Hofmeister Salts Affect Buildup of Thin Multilayer Films Surrounding Oil Droplets

The layer-by-layer electrostatic deposition method is a novel technique to precisely control the interfacial properties of multilayered films such as charge, thickness, permeability, and composition. The formation and stability of multilayered emulsions is however often plagued by extensive droplet flocculation and aggregation even at ideal polyelectrolyte concentrations where saturation should occur. Addition of salts may reduce the degree of attractive interactions ions and thus improve deposition. To test this hypothesis, the influence of different Hofmeister salts (KCl, NaCl, LiCl, and NH₄Cl) at various salt concentrations (0–2500 mM) on the aggregation behavior of multilayered emulsions was investigated. A simple coating process of fish gelatin interfacial membranes with sugar beet pectin was used. Our results show that mean particle diameter and particle size distribution of emulsions initially decreased from 600 nm to 328 nm with increasing salt concentrations up to 250 mM. Above a critical level (>500 mM), heavy aggregation of emulsions at the presence of chaotropic salts occurred whereas kosmotropes reduced flocculation and creaming. Microscopic images and isothermal titration calorimetry confirmed particle size measurements. Results thus suggest that addition of salts may be an extremely useful tool to modulate and improve depositioning of alternatingly charged polymers on surfaces.      

Alteration of Interfacial Stability of Oil-in-Water Emulsions Using Bio-Derived Additives

Oil-in-water (O/W) emulsions are widely used in the preparation of many cosmetics, foods, and pharmaceutical products. Microstructure and stability of such emulsions are of utmost importance for their acceptability by the end user. In the present work, we studied the O/W emulsions to know the effects of two bio-derived additives—juice of Coriander sativam L., and milk of Cocos nucifera L, which have good nutrient value for their use in food emulsions. Addition of Cocos nucifera L. milk resulted in enhanced stability with decrease in the polydispersity of dispersed droplets in the emulsions due to the presence of proteins in it. Addition of Coriander sativam L. provided better stability against pH variation from 4 to 8.     

A DOE Approach to Investigate the Influence of Process-Parameters and Composition on the Stability of Emulsions Stabilized by Marine Polysaccharides Prepared by High-Pressure Homogenization

The influence of pre-homogenization conditions (speed and duration at a rotor–stator system), homogenization pressure, and quantitative composition of the emulsions on the droplet size and stability of the resulting emulsions is investigated using design of experiments. A mix of marine polysaccharides (e.g., alginate and fucoidane) from Ascophyllum nodosum is used as emulsifier to form O/W-emulsions with medium-chained triglycerides. It was found that the amount of emulsifier is the most relevant parameter for emulsions' stability whereas the influence of the homogenization pressure is more distinct at low polysaccharide contents. In contrast, the parameters of pre-homogenization do not influence the droplet size significantly.      

Stability of W/O Emulsions Encapsulating Polysaccharides

In the frame of formulation of W/O emulsions entrapping polysaccharides devoted to agricultural applications, the aim of this work was to study the stability over time of these emulsions, stabilized with either soybean lecithin or polyglycerol polyricinoleate (PGPR) as emulsifiers. Emulsifiers were dissolved in oil phase, and polysaccharides (carboxymethycellulose (CMC), guar, xanthan) in ultrapure water. Emulsions stability was studied through natural aging tests and accelerated aging tests, using bottle tests, microscopy and calorimetry. Experiments showed that PGPR was more efficient than lecithin to stabilize emulsions containing the polysaccharides studied, and that emulsions prepared with CMC showed the best stability.     

Experimental Design Approach to Investigate the Effects of Operating Factors on the Surface Tension,Viscosity, and Stability of Heavy Crude Oil-in-Water Emulsions

In this article, the effects of various operating factors on the surface tension, viscosity, and stability of two heavy oil types in water emulsions for pipeline transportation are studied using the Taguchi experimental design approach. The surface tension of heavy crude oil-in-water emulsion is decreased by increasing the emulsifier concentration while the stability of emulsions is increased. The viscosity and stability are increased by an increase in oil content. An increase in the salinity and mixing speed leads to an increase in the stability of emulsion.     

Use of Formax High-Throughput Platform to Create a Specific Emulsion

The Formax high-throughput platform is capable of rapidly mapping out the formulation and process parameters required to produce an array of emulsions with a range of particle sizes. The specific emulsion in this instance is a stable emulsion with a small droplet size, preferably submicron. Using a combination of design of experimental software and high-throughput experimentation, the factors required to produce the emulsion with smallest droplet size were identified. Additionally, this work produced a template which allows the quick and efficient mapping of process and formulation space to determine for new systems which variables have the greatest impact upon the emulsion produced. (Supplemental materials are available for this article. Go to the publisher's online edition of the Journal of Dispersion Science and Technology to view the free supplemental file.)     

Semi-Solid o/w Emulsions Based on Sucrose Stearates: Influence of Oil and Surfactant Type on Morphology and Rheological Properties

Sucrose stearate blends of intermediate lipophilicity are mild surfactants with thermosensitive gelling behavior. Binary systems and emulsions with sucrose stearate S-970 or S-1170 were developed and investigated by thermoanalytical and rheological measurements. The presence of an oil phase promoted the gelling potential of the esters especially at higher production temperatures. Semi-solid emulsions with viscoelastic properties comparable to weak gels were obtained with different dermatologically acceptable oils. The complex internal structure as visualized by fluorescence microscopy exhibited changes during storage in dependence of oil and surfactant type. A combination of S-970 with cetearyl ethylhexanoate-based oil phases led to superior physical stability.     

Experimental Investigation of Rheological and Morphological Properties of Water in Crude Oil Emulsions Stabilized by a Lipophilic Surfactant

Rheological behavior of two crude oils and their surfactant-stabilized emulsions with initial droplet sizes ranging from 0.5 to 75 µm were investigated at various temperatures under steady and dynamic shear testing conditions. In order to evaluate the morphology and Stability of emulsions, microscopic analysis was carried out over three months and average diameter and size distribution of dispersed droplets were determined. The water content and surfactant concentration ranged from 10 to 60% vol/vol and 0.1 to 10% wt/vol, respectively. The results indicated that the rheological properties and the physical structure and stability of emulsions were significantly influenced by the water content and surfactant concentration. The crude oils behaved as Newtonian fluids over a wide range of shear rates, whereas the emulsions behaved as non-Newtonian fluids, indicating shear-thinning effects over the entire range of shear rates. The viscosity, storage modulus and degree of elasticity were found to be significantly increased with the increase in water content and surfactant concentration. The maximum viscosity was observed at the point close to the phase inversion point where the emulsion system changes from water-in-oil emulsion to oil-in-water emulsion. The results also indicated that the rheological properties of crude oils and their emulsions are significantly temperature-dependent.     

Influence of Hydrophobically Associating Polyacrylamide on Dispersion Property of Water-Soluble Phenol-For-maldehyde Resin

To improve dispersion stability of water soluble phenol-fomaldehyde resin (PFR) in relatively low salinity water, the effect of hydrophobically associating polymer (HAP) on the dispersion property of PFR in NaCl solution was studied by the measurement of the size and zeta potential of PFR, HAP, and PFR/HAP molecule aggregates in NaCl solution, and the turbidity of PFR and PFR/HAP dispersions. The results show that due to the hydrophobically group on HAP molecule has similar structure as molecular structure of PFR and stronger hydrophobically association of HAP molecules in NaCl solution, HAP, and PFR molecules can form complex molecule aggregates together. The formation of the complex molecule aggregates enhanced the stability of PFR dispersion in NaCl solution.     

Natural Brazilian Raw Material to Develop O/W Emulsions Containing Lamellar Gel Phase (Development and Analysis of Emulsion with Vegetable Oils)

Oil-in-water emulsions were developed employing the HLB system and emulsion phase inversion (EPI) method. X-ray diffraction revealed that the anisotropic structures around the inner phase globules were lamellar gel network phases. The calculated distances between the lamellae made after preparation and 3 month latter showed that there was no swelling of the lamellar gel network indicating good stability and few changes during storage. The developed emulsions were stable and have potential to be employed for cosmetic and pharmaceutical purposes. The gel phase network and vegetal components seemed to be contributing factors.      

Synergetic Effect of Reactive Surfactants and Clay Particles on Stabilization of Nonaqueous Oil-in-Oil (o/o) Emulsions

Although surfactants and particles are often used together in stabilization of aqueous emulsions, the contribution of each species to such stabilization at the oil-water interface is poorly understood. The situation becomes more complicated if we consider the nonaqueous oil-oil interface, i.e, the stabilization of nonaqueous oil-in-oil (o/o) emulsions by solid particles and reactive surfactants which, to our knowledge, has not been studied before. We have prepared Pickering nonaqueous simple (o/o) emulsions stabilized by a combination of kaolinite particles and a nonionic polymerizable surfactant Noigen RN10 (polyoxyethylene alkylphenyl ether). Different pairs of immiscible oils were used which gave different emulsion stabilities. Using kaolinite with equal volumes of paraffin oil/formamide system gave no stable emulsions at all concentrations while the addition of Noigen RN10 enhanced the emulsion stability. In contrast, addition of Noigen RN10 surfactant to silicon oil-in-glycerin emulsions stabilized by kaolinite resulted in destabilization of the system at all concentrations. For all systems studied here, no phase inversion in simple emulsion was observed by altering the volume fraction of the dispersed phase as compared to the known water-based simple Pickering emulsions.      

Physical and Rheological Characteristics of Emulsion Model Structures Containing Iranian Tragacanth Gum and Oleic Acid

The physical and rheological properties of oil in water model emulsion systems containing Iranian tragacanth gum (TG) (0.5, 1 g/100 ml emulsions), whey protein isolate (WPI) (2, 4 g/100 ml emulsions), and oleic acid (5, 10 ml/100 ml emulsions) were investigated for droplet-size distribution, creaming index, and rheological properties of emulsions. The shear-thinning behavior of all dispersions was modeled using power law, Cross, and Ellis models. The power law model described the flow behavior of dispersions for its lowest standard error (0.29) and highest determination coefficient (R²) (0.99). Rheological investigation showed that both loss (G″) and storage (G′) modules increased as gum and oil content increased. Delta degree was 0.1 and increased as frequency increased, indicating that liquid-like viscose behavior dominated solid-like elastic behavior. Droplet-size distribution was measured by light scattering and microscopic observations revealed a flocculated system. Gum, WPI, and oil contents decreased the emulsion creaming index with gum concentration having the greatest effect.     

Effect of Nanoparticle Hydrophobicity on Stability of Highly Concentrated Emulsions

The effect of hydrophobicity index (HI) of fumed nanosilica specimens on stability of water-in-oil (W/O) highly concentrated emulsions (HCE with ? = 90 vol%) with an overcooled dispersed phase was studied. A series of five silica with HI in the 0.60–1.34 range and HI > 3 were used separately and in combination with a low molecular weight traditional surfactant, Sorbitan MonoOleate (SMO). First, it was shown that SMO alone can stabilize W/O HCE whereas only silica nanoparticles with intermediate HI in the range 0.97 ≤ HI ≤ 1.34 could form W/O emulsions only up to 77–79 vol%. Then, on the contrary to SMO-based emulsions, Pickering emulsions are unstable under shearing. When mixed (silica plus SMO) emulsifier systems were used, firstly a thermodynamic consideration revealed that only SMO is likely to adsorb at the W/O interface and controls the emulsifying process by the decrease in the interfacial tension. Then, interestingly, all different kinds of emulsion stability investigated in this study demonstrate a breaking point (BP) at HI = 0.97. Below the BP the emulsions were found to be very unstable on shelf as well as under shear. Above the BP, a clear synergy between colloidal silica and SMO surfactant has been found.      

A Comparison Investigation of Coix Seed Oil Liposomes Prepared by Five Different Methods

The physicochemical properties of coix seed oil (CSO) liposomes prepared by five different methods were evaluated for morphology, encapsulating efficiency, particle size, storage stability, and in vitro release. The different preparation methods resulted in several types of vesicles with different properties. The type of vesicles was closely related to leakage pattern, which affected the storage stability and in vitro release profiles. Ethanol injection method was the best choice for preparing safe and stable liposomes with controlled release. The release mechanisms might account for the diffusion of CSO, and Higuchi was the most suitable model for liposomes stored at high temperature or released in simulated intestinal fluid (SIF).     

Removal of Mercury by Emulsion Liquid Membranes: Studies on Emulsion Stability and Scale Up

Emulsion liquid membranes (ELM) have received significant attention in the separation of various metal ions from industrial wastewater. Still efforts are needed to get the desired level of stability to overcome the hindrance in the application of ELM at industrial scale. In this paper, the effects of various parameters such as emulsification speed, concentration of cosurfactant, surfactant, carrier and impeller speed during extraction on the stability of an emulsion liquid membrane are studied. Dispersion destabilization of w/o emulsion is checked by Turbiscan. Drop size distribution and photomicrographs of the emulsions are also analyzed to evaluate stability of the emulsion. Instability of emulsion liquid membrane during extraction process is measured in terms of membrane breakage. A stable emulsion is used for the extraction of mercury from aqueous solution in small scale as well as in large scale.     

Thermal Dispersion Model Compared with Euler-Lagrange Approach in Simulation of Convective Heat Transfer for Nanoparticle Suspensions

Convective heat transfer characteristics of water/Al₂O₃ nanofluid flow inside a tube were evaluated in this study. A non-uniform concentration distribution was used in thermal dispersion model. Meanwhile, an experimental study was done to find the dispersion coefficient in addition to assess the accuracy of simulation results. The accuracy of the results of thermal dispersion model was compared with the numerical solution using discrete phase modeling and homogenous method, while the effective parameters on particle migration were considered to find the particle distribution for being used in the dispersion model. Non-uniformity of the particle distribution is increased by raising volume fraction and Reynolds number. Concentration distribution was obtained using discrete phase method and was compared with the distribution employed for the dispersion model. When a uniform concentration is used in the dispersion model, error of prediction is expected to be increased. The thermal dispersion model, in which the particles have followed a non-uniform distribution, provides acceptable results in spite of its lower calculational time as compared to the two-phase approach.     

Investigations of the Effects of Salt and Biopolymer Ratio on Sodium Caseinate-Xanthan Interactions in Aqueous Solution and Emulsions

The aim of this work was to investigate interactions that can take place between, proteins and polysaccharides, in the presence of electrolytes. Thus, our objective was to study the influence of NaCl addition on the associative and/or segregative interactions in the case of biopolymer mixtures and fine emulsions stabilized by sodium caseinate, by analysis of the rheological properties and zeta potential. From the experimental results, it was shown that the presence of salt affects the rheological and physicochemical properties of the aqueous phase and consequently the emulsion stability. Indeed, the electrolytes can modify the conformation of proteins and polysaccharides, by electric neutralization of their charge, as they can generate a complex coacervation or increase their incompatibility.     

Comparison of the Rheological Behavior of Solutions and Formulated Oil-in-Water Emulsions Containing Carboxymethylcellulose (CMC)

In this study, it was aimed to compare the rheological properties of carboxymethylcellulose (CMC) in aqueous solutions and their corresponding emulsions containing 0.05, 0.1, 0.25, and 0.5% CMC in the aqueous phase. Samples with 0.05 and 0.1% CMC showed Newtonian behavior, but shear-thinning behavior was observed in CMC solutions and emulsions with increasing CMC concentrations to 0.25% and 0.5%. Rheological behavior of all samples were modeled by Power law (R ² = 0.986–197) and Casson models (R ² = 0.968–1). According to the Ostwald–de Waele model, the consistency index of all samples was increased and the flow behavior index decreased with increasing CMC concentration. Comparison of our data with four predicting models (Einstein, Larson, Pal, and Dougherty-Krieger equations) showed that the viscosity of continuous phase controls the viscosity of emulsions with high CMC concentrations and these models are not applicable for such situations. Addition of CMC increased the emulsion stability of O/W emulsions. This stability was increased with increasing CMC concentrations.