Emulsification Of Oil In Water Research Articles

Freeze/Thaw-Induced Carbon Dioxide Trapping Promotes Emulsification of Oil in Water.

Freeze/Thaw-Induced Carbon Dioxide Trapping Promotes Emulsification of Oil in Water.

The Significance of Graphene Oxide-Polyacrylamide Interactions on the Stability and Microstructure of Oil-in-Water Emulsions.

The emulsification of oil in water by nanoparticles can be facilitated by the addition of costabilizers, such as polymers and surfactants. The enhanced properties of the resulting emulsions are usually attributed to nanoparticle/costabilizer synergy; however, the mechanism of this synergistic effect and its impacts on emulsion stability and microstructure remain unclear. Here, we study the synergistic interaction of graphene oxide (GO) and a high molecular weight anionic polyacrylamide (PAM) in stabilization of paraffin oil/water emulsion systems. We show that the addition of PAM reduces the amount of GO required to stabilize an emulsion significantly. In order to probe the synergistic effect of GO and PAM, we analytically analyze the oil-free GO and GO-PAM dispersions and directly image their morphology via Cryo-TEM and atomic force microscopy (AFM). X-ray diffraction results confirm the adsorption of PAM molecules onto GO sheets resulting in the formation of ultimate GO-PAM complexes. The adsorption phenomenon is a consequence of hydrogen bonding and acid-base interactions, conceivably leading to a resilient electron-donor-acceptor complex. The microstructure of emulsions is captured with two-color fluorescent microscopy and Cryo-TEM. The acquired images display the localization of GO-PAM complexes at the interface while large amount of GO-PAM flocs coexist at the interface and in between oil droplets. Localization of such complexes and flocs at the interface is found to be responsible for their slow creaming rates compared to their GO counterparts. Mechanical properties of both dispersions and emulsions are studied by shear rheology. Rheological measurements confirm that GO-PAM complexes have a higher desorption energy from the interface resulting in higher critical shear strain of GO-PAM emulsions. The results, with insights into both structure and rheology, form a foundational understanding for integration of other polymers and nanoparticles in emulsion systems, which enables efficient design of these systems for an application of interest.

Surface charge effect of nanogel on emulsification of oil in water for fossil energy recovery

Crosslinked polymeric hydrogels in nano-size, termed as nanogels, have significant technological applications by stabilizing Pickering emulsion. Herein, we present our experimental observations and the results of the emulsion stability analysis on the effects of nanogel concentration, oil-to-water ratio, nanogel charge, and ambient temperature. The nanogel with neutral-charge showed extraordinarily high emulsifying ability, interfacial tension between decane and water was reduced from 51.98 mN·m−1 to less than 6.04 mN·m−1, compared to 47.5 mN·m−1 by nanosilica. When treated with neutral-charged nanogel, the oil-in-water emulsion exhibited long-term stabilization, 90% emulsion remained after one month at room temperature, showing the highest stability among the reported literature of Pickering emulsions. However, inorganic silica nanoparticles displayed emulsion stability in minutes. Of particular interest was that the emulsion volume remained 82% after thermal treatment at 65 °C for 48 h. The resulting high emulsion stability was attributed to a combination of high hydrophilicity, sufficient steric repulsion, and high surface coverage of nanogel. These observations indicated that the resulting nanogel can be a promising candidate toward enhanced oil recovery.

Surfactant‐Enhanced Adsorption of Graphene Oxide for Improved Emulsification of Oil in Water

AbstractGraphene oxide (GO) can be enriched at the air–water interface by the adsorption of surfactant molecules to the surfaces of the GO sheets. The synergism between the surfactant and GO is shown to be responsible for the improved interfacial performance of the composite through a subtle balance of surface charge and surface activity. The use of a photoaddressable surfactant provides a unique probe for investigating the fundamental mechanisms that control adsorption, by inducing spatiotemporal modulation of the surfactant properties by irradiation with light of certain wavelengths. Tensiometry measurements uncover the interfacial activity of the materials, whereas X‐ray reflectivity serves to independently determine the interfacial structure and composition. The ratio between the surfactant and GO appears to be the key factor controlling adsorption, with pH and salt offering additional finer control of interfacial properties. This synergism between GO sheets and a surface active small molecule surfactant is utilized to stabilize oil‐in‐water emulsions with unprecedented effectiveness.

Use of vegetable oil in water emulsion achieved through ultrasonic atomization as cutting fluids in micro-milling

Significant amount of work is reported on development of vegetable oil based metalworking fluids (MWFs). Many also report on development and performance evaluation of vegetable based oils. For many of these water-based MWFs with vegetable oils, much effort is focused on stable emulsification of vegetable oil in water using a variety of surfactants. It has been found that surfactant-free stable emulsification of oil in water is possible through ultrasonic vibration. However, emulsification through ultrasonic atomization has not yet been considered, and the feasibility of emulsified metalworking fluids through ultrasonic atomization has not been investigated. In this paper, stable emulsification of vegetable oil in water has been achieved through ultrasonic atomization without using any surfactant. The emulsified vegetable oil in water is directly used to investigate its effectiveness as MWF in milling operations. Lower cutting forces, chip thickness, and burr amount are observed with vegetable oil-in-water emulsion compared to conventional MWF. The experimental results show strong potential for vegetable oil-in-water emulsion obtained through ultrasonic atomization as an effective MWF.

Effect of Adsorbed Amphiphilic Copolymers on the Interfacial Activity of Superparamagnetic Nanoclusters and the Emulsification of Oil in Water

A series of sub-100 nm superparamagnetic iron oxide nanoparticles with amphiphilic poly(acrylic acid-b-butylacrylate); PAA-b-PBA) copolymer shells were synthesized and characterized by NMR spectroscopy, dynamic light scattering (DLS), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), and a superconducting quantum interference device (SQUID) to investigate the effect of the polymer structure on the interfacial tension for nanoparticles adsorbed at the dodecane-water interface. Large reductions in interfacial tension of up to 27.6 mN/m were measured at nanoparticle concentrations of 0.27 wt %, indicating significant nanoparticle adsorption and interaction between the oil and water molecules at the interface. The adsorption energy of the polymer-coated nanoparticles at the dodecane/water interface was determined from the interfacial tension and nanoparticle radius, and analyzed in terms of the structure of the polymer stabilizer. Furthermore, the equilibrium adsorption of amphiphilic copolymer-functionalized iron oxide nanoclusters at the oil–water interface was determined by material balance from the concentration in the excess water phase and the known overall oil/water interfacial area. The formation and stabilization of oil droplets were on the order of 10 μm in water with unusually low nanoparticle concentrations was explained in terms of the high interfacial activity of the particles.

A Generic Single‐Step Synthesis of Monodisperse Core/Shell Colloids Based on Spontaneous Pickering Emulsification

Monodisperse core–shell colloids are widely applied in various fields such as biomedicine, catalysis, and optics, and are also important for fundamental studies in colloid and interface science. The synthesis of particles with a well-defined core–shell morphology still comprises several separate steps such as core preparation, its subsequent functionalization with a coupling agent and the deposition of one or several shells. This multi-step approach towards composite colloids has some serious drawbacks. First, both coupling chemistry and synthetic pathways need to be specifically designed for the materials involved. Second, multi-step reactions often require intermediate purifications or separations that not only reduce the net yield but also hamper the up-scaling of composite-colloid synthesis for applications such as those referred to above. In this communication we report a novel single-step synthesis of monodisperse latex-based core–shell colloids that completely relies on self-assembly of the components involved (Fig. 1). Recently we discovered that nano-particles may induce spontaneous emulsification of oil in water to thermodynamically stable, monodisperse Pickering emulsions. This novel emulsification phenomenon, first observed for magnetite (Fe3O4) nano-particles, turns out to be quite generic since also cobalt ferrite (CoFe2O4) and commercial silica particles (Ludox) lead to stable Pickering emulsions. It was also shown that using the chemically reactive oil (methacryloxypropyltrimethoxysilane, TPM), Pickering emulsions could be polymerized by addition of a radical initiator (potassiumpersulphate, KPS) resulting in stable colloidal dispersions (Fig. 2a and b). Here we investigate the use of such particle-stabilized emulsions (hereafter TPM-emulsions) in a seeded growth polymethylmethacrylate (PMMA) polymerization, to obtain in one single and simple step, PMMA colloids with various inorganic cores. Initially we focused on TPM-emulsions merely as a source for monodisperse inorganic cores to seed a surfactant-free PMMA polymerization. However, exploring what would happen when TPM-emulsions are prepared directly in the presence of methylmethacrylate (MM) we noticed that, surprisingly, MM does not interfere at all with the TPM emulsification. In fact, during the latter emulsification, MM remains present as a separate oil phase (Fig. 2c insert). Addition of a water-soluble radical initiator, however, not only induces polymerization of the TPM-emulsion droplets to solid spheres, but simultaneously also triggers the polymerization of PMMA shells onto these spheres. Thus the floating MM phase (Fig. 2) acts as a monomer source for this PMMA shell formation and, indeed, the shell thickness continues to grow until the whole MM phase is consumed. It turns out that, in addition, polymerized TPM-emulsions are also excellent seeds dispersions for growing polystyrene shells via surfactant free emulsion polymerization, as well as silica shells via the classical Stober synthesis, showing that the spontaneous Pickering emulsification allows for the preparation of polymeric as well as inorganic composite model colloids. C O M M U N IC A TI O N

Membrane emulsification with vibrating membranes: A numerical study

Membrane emulsification of oil in water may be enhanced by mechanically exciting the membrane, thereby enabling the formation of smaller droplets of a narrower size distribution, combined with higher specific production rate. To evaluate this potential, a force balance model was developed that includes the additional forces induced by the transversal membrane movement. This model yielded the ranges of interest of the excitation amplitude A and frequency f. In these ranges of interest, 3D transient simulations were carried out to predict the 3D droplet formation and detachment on a single pore under constant cross-flow. For conditions without membrane excitation, the force balance model agreed satisfactorily with experimental results reported in the literature and with the current 3D computations. The model also predicts a non-linear dependence of the droplet size on the pore diameter. However, under membrane excitation the extended force balance model does not seem to give reliable results. This is probably due to the simplifications in this model, which does not include the effects of the dispersed phase flux and viscosity, and the strongly non-spherical droplet geometry upon detachment. Moreover, for large vibration-induced forces coalescence occurred in the 3D model, which leads to much larger droplets. Thus, fully transient 3D CFD simulations appear to be required for reliable predictions. Ideally these should account for surfactant dynamics and a variable surface tension coefficient. The simulations show that membrane excitation potentially has a strong effect on the average droplet size in membrane emulsification, but that successful exploitation will require careful design of membrane and process. First estimates seem to indicate that systems with lower excitation frequency and larger excitation amplitude may perform better, but this will require experimental verification.

Emulsification of oil in water as affected by different parameters

The aim of this investigation was to develop a basic understanding of the emulsification process by considering simple systems such as n-hexane, n-heptane, n-decane, and kerosene oil in water. The technique employed for the purpose was ultrasonification. The effect of ultrasonification time, chain length, viscosity, surface tension, oil content, and ionic strength of the media on the quality of emulsion has been studied. The emulsions were viewed through microscope to measure the number, size, and size distribution of droplets. Quantification of turbidity and viscosity was also used to characterize the emulsions. It has been found that the number and size of the droplets vary with the time of ultrasonification, contents of oils, molecular mass of the oils, and ionic strength of the media, and hence the quality of the emulsion is influenced by these parameters. The droplet size decreases, whereas the number of drops increases with the time of emulsification, approaching an optimum distribution at about 15 min of ultrasonification. Further, the increase in the molecular mass of the oil increases the size of the droplets and hence decreases the stability of the emulsion. The addition of electrolytes encourages coalescence and enhances the instability in the system. The results are in accord with the equations proposed by us.

A novel mechanism of dynamic interfacial tension reduction in triglyceride-alkaline aqueous solution system

Abstract Emulsification of edible oils in aqueous solutions is of interest in diverse applications. The energy required for emulsification of oil in water is dependent on properties like the viscosity ratio, the local shear rates and the Interfacial Tension (IFT) of the oil–water interface, at the expansion rates prevailing during the process. This paper shows that dynamic IFT and emulsification in edible oil/water systems is dependent on the aqueous phase pH. Experiments aimed at identifying the causes of this are discussed. This study, of the pH dependence of dynamic IFT, reveals a novel mechanism for IFT lowering which is more effective than surfactant adsorption. The results of this study clearly show that the dynamic IFT of an edible-oil–aqueous solution interface, has marked pH dependence, at room temperature. However, when the commercial edible oil is purified, using known techniques for triglyceride purification, the sensitivity of its dynamic IFT to pH of the aqueous phase is significantly reduced. This study shows that the observed pH dependence of dynamic IFT and ease of emulsification at high aqueous phase pHs, is due to in-situ surfactant generation, which occurs during edible oil–alkaline aqueous solution contact. Surprisingly, in-situ surfactant generation is much more effective in reducing oil–water dynamic IFT compared with adsorption of its pre-formed equivalent. This study probes this observation. Not only is in-situ generation more effective in tension reduction, experiments discussed in this paper show that the presence of pre-formed surfactants is actually detrimental to the tension reduction that is achievable by in-situ generation.