Size Dependence of the Stability of Emulsion Drops Pressed against a Large Interface

Basheva, Elka S.; Gurkov, Theodor D.; Ivanov, Ivan B.; Bantchev, Grigor B.; Campbell, Bruce; Borwankar, Rajendra P.

doi:10.1021/la990186j

Cited by 60 publications

(87 citation statements)

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“…Jones and Wilson [12] is an important theoretical work on the film drainage problem of a drop over a plane interface, which shows the importance of interface mobility and the narrowing of the film at its periphery (the so-called dimple). Finally, the work of Basheva et al [13] showed experimentally for the first time the dependence of the coalescence time on drop diameter in a wide range where two distinct coalescence regimes have been predicted: a Taylor regime for very small drops where there is no drop deformation and the film lifetime decreases with drop diameter (lubrication regime), and a Reynolds regime for large drops where there is drop deformation and the film lifetime increases with drop diameter (independently of the interface mobility). As a result, the coalescence time as a function of drop diameter passes through a minimum.…”

Section: Introductionmentioning

confidence: 94%

“…We can then mention the works of Hartland [7][8][9][10], Hodgson and Lee [11], Jones and Wilson [12] and Basheva et al [13]. In Hartland [7][8][9], although there are no results on coalescence times, other aspects of drop/interface coalescence have been studied in detail such as the drop shape when resting on a plane interface, the variation of film thickness with time and radial position and the film retraction.…”

Section: Introductionmentioning

confidence: 99%

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Coalescence of contaminated water drops at an oil/water interface: Influence of micro-particles

Malmazet

Risso

Masbernat

et al. 2015

Colloids and Surfaces A: Physicochemical and Engineering Aspect

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International audienceThe effect of micro-particles and interface aging on coalescence of millimetre-sized water drops withan oil/water interface is studied over long times. The system is not pure and interface contaminationgrows with time, resulting in a slow but continuous decrease of interfacial tension over time (from 35to 10 mN/m), which is measured in situ using an original technique. Without added micro-particles,coalescence times are randomly distributed and uncorrelated to drop diameter or interfacial tension. Inpresence of 10 !m size hollow glass particles at the oil/water interface, coalescence times become morereproducible and show a clear dependence upon drop diameter and interface aging. Results are consistentwith a classical drainage model assuming that the critical thickness at which interstitial film rupturesscales as the micro-particle diameter, a result that tends to validate the bridging scenario. Interestingly,the film retraction speed during the coalescence process does not follow theoretical predictions in aplanar geometry. High-speed imaging of the retracting film reveals that the hole rim is bending upwardwhile retracting, resulting in a strong slowdown of retraction speed. This is caused by the difference ofinterfacial tension between oil/drop freshly formed interfaces and the aged oil/water interface

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Section: Introductionmentioning

confidence: 94%

Section: Introductionmentioning

confidence: 99%

Coalescence of contaminated water drops at an oil/water interface: Influence of micro-particles

Malmazet

Risso

Masbernat

et al. 2015

Colloids and Surfaces A: Physicochemical and Engineering Aspect

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“…Most of this theoretical and experimental research has been done for single droplets coalescing with a planar surface (e.g. Aryafar and Kavehpour, 2006;Basheva et al, 1999;Bozzano and Dente, 2011;Charles and Mason, 1960;Dickinson et al, 1988;Hartland, 1967aHartland, , 1967bHartland, , 1967cHool et al, 1998;Jeffreys and Hawksley, 1965;Kourio et al, 1994;Mackay and Mason, 1963;Mohamed-Kassim and Longmire, 2004;Ortiz-Duenas et al, 2010;Thoroddsen, 2006). Extensive theoretical research Postprint: Kamp, J.…”

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confidence: 99%

Influence of drop size and superimposed mass transfer on coalescence in liquid/liquid dispersions – Test cell design for single drop investigations

Kamp¹,

Kraume²

2014

Chemical Engineering Research and Design

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Postprint: Kamp, J. & Kraume, M.: Influence of drop size and superimposed mass transfer on coalescence in liquid/liquid dispersions -Test cell design for single drop investigations, Chem. Eng. Res. Des., Elsevier, 2014, 92, 635-643 http://dx.doi.org/10.1016/j.cherd.2013 1 Influence of drop size and superimposed mass transfer on coalescence in liquid/liquid dispersions -Test cell design for single drop investigationsJohannes Kamp a *, Matthias Kraume a a Chair of Chemical & Process Engineering, Technische Universität Berlin, FH 6-1, Fraunhoferstr. 33-36, 10587 Berlin * Corresponding author, e-mail: johannes.kamp@tu-berlin.de, phone: +49 30 314 23171 The detailed understanding of droplet coalescence is important for the accurate description of liquid/liquid dispersions. A test cell is designed which enables serial examinations of the random coalescence process with high repetition rate, good observability and accuracy of experimental parameters. Within this rectangular test cell a rising droplet collides with a pendant one, while recorded by a high speed camera. The gained experimental data allows a validation and further development of appropriate models. The investigated parameters in this work are the drop size and the superimposed mass transfer influencing the coalescence probability. These examinations were carried out in the EFCE standard test system toluene / acetone / water. The effect of varying the drop size seems to be interfered by the different rising velocities due to buoyancy. Introducing a transferring component has a significant impact on the coalescence process. A transfer direction from disperse to continuous phase results in a coalescence probability of almost 100%, whereas the reverse mass transfer direction induces a repulsion of nearly all droplets. Keywords coalescence; test cell; single drop; mass transfer; drop size; coalescence probability IntroductionDispersions of at least two liquids showing a miscibility gap are an integral part of several unit operations. Therefore, a detailed understanding and quantitative description of the characteristics and conditions of these systems is important for various technical applications. The most important characteristic of an emulsion is the drop size distribution which affects e.g. the interfacial area and settling time. The drop size distribution is determined by the phenomena breakage and coalescence of single droplets. Thus, these interactions determine the macroscopic behaviour of an emulsion directly. Although various models are available in literature for both phenomena Lucas, 2010, 2009), the prediction of the drop size distribution is only possible with restrictions when varying for example the power input or material and process conditions. Consequently, excessive and expensive experimental investigations are still necessary at different scales for process development. For instance, the design of extraction columns still requires pilot plants using high amounts of the original physical system. To diminish the number of influencing...

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“…According to recent emulsion stability simulations (ESS) an approximate threshold for drop deformation occurs around 2.5 µm [56,57,63,64]. Drops with radii smaller than 2.5 µm will mostly behave as non-deformable particles.…”

Section: Flocculation Of Oil Dropsmentioning

confidence: 99%

Nanoemulsion stability: Experimental evaluation of the flocculation rate from turbidity measurements

Rahn-Chique¹,

Puertas²,

Romero-Cano³

et al. 2012

Advances in Colloid and Interface Science

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The coalescence of liquid drops induces a higher level of complexity compared to the classical studies about the aggregation of solid spheres. Yet, it is commonly believed that most findings on solid dispersions are directly applicable to liquid mixtures. Here, the state of the art in the evaluation of the flocculation rate of these two systems is reviewed. Special emphasis is made on the differences between suspensions and emulsions. In the case of suspensions, the stability ratio is commonly evaluated from the initial slope of the absorbance as a function of time under diffusive and reactive conditions. Puertas and de las Nieves (1997) developed a theoretical approach that allows the determination of the flocculation rate from the variation of the turbidity of a sample as a function of time. Here, suitable modifications of the experimental procedure and the referred theoretical approach are implemented in order to calculate the values of the stability ratio and the flocculation rate corresponding to a dodecane-in-water nanoemulsion stabilized with sodium dodecyl sulfate. Four analytical expressions of the turbidity are tested, basically differing in the optical cross section of the aggregates formed. The first two models consider the processes of: a) aggregation (as described by Smoluchowski) and b) the instantaneous coalescence upon flocculation. The other two models account for the simultaneous occurrence of flocculation and coalescence. The latter reproduce the temporal variation of the turbidity in all cases studied (380 ≤ [NaCl] ≤ 600 mM), providing a method of appraisal of the flocculation rate in nanoemulsions.

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Size Dependence of the Stability of Emulsion Drops Pressed against a Large Interface

Cited by 60 publications

References 16 publications

Coalescence of contaminated water drops at an oil/water interface: Influence of micro-particles

Coalescence of contaminated water drops at an oil/water interface: Influence of micro-particles

Influence of drop size and superimposed mass transfer on coalescence in liquid/liquid dispersions – Test cell design for single drop investigations

Nanoemulsion stability: Experimental evaluation of the flocculation rate from turbidity measurements

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