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This study employed dissipative particle dynamics (DPD) simulations to investigate the self-propelled motion of oil droplets in water–oil–surfactant systems. It is the first attempt to replicate self-propulsion models of oil droplets at the molecular level, contrasting previous simulations focused on Brownian motion and hydrodynamic behaviour of colloidal particles. The DPD model reproduced droplet propulsion and visualised internal Marangoni flow, showing that larger droplet radii and greater interfacial tension differences increase propulsion speeds. Additionally, surfactants with stronger oil–oil repulsion enhanced propulsion speed, suggesting that surfactant-induced local structures are crucial for the self-propulsion mechanism. • DPD simulations reproduced self-propelled motion of oil droplets at the molecular level. • Larger oil droplet radii resulted in proportional increases in propulsion velocity. • A 2% interfacial tension difference significantly increased propulsion speed. • Surfactant structure impacted oil–oil interactions, influencing propulsion velocity. • The DPD approach explained molecular mechanisms in non-equilibrium active systems. [ABSTRACT FROM AUTHOR]

• Proteins can be used as emulsifiers due to their amphiphilic nature. • Cavitation events in sonication reduce the droplet size of the emulsion and enhance its stability. • Ultrasound ameliorates the emulsifying characteristics of natural emulsifiers like protein and improves the storage stability of the emulsion. • The study on sonication-assisted formation of protein-based stable emulsion is still limited. Emulsion systems are extensively used in the food processing sector and the use of natural emulsifiers like proteins for stabilizing emulsion has been in demand from consumers due to increased awareness about the consumption of healthy food. Numerous methods are available for the preparation of emulsion, but ultrasound got more attention among common methods owing to its economical and environment-friendly characteristics. The physical effects caused by to bursting of the cavity bubble, result in reduced droplet size, thus forming an emulsion with appreciable stability. Ultrasound ameliorates the emulsifying characteristics of natural emulsifiers like protein and improves the storage stability of the emulsion by positively boosting the rheological, emulsifying characteristics, improving zeta potential, and reducing average droplet size. The stability of protein-based emulsion is affected by environmental stresses hence conjugate of protein with polysaccharide showed good emulsifying characteristics. However, the data on the effect of ultrasound parameters on emulsifier properties is lacking and there is a need to develop a sonication device that can carry out large-scale emulsification operation. The review covers the principles and mechanisms of ultrasound-assisted formation of protein-based and protein-based conjugate emulsions. Further, the effect of ultrasound on various characteristics of protein-based emulsion is also explored. This review will provide concise data to the researchers to extend their experiments in the area of ultrasound emulsification which will help in commercializing the technology at the industrial scale. [ABSTRACT FROM AUTHOR]

• Systematic study of the rising motion of oil droplets in natural waters. • Discovered that oil droplet properties affect the rising motion process. • Modeling the terminal velocity of oil droplets in natural waters. • Modeling the drag coefficient of oil droplets in natural waters. This work focuses on investigating the dynamics of different types of oil droplets rising freely in water columns. Fifteen different types of oils were selected to cover most of the conventional oils. The particle size range of the study is 1.41∼13.58 mm, which can cover the largest oil droplet size that may occur in the real environment. Investigation results show that oil droplet characteristics greatly influence the dynamics process of oil droplet motion. The characteristics which play a dominant role will change as the oil droplet particle size increases. Meanwhile, a set of computational models applicable to the terminal velocity and drag coefficient of oil droplets in the range of 20 < Re < 1200 in a non-pure system are obtained by organizing the experimental data and comparing with the traditional correlation equation, respectively. The models involve dimensionless parameters such as Eo, Mo, and We numbers with fitting coefficients up to 0.984. [ABSTRACT FROM AUTHOR]

Highlights • The interactions between an oil droplet and a horizontal solid surface was analyzed. • There is a separation distance between an oil droplet and a solid surface. • The droplet and solid surface zeta potentials affect the droplet moving direction. • The droplet moving velocity increases with the decrease of the separation distance. Abstract This work numerically investigated the translational velocity of a negatively charged oil droplet in the water near a negatively charged solid surface under a DC electric field. The equilibrium separation distance between the charged oil droplet and the charged solid surface is calculated under different parameters and the translational motion of the droplet near the solid surface is simulated via a three-dimensional mathematical model. The results indicate that the velocity of the droplet is higher under a larger zeta potential of the solid surface and a smaller zeta potential of the droplet. When the absolute value of the negative zeta potential of the droplet is larger than that of the solid surface, the droplet will move in opposite direction of the electric field. It is also found that the droplet translational velocity increases with the decrease of the separation distance between the oil droplet and the solid surface. [ABSTRACT FROM AUTHOR]

Abstract Under oil droplet supply a simplified elastohydrodynamic lubrication (EHL) model incorporating slide-roll ratios has been established, and the lubrication behavior of one oil droplet passing through the contact zone was numerically simulated. The results showed that sliding elongates the oil droplet and the oil reservoir at the inlet, and thus the effective lubrication can be enhanced. However if the slide-roll ratio is too large lubrication failure may occur. The effect of the slide-roll ratio is markedly influenced by lubrication parameters η 0 u e , and the increase of η 0 u e leads to a decrease in the effective lubrication time. Heavy load reduces the effective lubrication time. Highlights • Considering the sliding effect, a simplified elastohydrodynamic lubrication model has been established under one oil droplet supply. • Results show that sliding elongates the oil droplet and thus the effective lubrication can be enhanced. • The effect of the slide-roll ratio is markedly influenced by lubrication parameters η 0 u e and load. • The reasonable choice of oil droplet volume can prevent lubrication failure under relatively large slide-roll ratio. [ABSTRACT FROM AUTHOR]

The oil dielectric has been used for enhancing the performance and durability of triboelectric nanogenerators (TENGs), but little is known about the contact-electrification (CE) (or triboelectrification) characteristics of the oil. Here, the CE behavior of different oil droplets with oleophobic surfaces is systematically investigated by dropping oil on a single-electrode TENG. The electrification trace is clearly imaged using a high-voltage scanning probe approach. Thermally stimulated discharge techniques are adopted for studying the detailed trapping characteristics of contact-generated charges with a homemade instrument, and the results are consistent with the thermionic emission model. The research provides systematic understandings on oil CE with oleophobic surfaces, together with general investigation paradigms and characterization methods for electrification phenomena on surfaces. Meanwhile, because typical oils are regarded as free of ions, their CE is attributed to electron transfer, which may contribute to the understanding of fundamental CE mechanisms. [Display omitted] • The contact-electrification behavior of different oil droplets is systematically investigated. • The electrification trace is clearly imaged using a high-voltage scanning probe approach. • Thermally stimulated discharge techniques are adopted for studying the trapping characteristics of static charges. [ABSTRACT FROM AUTHOR]

Highlights • There is a separation distance between an oil droplet and an air–water interface. • A negatively charged interface moves in opposite direction of the DC electric field. • The effect of the mobile air–water interface on the droplet velocity was analyzed. • This moving oil droplet surface and the inner flow affect the droplet velocity. Abstract A numerical study on the electrokinetic motion of a charged oil droplet near a charged air–water interface is presented in this paper. First, the separation distance between the oil droplet and the air–water interface is calculated, and then the electrokinetic velocity of the droplet is simulated utilizing a three-dimensional numerical model under different applied electric fields, droplet’s radii, ionic concentrations, zeta potentials of the oil–water interface, and zeta potentials of the air–water interface. The numerical results indicate that a negatively charged oil droplet near a negatively charged air–water interface moves in opposite direction of the direct current electric field and has larger velocity under higher electric field strength, droplet’s radius, ionic concentration, and absolute values of the two interface zeta potentials. [ABSTRACT FROM AUTHOR]

The wetting strategies of plants have inspired a wide range of biomimetic surfaces, such as water-droplet-capturing surfaces that imitate the fibrous system of dandelion seeds and water-droplet-repelling surfaces that mimic the superhydrophobicity of lotus leaves. Here, we developed an oil droplet manipulation device by causing a movable microfibre array to penetrate a superoleophobic mesh. The microfibre array tended to capture an oil droplet, and the superoleophobic mesh allowed the oil droplet to roll easily. The on/off switching of the device’s adhesion to oil droplets was controlled by moving the microfibre array. Our device could be used effectively to capture, transport and release four kinds of oil droplets (glycerol, rapeseed oil, peanut oil, and 100# machinery oil), which may enable the exploration of a wide range of applications involving switchable adhesion for handling oil droplets. [ABSTRACT FROM AUTHOR]

The alkali-surfactant-polymer (ASP) flooding as one of efficient enhanced oil recovery technology has attracted great interest in the recent years. Nevertheless, the high stability of the oily water has become a threat to the environmental security. And most of the separation methods have been gained through trial-and-error approaches at present. However, there is a lack of clear microscopic scale study with respect to the mechanisms that govern the separation efficiency. In this paper, the effects of alkali (A), surfactant (S) and polymer (P) on the coalescence behavior of oil droplets are experimentally investigated with high-speed photography. The results indicate that the composition of the ASP flooding solution substantially influences the coalescence patterns of oil droplets. The optimum solute concentration of each component in ASP for oil droplet coalescence is obtained based on the microscopic experimental results. Statistical investigation on contact angles of the coalesced oil droplets is concluded that effective contact angles are distributed asymmetrically within the ranges of conditions studied. And most of the oil droplets are found to coalesce at small contact angles (5–25°) or large contact angles (50–80°). The research findings are of great significance for developing high-efficient processing technology for ASP flooding produced water. [ABSTRACT FROM AUTHOR]

In recent years, significant progress has been achieved in the study of aqueous foams. Having said this, a better understanding of foam physics requires a deeper and profound study of foam elements. This paper reviews the studies in the microscale of aqueous foams. The elements of aqueous foams are interior Plateau borders, exterior Plateau borders, nodes, and films. Furthermore, these elements' contribution to the drainage of foam and hydraulic resistance are studied. The Marangoni phenomena that can happen in aqueous foams are listed as Marangoni recirculation in the transition region, Marangoni-driven flow from Plateau border towards the film in the foam fractionation process, and Marangoni flow caused by exposure of foam containing photosurfactants under UV. Then, the flow analysis of combined elements of foam such as PB-film along with Marangoni flow and PB-node are studied. Next, we contrast the behavior of foams in different conditions. These various conditions can be perturbation in the foam structure caused by injected water droplets or waves or using a non-Newtonian fluid to make the foam. Further review is about the effect of oil droplets and particles on the characteristics of foam such as drainage, stability and interfacial mobility. [ABSTRACT FROM AUTHOR]

Magnetic nanoparticles have unique properties such as extremely large surface area per volume substance and strong magnetic response. In addition, the possibilities for surface functionalization make them exciting candidates for separation applications in oil and gas production and processing. Relevant separation applications discussed in this review are emulsion separation, oil spill clean-up, produced water purification, and mitigation of undesired phase separation. Surface coatings entailing polymers, surfactants, or inorganic compounds are typically used to protect and stabilize the nanoparticles and for further functionalization in targeting specific applications. The adsorption, or separation efficiency, of the functionalized nanoparticles in certain processes is found to reach as high as 99.99% and depends on the type of surface coating, proper nanoparticle dispersion in the target medium, and the chosen separation technique. Several magnetically driven methods available for nanoparticle recovery, or nanoparticle purification, are discussed with respect to their efficiency and possibilities for optimization. Safety concerns regarding the use of the nanoparticles in industrial work environments and potential risks of exposure are presented in the last section. [ABSTRACT FROM AUTHOR]

During the Deepwater Horizon blowout, unprecedented volumes of dispersant were applied both on the surface and at depth. Application at depth was intended to disperse the oil into smaller microdroplets that would increase biodegradation and also reduce the volumes buoyantly rising to the surface, thereby reducing surface exposures, recovery efforts, and potential stranding. In forensically examining 5300 offshore water samples for the Natural Resource Damage Assessment (NRDA) effort, profiles of deep-plume oil droplets (from filtered water samples) were compared with those also containing dispersant indicators to reveal a previously hypothesized but undocumented, accelerated dissolution of the polycyclic aromatic hydrocarbons (PAH) in the plume samples. We interpret these data in a fate-and-transport context and conclude that dispersant applications were functionally effective at depth. [ABSTRACT FROM AUTHOR]

Multi-oil droplet target recognition is one of the applications of machine vision in the measurement of oil-water two-phase flow parameters , which could combine other algorithms to obtain the oil droplet velocity and the water holdup of oil water two-phase flow. Appropriate target representation features can improve the recognition effect of multiple oil droplets. However, due to shooting environment differences and quality differences of oil-water two-phase flow images, existing target representation features do not perform well in low-quality oil-water two-phase flow images. To improve the precision of multi-oil droplet target recognition in oil-water two-phase flow and reduce the miss rate, this paper constructs an integrated feature on the basis of aggregate channel features (ACF). The integrated feature named aggregate channel features with histogram of local gravitational feature（ACFHG） contains the color feature channels reflecting the overall color features of the oil droplet sample, the gradient amplitude channel reflecting the overall gradient of the oil droplet sample image, the gradient direction histogram feature channels reflecting the local gradient of the oil droplet sample image, and the local gravitational feature channels that ensure oil droplet target recognition in low quality photos and photos taken in complex shooting environments. Moreover, the rotation invariance is obtained by taking the oriented gradient histogram of the local gravitational feature to further improve the multi-oil droplet target recognition effect. Experiment results show that the average precision of multi-oil droplet target recognition using the integrated features is 83.38%, which is 9.93% higher than that with using ACF, and the miss rate is 9.13%, which is 57.18% lower than that with using ACF. Compared with other existing target detection methods, the method proposed in this paper still has an advantage in the rate of missed detection. • Integrated features for improving the precision and reducing the miss rate in the multi-oil droplet recognition process are proposed. • The average precision of using integrated feature is 9.93% higher than that of using aggregate channel features. • The miss rate of using integrated feature is 57.18% lower than that of using aggregate channel features. [ABSTRACT FROM AUTHOR]

Various methods of oil spill remediation exist, e.g., floating booms, controlled burning and the release of chemical surfactants. These surfactants facilitate the breakup of the slick into micron-sized droplets. Here, we studied the impact such a surfactant has on the size distribution of oil droplets in the water column and in the gut of the filter feeder Daphnia magna. We also studied the effect of surfactants on detachment conditions of chemically and mechanically dispersed oil (respectively MDO and CDO) droplets from capture fibers. Our results show that including solubilized dioctyl sulfosuccinate sodium salt in the mixing of the emulsion produces smaller droplets and a narrower size distribution in the water. In the gut, the size of ingested droplets does not change whether the oil is mixed mechanically or chemically. Also, surfactant coated droplets detach at a lower velocity than mechanically dispersed droplet because of their lower oil/water interfacial tension. • Addition of DOSS lowers the size distribution of oil droplets. • The sizes of CDO and MDO droplet ingested by Daphnia magna do not change. • Daphnia magna selects for smaller MDO droplets. • Surfactant-coated droplets detach from fibers at lower velocity than uncoated ones. [ABSTRACT FROM AUTHOR]

The characteristic amoeboid behavior of an oil droplet (decane with dissolved palmitic acid) on an aqueous phase containing a surfactant (stearyltrimethylammonium chloride) has been investigated and discussed. The formation and motion of assemblies of molecular aggregates were observed with the aid of a range of particle tracers. The quasi-elastic laser scattering method was employed to measure the surface tension of the aqueous phase as a function of time. From those measurements we found that the amoeboid behavior occurs in three stages. First, molecular aggregates formed at the oil-water interface and subsequently spread and absorbed at the aqueous surface thanks to a convective flow due to the Marangoni effect. In the second stage, the whole aqueous surface was saturated with those molecular aggregates and a phase transition to a liquid condensed monolayer membrane occurred. Finally, domains formed at the bottom of the oil droplet with permeable boundaries composed of branch-shaped assemblies of molecular aggregates. Blebs grew in those parts of the oil droplet rim with high accumulation of molecular aggregates. [ABSTRACT FROM AUTHOR]

In oil-air lubrication lubricants are supplied by droplets to tribo-pairs. Numerical work has been carried out to investigate transient EHL film when an oil droplet is entrained. Results show that entrainment speed, oil viscosity and wettability of the oil/solid interface significantly affect the lubricant side flow across the entrainment direction (termed as squeeze spread) at the inlet, and consequently different EHL behaviors are presented. For fast speeds, high oil viscosity and low wettability, when a small droplet passes through the central contact a dimple-shaped film is generated and bounding surfaces cannot be fully separated. Numerical results showed close correlation to the experiments. This study is beneficial to basic understanding of lubrication by limited lubricant supply. [ABSTRACT FROM AUTHOR]

The continuous separation of different types of droplets from a mixture is important in industrial and research applications. Currently researches for droplet separation focus on homogeneous emulsion droplets, and there is no study on the separation of heterogeneous droplets. The wall-induced dielectrophoresis, which originates from the non-uniform electrical field around a sphere nearby a planar wall, can be applied to separate dielectric particle and cells. In this work, the continuous separations of oil droplets and the electrically induced Janus droplets (EIJDs) in a microchannel by using the wall-induced dielectrophoresis method were presented. The wall-induced dielectrophoretic lateral migration of a droplet depends on the size and surface charge of the droplet. In this study, the wall-induced dielectrophoretic lateral migrations of oil droplets and Janus droplets in a straight microchannel under different strengths of electrical fields were investigated first, and the experimental results match well with the theoretical predictions. Then, the separations of oil droplets by size, separations of Janus droplets by size, and separation of mixtures of Janus droplets and oil droplets with the same size were conducted, respectively. The experimental results demonstrate that, with this method, the separations of target oil droplets or Janus droplets with specific size can be accomplished by simply adjusting the voltages applied to the microchannel. [ABSTRACT FROM AUTHOR]

The structure and dynamics at the surface of nanoscopic hexadecane droplets immersed in aqueous phase with and without emulsifiers (1-alkanols of varying chain length; pentanol, heptanol, decanol and dodecanol) have been studied using atomistic molecular dynamics simulations. The nature of layering of alcohol molecules on the oil droplet is governed by the hydrophobicity of alkanols. Longer chain alkanols are more likely to penetrate into the oil droplet. The probability of tangential orientation of hexadecane molecules at the interface decreases with decreasing hydrophobic environment around the droplet. The interfacial hexadecane molecules show greater probability to obtain a puckered conformation in binary oil–water system than in ternary oil–water–alkanol systems. Decrease in hydrophobic interaction between hexadecane and water molecules due to the efficient screening of oil surface by longer chain alkanols in ternary oil–water–alkanol systems leads to greater survival probability of water molecules in the oil–water interfacial layer and enhancement in life time of H-bonds formed between alcohol and water molecules. [ABSTRACT FROM AUTHOR]

• A mathematical model describing the kinetic behavior of oil droplets in water under horizontal wall constraints is developed and the model is validated based on a microscopic experimental system. • The dynamics behavior of oil droplets in water near the wall is analyzed from the perspective of damped vibration. • A motion pattern diagram of oil droplets near the wall with (G, Oh) as the regulation parameter is established to identify the motion law of oil droplets at different Mo numbers. The interaction problem of a freely-rising oil droplet in water due to the horizontal wall constraint is solved numerically. The motion equation, water film drainage equation, and Young-Laplace equation are coupled to establish a dimensionless mathematical model for describing the bounce behavior of oil droplets in water. In addition to buoyancy and flow resistance, the motion equation also introduces added mass force and film induced force caused by interaction with the wall. Further analysis shows that the coupling model conforms to the dynamics characteristics of a damped vibration system from the perspective of vibration. Based on the analysis of vibration parameters, We found that the bounce behavior of oil droplets is directly related to the oil-water system's Eo number and Oh number, in addition to the size dependence. Moreover, the bounce pattern diagram with (G, Oh) as the control parameter provides a suitable identification for the transition law of the bounce number of oil droplets under the horizontal wall constraint. The findings of this study facilitate quantifying the processes of oil droplet adhesion, coalescence, and spreading and provide a sub-model reference for the description of complex oil-water systems. [ABSTRACT FROM AUTHOR]

Accurate and fast determination of the diffusion coefficient of the CO 2 /oil system is essential in CO 2 enhanced oil recovery (CO 2 -EOR) and CO 2 geological sequestration practices. In this work, a novel methodology is proposed and demonstrated on measuring the diffusion coefficient of the immiscible CO 2 /oil binary systems based on quantification of the oil droplet swelling behavior. Five oil samples, including n-decane, n-dodecane, n-tetradecane, n-hexadecane and liquid paraffin, are employed as the oil phase and the diffusion coefficient for each CO 2 /oil system were determined. After validation of the methodology based on good agreements between the measurement and the reported results for both the pure component oil and the synthetic oil, the diffusion characteristics of the CO 2 /oil systems are scrutinized in the pressure range 2–10 MPa and the temperature range 26.9–82.1 ℃. The measurement results clearly show the elevated system pressure could lead to stronger diffusion processes between the CO 2 and the oil phase, while the temperature impacts on the diffusion process are more complex due to the synergistic effects of CO 2 density and the oil viscosity. Performed in the state-of-the-art drop shape analyzer within a short measurement period, it is expected the proposed methodology could provide an efficient supplementary for diffusion coefficient measurements of the CO 2 /oil binary systems. [Display omitted] [ABSTRACT FROM AUTHOR]

This article reports on the evaluation of the electrochemical noise technique consisting in measuring the fluctuations of the electrolyte resistance (ER, impedance at high frequency) between two metallic electrodes immerged in a conductive electrolyte to detect and characterize single particles circulating in a microfluidic device. Numerical simulations were performed with the finite element method to study the influence of the dimensions of the channel and the electrodes on the impedance. Excellent agreement was obtained between the theoretical and experimental results, which allowed the diameter of the oil droplets to be estimated with an accuracy of a few percents in the case of droplet diameters ranging from 60 to 100 μm. Developments of smaller microfluidic devices are under progress to detect and characterize particles of a few micrometers, such as biological cells for example. [ABSTRACT FROM AUTHOR]

This paper is devoted to the evaluation of the electrochemical noise technique consisting in measuring the fluctuations of the electrolyte resistance (ER) between two metallic electrodes immerged in a conductive electrolyte to detect and characterize single particles circulating in a microfluidic device, without the help of optical measurements that require good visibility of the detection region. Numerical simulations were performed with the finite element method to study the influence of the dimensions of the channel and the electrodes on the ER. Measurements of the ER variations due to the passage of oil droplets and plugs passing between the electrodes were carried out. Excellent agreement was obtained between the theoretical and experimental ER transients, which allowed the velocity and diameter of the oil droplets to be estimated with an accuracy of a few percents in the case of droplet diameters ranging from 60 to 100 μm. According to the numerical simulations and the amplitude of the background noise, oil droplets of diameter larger than 20–25 μm can be detected in the microchannel used (cross section of 100 μm × 100 μm and 100 μm × 100 μm electrodes separated by a gap of 100 μm). Developments of smaller microfluidic devices are under progress to detect and characterize particles of a few micrometers, such as biological cells for example. [ABSTRACT FROM AUTHOR]

The relative effects of hydrodynamic, thermodynamic, and geochemical factors on the fate and transport of oil in the subsea are not well understood to date. This glaring lack of knowledge in deep-sea spill studies precludes the parameterization of blowout far-field models. Here we use observations from the Macondo blowout to evaluate the importance of input variables in a numerical model of oil transport and fate. We adapt a multi-hydrocarbon fraction module to oil dissolution and run sensitivity analyses under various parameterization scenarios. We find that the inclusion of oil droplet atomization, variable flow rates (VFR), high-pressure biodegradation (HPB), and vertical currents׳ velocities (VV) affects significantly the subsea oil mass distribution in the water column as well as the evolution of deep plumes. In particular, droplets up to 50 μm are neutrally buoyant and moved by deep currents predominantly driven by the topography, while the depth of the deep plume is very sensitive to the VV of the hydrodynamic model. We find good agreement between CTD cast observations and modeled mean depth of the oil mass, whereby HPB provide increased accuracy of predictions with time. The model suggests that VFR and HPB are mechanisms for the persistence of the southwestern deep plume observed at 1100 m by increasing the residence time of the oil in the water column. Modeled oil concentrations range from 5 to 500 ppb and present the highest values in the western and deepest locations of the subsea plume, which corroborate with field observations. We hypothesize that a substantial amount of subsea oil mass might have interacted with the bottom of the Mississippi Canyon. [ABSTRACT FROM AUTHOR]

The initiation of lipid autoxidation within single oil droplets in Tween-20-stabilized oil-in-water emulsion was achieved by highly focused two-photon (2P) irradiation at excitation wavelength ( λ ex ) 700 nm. The radical formation was enhanced by inclusion of the photo-cleavable radical initiator di- tert -butyl peroxide (DTBP) into the droplets, and demonstrated with confocal microscopy using radical-sensitive probe BODIPY 665/676 . The radical chain reactions progressed up to 60 μm; however, there were no indications of oxidation in neighboring droplets demonstrating that radicals and oxidized probe molecules were not able to migrate between oil droplets. In addition, the spatial propagation of lipid autoxidation increased with the degree of oil unsaturation. [ABSTRACT FROM AUTHOR]

[Display omitted] • Van der Waals interaction is the main weak interaction between oil and water phases. • Dispersion attraction between oil phases is stronger than electrostatic attraction. • Negative electrophoretic migration of oil droplets occurs under a DC electric field. • Increasing ion concentration will reduce oil removal efficiency. • The inhibitory effect of three inorganic salts on oil droplet is MgCl 2 > CaCl 2 > NaCl. Oil-in-water (O/W) wastewater generally contains inorganic salt ions, which cause energy consumption in the process of electric demulsification. To reveal the influence mechanism of inorganic salt ions on the micro movement of oil droplets in O/W emulsion, the electrophoretic migration of oil droplets with different ion concentration was studied based on molecular dynamics simulation. The results showed that Na+ adsorbed the negative charge on the surface of the oil droplets while Cl- repelled it, leading to a decrease in the electrophoretic mobility and deformation of the oil droplets with the increase of ion concentration. The inhibitory effect of three inorganic salts on oil droplet electrophoretic migration was MgCl 2 > CaCl 2 > NaCl. The weak interaction between oil, water and ions was mainly van der Waals interaction. When the NaCl concentration was 0.4 mol/L, the oil–water interfacial tension was at its maximum value of 85.14 mN/m. and the deformation degree of oil droplets reached the minimum values of 0.45. The formation of hydrated ions reduces the freedom of water molecules. The above findings uncovered the effect of inorganic salt ions on the electrophoretic migration of oil droplets in O/W emulsions under a DC electric field, which can provide theoretical guidance for the purification of oily wastewater from the molecular level. [ABSTRACT FROM AUTHOR]

CO 2 miscible flooding is one of the most ideal scenarios in oil recovery practices. Accurate prediction of the minimum miscible pressure (MMP) of the CO 2 /oil system is essential for CO 2 Enhanced Oil Recovery (CO 2 -EOR) and carbon geological storage applications. In this paper, a novel method based on quantification of the oil droplet volume shrinkage behavior is proposed and demonstrated in the determination of the MMP of the CO 2 /n-hexadecane (n-C 16 H 34) system and the CO 2 /n-octadecane (n-C 18 H 38) system. Based on the specific quantitative criterion of the oil droplet volume reduction rate, the MMPs of the CO 2 /oil system under different temperature levels were determined. The accuracy of the measurement results has been validated with the corresponding thermodynamic phase equilibrium calculation results. To show the application potential of the proposed method, detailed discussions have been provided based on comparisons with the Vanishing Interfacial Tension (VIT) method. It is expected the proposed Oil Droplet Volume Measurement (ODVM) method could act as a robust supplementary for studying the miscibility characteristics of the CO 2 /oil system. [Display omitted] • A novel Oil Droplet Volume Measurement (ODVM) method is proposed to measure the MMPs of the CO 2 /medium oil system. • The measurement results are validated with the thermodynamic calculations. • Comparisons with the Vanishing Interfacial Tension (VIT) method are reported. [ABSTRACT FROM AUTHOR]

[Display omitted] • Oil phase molecules are attracted to each other mainly by Van der Waals forces. • The mechanism of droplet migration and deformation is explained by weak interaction. • Negative electrophoretic migration occurred in the oil droplets. • The negative charge of the droplet is aligned towards the anode. • The presence of NaCl hinders the migration of oil droplets under the electric field. Removing oil droplets from O/W emulsion is a difficult problem at present. In order to explore the effect of electric field intensity on the migration and deformation of oil droplets in O/W emulsion, in this paper, the motion behavior of oil droplets under DC electric field is studied based on molecular dynamics simulation. It is found that oil phase molecules are attracted together by Van der Waals interaction. When E = 0.7 V/nm, the deformation degree reaches the maximum 0.534, and the overall migration speed of the oil droplet is 0.03266 nm/ps. Negative electrophoretic migration of oil droplets occurs under electric field, which is similar to the experimental results. The effect of electric field intensity on oil droplet migration and deformation is explored for the first time, and the relevant results can provide theoretical guidance for improving the purification process of oily wastewater. [ABSTRACT FROM AUTHOR]

Under limited lubricant supply condition, the lubrication of a slider bearing can be enhanced by discontinuous oil droplets on the lubrication track induced by poor surface wettability. This experimental finding is contrary to the general perception that strong surface wettability favors lubricating film build up. Theoretical lubrication models with the lubricant supply in the forms of oil droplets (Model Ⅰ) and uniform oil layer (Model Ⅱ) are established to clarify the odd experimental observation. Results show that oil supply in the form of droplets can achieve better lubrication performance than the uniform oil layer, which are correlated to the experimental finding. The mechanism is probably due to the early film pressure initiation when oil droplets enter the bearing contact. [Display omitted] • Under conditions of limited lubricant supply, experimental finding is contrary to the general perception that strong surface wettability favors lubricating film build up. • Theoretical lubrication models with the lubricant supply in the forms of oil droplets and uniform oil layer are established, and numerical analyses have been conducted. • Oil droplets can achieve better lubrication performance than the uniform oil layer, which is attributed to the early film pressure building when oil droplets enter the bearing contact. • The specific droplet number, the lubricant supply quantity, the shape of the droplet (height-to-radius ratio) are dominating factors for the lubrication performance. [ABSTRACT FROM AUTHOR]

Abstract: Phospholipids are widely used to stabilize oil in water micron size emulsion droplets; the interfacial phospholipid density and tension of such droplets are difficult to estimate. In the present paper, we describe a simple approach by which the measurement of a micron size oil droplet interface fluorescence intensity provides directly both the interfacial phospholipid density and the interfacial tension. This method relies on two prior calibration steps: (i) the quantitative variation of the interfacial tension with fluorescence intensity at droplets interface through micro-manipulation techniques; (ii) the variation of interfacial tension with phospholipid density through monolayer isotherm. Here, we show the validity of this approach with the example of micron size oil droplets stabilized with a phosphatidylcholine phospholipid, in aqueous buffer. [Copyright &y& Elsevier]

Abstract: Low cost porous ceramic membrane support was prepared using kaolin, pyrophyllite, feldspar, ball clay, quartz and calcium carbonate mixture along with PVA as a binder. The main intention of this work is to study the changes in the properties of the membrane supports (pore size, porosity, mechanical strength and pure water permeability) by the addition of titanium dioxide (TiO2). Three membrane supports, namely, support-I, 3G and 6G supports (naming is based on the loading of TiO2) were prepared by uniaxial compaction method. All the membrane supports were sintered at 950°C and systematically analyzed using thermogravimetric (TG), particle size distribution (PSD), X-ray diffraction (XRD), N2 adsorption–desorption and scanning electron micrograph (SEM) analysis. The porosity of the support-I, 3G and 6G supports was found to be 44, 38 and 36% with an average pore diameter of 0.98, 0.93 and 0.83μm, respectively. The flexural strength of the membrane supports was increased with the addition of TiO2 and ranges between 28 and 33MPa. Solvent permeation studies through these membrane supports revealed that the non polar solvents were more permeable than the polar solvents and the transport mechanism was mainly controlled by viscosity of the solvents. Performance of the membrane supports was investigated for oil-in-water emulsion separation by varying the feed concentration and applied pressure. A maximum rejection of 99% was obtained with 6G support for an oil concentration of 200ppm. Also, an attempt has been made for the separation of bovine serum albumin (BSA) from its solution using these membrane supports and a reasonable rejection of 40% was obtained for 100ppm of BSA solution. Research highlights: ► Effect of addition of TiO2 on the properties of the porous ceramic membrane supports was investigated. ► Potential of the supports was tested for oil and BSA separation from its solution. ► Higher rejection for oil (99%) and moderate rejection for BSA (40%) were obtained. ► Pore fouling mechanisms were also investigated for the oil-in-water emulsion system. [Copyright &y& Elsevier]

Abstract: When a liquid droplet impacts on a solid surface, a transient impact force is developed at the interface between the liquid and the solid surface. Impact velocity, surface tension and density of the liquid are the important parameters that influence the impact force. In the present study, impact forces of two different oils’ droplet (hydraulic oil ISO VG 68 and lubrication oil SAE 30) are compared with the impact force of water droplet. The impact velocity is varied from about 1.38 to 2.96m/s. The impact force is determined experimentally using polyvinylidene difluoride (PVDF) piezoelectric film attached on the solid surface. The dynamic response of the PVDF piezoelectric film is acquired using data acquisition system with personal computer. The film is dynamically calibrated using bead drop impact method. A linear relationship between voltage output of the PVDF piezoelectric film and impact force is established. The droplet impact force is determined by measuring the voltage output delivered by the PVDF piezoelectric film and converted it into the impact force. Impact forces developed by both the oils’ droplets are lesser than the impact force of water droplet. The impact duration observed is about 600μs. [Copyright &y& Elsevier]

Abstract: A compressible turbulence analysis of the flow of oil mist in MQL finish-turning of Inconel 718 was conducted using a finite volume method for optimizing the spraying conditions of oil mist and reducing the oil consumption. First, a domain of the analysis including a rotating workpiece and a single point cutting tool with a spraying nozzle was discretized, and then, changes in the velocity, pressure and vorticity of compressed air, and mass flow rate of oil mist near the cutting edge were calculated for three types of spraying nozzles. It was found that when the distance from the outlet of a nozzle to the tool tip was decreased using cover-type nozzles, mass flow rate of oil mist to near the cutting edge increased drastically. Among the three types of nozzles, the mass flow rate was the largest for a cover-type nozzle for oblique spraying. These results were consistent with the performance of the nozzles in cutting experiments. Finally, the flight of an oil droplet and the lubrication mechanism in MQL machining were investigated using analysis results. [Copyright &y& Elsevier]

Abstract: Displacement of immiscible fluids is important in sub-surface processes such as enhanced oil recovery, oil sand processing and detergency. In this study, simulation of an oil droplet deformation on a solid substrate in simple shear flow has been carried out using computational fluid dynamics tool (Fluent 6.3) and the shape of the oil droplet is compared with that of the experimental observation. The dynamic behavior of a two-dimensional oil droplet subject to shear flow in a closed channel is considered under the condition of negligible inertial and gravitational forces. The volume of fluid method is used in Fluent to determine the dynamics of free surface of the oil droplet during the fluid flow. The oil droplet deformation increases with the increase in capillary number, Reynolds number and size of the oil droplet. The deformation of an oil droplet attached to channel surface in simple shear flow is studied experimentally in laminar flow through visual observation using microscope (Ziess, SV11 APO) with high speed camera (PCO). Aniline and isoquinoline was used to form oil droplet and distilled water was used as shearing fluid. The deformation of aniline and isoquinoline droplets was recorded using a high speed camera connected to a PC. The recorded image was replayed and the deformation of aniline and isoquinoline droplets was analyzed using Axio Vision software and compared with the results obtained from CFD simulation. The deformation of different sizes of aniline and isoquinoline droplets at different flow rates of shearing fluid and with time are well predicted by the CFD simulation. [Copyright &y& Elsevier]

Effects of salinity and clay type on the aggregation process of crude oil and clay particles (oil–mineral aggregates – OMA) were studied in the laboratory. OMA were generated by shaking various oil/clay mixtures in water at 20 °C and at a pre-determined energy level. Shape, median and maximum sizes, size distribution and concentration of oil droplets forming OMA were measured using epi-fluorescence microscopy. Results showed that the median and maximum sizes and the concentration of mineral-stabilized droplets increase rapidly when salinity increases from zero to a critical aggregation salinity in the range of 1.2–3.5 ppt. The magnitude of the increase of droplet size is controlled by clay type, while the increase of droplet concentration is influenced by oil type. Size distributions of oil droplets are self-similar, but their magnitudes depend on salinity and oil type. The effect of salinity on droplet size distribution is strongly influenced by clay type. Empirical relationships are derived to calculate concentration and size distribution of mineral-stabilized droplets. [Copyright &y& Elsevier]

The relative influence of oil type and temperature on the characteristics of oil droplets stabilized by mineral particles (oil–mineral aggregates––OMA) was studied in the laboratory. OMA were generated by shaking eight different oils under two temperatures with natural mineral fines in seawater at a pre-defined energy level. Shape, mean and maximum sizes, size distribution and concentration of oil droplets forming negatively buoyant OMA were measured by image analysis using epi-fluorescence microscopy. Results showed that oil droplets are, on average, spherical regardless of oil composition and temperature. Non-spherical “elongated” oil droplets form more at 20 °C than at 0 °C. Droplet shape and size were not correlated to oil viscosity. The concentration of oil droplets decreased rapidly with oil viscosity, temperature and asphaltenes–resins content (ARC). When normalized with ARC, mass concentration of oil droplets correlates well with oil viscosity, regardless of experimental temperature. A model was proposed to calculate mass of oil dispersed by OMA as a function of oil viscosity and ARC. Size distributions of oil droplets follow similar trends, but their magnitudes depend on oil type and temperature. A function was derived that describes all the data when size distributions were presented in a normalized form N/Nt=f(D/D50), where N is number of droplets of diameter D, Nt is the total number of droplets and D50 the mean size of the droplets. [Copyright &y& Elsevier]

Alkaline/surfactant/polymer (ASP) flooding technology has been used successfully in the Daqing oilfield, but the produced water is more difficult to treat than that from water flooding and polymer flooding. Simulation experiments were conducted to investigate the effects of ASP on the stability of oil droplets in the produced water. Settling experimental results showed that polymer favored oil–water separation when its concentration was less than 1000 mg l−1. Oil concentrations in the water after settling separation increased with the increase of surfactant concentration, and increased with the increase of NaOH concentration up to 200 mg l−1 and then decreased with the further increase of alkaline concentrations. The interfacial properties of oil–water were investigated to find the mechanisms for the stability of oil droplets in produced water from ASP flooding. The synergetic action of surfactant ORS-41 and NaOH was found to greatly influence the interfacial tension of oil and water. ORS-41 and polymer can increase the density of negative electrical charges on the surface of oil droplets and the interfacial elasticity of oil and water. Alkaline however can increase the density of negative electrical charges of oil droplets and the interfacial elasticity of oil and water in lower alkaline concentrations, but the effect is reversed in higher alkaline concentrations. On the other hand, the flocculating ability of the polymer also helps small oil droplets coalesce and form big ones. The flocs of oil droplets were found in produced water from ASP flooding with a microscope. [Copyright &y& Elsevier]

Due to the oil field development enters the period of high water cut, the flow drag of oil-water two-phase flow in nonmetallic pipes requires further research. Moreover the dynamic spreading behavior of oil droplet on a pipe's wall is of great significance to investigate the flow drag. However, the spreading behaviors of oil droplets on surfaces with different wettabilities in water system are still not clear. In this study, firstly, considering the effect of surface wettability and oil droplet diameter, the spreading behaviors of oil droplets on non-metallic and metallic substrates were observed using a high-speed imaging system. Then, according to the spreading behaviors of oil droplets on the substrates and based upon the energy balance theory, a theoretical model of the spreading behavior of oil droplets was developed for predicting the dimensionless maximum spreading diameter. The quantitative relationships among the dimensionless maximum spreading diameter, the diameter of oil droplets, the properties of oil and water, and the wettabilities of surfaces were obtained. Finally, the theoretical model was verified using experimental data with deviations generally ranging within ± 10%. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract: The oil droplet is used as a simple model system to study the physical basis of intelligence. The oil droplet is a structure produced by self-assembly. By coupling a chemical reaction in the oil droplet with a physical instability, the droplet displays life-like properties such as autonomous motility, sensory-motor coupling, gradient following and agent-to-agent signaling. By developing this system towards ICT capabilities that include information processing, transmission and transformation, data storage and production, we explore the minimal physicochemical basis of intelligence. [Copyright &y& Elsevier]

• Oil droplets repeat adsorption-desorption without spreading on DPPC membrane. • Resins and asphaltenes inhibit the transmembrane transport of alkanes and aromatics. • Flexible net structure of resins hinders the release of hydrocarbons to membrane. • Octane and toluene have different penetration patterns across DPPC membrane. The hazardous effects of petroleum contaminants in the soil and water environment are highly associated with their interactions with cellular membranes, but our understanding on the molecular-level mechanisms for the adsorption and penetration of heavy oil mixture on cellular membrane is very limited. In this study, microsecond molecular dynamics simulations were performed to gain insights into the morphological evolution and penetration dynamics of the multi-component and single-component oil droplets on the dipalmitoylphosphatidylcholine lipid membrane. Results highlighted the inhibition effect of the resins on the penetration of alkanes and aromatics, because they would form net structure making it difficult to release the latter two components from the oil droplet to the membrane. It also demonstrated the obviously different patterns of penetration between alkanes and aromatics. The overall steps for the toluene penetration included detachment from oil droplet, dispersion in water, adsorption on membrane surface, structure adjustment and penetration into membrane. By contrast, the step of dispersion in water was not necessary for the alkanes' penetration. Instead, it relied on the adsorption of the whole oil droplet on the membrane surface which resulted in the formation of pores on the membrane surface by local structure deformation in the lipid head group regions. [ABSTRACT FROM AUTHOR]

Filter feeding animals capture and lose oil droplets using cilia or ramified appendages. Here we demonstrate that copepod and barnacle appendages capture fish, canola and 1-decanol oil droplets up to 11 μ m without selectivity for size, chemistry, density, viscosity, or interfacial tension. Following capture, the droplets are ingested or lost via detachment. Capture and detachment did not differ between a barnacle appendage and stainless-steel wires of radii R f = 50 and 250 μ m. Key parameters to detachment include the ratio of oil droplet radius to fiber radius, and the Weber number. Smaller oil droplet size to fiber size ratio r = R o ∕ R f , required a higher W e for detachment. These data plot as a curve that predicts whether a droplet will remain captured or detach and re-enter the fluid stream, based on the fluid, the droplet radius to fiber radius ratio, and the oil droplet properties. Significantly, this curve may be used to plan responses to oil spills in marine environments. • Oil droplets are captured by copepods without selectivity for size and viscosity. • Oil droplets are then ingested or detach back into the fluid stream. • Detachment is determined by the oil droplet to fiber size ratio and Weber number. • Barnacles capture oil droplets via direct interception and inertial interaction. • These data are used to make a predictive curve of droplet capture vs. detachment. [ABSTRACT FROM AUTHOR]

We use the microfluidics technique to study the coalescence of model oil droplets in microchannels. Different stages of the coalescence: convergence of the droplets and liquid film drainage, collision, interfacial film rupture, and merging are captured by high-speed imaging. The coalescence time is studied, defined as the merging time for the droplets after physical contact. Adding salts into the water phase may slow down the coalescence process. Cations Na+, Ca2+ and Mg2+ do not significantly affect the coalescence time, while the presence of the anion SO 4 2− produces much higher times than of Cl-. The presence of a surface-active component, stearic acid, increases the coalescence time, in a clear correlation with the interfacial tension. At higher pH stearic acid is deprotonated into stearate; correspondingly, the interfacial tension decreases further and the electrostatic repulsion of the head groups of fatty acids increases. The interface between droplets and water is thereby stabilized and the coalescence time increases. A pH value higher than the pKa of stearic acid induces highly stable plastic-like oil-water interfaces. We discuss the implications of our results on the applications in the petroleum industry concerning e.g. enhanced oil recovery under smart waterflooding. [ABSTRACT FROM AUTHOR]

• There were two oscillation patterns for adhered oil drop in the flow water, which can be transformed into each other. • The contact angle evolution of oscillating oil drop was analyzed. • The force mechanism of the three-phase contact point of the oil drop on the surfaces was carried out. • The sensitivity analysis of the factors affecting the oil drop oscillation behaviors was obtained. The oscillation of oil droplets on surfaces with different wettability in laminar flow field affected the initial movement behaviors of oil droplets, which was studied experimentally and theoretically in the paper. In the initial oscillation stage, the contact line of the oil drop on the substrate did not move, while the center mass and contact angle hysteresis of the droplet have changed. It was found that there were two oscillation patterns for adhered oil drop in the flow water, one was the up-down oscillation, the other was left-right oscillation, which can be transformed into each other. The contact angle evolution of oscillating oil drop was analyzed. It was found that with the increase of water flow velocity, the difference between the maximum and minimum contact angles of adhered oil drops on different surfaces was increasing, and the contact angle of oil drops on oleophobic surfaces underwater was more likely to exceed the advancing contact angle during the oscillation process. The force analysis of the three-phase contact point of the oil drop on the surfaces was carried out, and the oscillation behaviors of the oil drop were explained theoretically. The sensitivity analysis of the factors affecting the oil drop oscillation behaviors was carried out, and the influences of the oil drop height and the surface wettability on the oil drop oscillation frequency and amplitude was obtained. [ABSTRACT FROM AUTHOR]