Separation of Water‐in‐Oil Emulsions Using Glass Fiber Media Augmented with Polymer Nanofibers

Water‐in‐oil emulsion separations are important to the petrochemical industry for product quality, safety, environmental, and economic reasons. Glass fiber filter media are often used to remove water droplets out of water‐in‐oil emulsions. The experimental results in this work show that 1% by mass of polyamide nanofibers with diameters of about 150 nm added to conventional micron‐sized glass fiber filter media improves the separation efficiency of the filter media from 71 to 84%. The addition of similar amounts of micron‐sized polyamide fibers to the glass fiber media do not improve filter capture efficiency.     

A visible coalescence of droplets on hydrophobic and hydrophilic fibers in water-in-oil emulsion

The droplets’ coalescence is instantaneous and rather complex in emulsion. The theoretical analysis of this process was presented by a former research, while visible experiments to verify these are still scarce. This work aims to show and analyze the visible water droplets’ coalescence on hydrophobic bamboo charcoal fibers and hydrophilic glass fibers in water-in-oil emulsion. An experimental setup with microscope and high-speed camera was designed and established to record the water droplets’ coalescence. The water droplets’ collision coalescence on bamboo charcoal fibers was observed, and the diameters of water droplets detaching from the fibers with different angles were measured. The angle between the fiber and the flow velocity can affect the diameters of water droplets detaching from the bamboo charcoal fibers, and cross-fibers can the enormously increase water diameters compared with single fiber. Meanwhile, the water droplets’ collision coalescence on glass fibers was observed and the result shows that the collision coalescence also occurred on the hydrophilic glass fibers when the droplet diameter was small. In addition, other factors, including flow velocity and droplets’ diameter for the coalescence on the hydrophilic glass fibers were investigated.     

Process diagnosis of coalescence separation of oil-in-water emulsions-two case studies

Coalescence separation is a widely applied technology for oil/water emulsion separation. In this paper, we first review the existing coalescence theories regarding droplet capture, attachment and release. Two case studies are considered, dealing with the separation of oil-in-water emulsions using our recently developed coalescing filters. The first case (Case I) is associated with the separation of surfactant-stabilized hexadecane/water emulsions. The second case (Case II) addresses the separation of sulfonated kerosene/water emulsions in a continuous bench operation. In Case I, known wetting and collision theories were applied to understand the complex coalescence process occurring on the surface of the fibers. For this, the detrimental effect of surfactants on coalescence separation was taken into account. It was found that the best oil wetting coalescing material under water was not the most desired for coalescence, contradicting the existing theory. In addition, once the materials were pre-saturated with surfactant-containing emulsions, the oil wetting was enhanced significantly. However, the separation efficiency was maintained at the same level, unless the material adsorbed surfactant, resulting in minor reductions in the wetting angle. In Case II, based on the fiber properties and operation conditions, the droplet capture efficiency and released droplet size were calculated using the existing models. Fiber diameter and medium face velocity were found to affect not only the capture, but also drop release. Based on model predictions, the dominant capture mechanism was identified as interception followed by van der Waals forces. Overall, this work offers insights about the influencing parameters on oil/water emulsion separation for better designing coalescence systems.     

Separation of water-in-oil emulsion with microfiber glass coalescing bed

Water-in-oil emulsion separation through a fibrous media bed is a complex and challenging process in industries. In this article, we used a vertical column separator to investigate the effects of the height and porosity of the fiber bed, the structure arrangement (the mixed or the layered fibrous bed), the superficial velocity of the water-in-oil emulsion through the bed, and the influent water content of the emulsion on water removal. Four kinds of glass microfibers (GF1-GF4) with mean diameters of 0.6, 2.6, 4.6, and 8.0?µm, respectively, acted as the coalescence medium and composed the fibrous bed with different structure types. The separation efficiency could reach 97.1% with a relatively low pressure drop under the optimal bed structure and operational conditions. It also showed that the mixed bed had higher separation performance compared to the layered fibrous bed.     

Photocurable pickering emulsion for colloidal particles with structural complexity

We prepared polymeric microparticles with coordinated patches using oil-in-water emulsion droplets which were stabilized by adsorbed colloidal polystyrene (PS) latex particles. The oil phase was photocurable ethoxylated trimethylolpropane triacrylate (ETPTA), and the particle-armored oil droplets were solidified by UV irradiation within a few seconds to produce ETPTA-PS composite microparticles without disturbing the structures. Large armored emulsion drops became raspberry-like particles, while small emulsion drops with a few anchored particles were transformed into colloidal clusters with well-coordinated patches. For high-molecular-weight PS particles with low chemical affinity to the ETPTA monomer, the morphology of the patchy particle was determined by the volume of the emulsion drop and the contact angle of the emulsion interface on the PS particle surface. Meanwhile, for low-molecular-weight PS particles with high affinity, the ETPTA monomers were likely to swell the adsorbed PS particles, and distinctive morphologies were induced during the shrinkage of emulsion drops and the phase separation of ETPTA from the swollen PS particles. In addition, colloidal particles with large open windows were produced by dissolving the PS particles from the patchy particles. We observed photoluminescent emission from the patchy particles in which dye molecules were dispersed in the ETPTA phase. Finally, we used Surface Evolver simulation to predict equilibrium structures of patchy particles and estimate surface energies which are essential to understand the underlying physics.     

膜乳化-液中干燥法制备单分散高分子微球

粒径可控的单分散高分子微球,在分析化学中可用作高效液相色谱填料^[1,2];在化学工业中可用作催化剂载体;在生物领域中用于药物释放、癌症与肝炎等临床诊断、细胞标记与识别等^[3].高分子微球的制备方法大致可分为两类,一是利用由单体出发的聚合反应或缩聚反应形成微球,二是高分子溶液经物理或物理化学手段处理后形成微球^[4]     

The effect of wettability on drop attachment to glass rods

The coalescence of droplets in fibrous filters depends on many parameters such as wettability, filter depth, flow velocity, and filter materials. The objective of this work is to determine the effect of the wettability on the coalescence mechanism. Experimental results from tests on coated glass rods are presented. Three different silanes are deposited on the glass rod surfaces to change the surface wettability. Flow of water-in-oil emulsion past the glass rods is observed. When the rod surface is wetting the dispersed phase coats the rod. When the surface is nonwetting the drops do not stick easily to the surface and do not coat it but slide around to the downstream side, where they are dragged off the rod. Such behavior is important in understanding the performance of coalescing filter media.     

Fabrication of macroporous polystyrene/graphene oxide composite monolith and its adsorption property for tetracycline

Macroporous polystyrene microsphere/graphene oxide(PS/GO) composite monolith was first prepared using Pickering emulsion droplets as the soft template. The Pickering emulsion was stabilized by PS/GO composite particles in-situ formed in an acidic water phase. With the evaporation of water and the oil phase(octane), the Pickering emulsion droplets agglomerated and combined with each other, forming a three-dimensional macroporous PS/GO composite matrix with excellent mechanical strength. The size of the macrospores ranged from 4 mm to 20 mm. The macroporous PS/GO composite monolith exhibited high adsorption capacity for tetracycline(TC) in an aqueous solution at p H 4–6. The maximum adsorption capacity reached 197.9 mg g 1at p H 6. The adsorption behaviour of TC fitted well with the Langmuir model and pseudo-second-order kinetic model. This work offers a simple and efficient approach to fabricate macroporous GO-based monolith with high strength and adsorption ability for organic pollutants.     

静电纺丝法制备超细聚苯乙烯纳米纤维

采用静电纺丝方法制备了超细聚苯乙烯纤维, 通过向溶液中添加有机胺盐并降低溶液浓度将纤维的平均直径降至100 nm, 并研究了盐的添加量对纤维直径的影响.     

Preparation of Monodispersed Polymer Microspheres by SPG Membrane Emulsification‐Solvent Evaporation Technology

The membrane emulsification coupled with solvent evaporation was adopted to prepare monodispersed polystyrene (PS) microspheres. Firstly, stable oil‐in‐water emulsion has been successfully obtained by pressing PS solution through SPG membrane into continuous phase at appropriate pressures. Then monodispersed PS microspheres with size of 2–20 µm were obtained following the removal of solvent. The size of the PS microspheres was strongly dependent on the mean pore size of SPG membrane and concentration of PS solution. Furthermore, the effect of emulsion stability, operation pressure and emulsifier on the size and size distribution of microspheres were systemically investigated. Finally, the surface character of PS microspheres was examined via SEM.     

Synthesis and Characterization of β‐CD‐Coated Polystyrene Microspheres by γ‐Ray Radiation Emulsion Polymerization

Polystyrene (PS) microspheres coated with β‐cyclodextrin (β‐CD) were fabricated via γ‐ray‐induced emulsion polymerization in a ternary system of styrene/β‐CD/water (St/β‐CD/water). The solid inclusion complex of St and β‐CD particles formed at the St droplets–water interface can stabilize the emulsion as the surfactant. TEM and XPS results showed that β‐CD remains on the surface of PS particles. The average size of the PS particles increases from 186 to 294 nm as the weight ratio of β‐CD to St rises from 5% to 12.5%. The water contact angle (CA) of PS latex film is lower than 90°, and reduces with the β‐CD content even to 36°. Thus, this work provides a new and one‐pot strategy to surface hydrophilic modification on hydrophobic polymer particles with cyclodextrins through radiation emulsion polymerization.     

Emulsion electrospinning: composite fibers from drop breakup during electrospinning

We evaluate the feasibility of electrospinning oil‐in‐water type emulsions. The emulsions had an aqueous solution of polyethylene oxide (PEO) as the continuous phase, and either mineral oil or a polystyrene (PS) in toluene solution as the drop phase. The Taylor cones and electrified liquid jets were stable even when the emulsion drops were as large as a few‐ten microns in diameter. The resulting electrospun PEO fibers incorporated the dispersed phase of the emulsion in the form of drops (in case of mineral oil), or in the form of solid particles (in case of PS). Mineral oil drops appear to be completely encapsulated in the PEO fibers, whereas the PS particles are either incompletely encapsulated, or covered by only a very thin layer of PEO. Calculations show that in both cases, the initially large emulsion drops are broken during the electrospinning process. Copyright © 2007 John Wiley & Sons, Ltd.     

Homogeneous and heterogeneous binary colloidal clusters formed by evaporation-induced self-assembly inside droplets

In this paper, we report the preparation of binary clusters of colloidal particles with different sizes or species into complex structures using oil-in-water emulsion droplets as confining geometries. First, polystyrene or silica particles with bimodal size distribution were packed densely by evaporation-induced self-assembly inside oil-in-water emulsion droplets. The configurations of larger particles inside the droplets minimize the second moment of the particle locations for the ratio of large to small particle sizes less than 3. Also, the configurations of bimodal clusters were predicted by using a surface evolver simulation, and the simulation predictions were compared with the experimental results. In addition, heterogeneous colloidal clusters were produced by emulsifying the binary mixture suspension of polystyrene and silica particles in aqueous medium followed by evaporating the oil phase. A density gradient centrifugation was applied to fractionate the asymmetric binary dimers comprised of PS and silica microspheres.     

Mass preparation of nanofibers by high pressure air‐jet split electrospinning: Effect of electric field

A novel electrospinning method using airflow, namely high pressure air‐jet split electrospinning, was proposed to fabricate polymer nanofibers with ultrahigh production rate. 7 wt % polyacrylonitrile spinning solution with a 0.157 Pa s viscosity was divided into micron size droplets by the filter screen in the front of the nozzle, and then these droplets were divided and split through high pressure airflow, which were drafted into nanofibers directly in the electric field and airflow field. In this study, the electric field distributions with different positive electrodes were simulated and their effect on fiber formation was investigated. The results show that electric field distribution and its intensity depended on electrodes area, a broader electric field distribution with a stronger intensity would bring about a larger cone angle of spraying jet region, at the same time, the contrast in the spray region enhanced. When the whole nozzle was charged, thinner fibers with about 170 nm could be prepared and the fiber production was 75.6 g/h. Compared with the conventional needle electrospinning, the throughput of nanofibers could be improved by thousands of times based on this novel electrospinning method. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014 , 52, 993–1001     

Structure and nanomechanical characterization of electrospun PS/clay nanocomposite fibers

Electrospinning has been emerging as one of the most efficient methods to fabricate polymer nanofibers. In this paper, PS/clay nanocomposite fibers with varying diameters were electrospun onto solid substrates. The fiber diameters were adjusted from 4 microm to 150 nm by changing the solution concentration. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and atomic force microscopy (AFM) were used to characterize the fiber morphology. Shear modulation force microscopy (SMFM) was utilized to investigate the surface nanomechanical properties of electrospun fibers as a function of the fiber diameter and temperature. In the absence of clay, no change in T(g) was observed, even though a large increase of shear modulus below the glass transition temperature was found. This effect was postulated to result from the molecular chain alignment during electrospinning. The addition of functionalized clays to the spinning solution produced fibers with a highly aligned montmorillonite layer structure at a clay concentration of 4 wt %. Clay agglomerates were observed at higher concentrations. The existence of clay further enhanced the shear modulus of fibers and increased the glass transition temperature by nearly 20 degrees C.     

Formation of Pickering emulsions stabilized via interaction between nanoparticles dispersed in aqueous phase and polymer end groups dissolved in oil phase

The influence of end groups of a polymer dissolved in an oil phase on the formation of a Pickering-type hydroxyapatite (HAp) nanoparticle-stabilized emulsion and on the morphology of HAp nanoparticle-coated microspheres prepared by evaporating solvent from the emulsion was investigated. Polystyrene (PS) molecules with varying end groups and molecular weights were used as model polymers. Although HAp nanoparticles alone could not function as a particulate emulsifier for stabilizing dichloromethane (oil) droplets, oil droplets could be stabilized with the aid of carboxyl end groups of the polymers dissolved in the oil phase. Lower-molecular-weight PS molecules containing carboxyl end groups formed small droplets and deflated microspheres, due to the higher concentration of carboxyl groups on the droplet/microsphere surface and hence stronger adsorption of the nanoparticles at the water/oil interface. In addition, Pickering-type suspension polymerization of styrene droplets stabilized by PS molecules containing carboxyl end groups successfully led to the formation of spherical HAp-coated microspheres.     

Microwave-Assisted Self-Organization of Colloidal Particles Inside Water-in-Oil Emulsions

Commercial amidine polystyrene microspheres were self-organized to obtain colloidal microclusters from water-in-oil emulsion droplets as confining geometries. For demulsification process, microwave was irradiated to remove water droplets selectively resulting in the shrinkage of water droplets which induces inward capillary pressure for the particle self-assembly. The amidine polystyrene clusters were coated with silica nanospheres or titania nanoparticles by co-organizing the mixed particle suspensions inside water droplets by microwave heating. Titania-coated polystyrene clusters were calcined to produce hollow macroporous titania powders. Finally, sulfate-coated polystyrene microspheres were self-assembled with silica nanoparticles to generate polystyrene/silica composite clusters by microwave irradiation method.     

Experimental observation and prediction of interfacial tension and viscoelastic emulsion model behavior in novel phosphate glass-polymer hybrids

The interfacial tension of hybrids composed of a tin-based phosphate glass (Pglass) and thermoplastic polymers, low-density polyethylene (LDPE), polystyrene (PS), and polypropylene (PP) was investigated using pendant drop and droplet deformation methods. High surface tension values were determined for the pure Pglass and subsequently used to obtain interfacial tension values that were found to be greater than that of most polymer blends reported in the literature. Small amplitude oscillatory shear data were fitted to the Choi-Schowalter and Palierne emulsion models in order to estimate the interfacial tension and to validate the accuracy (or lack thereof) of using a polymer emulsion model on the special Pglass-polymer systems. Although some of the hybrids showed satisfactory agreement with the emulsion models, wide ranges of interfacial tensions were obtained, suggesting that a more complicated theory that explicitly takes the Pglass-polymer interactions, shape factor, and size distributions of the dispersed Pglass phase into account may be necessary for more accurate modeling of these special hybrid systems with enhanced benefits.     

Physicochemical properties of structured phosphatidylcholine in drug carrier lipid emulsions for drug delivery systems

Drug carrier emulsions were prepared with structured phosphatidylcholine (PC-LM) which has both a long hydrocarbon chain and a medium hydrocarbon chain, and the characteristics of PC-LM as an emulsifier were investigated by measuring the creaming ratio, the surface tension of the emulsion system, and the mean particle size and zeta potential of the oil droplets in emulsions. The emulsion prepared with PC-LM as an emulsifier kept the condition and the ratio of separation was lower than those with purified egg yolk lecithin (PEL). The mean particle size of the emulsion prepared with PC-LM was smaller than that with PEL when using only sonication, approximately 250 nm. When using a high-pressure homogenizer after sonication, the mean emulsion size with PC-LM was also smaller than with PEL, approximately 150 nm. The surface tension of the various emulsions and the zeta potential of the emulsion droplets were measured to investigate the stability of the systems. In emulsions with PC-LM or PEL, the surface tension as an index of stability increased as the pressure of the homogenizer increased. Moreover, the zeta potential of the emulsion droplets prepared with PC-LM also increased with an increase in pressure of the homogenizer. As a result, it was found that the drug carrier emulsion prepared with PC-LM had significant advantages in terms of stability and mean diameter. We considered it could be used for the preparations of nanoparticle dispersion systems in drug delivery systems.     

Demulsification of water-in-oil emulsions by permeation through Shirasu-porous-glass (SPG) membranes

To investigate the effect of the droplet/pore size ratio on membrane demulsification, water-in-oil (W/O) emulsions with uniform-sized droplets was demulsified by permeation through Shirasu-porous-glass (SPG) membranes with a narrow pore size distribution at mean droplet/pore diameter ratios of 0.52–5.75. At transmembrane pressures above a critical pressure, the water droplets larger than the membrane pore size were demulsified, where the SPG membrane acted as a coalescer because the hydrophilic membrane surface had a high affinity for the water droplets. By contrast, at transmembrane pressures below the critical pressure, the larger water droplets were all retained by the membrane due to the sieving effect of the uniform-sized pores. When a W/O emulsion with a mean droplet diameter of 2.30 μm was allowed to permeate through a membrane with a mean pore diameter of 0.86 μm, the demulsification efficiency increased with increasing transmembrane pressure, to a maximum value of 91% at a transmembrane pressure of 392 kPa, and then decreased, while the transmembrane flux increased almost linearly with increasing transmembrane pressure. The demulsification efficiency was higher for higher water phase content and lower concentration of the surfactant, tetraglycerin condensed ricinoleic acid ester, in the emulsions due to the reduction of the emulsion stability.