Factors Affecting the Droplet Size of Water‐in‐Oil Emulsions (W/O) and the Oil Globule Size in Water‐in‐Oil‐in‐Water Emulsions (W/O/W)

Multiple emulsions of the W₁/O/W₂ type are promising tools for encapsulating bioactive ingredients in the inner aqueous droplets. It is necessary, however, to control the factors influencing their encapsulation efficiency. One important factor is the particle size because it determines the surface area available for mass transport. Because of the coexistence of water and oil droplets in multiple emulsions, there are numerous factors that have an impact on particle size, for example, oil phase composition, interfacial properties, and viscosity of the phases. The purpose of this study was to systematically investigate the effect of these factors on particle sizes in multiple emulsions.     

Characterization and Evaluation of Electrolyte Influence on Canola Oil/Water Nano‐Emulsion

Emulsion stability is controlled by the physicochemical properties of the adsorbed layers formed on the surface of the droplets. Zeta potential and droplet size measured initially and during storage can estimate O/W emulsion stability. The aim of this study was to characterize and evaluate the effects of different hydrolyzable compounds employed in pharmaceutical and cosmetic preparations on the zeta potential and droplet size of canola O/W nano‐emulsions and, consequently, the emulsion stability. The samples containing additives demonstrated significant change in zeta potential, but in spite of that, no macroscopic instability was observed. Yet the droplet size values did not undergo significant change.     

Synthesis of Cationic PEM Emulsion and Application in Waste Water Treatment

Cationic polymer as a kind of flocculant is widely applied in purification treatment of waste water. Because it has positive charge group, it is able to connect strongly the suspended matters, short cellulose and other microparticles. The research on synthesis of cationic polymer and application in treatment of waste water is very universal abroad. But domestic research on those is not general. The technology of synthesis of PEM is simple , and the production cost is low. It is easy to apply…     

Probing the Water Stability Limits and Degradation Pathways of Metal–Organic Frameworks

A comprehensive model to describe the water stability of prototypical metal–organic frameworks (MOFs) is derived by combining different types of theoretical and experimental approaches. The results provide an insight into the early stages of water-triggered destabilization of MOFs and allow detailed pathways to be proposed for the degradation of different MOFs under aqueous conditions. The essential elements of the approach are computing the pK_a values of coordinated water molecules and geometry relaxations. Variable-temperature and pH infrared spectroscopy techniques are used to corroborate the main findings. The model developed herein helps to explain stability limits observed for several prototypical MOFs, including MOF-5, HKUST-1, UiO-66, and MIL-101-Cr, in aqueous solutions, and thus, provides an insight into the possible degradation pathways in acidic and basic environments. The formation of a metal hydroxide through the autoprotolysis of metal-coordinated water molecules and the strength of carboxylate–metal interactions are suggested to be two key players that govern stability in basic and acidic media, respectively. The methodology presented herein can effectively guide future efforts, which are especially significant for in silico screening, for developing novel MOFs with enhanced aqueous stability.     

Influence of Interaction Between Heavy Oil Components and Petroleum Sulfonate on the Oil–Water Interfacial Tension

The purpose of this study is to obtain the interaction between heavy oil components and petroleum sulfonate (NPS). In this article, the effects of pH, NaCl concentration, and NPS on the oil–water interfacial tension (IFT) of Gudao crude oil and its polar components were investigated. The results show that the NPS concentration corresponding to turning point of IFT is 0.001 g·mL^?1. This is lower than the CMC of NPS (0.0015 g·mL^?1) as there is a positive synergetic effect between NPS and the active substances of crude and its components, and the strength of their interaction depends on the interfacial activity of crude components. In simulated system of crude and polar components with 0.1 wt% NPS, at basic condition, the acidic substances in the polar components create naphthenates (the component whose acid number is higher creates more naphthenates), leading to lower IFT, so the interaction between heavy oil components and NPS is stronger in the basic condition. Proper concentration of NaCl in the stimulated systems improved the hydrophile-lipophile balance of emulsifier (NPS), accelerated the well-regulated adsorption of NPS in oil–water interface, and increased the interfacial activity of NPS, the interaction between heavy oil components and NPS was also enhanced.     

Structure and Orientation of Tetracarboxylic Acids at Oil–Water Interfaces

Fouling caused by tetracarboxylic acids in transport and separation process chains involving petroemulsions occurs when the interfacial concentration of tetraacids becomes large enough for calcium ions in the water phase to “crosslink” the adsorbed tetraacid molecules and form a precipitate. At present, the structure and orientation of tetraacid molecules at oil–water interfaces, which influences the precipitation behavior, has not been studied in detail. In this work, molecular dynamics simulations of indigenous and synthetic tetracarboxylic acid compounds are presented to describe the structure and spatial orientation of tetraacid molecules at oil–water interfaces. Molecular distributions relative to the oil–water dividing surface along with the length and orientation angle distributions of the acidic arm groups are presented. The probability distributions determined here that describe the tetraacids at an oil–water interface can be employed to reconstruct the density of carboxylic acid groups at the oil–water interface. The interfacial carboxylic acid density can be employed to determine the fraction of adsorbed tetraacid molecules that are “crosslinked” with calcium ions based on the distances between carboxylic acid groups. The simulations presented also form a basis to calculate interfacial molecular areas and virial coefficients to employ in molecular mixed monolayer adsorption isotherms.     

Synthesis of a Novel Core-shell Type Acrylic-polyurethane Hybrid Emulsion Containing Siloxane and Fluorine as well as Water and the Oil Resistances of Cured Film

Aqueous acrylic-polyurethane dispersions have become one of the major types of materials used in coating, paint and adhesive industries, because of excellent properties and environmental advantages1-5. However, some properties for cured film such as water…     

Impact on Morphological Characterization and Emulsion Stability of Lactoferrin–Beet Pectin Electrostatic Complexes

Interfacial protein–polysaccharide complexes can be utilized in emulsion-based delivery system and contained functional component or medical ingredient. In the present work, the interaction of lactoferrin (LF, 0.2 wt%) with beet pectin (BP, 0–0.15 wt%) was researched in aqueous solutions at different pH (2–9) and ionic strength (0–800 mM) to provide the information about properties of complexes. A simulative environment was created to explore the optimal concentration of BP to formulate LF-coated stabilized emulsion and how the emulsion responded to the changing environmental pH (2–9) and ionic strength (0–500 mM). Particle size, particle distribution index, zeta-potential, turbidity, Turbiscan stability index,, and peak thickness were used to characterize the physical stability of emulsions. The confocal laser scanning microscopy was used to derive the microscopy images of droplets. The results indicated that 0.4 wt% was the optimal concentration to formulate emulsions, and the LF-BP-coated bilayer emulsion has a preferable stability in more extensive range than the pure LF-stabilized emulsions under the environmental stresses through electrostatic interactions. The results of this study will play an important role in facilitating the utilization of LF-BP complexes as an emulsifier in the development of incorporating functional component or medical ingredient into commercial products.     

Effect of Demulsifier Structures on the Interfacial Dilational Properties of Oil–Water Films

The dilational properties of a branch-shaped polyether-type nonionic demulsifier (PEB), a comb-shaped polyether-type nonionic demulsifier (PEC), and a star-shaped polyether-type nonionic demulsifier (PES) at the decane–water interfaces were investigated by Langmuir trough method through oscillating barrier and interfacial tension relaxation methods, which are mainly in the influences of oscillating frequency and bulk concentration on dilational properties. Meanwhile, the effect of demulsifiers on interfacial dilational modulus of diluted crude oil was also explored. The experimental results indicate that all demulsifiers can decrease the dilational modulus of diluted crude oil at the experimental concentration. The addition of PEB causes the dilational modulus of crude oil to be lower than that at the water–decane interface. The demulsifier PEC has a similar effect with PES to influence the interfacial film of crude oil: at low concentration, the dilational modulus of mixed interfacial film is lower than that of demulsifier alone, while at high concentration, the dilational modulus of mixed interfacial film is slightly higher than that of demulsifier alone. The dependence of static modulus on the bulk concentration is consistent with the trend of interfacial dilational modulus with concentration for demulsifiers PEB, PEC, and PES. The studies about the structure modulus show that the new demulsifiers PEC and PES have a stronger ability than branch-shaped demulsifier PEB to destroy the interfacial film.     

Potentiometric Determination of the Stability Constants of Trimethyltin(IV) Chloride Complexes with Imino-bis(Methylphosphonic Acid) in Water and Dioxane–Water Mixtures

The interaction of trimethyltin(IV) (TMT) with imino-bis(methylphosphonic acid) (IDP), abbreviated as H₄L, was investigated at 25 °C and at ionic strength 0.1 mol⋅dm⁻³ (NaNO₃) using a potentiometric technique. The formation constants of the complexes formed in solution were calculated using the nonlinear least-squares program MINIQUAD-75. The stoichiometry and stability constants are reported for the complexes formed. The results show the formation of 110, 111, 112 and 11-1 complexes for the TMT–IDP system. The concentration distribution of the various complex species was evaluated. The effect of dioxane as a solvent, on both the protonation constants and the formation constants of trimethyltin(IV) complexes with IDP, is discussed. The thermodynamic parameters ΔH ^∘ and ΔS ^∘ calculated from the temperature dependence of the equilibrium constants were evaluated. The effect of ionic strength on the protonation constants of IDP is also discussed.     

Effect of Cationic and Zwitterionic Surfactants on Contact Angle of Quartz–Water–Crude Oil System

The influences of four cationic surfactants hexadecyl glycidyl ether ammonium chloride and four zwitterionic surfactants hexadecyl glycidyl ether glycine Betaine solutions on contact angle of crude oil on a quartz surface were investigated using a captive drop method. The effects of surfactant type, structure, and concentration on contact angle were expounded. From obtained results it appears that the adsorbed surfactant at oil–water interface reduces the interfacial tension and the adsorption at quartz–water interface improves interfacial free energy, which results in reducing the stable value of contact angle and weakening dynamic behavior. At high concentration, the zwitterionic surfactant with branched-chain may form semi-micelle at quartz surface. As a result, the stable value of contact angle passes through a sharp minimum with the increasing concentration.     

Thermodynamics of Adsorption of L-Amino Acids at Oil–Water Interfaces

Lowering of the interfacial tension of heptane–water, benzene–water, and nitrobenzene–water interfaces due to addition of 20 different amino acids to the aqueous phase has been measured. From the plot of surface pressure against molar concentration of amino acids, the initial slope and the surface excess ₂ ¹ for different amino acids have been calculated using the Gibbs adsorption equation. ₂ ¹ for most amino acids at benzene–water and heptane–water interfaces was found to be positive, with only a few being negative. At the nitrobenzene–water interface, both positive and negative ₂ ¹ values were observed. The area per adsorbed molecule at surface saturation A _m was found to vary widely, indicating different orientations of amino acid molecules at the interfaces. Using the integrated form of the Gibbs adsorption equation, the standard Gibbs energy change G ^o in kJ-m² of the adsorbed surface have been calculated for various interfaces. G ^o was found to vary linearly with the ₂ ¹ of different amino acids and the slope of the line, designated as –G _B ⁰ was found to be 22 kJ-mol^–1 for heptane–water, 23.2 kJ-mol^–1 for benzene–water, and 19.3 kJ-mol^–1 for nitrobenzene–water interfaces, irrespective of the nature of the amino acid. The origin of the linear scale of the Gibbs energy for heptane–water, benzene–water and nitrobenzene–water interfaces has been discussed in terms of hydrophobic and other interactions.     

Stabilization of Water‐Soluble Antioxidant in Water‐in‐Oil‐in‐Water Double Emulsions

Abstract

In this study, we are introducing a method that can effectively stabilize antioxidants in water‐in‐oil‐in‐water (W/O/W) double emulsions. Preliminarily, stable W/O/W double emulsions were produced by manipulating the characteristics of internal aqueous phase via two‐stage emulsification, resulting consequently in the formation of fine internal water droplets in the dispersed oil droplets. From conductivity measurements that can determine the elution amount of internal aqueous phase, it was confirmed that the double emulsion stability could be improved by treating the internal aqueous phase with a hydroxypropyl‐beta‐cyclodextrin. In this study, kojic acid, 5‐hydroxy‐2‐(hydroxymethyl)‐4‐pyrone was selected as a model antioxidant. The stabilization of kojic acid was attempted by locating it in the internal water droplets of the stable W/O/W double emulsions. The stability of kojic acid in the double emulsion system could be maintained at 90% for 10 weeks at high temperature. We believe that these stable W/O/W double emulsions could be used meaningfully as a carrier for many unstable antioxidants.     

Relationship Between the Polymer Structures and Destabilization of Polymer‐Containing Water‐in‐Oil Emulsions

The viscous properties, scanning electronic microscopy (SEM), and water/oil interfacial tension (IFT) of partially hydrolyzed polyacryamide (HPAM) and hydrophobically associating hydrolyzed polyacryamides modified with N‐dodecylacrylamide were studied with the objective of investigating the influence on destabilization of emulsions. As expected, the copolymers exhibit significant viscosity enhancing capacity and three‐dimensional network structures due to intermolecular hydrophobic associations, and also present high interfacial activities as the IFT decrease with increasing polymer concentration. As a result, the existences of copolymers increased both the viscosity of emulsions and the intensity of interfacial film, in which case slow down the diffusion of demulsifier molecules and enhance the stability of emulsions, finally, the separation of water from oil becomes more difficult.     

Effect of Demulsifiers on Dilatational Properties of Crude Oil–Water Interfaces

The dilatational properties of polyether demulsifiers PEA, PEB, PEC, PED, PEF, and PEG at the decane-water interface were investigated. Meanwhile, the effect of demulsifiers with different structures on interfacial dilatational modulus of diluted crude oil also was explored. The properties of demulsifiers are compared and analyzed in combine with the dilatational parameters at decane-water interface and at 5% crude oil-water interface. The results show that interfacial dilatational viscoelasticity could characterize the interfacial behavior of demulsifiers. The demulsifiers, which have different kinds or structures, have different effects on destroying the interfacial film of crude oil with increasing bulk concentration. Therefore, the dosage of demulsifier is a very important role in controlling nature of crude oil film.     

Stability Constants of Copper(II) Glycylglycinate Complexes in Water–Dimethylsulfoxide Solutions

Russian Journal of Physical Chemistry A - Stability constants of normal and copper(II) bis-glycylglycinate complexes in water–dimethylsulfoxide solutions of variable composition are...