Influence of alkali concentration, electric waveform, and frequency on the critical electric field strength of droplet–interface partial coalescence

Sun, Yongxiang; Yang, Donghai; He, Limin; Luo, Xiaoming; Lü, Yuling

doi:10.1016/j.ces.2019.07.054

Cited by 25 publications

(18 citation statements)

References 43 publications

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“…It can be seen from Table that with the increase in the NaOH concentration, the instability rate of the O/W emulsion gradually decreases and the half-life of instability gradually increases. The reason is that NaOH reacts with acidic substances in the oil phase to form certain surfactants, which improves the strength of the interfacial film . The influence of surfactants on the oil–water interface film is shown in Figure and Table .…”

Section: Resultsmentioning

confidence: 99%

“…It can be found from eq 1 that the influence of alkali on the lifetime of the interfacial film cannot be directly analyzed by this model. However, it can be found 39 that the effect of alkali on the interfacial film of oil droplets has two main aspects: first, the alkali can react with the acidic substances in the crude oil to form surfactant; thus, high strength of the interfacial film can be obtained. Second, as the alkali concentration continues to increase, the ions electrolyzed will compress the electric double layer at the interface of the oil droplet, weaken the strength of the interface film of the oil droplet, and reduce the lifetime of the interfacial film.…”

Section: Resultsmentioning

confidence: 99%

“…The reason is that NaOH reacts with acidic substances in the oil phase to form certain surfactants, which improves the strength of the interfacial film. 39 The influence of surfactants on the oil−water interface film is shown in Figure 6 and Table 2. With the increase in the surfactant concentration, the lifetime of the O/W droplet and the half-life of instability increase and the instability rate constant decreases, indicating that the increase in the surfactant enhances the strength of the oil−water interface film of the emulsion.…”

Section: Effect Of the Polymer On The Stability Dynamic Characteristi...mentioning

confidence: 99%

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Stability Dynamic Characteristic of Oil-in-Water Emulsion from Alkali–Surfactant–Polymer Flooding

Nie

Han

et al. 2021

ACS Omega

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The relationship model between the droplet lifetime and interface properties is established to characterize the stability of oil droplets, and then, the influence of the alkali–surfactant–polymer (ASP) concentration on the lifetime is analyzed by theoretical calculations. The stability dynamic characteristics of oil-in-water (O/W) emulsions from ASP flooding were evaluated using the emulsion stability model (Civan model) based on two-phase separation. The effect of ASP on dynamic characteristics of the emulsion was explored by analyzing film strength qualitatively and measuring interfacial tension and ζ potential. The results showed that the Civan model was suitable to evaluate the stability of the O/W emulsion and to obtain the corresponding dynamic characteristics. The O/W emulsions became more stable with the increasing alkali concentration first at a low alkali concentration (c NaOH < 200 mg/L) and then became less stable with the increasing alkali concentration at a high alkali concentration (c NaOH > 200 mg/L). The stabilities of O/W emulsions were improved with the increasing concentrations of the surfactant and polymer. The mechanism of stabilization of the O/W emulsion by ASP is as follows. The surface-active substances formed by the reaction of alkali and acidic substances in the oil phase, together with surfactants, adsorb at the oil–water interface, reducing the interfacial tension and increasing the strength of the oil–water interface film. The polymer only increases the strength of the interface film by increasing the viscoelasticity of the oil–water interface film.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Effect Of the Polymer On The Stability Dynamic Characteristi...mentioning

confidence: 99%

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Stability Dynamic Characteristic of Oil-in-Water Emulsion from Alkali–Surfactant–Polymer Flooding

Nie

Han

et al. 2021

ACS Omega

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“…This result suggests that H 2 PO 4 – -MIL-100(Fe) has a greater responsibility for the pH of the emulsion than that of HPO 4 2– -MIL-100(Fe), which aligns well with the surface properties of the as-prepared materials. Salinity is another key factor for the demulsification performance because of the effect on the interfacial double electric layer both for the demulsifier and emulsion. − The DE of the phosphate-exchanged MIL-100(Fe) for the CTAB-stabilized O/W emulsion is reduced obviously when the NaCl concentration increases from 0 to 10 mmol/L (Figure S8). According to the theory of the electric double layer, the counterion can compress the double electric layer, thus weakening the stability of the emulsion and the demulsification ability of the demulsifier.…”

Section: Results and Analysismentioning

confidence: 99%

Surface Charge Regulation of MIL-100(Fe) by Anion Exchange for Demulsifying the Cationic Surfactant-Stabilized O/W Emulsion

Wang

Yang

et al. 2021

ACS Appl. Mater. Interfaces

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Demulsifying ionic surfactant-stabilized emulsions remains an emerging issue due to the stringent electrostatic barriers. In this work, a phosphate-mediated anion exchange strategy was proposed to fabricate a metal−organic framework, MIL-100(Fe), with adjustable surface charge for effective demulsification toward a cationic surfactant-stabilized emulsion. By adjusting the pH of the phosphate precursor solution, the surface charge of MIL-100(Fe) can be fine-tuned. At pH 3.0, the phosphate-exchanged MIL-100(Fe) with the zeta potential decreasing from 21.4 to 6.1 mV exhibited a significant enhancement of the demulsification efficiency (DE) from 35 to 91%. Further elevating the pH to 9.0 results in the zeta potential of the phosphate-exchanged MIL-100(Fe) to be reversed to −2.0 mV, and the DE can be optimized to 96% within 5 min. The demulsification mechanism was systematically explored based on the zeta potential, distribution of the surfactant, viscoelastic modulus evaluation, and morphological characterization of the emulsion in combination with monitoring of the dynamics process of demulsification. It was found that the phosphate-exchanged MIL-100(Fe) captured by the emulsion can lead to the release of the surfactant and heterogenization of the interfacial film, causing the elasticity of the emulsion to decrease and the irreversible deformation of emulsion droplets. Consequently, the destabilized emulsion could be subjected to the effective demulsification either by the fusion pathway mediated by the phosphate-exchanged MIL-100(Fe) or direct rupture. This work emphasized a facile and promising approach to deal with the cationic surfactant-emulsified oily wastewater and disclosed the fundamental demulsification process.

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“…The critical strength of the electric field was found to depend on the surface tension, radius, conductivity, permittivity, density of the droplet, and the frequency of the AC or pulsed electric field. 67,128 In the absence of an electric field, the Ohnesorge number indicates the transition from complete to partial coalescence, 122,123,127 while under an electric field, partial coalescence can occur at a critical electrocapillary number, reportedly around 0.055 and regardless of the Ohnesorge number. 68 The partial coalescence under a strong electric field may result from charge transfer during the process.…”

Section: Partial Coalescencementioning

confidence: 99%

Electrohydrodynamics of droplets and jets in multiphase microsystems

Cheng

Liu

et al. 2020

Soft Matter

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Influence of alkali concentration, electric waveform, and frequency on the critical electric field strength of droplet–interface partial coalescence

Cited by 25 publications

References 43 publications

Stability Dynamic Characteristic of Oil-in-Water Emulsion from Alkali–Surfactant–Polymer Flooding

Stability Dynamic Characteristic of Oil-in-Water Emulsion from Alkali–Surfactant–Polymer Flooding

Surface Charge Regulation of MIL-100(Fe) by Anion Exchange for Demulsifying the Cationic Surfactant-Stabilized O/W Emulsion

Electrohydrodynamics of droplets and jets in multiphase microsystems

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