Mechanism Of Emulsification Research Articles

Characterization and Inversion Method of Relative Permeability of Emulsion Flooding.

Relative permeability curves are one of the crucial factors that control the behavior of multiphase flow in petroleum reservoirs. Accurate prediction of the relative permeability curve involving emulsification and emulsion transport in emulsion flooding is vital to enhancing heavy oil recovery. In this study, a relative permeability characterization model including the emulsification mechanism and emulsion transport is developed, in which residual oil saturation and end-point permeability for water are parametrized as functions of emulsion concentration and capillary number. Based on the built characterization model, an inversion method (ensemble Kalman filter) is used to estimate the relative permeability curves of emulsion flooding. The inversion results of four sets of emulsion flooding experiments show that the errors of end points between the Johnson-Bossler-Neumann method and inversion method are less than 10%. For the continuous emulsification process in the in situ emulsion flooding tests, the inversed relative permeability curves shift between the upper and the inferior limits of the permeability. The error of residual oil saturation between the inversion and the experiment is less than 10%. In summary, this study demonstrates the feasibility of using the characterization model and inversion method to infer the relative permeability curves of emulsion flooding, which can aid in the predictions of multiphase flow in heavy oil reservoirs.

Thermomechanically micronized sugar beet pulp: Elucidating the interaction of soluble elements and insoluble fibrous particles for enhancing emulsification

The micronization of plant particles usually transfers substantial insoluble fraction into soluble elements, resulting in a soluble-insoluble binary system and the content of soluble elements can not be neglected. The present work aims to investigate the interaction between soluble elements and insoluble particles obtained from sugar beet pulp by microwave heating with ultrasonication, and their contribution to the synergistic emulsification performance. The soluble elements (∼40%) (sugar beet pectic substance, SBPS) and insoluble fibrous particles (IFPs) were separated from micronized sugar beet pulp (MSBP). Quartz crystal microbalance with dissipation analysis revealed that SBPS could irreversibly adsorb onto IFPs with an adsorbed mass of 32.2 μg/mg Fiber. By adopting sequential extraction and specific enzymatic hydrolysis for the modification of IFPs and SBPS, it was found that their non-saccharide fraction played an important role in the interaction. Larger molecular weight subfractions with abundant protein and ferulic acid content were the main adsorbable fraction in SBPS, and the interaction was driven by hydrophobic interaction. The soluble-insoluble binary system promoted the interfacial adsorption of both IFPs (from 65.6% to 82.2%) and SBPS (from 9.6% to 19.6%), forming a hybrid interfacial coverage (with SBPS-coated IFPs and SBPS) and endowing emulsion with better stability. These findings provided a guideline for understanding the emulsification mechanism of plant particles.

Study on the interactions and interfacial behaviors of cellulose nanocrystal/β-lactoglobulin complexes for pickering emulsions

Pickering emulsions stabilized by polysaccharides and protein complexes have attracted increasing attention. Exploring their interfacial activities and adsorption behaviors at the oil–water interface is of great significance for deepening our understanding of the emulsification mechanism and improving the properties of polysaccharide/protein-stabilized emulsions. Here, cellulose nanocrystals (CNCs) with rod-like structures and spherical β-lactoglobulin (β-LG) proteins were selected as representative stabilizers. We initially investigated the interaction between the 2 at pH 2.0–7.0 through a multiscale approach. Then, oil–water interfacial tension tests were used to assess the interfacial activities of CNCs and β-LG, revealing that β-LG exerted primary influence over the interfacial behavior in their complexes. Meanwhile, quartz crystal microbalance with dissipation was used to monitor the interfacial adsorption behaviors of CNCs, β-LG, and CNC/β-LG complexes, demonstrating that the interfacial layer formed by the CNC/β-LG complexes on the oil film (∼696.7 ng/cm2) was thicker and more stable compared with that formed by individual CNCs (∼48.4 ng/cm2) or β-LG (∼87.1 ng/cm2). Finally, we applied the CNC/β-LG complexes as stabilizers in Pickering emulsions and the emulsions prepared with the complexes at concentrations above 0.8 wt% exhibited storage stability for up to 28 d which confirmed their exceptional emulsifying ability and practical value. This study provides profound insights into the interfacial behavior of polysaccharide–protein complexes in Pickering emulsions and is expected to facilitate the design of novel food-grade emulsifiers.

A natural protein-lipid co-assembly as efficient Pickering emulsifier from egg yolk sphere microgel prepared via high-pressure homogenization

Egg yolk sphere is a kind of natural colloidal histological structure formed by the co-assembly of a large number of proteins and lipids, which has the dual functions of hydrophilic and lipophilic for application in emulsion. In this study, egg yolk sphere microgels (EYSMs) were prepared by high pressure homogenization (HPH) technique at various pressures (0–90 MPa) and used as Pickering emulsifiers for emulsification to obtain oil-in-water emulsions with an oil-water ratio of 11:9. The microscopic morphology, structure, and physicochemical properties of EYSMs were analyzed. The results showed that EYSMs obtained at 60 MPa (60-EYSMs) exhibited superior emulsifying properties with an emulsifying activity index (EAI) of 2.8 m2/g and an emulsifying stability index (ESI) of 356.6 min, resulting in enhanced storage stability of the emulsion for 30 d. The HPH treatment decreased the lipid content in EYSMs while creating a more homogeneous protein-lipid arrangement, which provided EYSMs with balanced hydrophilic and hydrophobic sites to improve emulsifying properties. Furthermore, the free sulfhydryl groups and hydrophobic moieties exposed by HPH promoted -S-S- formation on the EYSMs surface, promoting the increase in surface hydrophobicity and emulsifying ability. The confocal laser scanning microscopy (CLSM) and cryogenic scanning electron microscopy (cryo-SEM) revealed that the EYSMs adsorbed at oil-water interface and formed an intercross-linked spatial three-dimensional network structure, which worked as a physical barrier to the stable emulsion formation. This study introduces a novel research concept and delves into the emulsification mechanism of protein-lipid composite particles, offering a fresh insight for the development and utilization of emulsifiers.

Factors influencing demulsification of refinery oily sludge via ultrasonic treatment

Ultrasonic demulsification treatment is essential to dehydrate refinery sludge with complex composition, high water content, and demulsification difficulty. Herein, the influencing factors and the demulsification mechanism are studied in oily sludge treatment. The effects of initial temperature, ultrasonic amplitude, and time, as well as a diversity of additives on the ultrasonic dehydration rate of oily sludge demulsification, are investigated. The optimal demulsification conditions are confirmed (temperature: 20 °C, ultrasonic amplitude: 100 %, and ultrasonic time: 5 min), based on the effectiveness and economy of dehydration. The combined ultrasonication and pyrolysis of the solid residue of sludge shows a dehydration rate of 60.49 %, beneficial for the green transformation and utilization of subsequent demulsification products. Moreover, the mechanism of ultrasonic emulsification is proposed, as well. This work provides an important reference for the subsequent resource utilization of oily sludge in the industry.

Emulsification characteristics of crude oil with a high content of heavy components and its emulsification mechanism in porous media

There are occurrences of crude oil emulsification following the fracturing shut-in wells in the Jimushar, but the emulsification characteristics and mechanism remain unclear. In this study, the low-field nuclear magnetic resonance technique and visual microdisplacement tests are employed to investigate the emulsification characteristics of crude oil, along with its emulsification mechanism in porous media. Experimental results revealed that the heavy components (asphaltene and resin) enhance crude oil emulsification by increasing the viscous force of water droplets in the oil phase, affecting the size and stability of small water droplets in the oil phase. In the process of flowing through pore throats, emulsions are formed primarily by stretching and snap-off action, with stretching preferring to form smaller droplet-size emulsions, while snap-off results in the division of larger oil droplets into two smaller ones. The primary factors causing a large oil droplet to be stretched into smaller droplets include changes in the composition of the oil droplet, external tension, and the duration of these forces acting on the droplet. Capillary forces can emulsify crude oil and water at the pore scale, resulting in a reduction of the absorption rate. However, this rate can be restored when the capillary forces are strong enough for the water phase to penetrate and break through the emulsified layer. This study offers valuable insights into understanding the adaptability of the emulsification flooding mechanism.

Insights into the preparation and mechanism of Non-Alkali viscosity reducer for enhancing heavy oil recovery under Low-Shear condition

Viscosity reducer flooding technology has been applied for enhanced oil recovery (EOR) in ordinary heavy oil reservoirs. However, the non-alkali viscosity reducer for heavy oil reservoir under low-shear condition has not been systematic studied. Thus, in terms of emulsifying ability and stability, oil–water interfacial tension and viscosity reduction performance, the non-alkali viscosity reducer was prepared under low-shear condition by the bottle inversion test method and shaker shaking method. Then the enhanced oil recovery ability of the non-alkali viscosity reducer was evaluated and the pore-scale EOR mechanism was investigated via microscopic visual flooding experiments. Results show that the non-alkali viscosity reducer consisting of C12-14 alkyl glucoside (APG1214) surfactant and sodium linear-dodecyl benzenesulfonate (LAS-30) surfactant was prepared with the oil–water interfacial tension of 0.15mN·m−1 and viscosity reduction rate of 97.9%. Compared with water flooding, the non-alkali viscosity reducer can significantly increase the sweep efficiency and the oil displacement efficiency and enhance oil recovery by 8.94% by the mechanism of emulsification, reducing interfacial tension and changing wettability.

Factors, Mechanisms, and Kinetics of Spontaneous Emulsification for Heavy Oil-in-Water Emulsions.

In challenging reservoirs where thermal recovery falls short, cold or chemical oil recovery methods are crucial. Spontaneous emulsification (SE), triggered by gentle disturbance, significantly enhances oil recovery. In elucidating SE mechanisms and kinetics, SE processes via direct contact between oil and aqueous phases without stirring were conducted. The effects of temperature, emulsifier concentration, pH, NaCl concentration, and the oil-to-water ratio on SE were investigated through droplet size analysis and turbidity measurements. Furthermore, the emulsification mechanism and derived emulsification kinetics based on turbidity data were obtained. The results underscore the feasibility of SE for oil-water systems, reducing viscous and capillary resistances without agitation. The emulsified oil mass increased with the temperature, pH, and aqueous-to-oil phase volume ratio while decreasing with the NaCl concentration. In this study, for GD-2 crude oil, the optimal emulsified oil amount occurred at a betaine surfactant (BetS-2) emulsifier concentration of 0.45%. Microscopic photo analysis indicated narrow particle size distributions and small droplets, which remained stable over time under various experimental conditions. A combined SE mechanism involving ultralow interfacial tension, interfacial turbulence due to Marangoni effects, and "diffusion and stranding" due to in situ emulsifier hydrophilicity, was speculated. Additionally, an analogous second-order kinetic equation for SE was proposed, indicating exceptional correlation with calculated and experimentally measured values. This study offers theoretical insight for enhancing oil recovery in chemical and cold production of heavy oil in oilfields.

Stability and release mechanism of double emulsification (W1/O/W2) for biodegradable pH-responsive polyhydroxybutyrate/cellulose acetate phthalate microbeads loaded with the water-soluble bioactive compound niacinamide

Microbeads of biodegradable polyhydroxybutyrate (PHB) offer environmental benefits and economic competitiveness. The aim of this study was to encapsulate a water-soluble bioactive compound, niacinamide (NIA), in a pH-responsive natural matrix composed of PHB and cellulose acetate phthalate (CAP) by double emulsification (W1/O/W2) to improve the encapsulation efficiency (%EE) and loading capacity (%LC). PHB was produced in-house by Escherichia coli JM109 pUC19-23119phaCABA-04 without the inducing agent isopropyl β-D-1-thiogalactopyranoside (IPTG). The influences of PHB and polyvinyl alcohol (PVA) concentrations, stirring rate, PHB/CAP ratio and initial NIA concentration on the properties of NIA-loaded pH-responsive microbeads were studied. The NIA-loaded pH-responsive PHB/CAP microbeads exhibited a spherical core-shell structure. The average size of the NIA-loaded pH-responsive microbeads was 1243.3 ± 11.5 μm. The EE and LC were 33.3 ± 0.5 % and 28.5 ± 0.4 %, respectively. The release profiles of NIA showed pH-responsive properties, as 94.2 ± 3.5 % of NIA was released at pH 5.5, whereas 99.3 ± 2.4 % of NIA was released at pH 7.0. The NIA-loaded pH-responsive PHB/CAP microbeads were stable for >90 days at 4 °C under darkness, with NIA remaining at 73.65 ± 1.86 %. A cytotoxicity assay in PSVK1 cells confirmed that the NIA-loaded pH-responsive PHB/CAP microbeads were nontoxic at concentrations lower than 31.3 μg/mL, in accordance with ISO 10993-5.

Synergistic collaborations between surfactant and polymer for in-situ emulsification and mobility control to enhance heavy oil recovery

Surfactant-polymer (SP) combined systems is an effective nonthermal method to enhance the heavy oil recovery, through in-situ emulsification and mobility control mechanisms. In this study, a novel SP system was developed using 0.2 wt% anionic surfactant (alkyl naphthol polyoxyethylene ether sulfonate, ANES) and 0.1 wt% polymer (partially hydrolyzed polyacrylamide, HPAM). The SP system had viscosity reduction rate of ∼ 98 %, viscosity ratio of oil to displaced water (μo/μd) of ∼ 3.95 and IFT of ∼ 0.29 mN/m, beneficial for decreasing the mobility ratio of water to heavy oil. Then, the applied performances including emulsion morphologies and stability, wettability alteration ability were systematically characterized. The results showed that the freshly O/W emulsions formed by SP system displayed uniform droplet size distribution, as well as high stability with tight interfacial film. In addition, the SP system exhibited excellent wettability alteration property with low contact angle of 18.3°. The synergistic collaboration mechanisms of surfactant and polymer include heavy oil–water interfacial tension reduction, in-situ emulsification, oil-viscosity reduction and water-viscosity increase. Finally, the static oil washing and dynamic sand-pack flooding experiments showed that the SP system exhibited high oil washing efficiency (62.89 %) and enhanced oil recovery efficiency (56.9 %) with improving the mobility controllability after the primary water-flooding process. This study indicated that the synergistic collaborations between surfactant and polymer had great potential to enhance the heavy oil recovery.

Effects and mechanisms of ultrasound-assisted emulsification treatment on the curcumin delivery and digestive properties of myofibrillar protein-carboxymethyl cellulose complex emulsion gel

Different emulsion gel systems are widely applied to deliver functional ingredients. The effects and mechanisms of ultrasound-assisted emulsification (UAE) treatment and carboxymethyl cellulose (CMC) modifying the curcumin delivery properties and in vitro digestibility of the myofibrillar protein (MP)-soybean oil emulsion gels were investigated. The rheological properties, droplet size, protein and CMC distribution, ultrastructure, surface hydrophobicity, sulfhydryl groups, and zeta potential of emulsion gels were also measured. Results indicate that UAE treatment and CMC addition both improved curcumin encapsulation and protection efficiency in MP emulsion gel, especially for the UAE combined with CMC (UAE-CMC) treatment which encapsulation efficiency, protection efficiency, the release rate, and bioaccessibility of curcumin increased from 86.75 % to 97.67 %, 44.85 % to 68.85 %, 18.44 % to 41.78 %, and 28.68 % to 44.93 % respectively. The protein digestibility during the gastric stage was decreased after the CMC addition and UAE treatment, and the protein digestibility during the intestinal stage was reduced after the CMC addition. The fatty acid release rate was increased after CMC addition and UAE treatment. Apparent viscosity, storage modulus, and loss modulus were decreased after CMC addition while increased after UAE and UAE-CMC treatment especially the storage modulus increased from 0.26 Pa to 41 Pa after UAE-CMC treatment. The oil size was decreased, the protein and CMC concentration around the oil was increased, and a denser and uniform emulsion gel network structure was formed after UAE treatment. The surface hydrophobicity, free SH groups, and absolute zeta potential were increased after UAE treatment. The UAE-CMC treatment could strengthen the MP emulsion gel structure and decrease the oil size to increase the curcumin delivery properties, and hydrophobic and electrostatic interaction might be essential forces to maintain the emulsion gel.

The Emulsification and Stabilization Mechanism of an Oil-in-Water Emulsion Constructed from Tremella Polysaccharide and Citrus Pectin.

The objective of this study was to investigate the feasibility of the mixture of tremella polysaccharide (TP) and citrus pectin (CP) as an emulsifier by evaluating its emulsifying ability/stability. The results showed that the TP:CP ratio of 5:5 (w/w) could effectively act as an emulsifier. CP, owing its lower molecular weight and highly methyl esterification, facilitated the emulsification of oil droplets, thereby promoting the dispersion of droplets. Meanwhile, the presence of TP enhanced the viscosity of emulsion system and increased the electrostatic interactions and steric hindrance, therefore hindering the migration of emulsion droplets, reducing emulsion droplets coalesce, and enhancing emulsion stability. The emulsification and stabilization performances were influenced by the molecular weight, esterified carboxyl groups content, and electric charge of TP and CP, and the potential mechanism involved their impact on the buoyant force of droplet size, viscosity, and steric hindrance of emulsion system. The emulsions stabilized by TP-CP exhibited robust environmental tolerance, but demonstrated sensitivity to Ca2+. Conclusively, the study demonstrated the potential application of the mixture of TP and CP as a natural polysaccharide emulsifier.

Effect of in-situ emulsification on CO2/N2-based cyclic solvent injection process for enhancing heavy oil recovery and CO2 storage

Surfactant-assisted CO2/N2-based CSI (SA CO2/N2-CSI) process emerges as a strategic solution to migrate the high energy consumption and carbon intensity associated with traditional thermal operations for heavy oil recovery. However, the interphase mass transfer makes the emulsification behavior in this process complex. In this study, the effect of in-situ emulsification on CO2/N2-CSI is assessed using a sandpack model and microchannel chip. Mesoscopically, SA CO2/N2-CSI outperforms conventional CO2/N2-CSI in terms of both oil recovery and CO2 storage, owing to the enhanced CO2 diffusion, oil solubilization, and foamy oil stability due to emulsification. Microscopically, the impact of emulsifier injection rate on oil removal efficiency in the dead-end pores becomes negligible when the injection rate exceeds 50 nL/min, providing insights to the emulsification mechanisms underlying the optimal pressure depletion rate (9 kPa/min) in SA CO2/N2-CSI. This study demonstrates the applicability of the SA CO2/N2-CSI in fostering sustainable heavy oil production and CO2 storage.

Photonic Pigments of Polystyrene-block-Polyvinylpyrrolidone Bottlebrush Block Copolymers via Sustainable Organized Spontaneous Emulsification.

Prior studies on photonic pigments of amphiphilic bottlebrush block copolymers (BBCPs) through an organized spontaneous emulsification (OSE) mechanism have been limited to using polyethylene glycol (PEG) as the hydrophilic side chains and toluene as the organic phase. Herein, a family of polystyrene-block-polyvinylpyrrolidone (PS-b-PVP) BBCPs are synthesized with PVP as the hydrophilic block. Biocompatible and sustainable anisole is employed for dissolving the obtained BBCPs followed by emulsification of the solutions in water. Subsequent evaporation of oil-in-water emulsion droplets triggers the OSE mechanism, producing thermodynamically stable water-in-oil-in-water (w/o/w) multiple emulsions with uniform and closely packed internal droplet arrays through the assembly of the BBCPs at the w/o interface. Upon solidification, the homogeneous porous structures are formed within the photonic microparticles that exhibit visible structural colors. The pore diameter is widely tunable (150∼314 nm) by changing the degree of polymerization of BBCP (69∼110), resulting in tunable colors across the whole visible spectrum. This work demonstrates useful knowledge that OSE can be generally used in the fabrication of ordered porous materials with tunable internal functional groups, not only for photonic applications, but also offers a potential platform for catalysis, sensing, separation, encapsulation, etc.

Correlation between emulsification and butyryl group distribution in various butyrylated starches

Butyrylated starch, a modified starch with significant applications in the food and pharmaceutical industries, lacks sufficient research on its emulsification. In this study, butyrylation was performed using waxy corn starch, tapioca starch and corn starch as raw materials, and their group distribution were determined. X-ray photoelectron spectroscopy (XPS), Raman microscopy and water contact angle measurements showed that the distribution of butyryl group in B-WCS was highly uniform. The results of the emulsification assay illustrated that B-WCS exhibited significant emulsifying potential at similar degrees of substitution. Analysis of the interface behavior demonstrated that B-WCS reduced the oil-water interfacial tension and formed a rigid interface film that resisted external deformation, thereby maintaining emulsion stability. This indicates that B-WCS exhibiting a highly uniform group distribution has significant emulsification potential. This study revealed the emulsification mechanism of butyrylated starch from an interface perspective and analyzed the relationship between the butyryl group distribution and emulsifiability.

Interfacial Behavior and Long-Term Stability of the Emulsions Stabilized by Sugar Beet Pectin-Ca2+ Complexes with Different Cross-Linking Degrees.

Recent studies showed that sugar beet pectin exhibited more excellent emulsifying properties than traditional citrus peel pectin and apple pectin ascribed to the higher content of neutral sugar, protein, ferulic acid, and acetyl groups. It is precisely because of the extremely complex molecular structure of pectin that the emulsifying properties of the pectin-Ca2+ complex are still unclear. In this study, SBP-Ca2+ complexes with different cross-linking degrees were prepared. Subsequently, their interfacial adsorption kinetics, the resistance of interfacial films to external perturbances, and the long-term stability of the emulsions formed by these SBP-Ca2+ complexes were measured. The results indicated that the highly cross-linked SBP-Ca2+ complex exhibited slower interfacial adsorption kinetics than SBP alone. Moreover, compared with SBP alone, the oil-water interfacial film loaded by the highly cross-linked SBP-Ca2+ complex exhibited a lower elasticity and a poorer resistance to external perturbances. This resulted in a larger droplet size, a lower ζ-potential value, a larger continuous viscosity, and a worse long-term stability of the emulsion formed by the highly cross-linked SBP-Ca2+ complex. This study has very important guiding significance for deeply understanding the emulsification mechanism of the pectin-Ca2+ complex.

Elucidating pH dynamics in Pickering emulsions stabilized by soybean protein isolate and nicotinamide mononucleotide: Enhancing emulsification and curcumin delivery mechanisms

This research investigates the intricate dynamics of fish oil Pickering emulsions emulsified by soybean protein isolate/nicotinamide mononucleotide (SPI/NMN) under varying pH conditions and curcumin (CUR) concentrations. The study reveals that the droplet size distribution of the emulsion attains its minimum at a CUR concentration of 0.5 wt%, attributed to optimal interfacial interactions between CUR and SPI/NMN. Beyond this concentration, droplet size distribution increases due to potential droplet aggregation. In the realm of drug encapsulation, the encapsulation efficiency of CUR peaks at 87% at this concentration, underscoring the need for a balance between drug load and encapsulation efficiency. Notably, pH significantly affects emulsion stability, with optimal stability achieved at pH∼9. Under acidic conditions, the emulsion is less stable, with CUR adopting an open enolic tautomeric conformation that enhances its binding behavior. The release of CUR from the emulsions is modulated by pH, exhibiting a 92% release at pH∼2 over 16 h, in contrast to a 60% release in the pH 5–9 range. The findings provide crucial insights into the behavior and stability of SPI/NMN emulsified systems, offering potential applications in drug delivery system design. The use of SPI/NMN complex for stabilizing Pickering emulsions presents an advanced approach to enhancing emulsion stability. Precise control over drug release is attainable through pH modulation, providing substantial benefits in terms of improved drug efficacy, reduced side effects, and augmented patient convenience.

Insights into the emulsification mechanism of the surfactant-like protein oleosin

Oleosins are proteins with a unique central hydrophobic hairpin designed to stabilize lipid droplets (oleosomes) in plant seeds. For efficient droplet stabilization, the hydrophobic hairpin with a strong affinity for the apolar droplet core is flanked by hydrophilic arms on each side. This gives oleosins a unique surfactant-like shape making them a very interesting protein. In this study, we tested if isolated oleosins retain their ability to stabilize oil-in-water emulsions, and investigated the underlying stabilization mechanism. Due to their surfactant-like shape, oleosins when dispersed in aqueous buffers associated to micelle-like nanoparticles with a size of ∼33 nm. These micelles, in turn, clustered into larger aggregates of up to 20 µm. Micelle aggregation was more extensive when oleosins lacked charge. During emulsification, oleosin micelles and micelle aggregates dissociated and mostly individual oleosins adsorbed on the oil droplet interface. Oleosins prevented the coalescence of the oil droplets and if sufficiently charged, droplet flocculation as well.

The Phase Inversion Mechanism of the pH-Sensitive Reversible Invert Emulsion.

Reversible emulsification drilling fluids can achieve conversion between oil-based drilling fluids and water-based drilling fluids at different stages of drilling and completion, combining the advantages of both to achieve the desired drilling and completion effects. The foundation of reversible emulsion drilling fluids lies in reversible emulsions, and the core of a reversible emulsion is the reversible emulsifier. In this study, we prepared a reversible emulsifier, DMOB(N,N-dimethyl-N'-oleic acid-1,4-butanediamine), and investigated the reversible phase inversion process of reversible emulsions, including the changes in the reversible emulsifier (HLB) and its distribution at the oil-water interface (zeta potential). From the perspective of the acid-alkali response mechanism of reversible emulsifiers, we explored the reversible phase inversion mechanism of reversible emulsions and reversible emulsification drilling fluids. It was revealed that the reversible phase inversion of emulsions could be achieved by adjusting the pH of the emulsion system. Then the proportion of ionic surfactants changed in the oil-water interface and subsequently raised/lowered the HLB value of the composite emulsifier at the oil-water interface, leading to reversible phase inversion of the emulsion. The introduction of organic clays into reversible emulsification drilling fluid can affect the reversible conversion performance of the drilling fluids at the oil-water interface. Thus, we also investigated the influence of organic clays on reversible emulsions. It was demonstrated that a dosage of organic clay of ≤2.50 g/100 mL could maintain the reversible phase inversion performance of reversible emulsions. By analyzing the microstructure of the emulsion and the complex oil-water interface, we revealed the mechanism of the influence of organic clay on the reversible emulsion. Organic clay distributed at the oil-water interface not only formed a complex emulsifier with surfactants, but also affected the microstructure of the emulsion, resulting in a difficult acid-induced phase transition, an easy alkali-induced phase transition, and improved overall stability.

Conformational flexibility and molecular weight influence the emulsification performance of pectin: A comparative study of sugar beet pectin and citrus pectin

Due to the complex composition and structure of plant polymers, a detailed investigation into the emulsification mechanism of pectin is still warranted. Herein, we aimed to clarify the relationship between the macromolecular structure (conformational flexibility and molecular weight (Mw) and the emulsification performance of pectin, which was obtained from two sources (sugar beet pectin (SBP) and citrus pectin (CP) and treated by hydrothermal depolymerization (dominated by acid hydrolysis), following which the overall flexibility was assessed using the persistence length (Lp)/Mw per unit contour length (ML) ratio. The results showed that depolymerization reduced the conformational flexibility of SBP (Lp/ML increased from 0.0169 to 0.0219 nm2 mol/g) and improved the flexibility of CP (Lp/ML decreased from 0.0551 to 0.0403 nm2 mol/g). Interfacial tension analysis revealed that the higher flexibility of pectin conferred superior surface activity, leading to decreased interfacial tension. Consequently, the fabricated emulsion was finer and more stable, with smaller changes in droplet size, as measured by a laser particle analyzer. The improved emulsification was attributed to the better exposure of hydrophobic proteins due to the conformational changes caused by the stretching and twisting of the more flexible polysaccharide chains in pectin, which facilitated higher interfacial adsorption of CP, increasing it from 43.4% to 61.8%. Moreover, the smaller interfacial concentration of the flexible pectins suggested that they had higher emulsification efficiency, in which the pectins might be densely packed at the interface to form a compact interfacial layer to stabilize the emulsion.