated during the coalescence between water droplets in oil and the oil-water interface (so-called the droplet-interface partial coalescence phenomenon), resulting in a lower efficiency of droplet electrocoalescence. This study employs molecular dynamics (MD) simulations to investigate the droplet-interface partial coalescence phenomenon under direct current (DC) electric fields. The results demonstrate that intermolecular interactions, particularly the formation of hydrogen bonds, play a crucial role in dipole-dipole coalescence. Droplet-interface partial coalescence is categorized into five regimes based on droplet morphology. During the contact and fusion of the droplet with the water layer, the dipole moment of the droplet exhibits alternating increases and decreases along the electric field direction. Electric field forces acting on sodium ions and the internal interactions within droplets promote the process of droplet-interface partial coalescence. High field strengths cause significant elongation of the droplet, leading to its fragmentation into multiple segments. The migration of hydrated ions has a dual impact on the droplet-interface partial coalescence, with both facilitative and suppressive effects. The time required for droplet-interface partial coalescence initially decreases and subsequently increases as the field strength increases, depending on the competitive relationship between the extent of droplet stretching and the electric field force. This work provides molecular insights into the droplet-interface coalescence mechanisms in water-in-oil emulsions under DC electric fields.
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Affiliation(s)
- Ning Li
- College of New Energy, China University of Petroleum (East China), Qingdao 266580, China
- Department of Chemical and Materials Engineering, University of Alberta, Edmonton, Alberta T6G1H9, Canada
| | - Yunhui Pang
- College of New Energy, China University of Petroleum (East China), Qingdao 266580, China
| | - Zhiqian Sun
- College of New Energy, China University of Petroleum (East China), Qingdao 266580, China
| | - Xiaoyu Sun
- Department of Chemical and Materials Engineering, University of Alberta, Edmonton, Alberta T6G1H9, Canada
| | - Wangqing Li
- College of New Energy, China University of Petroleum (East China), Qingdao 266580, China
| | - Yongxiang Sun
- Department of Chemical and Materials Engineering, University of Alberta, Edmonton, Alberta T6G1H9, Canada
| | - Liyun Zhu
- College of New Energy, China University of Petroleum (East China), Qingdao 266580, China
| | - Bin Li
- School of Energy and Power Engineering, Jiangsu University, Zhenjiang 212013, China
| | - Zhenbo Wang
- College of New Energy, China University of Petroleum (East China), Qingdao 266580, China
| | - Hongbo Zeng
- Department of Chemical and Materials Engineering, University of Alberta, Edmonton, Alberta T6G1H9, Canada
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Guo K, Liu X, Du L, Lü Y, Luo X, Ling X. Electrocoalescence Behavior of Droplets Dispersed with Na 2CO 3 in Oil under the Electromagnetic Synergy Field. J Phys Chem B 2023. [PMID: 37311091 DOI: 10.1021/acs.jpcb.3c01217] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Electromagnetic synergy is a more effective physical method than a single AC electric field (ACEF) to enhance oil-water separation. However, the electrocoalescence behavior of droplets dispersed with salt ions in oil under the synergistic electromagnetic field (EMSF) still lacks research. Herein, the evolution coefficient of liquid bridge diameter (C1) characterizes the growth rate of the liquid bridge diameter, a series of Na2CO3-dispersed droplets with different ionic strengths were prepared, and C1 values of droplets under ACEF and EMSF were compared. Micro high-speed experiments revealed that C1 under ACEF is larger than C1 under EMSF. In particular, when σ = 100 μS·cm-1and E = 629.73 kV·m-1, C1 under the ACEF is 15% larger than C1 under EMSF. Additionally, the theory of ion enrichment is put forward, which explains the influence of salt ions on ζ potential and total surface potential in EMSF. This study provides guidance for designing high-performance devices by introducing electromagnetic synergy in water-in-oil emulsion treatment.
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Affiliation(s)
- Kai Guo
- College of Petrochemical Technology, Lanzhou University of Technology, Lanzhou 730050, PR China
| | - Xiaoya Liu
- College of Petrochemical Technology, Lanzhou University of Technology, Lanzhou 730050, PR China
| | - Ling Du
- College of Petrochemical Technology, Lanzhou University of Technology, Lanzhou 730050, PR China
| | - Yuling Lü
- College of Pipeline and Civil Engineering, China University of Petroleum, Qingdao 266580, PR China
| | - Xiaoming Luo
- College of Pipeline and Civil Engineering, China University of Petroleum, Qingdao 266580, PR China
| | - Xiao Ling
- College of Petrochemical Technology, Lanzhou University of Technology, Lanzhou 730050, PR China
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Electrocoalescence of water droplet trains in sunflower oil under the coupling of Non-uniform electric and Laminar flow fields. Chem Eng Sci 2022. [DOI: 10.1016/j.ces.2021.117158] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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Molecular dynamics simulations of nanoparticle-laden drop–interface electrocoalescence behaviors under direct and alternating current electric fields. J Mol Liq 2021. [DOI: 10.1016/j.molliq.2021.117875] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Granda R, Plog J, Li G, Yurkiv V, Mashayek F, Yarin AL. Evolution and Shape of Two-Dimensional Stokesian Drops under the Action of Surface Tension and Electric Field: Linear and Nonlinear Theory and Experiment. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2021; 37:11429-11446. [PMID: 34559540 DOI: 10.1021/acs.langmuir.1c01015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
The creeping-flow theory describing evolution and steady-state shape of two-dimensional ionic-conductor drops under the action of surface tension and the subcritical (in terms of the electric Bond number) electric field imposed in the substrate plane is developed. On the other hand, the experimental data are acquired for drops impacted or softly deposited on dielectric surfaces of different wettability and subjected to an in-plane subcritical electric field. Even though the experimental situation involves viscous friction of drops with the substrates and wettability-driven motion of the contact line, the comparison to the theory reveals that it can accurately describe the steady-state drop shape on a non-wettable substrate. In the latter case, the drop is sufficiently raised above the substrate, which diminishes the three-dimensional effects, making the two-dimensional description (lacking the no-slip condition at the substrate and wettability-driven motion of the contact line) relevant. Accordingly, it is demonstrated how the subcritical electric field deforms the initially circular drops until an elongated steady-state configuration is reached. In particular, the surface tension tends to round off the non-circular drops stretched by the electric Maxwell stresses imposed by the electrodes. A more pronounced substrate wettability leads to more elongated steady-state configurations observed experimentally than those predicted by the two-dimensional theory. The latter cases reveal significant three-dimensional effects in the electrically driven drop stretching. In the supercritical electric fields (corresponding to the supercritical electric Bond numbers), the electrical stretching of drops predicted by the present linearized two-dimensional theory results in splitting into two separate droplets. This scenario is corroborated by the predictions of the fully nonlinear results for similar electrically stretched bubbles in the creeping-flow regime available in the literature as well as by the present experimental results on a substrate with slip.
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Affiliation(s)
- Rafael Granda
- Department of Mechanical and Industrial Engineering, University of Illinois at Chicago, 842 West Taylor Street, Chicago, Illinois 60607-7022, United States
| | - Jevon Plog
- Department of Mechanical and Industrial Engineering, University of Illinois at Chicago, 842 West Taylor Street, Chicago, Illinois 60607-7022, United States
| | - Gen Li
- Department of Mechanical and Industrial Engineering, University of Illinois at Chicago, 842 West Taylor Street, Chicago, Illinois 60607-7022, United States
| | - Vitaliy Yurkiv
- Department of Mechanical and Industrial Engineering, University of Illinois at Chicago, 842 West Taylor Street, Chicago, Illinois 60607-7022, United States
| | - Farzad Mashayek
- Department of Mechanical and Industrial Engineering, University of Illinois at Chicago, 842 West Taylor Street, Chicago, Illinois 60607-7022, United States
| | - Alexander L Yarin
- Department of Mechanical and Industrial Engineering, University of Illinois at Chicago, 842 West Taylor Street, Chicago, Illinois 60607-7022, United States
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Study on the Effect of Nanoparticle Used in Nano-Fluid Flooding on Droplet-Interface Electro-Coalescence. NANOMATERIALS 2021; 11:nano11071764. [PMID: 34361150 PMCID: PMC8308123 DOI: 10.3390/nano11071764] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/14/2021] [Revised: 06/26/2021] [Accepted: 06/29/2021] [Indexed: 12/04/2022]
Abstract
Nano-fluid flooding is a new method capable of improving oil recovery; however, nanoparticles (NPs) significantly affect electric dehydration, which has rarely been investigated. The effect of silica (SiO2) NPs on the droplet–interface coalescence was investigated using a high-speed digital camera under an electric field. The droplet experienced a fall, coalescence, and secondary droplet formation. The results revealed that the oil–water interfacial tension and water conductivity changed because of the SiO2 NPs. The decrease of interfacial tension facilitated droplet deformation during the falling process. However, with the increase of particle concentration, the formed particle film inhibited the droplet deformation degree. Droplet and interface are connected by a liquid bridge during coalescence, and the NP concentration also resulted in the shape of this liquid bridge changing. The increase of NP concentration inhibited the horizontal contraction of the liquid bridge while promoting vertical collapse. As a result, it did not facilitate secondary droplet formation. Moreover, the droplet falling velocity decreased, while the rising velocity of the secondary droplet increased. Additionally, the inverse calculation of the force balance equation showed that the charge of the secondary droplet also increased. This is attributed to nanoparticle accumulation, which resulted in charge accumulation on the top of the droplet.
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