Emulsified Oil Droplets Research Articles

Effect of soluble dietary fiber on soy protein isolate emulsion gel properties, stability and delivery of vitamin D3

Emulsion gels with denser network microstructure and stronger mechanical properties have attracted increasing attentions for delivering lipophilic compounds. In this study, the effect of three distinct soluble dietary fiber (inulin (IN), resistant dextrin (RD) and stachyose (ST)) on the rheological, mechanical and microstructural properties of soy protein isolate (SPI) emulsion gel were firstly investigated. Compared with RD and IN, ST significantly accelerated water holding capacity and thermal stability, which exhibited more compact microstructure and more uniform emulsified oil droplets. Subsequently, the stability and bioavailability of vitamin D3 (VD3) in different delivery systems (medium chain triglycerides (MCT) embedding, SPI-ST emulsion embedding, SPI emulsion gel embedding and SPI-ST emulsion gel embedding) were continue evaluated. In vitro simulated digestion experiment demonstrated that the bioaccessibility of encapsulated VD3 in SPI-ST emulsion gel (69.95 %) was much higher than that of free embedding (48.99 %). In vivo pharmacokinetic experiment revealed that the bioavailability of VD3 was significantly enhanced in SPI-ST gel (p < 0.05), with the AUC0-24h value of 25-OH VD3 (the main circulating form of VD3) were 1.34-fold, 1.23-fold higher than that of free embedding, MCT embedding, respectively. These findings provide a possible approach for the development of high protein/fiber functional foods containing enhanced hydrophobic bioactives.

Fabrication of hollow fiber membrane microstructures and the investigation of antifouling mechanism for vegetable oil wastewater

In this study, four kinds of hollow fiber ultrafiltration membranes with different hydrophilic chains and surface microstructures were prepared via the “physical blending-surface grafting” method. The influence of surface microstructures for the formation process of the vegetable oil fouling layer on the surface of membranes and antifouling performance were investigated. By characterizing the changes in adhesion force on the surface of membranes and the surface charge of emulsified oil droplets before and after separation, the differences in the flocculation and coalescence processes for emulsified oil droplets on different membrane surfaces were revealed. The synergistic effect of “the flocculation of physical contact by polymer chains, the hydrophilic repulsion of hydration layer and electrostatic neutralization”, led to the formation of large-sized oil droplets on the surface of membranes with weakly charged surface and loose accumulation ultimately, which will in turn weaken the adsorption of pollutants and the irreversible fouling can be delayed. The synergistic antifouling mechanism of “hydrophilic repulsion of the hydration layer-grafting long chains barrier & coalescence” was proposed based on the membrane's antifouling performance, the adhesion and spreading process of pollutants on the membrane surface, as well as the differences of the surface hydration layer microstructure. The membrane modified by grafting PEI and PVA exhibits excellent retention performance (oil rejection rate ∼100 %) and resistance to oil-in-water emulsion fouling (flux recovery rate (FRR) = 99.12 %), weakest adhesion force (9.32 nN) and minimal adhesion mass (1.7 mg) of pollutants on the surface of membrane. This work offers new research insights into the theoretical study and fabrication of hollow fiber ultrafiltration membranes with high oil fouling resistance.

Serial-module with hydrophilic and hydrophobic membranes applied for oil recovery from O/W emulsion

Membrane demulsification has been extensively employed for separating various oil–water mixtures, however, the recovery oil droplets from highly emulsified O/W mixtures remains a challenge. Herein, we develop a serial-module comprising arranged hydrophilic and hydrophobic membranes to recover the oil phase from O/W emulsion. Firstly, hydrophobic ceramic membranes were prepared through silane modification and separation performance towards emulsion with oil–water ratio of 1:1 was evaluated for both original hydrophilic membranes and modified hydrophobic ones. Subsequent, the sclareol extraction emulsion was chosen as a representative object to investigate and explore the separation performance of preferred membranes under varying oil–water ratios and surfactant concentrations. Ultimately, the results shows that serial-module demonstrated remarkable capability to recover emulsified oil droplets from sclareol extraction emulsion with 10 vol% oil even under complex conditions with yeast addition. This innovative serial-module provides a novel approach for efficiently separating emulsified mixtures of oil and water.

Modulating in vitro digestion of whey protein cold-set emulsion gels via gel properties modification with gallic acid and EGCG

Gallic acid (GA) and epigallocatechin gallate (EGCG), cooperated at varied ratios (1:0, 3:1, 1:1, 1:3, and 0:1), were employed to modify gel properties of calcium induced-whey protein emulsion gel. The effects of GA/EGCG on emulsion morphology, as well as gel properties and in vitro digestive behavior of the emulsion gels were investigated. Compared with emulsions without phenolics, GA/EGCG induced slightly smaller particle size and stronger electrostatic repulsion between emulsion droplets. Moreover, GA/EGCG, notably at a ratio of 3:1, promoted electrostatic and hydrophobic interactions between protein molecules and the formation of a compact and filamentous gel microstructure, resulting in a remarkable increment in the gel strength (up to 106 %). Furthermore, in vitro oral digestion, dynamic gastric digestion (using an artificial gastric digestive system, AGDS), and intestinal digestion of the emulsion gels were simulated. Particle size and protein hydrolysis results revealed that GA/EGCG was prone to weaken the physical disintegration of gels, reduce protein hydrolysis, and enhance the stability of emulsified oil droplets during dynamic gastric digestion. As a consequence, delayed release of oil droplets was observed in the gels and more free fatty acids were released in the intestinal digestion, particularly in the gel with GA/EGCG (3:1). These findings would provide novel strategies for application of phenolic compounds in developing protein gel-based delivery systems.

A biomimetic superwetting Bi2MoO6-dotted PAA/CS@CuC2O4 membrane with self-cleaning and self-healing ability to aggregate oil droplets for enhanced demulsification of O/W emulsion

Separation of thermodynamically-stable emulsions is of great significance, yet challenging due to the low efficiency and membrane fouling associated with existing methods. Inspired by the water-collection functionality of the hierarchically-structured back of desert beetles, we fabricated a novel inversely beetle-back-like copper mesh membrane, featuring superhydrophobic bumps on a superhydrophilic surface to facilitate the capture-aggregation of tiny oil droplets in oil-in-water (O/W) emulsions. Such membrane was composed of superhydrophobic (SH) Bi2MoO6 microparticles-dotted superhydrophilic polyacrylic acid/chitosan-coated CuC2O4 nanosheet arrays on copper mesh membranes. A cross-flow asymmetric filtration (CAF) device was constructed using the as-prepared membrane to continuously and efficiently separate O/W emulsions. The dispersed oil droplets were captured and coalesced by SH Bi2MoO6 on the superhydrophilic nanoarrays, then detached from the mesh membrane. Simultaneously, the continuous water phase could permeate freely through the mesh pores. The combination of the SH Bi2MoO6-dotted superhydrophilic membrane and CAF device ensured an excellent separation efficiency with an average water permeation flux of 2.7 kL m−2 h−1 for different surfactant-stabilized O/W emulsions and oil residual contents in the filtrate being less than 40 mg L−1. Moreover, the cross-flow of the feed solution in the CAF system strengthened the separation of the coalesced oil phase on the membrane surface, thus preventing the formation of a filter cake caused by the aggregation of emulsified oil droplets.

Application of chitosan-based materials in wastewater treatment

Chitosan, as a natural polysaccharide material, plays a great role in the field of wastewater treatment due to its good biodegradability, antimicrobial activity, and other properties. However, it may have some differences in the processes of adsorption, flocculation, and membrane separation. We comprehensively describe the application effect and mechanism of action of chitosan-based materials on the above three major water treatment processes. In the adsorption process, chitosan-based adsorbents such as hydrogels and chitosan beads are prepared by cross-linking, impregnation, and the introduction of functional groups. These chitosan-based materials exerted efficient removal performance in the adsorption of heavy metals, organic dyes, anionic pollutants, etc., which was attributed to their large specific surface area and abundant functional groups. In the flocculation process, the chitosan-based materials were modified by grafting and modifying their shape, while heavy metal ions, organic dyes, and algae were removed using processes such as chelation and charge neutralization. In the membrane separation process, a number of nanofiltration and microfiltration membranes were created by coating chitosan ions, and physicochemical modification was done for the separation of heavy metal ions and emulsified oil droplets in water to improve the fouling resistance and retention rate of the membrane materials. This paper reviews the application of chitosan-based materials in wastewater treatment and proposes that in-depth studies on their toxicity and reusability should be conducted in the future, with a view to playing a role in areas such as the removal of malodorous water odors.

Enhanced micro-explosion to improve the yield of light oil in catalytic cracking of water-in-heavy oil emulsion prepared by continuous membrane emulsification

Membrane emulsification provides new ideas for improving the atomization performance of high viscosity heavy oil in catalytic cracking process, thereby improving the distribution of catalytic cracking products. A comprehensive understanding of the micro-explosion characteristics and catalytic cracking of low water content heavy oil emulsion is the key to the application of membrane emulsification technology in heavy oil catalytic cracking process. Therefore, different water droplet sizes and water content of heavy oil emulsion were controllably prepared by continuous membrane emulsification, and their micro-explosion characteristics and catalytic cracking performance were investigated. The evaporation of heavy oil emulsion droplets (water content over 3 vol%) only underwent the heat transfer stage and the fluctuating evaporation stage due to the strong micro-explosion. The micro-explosion delay time of emulsion droplets decreased from 2.631 to 0.434 s/mm2 with increased temperature (300–600 ℃), increased from 0.645 to 1.042 s/mm2 with increased water content (1–5 vol%), and increased from 0.642 to 1.237 s/mm2 with increased average droplet size (1.80–14.6 μm). The child droplets generated after micro-explosion were characterized, and the different heating behaviors were quantitatively distinguished by the average size of the child droplets. Additionally, the micro-explosion performance (i.e. child droplets size and strong micro-explosion probability) of emulsion droplets improved with increasing water content and average water droplet size, while it initially decreased and then increased when the temperature increased. Furthermore, the improvement of micro-explosion performance by membrane emulsification can increase the yield of light oil (up to a maximum increase of 10.82 %) and reduce the yield of coke (up to a maximum decrease of 5.99 %) in the heavy oil emulsion catalytic cracking.

Investigation on the mechanism of air/condensate bubble flotation of emulsified oil droplet

Crude oil droplets in oilfield-produced water are highly emulsified, and the poor attachment between gas bubbles and oil droplets limits the effectiveness of oil-water separation during flotation processes. This paper proposes a new surface-functionalized bubble called a condensate bubble and evaluates its flotation performance based on surface properties and adhesion theory mechanism to address this issue. The surface chemical properties of the oil droplets were characterized using X-ray photoelectron spectroscopy (XPS), contact angle measurement, and zeta potential. Induction time and flotation tests were conducted to compare the attachment effects between air or condensate bubbles and emulsified oil droplets. The interaction forces were calculated using DLVO and extended DLVO theory. The experimental results showed that crude oil contains functional compounds containing oxygen that make it tough to float. However, the contact angle between the oil surface and condensate bubble was greater than 150°, demonstrating that the condensate liquid bubbles have better hydrophobicity than air bubbles. The micro-flotation experiments indicated that condensate bubbles have a strong collection capacity for emulsified oil droplets, which was confirmed by induction time tests. In 70 mM NaCl brine, the oil removal efficiency of condensate bubble flotation could reach 82%, which was a 30% improvement compared to air bubble flotation. However, DLVO theory failed to predict the flotation with a concentration higher than 10 mM NaCl. The extended DLVO theory accounted for hydrophobic interactions, which were observed due to similar solvent extraction and hydrophobicity of the condensate liquid film. As a result, the condensate bubble-oil droplet system exhibited stronger hydrophobic attraction, successfully confirming and illustrating the superiority of the condensate bubble in flotation.

Encapsulation of alkenyl succinic anhydride oil droplets in emulsions: Preparation, characterization, stability properties and application in papermaking

This paper aimed to explore the influence of the guar and xanthan gum complex (GG/XG) on the physicochemical properties, microstructure, and sizing efficiency of alkenyl succinic anhydride (ASA) loaded emulsions. The centrifugal stability of the emulsions was measured using a Turbiscan equipment, the droplets morphology through an optical microscopy, the size of droplets and its distribution through a Mastersizer, and the sizing efficiency through the penetration method. Furthermore, Cryo-SEM and CLSM were used to elucidate the adsorption mechanism of polysaccharides at the ASA-water interface. When the concentration of GG/XG exceeded 0.35%, the ASA emulsions displayed excellent stability and low viscosity, and no water separation was observed even after high-speed centrifugation. By absorbing GG/XG at the oil-water interface, a dense interfacial film was formed, which blocked any interaction between the oil and water, thus hindering the hydrolysis of ASA. The sizing degree of the paper sized by ASA emulsion stored for 2 h was still higher than 88 s. By encapsulating ASA in emulsions that are stabilized exclusively by natural polysaccharides, the need for surfactants is eliminated, which in turn decreases the amount of foam present in the papermaking process, thus making it a more environmentally friendly production method.

Recycled waste masks as oil absorbent based on stable SiO2 coating for efficient separation of oil-water mixtures and oil-in-water emulsions

Due to the COVID-19 pandemic, mask contamination has become a global concern, and proper disposal of used masks is crucial. In this study, Waste Masks (WM) were modified into a highly efficient oil adsorption material by in-situ growth of SiO2 and subsequent grafting with Octadecyl trichlorosilane (OTS). The modified masks had a water contact angle of 153.2°, showed attractive adsorption capacity (27.33, 31.84, and 32.81 g·g−1) for soybean oil, lubricating oil and engine oil. The modified WM can adsorb not only the light oil on the water surface but also the heavy oil under water. Furthermore, the modified WM was able to separate oil-in-water emulsions of n-hexane and toluene by adsorbing the oil emulsion droplets. Molecular dynamic (MD) simulation was used to investigate the oil-water separation mechanism and calculate the adsorption energy of oil molecules on the OTS-grafted surface. This study provides an interesting solution to the environmental problems caused by discarded masks and the production of low-cost, reusable, and eco-friendly oil-absorbing materials.

Experimental Study of Condensate Vaporization into Bubbles under Different Operating Parameters

Produced water (PW) is a natural by-product of the oil and gas production process, where crude oil is dispersed in the form of micron-sized emulsified droplets in the produced water due to mixing between crude oil and water caused by equipment, piping and valve shear action. Flotation is the main method for treating emulsified oil droplets in oilfield produced water. The conventional flotation technology suffers from a series of problems such as large reflux ratio and poor flotation effect, thus limiting its further application. In this paper, bubbles are prepared by vaporization of low boiling point condensate through theoretical analysis and experimental study. In this paper, the law of bubble generation from condensate solution at different temperatures after decompression and release is investigated. The results demonstrate that the median particle size of gas bubbles generated from condensate is related to the condensate content, mixing pressure, release pressure, and temperature. The median particle size can reach 9.65 μm when mixed at 2.0% condensate content, 0.2 MPa mixing pressure, and 35°C, and released at atmospheric pressure, which is much smaller than the size of gas bubbles generated by dissolved air flotation. The condensate bubbles as alkane congeners are more likely to adhere to the oil droplets in the extracted water, which is conducive to improving the air flotation oil removal efficiency of oily wastewater.

Role of condensate bubbles in enhancing oil droplets and organic acid flotation

Poor adhesion of oil droplet-bubble and the inability to manage dissolved organic matter have hindered flotation efficiency. X-ray photoelectron spectroscopy (XPS) was used for this research to describe the surface chemistry of oil droplets. Multi-component condensate droplet vaporization experiments in produced water (PW). PW at different temperatures was used to investigate droplet vaporization behavior, and the interfacial energy theory and vapor boiling theory were employed to explain the vaporization nucleation mechanism. Contact angle, induction time measurements, and flotation analyses were used to assess the surface chemistry of condensate bubbles and the oil removal effect. The results revealed that when multi-component condensate was vaporized in PW at different temperatures, the light components nucleated inside the condensate droplets and generated bubbles enveloped by the condensate film, and the diameter of the bubbles rose as the temperature increased. X-ray photoelectron spectrometry (XPS) investigation showed the existence of hydrophilic oxygen-containing functional groups on the crude oil's surface. The contact angle between the condensate bubbles and the mask oil surface in PW is >150° and spreads faster, while the contact angle between the methane bubbles, the air bubbles and the oil surface are both <90°. The contact angle and the induction time decrease as the organic acid content of the water increases. Condensate bubble flotation has a greater oil removal efficiency than methane bubble and air bubble, which can achieve the extraction and flotation of emulsified oil droplets (83 %) and dissolved acid (63 %).

Synergistic effects between anionic surfactant SDS and hydrophilic silica nanoparticles in improving foam performance for foam flooding

In foam flooding, foams stabilized by conventional anionic surfactants are usually raptured in contacting with crude oil, which behaves as a strong defoamer. In this article the synergistic effects between anionic surfactant SDS and negatively charged hydrophilic silica nanoparticles in stabilization of aqueous foams were examined. The results show that in either deionized (DI) water at 25 °C or Daqing simulated connate (SC) water with a total salinity of 6,778 mg/L at 45 °C, in absence of oil adding low concentration of silica nanoparticles into the SDS aqueous solutions can improve the foam performance of SDS mainly by increasing foam stability, as indicated by a synergistic effect index Se(d/s) (ratio of the composite foaming index of dispersion to that of solution) of 2.7 to 2.8. In presence of oil the foam performance of SDS in SC water at 45 °C can still be improved as indicated by an increased Se(d/s) of 3.7, but the maximum composite forming index is catastrophically reduced from 3222 Ls in absence of oil to 470 Ls in presence of oil. As similarly charged nanoparticles the silica nanoparticles do not adsorb at gas/liquid or oil/water interface to stabilize Pickering foams or Pickering emulsions but can improve emulsification of the oil, and the emulsified oil droplets together with the silica nanoparticles distribute in aqueous lamellae enhancing liquid viscosity and slowing down the liquid drainage in the foams. However, this effect weakens at high surfactant concentration, and addition of silica nanoparticles does not significantly reduce the interfacial tensions involved. The Enter (E), Spreading (S) and Bridging (B) coefficients of the oil in the foam systems are therefore still positive. The defoaming action of the oil in this system is not eliminated by only partially inhibited by addition of silica nanoparticles.

Confined self‐assembly of block copolymers in emulsion droplets: Preparation, shape and internal structure, and applications

AbstractConfined assembly of block copolymers (BCPs) in emulsion droplets receives considerable attention since self‐assembly in flexible geometry pioneers an efficient yet promising route to prepare unconventional polymer materials that cannot be acquired in the bulk state or solution. The deformability and interfacial property regulation of the soft emulsion droplets offer tremendous potential for the design and construction of BCP nanoparticles with desired shape and internal nanostructures. This review summarizes the recent developments of BCP assembly behavior in three‐dimensional (3D) soft oil emulsion droplets, including preparation methods, shape and internal structure control, as well as advanced applications of the generated BCP materials. Typical experimental parameters and post processes, including intrinsic property of BCPs, surfactant property, confinement degree, interfacial instability, additives, evaporation rate, post‐annealing, and disassembly, that have significant influence on the precise control and regulation of emulsion interface properties and the prepared assembly structures are well systematically summarized. Finally, the challenges and further perspective in this area are presented.

Tiny, yet impactful: Detection and oxidative stability of very small oil droplets in surfactant-stabilized emulsions

HypothesisThe shelf life of multiphase systems, e.g. oil-in-water (O/W) emulsions, is severely limited by physical and/or chemical instabilities, which degrade their texture, macroscopic appearance, sensory and (for edible systems) nutritional quality. One prominent chemical instability is lipid oxidation, which is notoriously complex. The complexity arises from the involvement of many physical structures present at several scales (1–10,000 nm), of which the smallest ones are often overlooked during characterization. ExperimentsWe used cryogenic transmission electron microscopy (cryo-TEM) to characterize the coexisting colloidal structures at the nanoscale (10–200 nm) in rapeseed oil-based model emulsions stabilized by different concentrations of a nonionic surfactant. We assessed whether the oxidative and physical instabilities of the smallest colloidal structures in such emulsions may be different from those of larger colloidal structures. FindingsBy deploying cryo-TEM, we analyzed the size of very small oil droplets and of surfactant micelles, which are typically overlooked by dynamic light scattering when larger structures are concomitantly present. Their size and oil content were shown to be stable over incubation, but lipid oxidation products were overrepresented in these very small droplets. These insights highlight the importance of the fraction of “tiny droplets” for the oxidative stability of O/W emulsions.

Effect of Heat Treatment on Yellow Field Pea (Pisum sativum) Protein Concentrate Coupled with Membrane Ultrafiltration on Emulsification Properties of the Isolated >50 kDa Proteins.

The aim of this paper was to determine the emulsification properties of protein aggregates obtained from heat pretreated yellow field pea protein concentrate (PPC). PPC dispersions were prepared in distilled water (adjusted to pH 3.0, 5.0, 7.0, or 9.0), heated in a water bath (100 °C) for 30 min, centrifuged and the supernatant passed first through a 30 kDa membrane and, then, the first retentate (>30 kDa) through a 50 kDa membrane. The 50 kDa membrane separation yielded a second retentate (>50 kDa proteins), which was isolated for emulsification studies. The near UV circular dichroic spectra of the protein samples showed more unfolded structures at pH 3.0 and 5.0 than at pH 7.0 and 9.0. The presence of small and spherical oil droplets of emulsions stabilized by the >50 kDa proteins at pH 3.0, 7.0, and 9.0 was confirmed by confocal laser scanning microscopy images. Emulsions stabilized at pH 7.0 and 9.0 had a narrower size distribution range than at pH 3.0 and 5.0. A narrow oil droplet size distribution range and lower interfacial protein concentrations of the emulsions stabilized by the >50 kDa proteins were observed at the corresponding pH of the heat treatment when compared to other pH values. Emulsions stabilized by the >50 kDa proteins exhibited a relatively low flocculation and coalescence index, which infers relative stability. The results from this work suggest that heat pretreatment of the PPC led to the formation of new protein aggregates, especially FT9 with enhanced emulsification properties, at some of the test conditions when compared to the unheated PPC.

Chitosan-Based Nanocarriers for Delivery of Remdesivir

Stable multicomponent capsules for the delivery of remdesivir (Veklury®) are produced through subsequent electrostatic adsorption of oppositely charged components on oil emulsion droplets. For the first time, the encapsulation and release of the medicine Veklury® from polymer capsules was reported. In this study, the effect of the physicochemical properties of chitosan on the size and stability of the produced structures is investigated, on the loaded amount of drug and on the kinetics of drug release in conditions close to the physiological ones. Microbiological studies of the capsules and their constituents were performed via in vitro assays against HCT-8 cell lines and human coronavirus HCoV-OC43. A detailed analysis was performed on the influence of the properties of produced capsules on cytotoxicity against the chosen cell line, as well as their effect on the replication cycle of the virus, the virucidal activity of the samples against the viability of the extracellular virions, and their effect on viral adsorption on the cell membrane.

Sequential Demulsification through the Hydrophobic-Hydrophilic-Hydrophobic Filtration Layer toward High-Performing Oil Recovery.

Demulsification using membranes is a promising method to coalesce highly stable emulsified oil droplets for oil recovery. Nevertheless, a structure of the current filtration medium that is not efficient for oil droplet coalescence impedes rapid permeability, thereby inevitably restricting their practical applications. Herein, we report a hydrophobic-hydrophilic-hydrophobic (3H) demulsification medium that exhibits a benchmark permeability of ∼2.1 × 104 L m-2 h-1 with a demulsification efficiency of >98.0%. Remarkably, this 3H demulsification medium maintains over 90% demulsification efficiency in the oil-in-water (O/W) emulsions with a wide range of surfactant concentrations, which shows excellent applicability. Based on the combined results of quasi situ microscope images and molecular dynamics simulations, we show that the polydimethylsiloxane-modified hydrophobic layer facilitates the capture and coalescence of oil droplets, the hydrophilic inner layer assists in squeezing the coalescence of enlarged droplets, and the third hydrophobic layer accelerates the discharge of demulsified oil to sustain permeability. The sequential demulsification mechanism between this 3H filtration layer provides a general guide for designing a demulsifying membrane with high demulsification efficiency and high flux toward oil recovery.

The linear/nonlinear rheological behaviors of Pickering emulsion stabilized by Zein and Xanthan gum: Effect of interfacial assembly strategies

Protein/polysaccharide complexes have been widely used to fabricate Pickering emulsions, yet their linear and nonlinear rheological behaviors have received little attention. In this work, two interfacial assembly strategies of layer-by-layer (LBL) and directly mixed (DM) were employed to create zein (2%, 1%, w/v)/xanthan gum (XG) (0.8%, 0.4%, 0.2%, w/v) complex Pickering emulsions (oil phase: aqueous phase = 1:2). Both small amplitude oscillatory shear (SAOS) and large amplitude oscillatory shear (LAOS) behaviors were investigated. Results showed that regardless of interfacial assembly strategies, emulsions exhibited relatively smaller droplet size, but had higher viscosity and storage modulus (SAOS test) with XG concentrations at 0.8% (w/v). The steady shear test showed LBL emulsions had superior viscosity, with a minor difference between DM and LBL emulsions in the linear SAOS test. Both interfacial assembly strategies resulted in emulsions exhibiting a hysteresis loop and a thixotropic recovery rate above 85%. The Elastic/Viscous Lissajous plots revealed that the elasticity and stiffness were affected by interfacial assembly strategies. LBL emulsions showed a more pronounced secondary loop, accompanied by a greater thixotropic restructuring time scale. The micromorphology contributed to the diverse linear and nonlinear behaviors, with the zein-XG complex mixed layer coating the oil droplets in DM emulsions and XG being added to a previously zein-emulsified emulsion to form a multilayer in LBL emulsions. In addition, emulsions showed a well-distributed nature, with no oil-off phenomena observed during centrifugal, salt, and thermal treatments. Results illustrated the effect of interfacial assembly strategies on the linear/nonlinear rheological behavior of Pickering emulsion. Our study might be helpful in preparing Pickering emulsion as edible ink for 3D printing and as a fat replacer.

Improved emulsified oil removal approach for industrial coal pyrolysis wastewater by flocculation under pressurized CO2 atmosphere

Coal pyrolysis wastewater pretreatment suffers from equipment fouling and inferior mass transfer efficiency brought by low emulsified oil removal efficiency. This paper comprehensively analyzed the properties of emulsified oil and found this inadequacies attribute to its high stability and penetrability derived from high ζ potential of −33.1 mV and tiny average particle size of 114.7 nm in initial condition. H3O+ adjustment is developed to compress diffusion layer thickness and facilitate natural coalescence of emulsified oil droplets. Results of H2SO4 acidification present the peaks of average particle size sustainably stabilized between 782.9 and 1009.0 nm and emulsified oil was mostly coagulated and subsequently settled/floated without further treatment. CO2 was selected as a suitable donor of H3O+ to improve application potential, and flocculants was coupled with pressurized dissolved CO2 to intensify emulsified oil removal whose optimal efficiency achieved 93.82 wt% by changing flocculant types and operation conditions. Response surface analysis results introduced emulsified oil removal efficiency reached 95.17 wt% at PAC concentration of 1065 mg/L, CPAM concentration of 20 mg/L and operating pressure of 0.67 MPag. For renovation projects with limitations, the optimal emulsified oil removal efficiency achieved 94.33 wt% at PAC concentration of 1032 mg/L, CPAM concentration of 21 mg/L and operating pressure of 0.60 MPag. Process simulation of sour gas and ammonia stripper signified that CO2 addition has little effect on current industrial process. By comparison, the proposed approach performs high efficiency, low impact to wastewater, strong feasibility, and great prospect in pretreatment.