Oil Droplets In Water Research Articles

Study on the Micro-explosion Mechanism and Influencing Factors of Oil Water Mixed Fuel

In this study, the mechanism of micro-explosion/puffing of diesel-water and tail oil-water single droplet during evaporation was investigated, and the influence of temperature, water content, eccentricity, and their interaction on fragmentation time was analyzed. Separate single droplets into composite droplets and mixed droplets based on different nucleation methods. During the evaporation process of a single droplet, it underwent nucleation, bubble generation and growth, and fragmentation. The fragmentation modes of composite droplets and mixed droplets are manifested as micro-explosion and puffing. Specifically, the micro-explosion of mixed droplets can be divided into strong micro-explosion and weak micro-explosion. The occurrence of weak micro-explosion can be attributed to the following reasons: insufficient development of water(bubbles) near the surface leading to premature ejection, and preferential bubble growth near the surface impeding internal bubble expansion. In addition, temperature and water content had a dual effect on the micro-explosion characteristics of diesel-water droplets, and higher temperature and water content were conducive to the occurrence of micro-explosion in tail oil-water droplets. Temperature had the least effect on fragmentation time, followed by water eccentricity, and water content had the most significant impact. And the interaction between water content and eccentricity substantially affected fragmentation time, equating to the minimum distance from the water to the outer surface of the fuel droplet.

Contributions of Colloidal Forces to the Heterogeneous Separation of Stable Oil-In-Water Emulsions.

We use theory to study the distribution of spherical emulsion oil droplets in water near a lipophilic surface as a guideline for designing membranes for oil/water phase separation. Heterogeneous phase separations are shown in our laboratory using hydrophilic and hydrophobic membrane designs, where the affinity of the membrane surface to one of the phases in the mixture locally increases its concentration. Considering a colloidal emulsion (nano- to microemulsions) of spherical and noncoalescing droplets, we assess the contribution of colloidal forces, i.e., van der Waals, electrical double layer, and hydrophobic interactions and the finite size of the droplets to the accumulation of spherical emulsion droplets near a surface. We use our theory to study an experiment-inspired case study and find that an isolated lipophilic membrane surface in contact with an oil-in-water emulsion supports the oil-enriched emulsion phase in a thin layer near the membrane surface, suggesting that a membrane pore size comparable to this thickness should support oil-enriched emulsion in the membrane pores and hence past the membrane.

Molecular modelling of active oil droplet propulsion: Insights from dissipative particle dynamics simulation

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 behavior of colloidal particles. The DPD model reproduced droplet propulsion and visualized 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.

Charge-induced aggregation of emulsified oil droplets in water with the presence of functionalized stainless steel felt

Oil-water mixtures, especially the surfactant-stabilized oil-in-water emulsions with high stability, are causing great difficulties in effective separation. In this work, a modification strategy was established to prepare functionalized stainless steel felt for emulsion separation by coating the felt with 3-triethoxysilylpropylamine, followed by the introduction of silica nanoparticles using a sulfur-based three-component coupling reaction. To satisfy the pore size requirement for effective emulsion separation, the developed felt was processed using a compression molding. With special wettability, optimized pore size, and electrostatic demulsification mechanism, the positive charged felt delivered outstanding separation capabilities for oil-in-water emulsions stabilized by various surfactants. Specifically, the flux and COD removal efficiency for the anionic-stabilized emulsion were up to 3911 L m-2h−1 and 95.3 %, while for cationic-stabilized emulsions, which were 1305 L m-2h−1 and 93.1 %. Our comparative results indicated that surface charges played an essential role in governing the separation performance of the felt, and the demulsification arising from the electrostatic attraction demonstrated better separation capability than that caused by the electrostatic repulsion. In addition, the developed felt showed controlled surface charge and anti-fouling performance under cyclic operations. The findings of this study are beneficial for constructing separation material with high separation efficiency and long-term durability for practical applications.

Multiresponsive Behavior of the Pickering Emulsifier and Its Application for Collecting Small Oil Droplets in Water.

Responsive Pickering emulsions, with unique nanoparticle interfaces and sensitivity to external stimuli, significantly enhanced the stability and applicability of Pickering emulsions. Multifunctional composite material poly((2-(dimethylaminoethyl methacrylate)-b-(acrylate cyclodextrin))/Fe3O4 nanoparticles, namely P(DMAEMA-b-A-CD)/Fe3O4, with both multiresponsive characteristics and emulsifying capabilities had been designed to remove small oil droplets from water. Using the reversible addition-fragmentation chain transfer (RAFT) method, diblock polymers P(DMAEMA-b-A-CD) were grown in a controlled manner on the surface of Fe3O4. The Fe3O4 core showed responsiveness to a magnetic field, and the block copolymers prepared via the RAFT method demonstrated reactivity to both pH and CO2. The P(DMAEMA-b-A-CD)/Fe3O4 nanoparticles exhibited the capability to form Pickering/Oxford emulsions with exceptional stabilization properties. It could be observed that the introduction of CO2, acid, and a magnetic field led to the breakage of the emulsion, while the emulsion could be restabilized by removing the CO2 and the magnetic field or by adding alkali. Measurements of interfacial tension, ζ-potential, and contact angle demonstrated that the emulsification/breakdown mechanisms associated with pH and CO2/N2 were related to the surface wettability of the nanoparticles. In addition, the emulsifier had an excellent cycling capacity with at least 10 cycles by CO2/N2. Additionally, P(DMAEMA-b-A-CD)/Fe3O4 nanoparticles exhibited excellent stability in oil phases with large polarity differences and various real oil phases with different viscosities. Importantly, the P(DMAEMA-b-A-CD)/Fe3O4 nanoparticles could serve as functional materials for efficiently separating small oil droplets from water through the application of a magnetic field. Therefore, P(DMAEMA-b-A-CD)/Fe3O4 nanoparticles held promising potential as materials with economic and commercial value for oil-water separation applications.

Effect of droplet angle on droplet coalescence under high-frequency pulsed electric fields: Experiments and molecular dynamics simulations

The droplet angle plays a key role in affecting electro-coalescence behavior of water droplets in oil. This work delves into the impact of the droplet angle on electrostatic coalescence in the high-frequency pulsed electric field by experiments and molecular dynamics simulations. Our findings revealed that a pulsed electric field promotes droplet coalescence before the droplets physically contact each other. Upon contact, notable oscillations ensue, with the electric field forces showing an adverse impact on the coalescence process. Depending on the degree of deformation, the droplet exhibits primary and secondary polarization states. Droplets exhibit a tendency to move apart when the initial droplet angle exceeds 75.93°, due to the same-charge repulsion and insufficient torque. An increase in the center distance ratio of droplets inhibits coalescence, resulting in a negative value in the decreasing rate of the droplet angle. These research findings offer valuable insights into improving the electrostatic demulsification process.

Effect of fluid properties on intensification of heat transfer process in oil-water droplet flow in a T-shaped microchannel

Droplet-based microfluidics refers to the production and utilization of micrometer-sized droplets. This technology has found widespread applications in drug delivery, biotechnology, disease prevention, chemical analysis, cell research, and functional material synthesis. Cooling of high heat flux electronic systems and hot spots is another application of the droplet flow which is focused by the current work. In this paper, formation and hydrothermal performance of oil droplets in water flow in a T-junction microchannel is studied by a 3D numerical simulation. Effects of different parameters such as surface tension, wettability and heat flux on the droplet size, heat transfer rate and pressure drop are investigated. It is observed that the shear between the discrete and continuous phases results in recirculating zones in both phases which contribute to improved mixing and heat transfer rates. Liquid film thickness adjacent to the heated surface and the droplet velocity are two other factors that positively affect the heat transfer. Decreasing the surface tension is shown to enhance the heat transfer rate. Moreover, an optimum value is found for the contact angle as 135° at which a 23 % heat transfer enhancement is achieved. Results also indicate that droplet size decreases with increase of contact angle while it slightly increases with increase of the surface tension and negligibly varies with the applied heat flux.

Selective Sparse Sampling of Water Droplets in Oil with Acoustic Tweezers.

In microfluidics, water droplets are often used as independent biochemical microreactor units, enabling the implementation of massively parallel screening assays where only a few of the reacting water droplets yield a positive result. However, sampling the product of these few successful reactions is an unsolved challenge. One possible solution is to use acoustic tweezers, which are lab-free, easily miniaturized, and biocompatible manipulation tools, and existing acoustic tweezers manipulating particles or cells, and water droplet manipulation in oil with an acoustic tweezer is absent. The first challenge in attempting to recover a few water droplets from a large batch is the selective manipulation of water droplets in an oil system. In this paper, we trap and manipulate single water droplets in oil using integrated single-beam (focused beam/vortex beam) acoustic tweezers for the first time. We find that water droplets with a diameter smaller than half a wavelength are trapped by acoustic vortices, while larger ones are better captured by focused acoustic beams. It is the first step to extract the target water droplet microreactors (positive ones) in an oil system and analyze their content. Compared to previous techniques, such as fluorescence-activated cell sorting (FACS), our technique is sparse, meaning that the sampling time is proportional to the number of droplets required and very insensitive to the total number of microreactors, making it well suited for large-scale screening assays.

Stability enhancement of pickering emulsions based on κ-carrageenan microgel: Synergistic effect of l-lysine and potassium ions at low ionic strength

The study utilized the synergistic effect of l-lysine and K+ to improve the stability of Pickering emulsions based on κ-carrageenan microgels. The gel strength of κ-carrageenan gels, the zeta potential and particle size revealed that the microgel particles prepared with l-lysine and K+ had the potential to be Pickering particles. l-lysine formed electrostatic interactions and hydrogen bonds with κ-carrageenan. Structural modifications of microgel particles by l-lysine (0.05%–0.10%) and low K+ strength (≤40 mmol/L) promoted the formation of a dense interface layer at the oil-water droplet surface to prevent the accumulation of oil droplets and further significantly enhance the appearance and centrifugal stability of Pickering emulsions. The microstructure and rheological analysis showed that K+ at low ionic strength, in cooperation with l-lysine, formed a more tightly structured layer between the microgel particles wrapped on the surface of oil droplets, thereby enhancing the stability of emulsions. In conclusion, these Pickering emulsions with prolonged stability are expected to be suitable healthy animal fat substitutes for use in food applications.

Rigorous Accounting for Dependent Scattering in Thick and Concentrated Nanoemulsions.

Concentrated and thick oil-in-water nanoemulsions have been observed to become more transparent with increasing oil volume fraction. This study demonstrates rigorously experimentally and numerically that such unusual behavior is due to dependent scattering including not only far-field but also near-field effects. Indeed, when the droplet concentration is sufficiently large, their interparticle distance becomes small compared to the wavelength of light and scattering by a given droplet may be affected by the proximity of others. This situation is referred to as dependent scattering. Light transfer through nanoemulsions and other colloids has previously been modeled by solving the radiative transfer equation accounting for dependent scattering using the static structure factor based on far-field approximations. Here, oil-in-water nanoemulsions were prepared with oil volume fraction ranging between 1 and 20% and a peak droplet radius of 16 nm. The spectral normal-hemispherical transmittance of the different nanoemulsions in 10 mm thick cuvettes was measured experimentally between 400 and 900 nm. Numerical predictions for nonoverlapping randomly distributed nanoscale oil droplets in water and accounting for dependent scattering including near-field effects-using the recently developed radiative transfer with reciprocal transactions (R2T2) method-were in excellent agreement with experimental measurements. Simulations revealed that assuming independent scattering underestimated the normal-hemispherical transmittance even for a relatively small oil volume fraction. Additionally, simulations using the dense medium radiative transfer (DMRT) and static structure factor predicted that dependent scattering prevailed for oil volume fractions slightly greater than those predicted by the R2T2 method. Interestingly, the DMRT method predicted large increases in transmittance when the oil droplet size and volume fraction were larger than 10 nm and 10%, respectively. Finally, simulations also revealed that dependent scattering enables the design of oil-in-water nanoemulsions to backscatter or absorb light by tuning the oil droplet size and volume fraction. The results validate that the R2T2 method could be used to characterize nanoemulsions or to investigate their formation, composition, and stability for drug delivery, food, and cosmetics applications. Future studies could extend the use of the R2T2 method to colloidal suspensions with particles of arbitrary shapes and to radiation transfer of polarized light in turbid media.

Unraveling Partial Coalescence Between Droplet and Oil-Water Interface in Water-in-Oil Emulsions under a Direct-Current Electric Field via Molecular Dynamics Simulation.

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.

Study on the self-adaptive process of droplet traffic to a perturbation of flow resistance at the arms of a micro-T-junction

The response of the water–oil droplet flow to a perturbation of flow resistance added at the arms of a bypassed micro-T-junction is studied through a numerical method. The capillary number of the continuous flow varies between 0.007 and 0.034. Once an additional flow resistance is introduced at the arms of the T-junction, the flow self-adapts to the perturbation and droplets show complex dynamics at the junction, including splitting, merging, and reshaping. During the self-adaptive process, the instantaneous splitting ratios of the dispersed flow show positive correlations with that of the continuous flow. The correlation coefficient reduces as the increase in the amplitude of the perturbation. The ensemble splitting ratios of them, however, are independent. It shows a rather simple law that the ensemble splitting ratios of oil anchor at around a constant value while the corresponding parameter of water varies from 0 to 1. It illustrates that the droplet flow splitting at a T-junction resembles a resilient system, the stiffness of which depends on the capillary number of the flow. The energy loss of the system induced by a perturbation of the flow resistance is self-reduced by just redistributing of droplets into the two arms.

Self-Healing Composite Coating Fabricated with a Cystamine Cross-Linked Cellulose Nanocrystal-Stabilized Pickering Emulsion.

A gelled Pickering emulsion system was fabricated by first stabilizing linseed oil droplets in water with dialdehyde cellulose nanocrystals (DACNCs) and then cross-linking with cystamine. Cross-linking of the DACNCs was shown to occur by a reaction between the amine groups on cystamine and the aldehyde groups on the CNCs, causing gelation of the nanocellulose suspension. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy were used to characterize the cystamine-cross-linked CNCs (cysCNCs), demonstrating their presence. Transmission electron microscopy images evidenced that cross-linking between cysCNCs took place. This cross-linking was utilized in a linseed oil-in-water Pickering emulsion system, creating a novel gelled Pickering emulsion system. The rheological properties of both DACNC suspensions and nanocellulose-stabilized Pickering emulsions were monitored during the cross-linking reaction. Dynamic light scattering and confocal laser scanning microscopy (CLSM) of the Pickering emulsion before gelling imaged CNC-stabilized oil droplets along with isolated CNC rods and CNC clusters, which had not been adsorbed to the oil droplet surfaces. Atomic force microscopy imaging of the air-dried gelled Pickering emulsion also demonstrated the presence of free CNCs alongside the oil droplets and the cross-linked CNC network directly at the oil-water interface on the oil droplet surfaces. Finally, these gelled Pickering emulsions were mixed with poly(vinyl alcohol) solutions and fabricated into self-healing composite coating systems. These self-healing composite coatings were then scratched and viewed under both an optical microscope and a scanning electron microscope before and after self-healing. The linseed oil was demonstrated to leak into the scratches, healing the gap automatically and giving a practical approach for a variety of potential applications.

Flow and clogging of capillary droplets.

Capillary droplets form due to surface tension when two immiscible fluids are mixed. We describe the motion of gravity-driven capillary droplets flowing through narrow constrictions and obstacle arrays in both simulations and experiments. Our new capillary deformable particle model recapitulates the shape and velocity of single oil droplets in water as they pass through narrow constrictions in microfluidic chambers. Using this experimentally validated model, we simulate the flow and clogging of single capillary droplets in narrow channels and obstacle arrays and find several important results. First, the capillary droplet speed profile is nonmonotonic as the droplet exits the narrow orifice, and we can tune the droplet properties so that the speed overshoots the terminal speed far from the constriction. Second, in obstacle arrays, we find that extremely deformable droplets can wrap around obstacles, which leads to decreased average droplet speed in the continuous flow regime and increased probability for clogging in the regime where permanent clogs form. Third, the wrapping mechanism causes the clogging probability in obstacle arrays to become nonmonotonic with surface tension Γ. At large Γ, the droplets are nearly rigid and the clogging probability is large since the droplets can not squeeze through the gaps between obstacles. With decreasing Γ, the clogging probability decreases as the droplets become more deformable. However, in the small-Γ limit, the clogging probability increases since the droplets are extremely deformable and wrap around the obstacles. The results from these studies are important for developing a predictive understanding of capillary droplet flows through complex and confined geometries.

Insight into the growth kinetics of CsPbBr3 perovskite nanocrystals using an oil-water droplet fluidic synthesis route

All-inorganic lead halide perovskite nanocrystals (PNCs) have attracted extensive attention in the optoelectronic fields owning to their exceptional photoluminescence characteristics. However, the ultra-fast growth rate of PNCs leads to challenges in controlling their size and optical properties. Here, we report a water–oil droplet fluidic synthesis method that successfully slow down the growth rate of CsPbBr3 PNCs by segregating the cation and anion precursors in the respective phases. Reaction mechanism study revealed a fast nucleation via a nanoplate-intermediate pathway upon HBr diffusion and subsequent slow growth through ripening, leading to a wide range of spectral tunability of the PNCs from 445 nm to 520 nm. The theoretical investigation into growth kinetics showed the combined effect of the ligands and temperature on the growth of the PNCs. This method provides an efficient means for producing high-performance PNCs with tunable size and wavelength while also eliminating the requirement for a Pb-rich reaction environment.

Acoustophoresis of monodisperse oil droplets in water: Effect of symmetry breaking and non-resonance operation on oil trapping behavior.

Acoustic manipulation of particles in microchannels has recently gained much attention. Ultrasonic standing wave (USW) separation of oil droplets or particles is an established technology for microscale applications. Acoustofluidic devices are normally operated at optimized conditions, namely, resonant frequency, to minimize power consumption. It has been recently shown that symmetry breaking is needed to obtain efficient conditions for acoustic particle trapping. In this work, we study the acoustophoretic behavior of monodisperse oil droplets (silicone oil and hexadecane) in water in the microfluidic chip operating at a non-resonant frequency and an off-center placement of the transducer. Finite element-based computer simulations are further performed to investigate the influence of these conditions on the acoustic pressure distribution and oil trapping behavior. Via investigating the Gor'kov potential, we obtained an overlap between the trapping patterns obtained in experiments and simulations. We demonstrate that an off-center placement of the transducer and driving the transducer at a non-resonant frequency can still lead to predictable behavior of particles in acoustofluidics. This is relevant to applications in which the theoretical resonant frequency cannot be achieved, e.g., manipulation of biological matter within living tissues.

Effects of surfactants on droplet deformation and breakup in water-in-oil emulsions under DC electric field: A molecular dynamics study

The presence of surfactants in water-in-oil (W/O) emulsions can increase the susceptibility of water droplets to breakup under an electric field, resulting in intensified emulsification. To elucidate the mechanism underlying the electrodynamic behavior of surfactant-containing water droplets in oil, this study has employed molecular dynamics (MD) simulations to investigate the impact of surfactants on droplet deformation and breakup under a DC electric field. The results indicate that despite the formation of hydrogen bonds between surfactants and water molecules, a higher number of van der Waals interactions were formed between them. Upon reaching maximum deformation, the droplet experiences a reduction in deformation due to increased steric hindrance of the oil phase and decreased surfactant adsorption. Eventually, the droplet reaches a steady state with a lower degree of deformation. The enhanced dispersion attraction between n-hexane and Span-80 facilitates the migration of surfactants to the oil phase, weakening the interaction between surfactants and the droplets. The migration of the surfactant drags the surrounding water molecules, increasing droplet deformation. During droplet deformation, hydrogen bonds with a lifetime of 0.88 ps can be formed between the surfactants. The combined influence of hydrated ions, surfactant-related interactions, media effects, and migration effects leads to the breakup of surfactant-containing droplets. During droplet breakup, there is an uneven distribution of surfactants on the droplet surface. Increasing the concentration of surfactants appropriately can prolong the time required for droplet breakup. The simulation findings presented in this paper offer new insights and inspiration for enhancing the electrostatic demulsification of emulsions containing surfactants.

Application of chitosan-based materials in wastewater treatment

Chitosan, as a natural polysaccharide material, plays a great role in the field of wastewater treatment due to its good biodegradability, antimicrobial activity, and other properties. However, it may have some differences in the processes of adsorption, flocculation, and membrane separation. We comprehensively describe the application effect and mechanism of action of chitosan-based materials on the above three major water treatment processes. In the adsorption process, chitosan-based adsorbents such as hydrogels and chitosan beads are prepared by cross-linking, impregnation, and the introduction of functional groups. These chitosan-based materials exerted efficient removal performance in the adsorption of heavy metals, organic dyes, anionic pollutants, etc., which was attributed to their large specific surface area and abundant functional groups. In the flocculation process, the chitosan-based materials were modified by grafting and modifying their shape, while heavy metal ions, organic dyes, and algae were removed using processes such as chelation and charge neutralization. In the membrane separation process, a number of nanofiltration and microfiltration membranes were created by coating chitosan ions, and physicochemical modification was done for the separation of heavy metal ions and emulsified oil droplets in water to improve the fouling resistance and retention rate of the membrane materials. This paper reviews the application of chitosan-based materials in wastewater treatment and proposes that in-depth studies on their toxicity and reusability should be conducted in the future, with a view to playing a role in areas such as the removal of malodorous water odors.

Dynamics Analysis of Droplets Collision with the Wall Driven by Buoyancy

Dynamics analysis of the oil droplet in water impacting on a rigid wall in the range of Re=9.3 ∼ 231.39, We=0.003 ∼ 0.637 was carried out by combining microscopic experiment with theoretical study. In the oil droplet’s force equation, we consider the added mass force and the water film induced force, in addition to the conventional forces, i.e. buoyancy and resistance to flow. Stokes-Reynolds drainage equation (i.e. SR model) and Young-Laplace equation (i.e. YL model) are combined with the force equation to numerically solve the motion law of oil droplets near the wall for different control parameters. The study indicates that coupled model would expect oil droplet velocities, motion trajectories and capture the kinetic behaviors of the water-film drainage evolution. The interfacial deformation of oil droplets causes changes in the pressure and the pressure distribution pattern has an important relationship with the shape of the oil droplet interface. These two forces play a dominant role in droplet motion during the collision and the maximum value of these two forces increases with increasing droplet size and Re number. Future research should shift towards complex oil-water systems and consider the effects of chemicals on oil droplets so that the application of the model will be more generalisable. At the same time, computer technology should be used to transfer the two-dimensional view to a three-dimensional view to analyse the deformation of the oil-water interface and to better understand the drainage process of the water film.

Tuning the membrane rejection behavior by surface wettability engineering for an effective water-in-oil emulsion separation

Membrane-based separation is a promising technology to eliminate water impurities from the oil phase. However, it remains a great challenge to separate water from highly emulsified viscous oil owing to the high stability of the water droplets in oil. Herein we report a surface wettability engineering on an alumina ceramic membrane to achieve an efficient separation of a water-in-oil (W/O) emulsion. Silanes with different carbon chain lengths and fluorinated status were introduced to endow the alumina membrane with different surface wettabilities. While all the modified membranes exhibited excellent separation of the W/O without Span 80 (surfactant), the one with amphiphobic wettability and lowest surface energy failed to separate the Span 80 stabilized W/O. The presence of Span 80 reduced the interfacial tension of water droplets, making them easier to deform and penetrate the modified membrane with the lowest surface energy. It reveals that engineering proper surface wettability is the key to separating the oil and water phases. Besides, the modified membranes maintained decent separation performance and stability under long-term run separation of the emulsified W/O.