Nano-sized Oil Droplets Research Articles

Faveolate cell-engineered and multi-heterostructured flexible ceramic nanofibrous membranes with confined coalescent nanochannels enable sustainable oily water remediation

Oily wastewater, resulting from oil recovery, petrochemical industries, or accidents, poses a significant threat to the aquatic environment. Membrane separation technology can offer unprecedented opportunities for highly efficient water remediation but at the cost of poor permeability and serious oil fouling. Here, we report a faveolate nanofibrous membrane through the steric growth of bismuth oxybromide-bismuth oxyiodide nanoflakes on the TiO2/polypyrrole nanofibers. The spatially faveolate cells create highly covered confined spaces that efficiently capture and coalesce nanosized oil droplets, thus achieving substantial selectivity for micron porous membranes. The faveolate membranes are capable of efficiently separating various oil-in-water emulsions, particularly nanoscale surfactant-stabilized emulsions with a high permeation flux of 6075 L m-2h−1 and a good separation efficiency of 99.95 %. Moreover, the membranes with multi-heterostructure act as efficient photocatalysts, giving rise to visible light-induced sufficient fouling-tolerant property with nearly zero irreversible oil fouling. This study could provide a novel strategy for developing a new generation of membranes with high performance and long service lifetime for oily sewage remediation.

Application of Functionalized Fe3O4 Magnetic Nanoparticles Using CTAB and SDS for Oil Separation from Oil-in-Water Nanoemulsions.

Using magnetic nanoparticles (MNPs) for emulsified oil separation from wastewater is becoming increasingly widespread. This study aims to synthesize MNPs using amphiphilic coatings to stabilize the MNPs and prevent their agglomeration for efficiently breaking oil-in-water nanoemulsions. We coat two different sizes of Fe3O4 nanoparticles (15-20 and 50-100 nm) using cetyltrimethylammonium bromide (CTAB) and sodium dodecyl sulfate (SDS) with surfactant-to-MNP mass ratios of 0.4 and 0.8. We study the effect of various variables on the demulsification performance, including the MNP size and concentration, coating materials, and MNP loading. Based on the oil-water separation analysis, the smaller size MNPs (MNP-S) show a better demulsification performance than the larger ones (MNP-L ) for a 1000 ppm dodecane-in-water emulsion containing nanosized oil droplets (250-300 nm). For smaller MNPs (MNP-S) and at low dosage level of 0.5 g/L, functionalizing with surfactant-to-MNP mass ratio of 0.4, the functionalization increases the separation efficiency (SE) from 57.5% for bare MNP-S to 86.1% and 99.8 for the SDS and CTAB coatings, respectively. The highest SE for MNP-S@CTAB and the zeta potential measurements imply that electrostatic attraction between negatively charged oil droplets (-55.9 ± 2.44 mV) and positively charged MNP-S@CTAB (+35.8 ± 0.34 mV) is the major contributor to a high SE. Furthermore, the reusability tests for MNP-S@CTAB reveal that after 10 cycles, the amount of oil adsorption capacity decreases slightly, from 20 to 19 mg/g, indicating an excellent stability of synthesized nanoparticles. In conclusion, functionalized MNPs with tailored functional groups feature a high oil SE that could be effectively used for oil separation from emulsified oily wastewater streams.

Electro-enhanced rapid separation of nanosized oil droplets from emulsions via the superhydrophilic micro-sized pore membrane

Waste oil-in-water emulsion is a special and unmanageable oily wastewater produced by several industries. Based on the sieving effect, the use of a membrane is a promising method to separate emulsion, whereas low flux remains a fundamental challenge. In this study, the coupling of an electric field with superhydrophilic fibrous membranes helped separate micro-/nano- paraffin in water emulsions (247–1887 nm) stabilized by SDS (100–500 mg/L) with a general applicability. The micro-sized pore membrane (0.634 μm) achieved outstanding rejection of nano-sized oil droplets (247 nm) using an electric field. It promoted flux from 1,202 to 18,388 LMH/bar by 1,429 % which was more than that in other literature by 1–2 orders of magnitude and improved oil removal from 97.61 % to 99.88 %. The reduction of equivalent pore size of membrane by the double layer force and the promotion of coalescence of oil droplets driven by the Laplace force rooted in the fibrous spindle of the membrane achieved enhanced selectivity. Electrophoretic force and double layer force mitigated the formation of the filter cake and irreversible fouling, respectively, to promote permeability and antifouling. This research provides a method for the simultaneous promotion of flux and improvement in effluent quality using an electric field, which breaks the limit of the trade-off effect.

In-Situ Visualization of Imbibition Process Using a Fracture-Matrix Micromodel: Effect of Surfactant Formulations toward Nanoemulsion and Microemulsion

Summary Spontaneous imbibition can help to improve the oil recovery of unconventional reservoirs owing to the significant capillarity. Although the dependence of imbibition dynamics of surfactants on wettability and interfacial tension (IFT) is understood, the mechanisms of nanoemulsion and microemulsion forming surfactants for higher imbibition recovery are not as clear. Herein, we conducted a series of imbibition experiments on a visual fracture-matrix micromodel, aiming to directly observe the imbibition processes of these surfactant formulations. Four surfactant-based fluids, including a common surfactant [fatty alcohol polyoxyethylene ether, sodium sulfate (AES)], a surfactant composition of nanoemulsion (nE-S), an ex-situ nanoemulsion (nE), and a situ microemulsion forming surfactant (mE-FS), were designed and used in this work for comparison with brine. The results suggested that AES, nE-S, nE, and mE-FS could substantially stimulate the imbibition invasion, and mE-FS generated the greatest imbibition depth and sweeping area followed by nE. The imbibition dynamics were governed by the interfacial interactions among oil, aqueous phase, and solid surface, leading to different imbibition patterns for these five fluids. AES and nE-S could reduce the oil-aqueous IFT to 10−1 mN/m and alter the wettability to a weak water-wet state as a result of surfactant adsorption, leading to a slightly higher imbibition invasion compared with brine. AES imbibition produced large oil droplets mainly because of the snap-off effect at the nozzle to the fracture, whereas nE-S produced smaller oil droplets due to the weak in-situ emulsification. nE as a formed nanoemulsion with an internal oil phase demonstrated a lower IFT of 10−2 mN/m and superior capacity in changing surface wettability mainly through the adsorption and spreading of nanosized oil droplets on the surface. The oil phase was heavily emulsified forming dense droplets on the oil-aqueous interface. mE-FS readily formed Winsor Type III microemulsion and produced an IFT of 10−3 mN/m magnitude. The wettability was changed mainly because of the peeling oil film and formation of microemulsion on the surface induced by solubilization. The dynamic increase of the oil-aqueous IFT at the imbibition front caused by the adsorption loss of surfactant to the surface and partitioning to the oil phase promoted capillary-driven imbibition for nE and mE-FS. We modified an imbibition model to incorporate the solubilization effect, leading to a much better fitting with the experimental data.

Outstanding Separation Performance of Oil-in-Water Emulsions with TiO2/CNT Nanocomposite-Modified PVDF Membranes

Membrane filtration is an effective technique for separating micro- and nano-sized oil droplets from harmful oil-contaminated waters produced by numerous industrial activities. However, significant flux reduction discourages the extensive application of this technology; therefore, developing antifouling membranes is necessary. For this purpose, various titanium dioxide/carbon nanotube (TiO2/CNT) nanocomposites (containing 1, 2, and 5 wt.% multi-walled CNTs) were used for the modification of polyvinylidene fluoride (PVDF) ultrafilter (250 kDa) membrane surfaces. The effects of surface modifications were compared in relation to the flux, the filtration resistance, the flux recovery ratio, and the purification efficiency. TiO2/CNT2% composite modification reduced both irreversible and total filtration resistances the most during the filtration of 100 ppm oil emulsions. The fluxes were approximately 4-7 times higher compared to the unmodified PVDF membrane, depending on the used transmembrane pressure (510, 900, and 1340 L/m2h fluxes were measured at 0.1, 0.2, and 0.3 MPa pressures, respectively). Moreover, the flux recovery ratio (up to 68%) and the purification efficiency (95.1-99.8%) were also significantly higher because of the surface modification, and the beneficial effects were more dominant at higher transmembrane pressures. TiO2/CNT2% nanocomposites are promising to be applied to modify membranes used for oil-water separation and achieve outstanding flux, cleanability, and purification efficiency.

Understanding Imbibition Mechanisms of Catanionic Surfactant–Stabilized Nanoemulsion for Enhanced Oil Recovery in Tight Sandstone Reservoirs: Experimental and Numerical Assessment

Summary Surfactant-induced imbibition is considered a promising method for increasing oil recovery from tight oil reservoirs beyond primary production. Nanoemulsion (nE) offers a great potential for this application owing to its unique physicochemical properties, such as kinetic stability, large surface area, and low oil-aqueous interfacial tension (IFT). Herein, we designed and prepared a series of surfactant-stabilized oil-in-water (O/W) nE using efficient catanionic surfactants by a low-energy method. The physicochemical properties of the nE samples were comprehensively characterized to better perform experimental and numerical simulations and constrain the modeling. We conducted imbibition tests on Chang 7 tight cores using nE and brine and also assessed the imbibition dynamics. Results indicated that nE was successfully synthesized at a surfactant concentration ranging from 0.4 to 1.0 wt%. The oil droplets in nE had a mean size of 10 nm. All the nE samples were able to lower the oil-aqueous IFT to an ultralow level of 10–3 mN/m. In addition, nE demonstrated superior capacities in wettability alteration, and oil solubilization and emulsification, which were all integrated into numerical modeling. The imbibition oil recovery was increased by 18.8% of the initial oil in place when nE1 (0.4 wt%) was used compared to that of brine. Because of the interactions among oil, nE, and rock surface, nE required a longer time to reach imbibition equilibrium than brine. The simulation results, for the first time, suggested that the dominant imbibition mechanisms of nE varied with time, during which IFT reduction and wettability alteration played the leading roles in the first 50 hours. The reactions of oil solubilization and emulsification became significant after 50 hours and then contributed equally to the oil recovery with IFT reduction and wettability alteration. The diffusion of nanosized oil droplets increased the equilibrium time of imbibition, thereby promoting the ultimate oil recovery.

Hydrophilic polyethyleneimine-TiO2 hybrid layer on polyethersulfone/sulfonated polysulfone blend membrane with antifouling characteristics for the effective separation of oil-in-water emulsions

Polyethersulphone/sulfonated polysulfone/TiO2 (PES/SPSf/TiO2) ultrafiltration (UF) mixed matrix membranes (MMMs) were coated with a hybrid layer composed of branched polyethyleneimine (PEI) and TiO2 nanoparticles (NPs) crosslinked by glutaraldehyde (GA) to enhance its stability. The effect of TiO2 NPs loadings on the thickness, surface wettability, surface charge and molecular weight cut-off (MWCO) was explored. The corresponding MWCO decreased from 96 kDa for the pristine PES/SPSf/TiO2 MMM (M0) to 8.5 kDa for PEI-GA@MMMs (M1), and then gradually increased to the range of 15 kDa–40 kDa for PEI-TiO2/GA@MMMs. TiO2 NPs having abundant –OH groups also increased electronegativity and hydrophilicity of the composite membranes. At neutral pH, the zeta potential changed from negative charge of MMMs (−33 mV) into positive charge of M1 (1.3 mV), then into negative charge (−7.4 mV) in the optimum hybrid coated membrane PEI-TiO2 (0.025 wt%)/GA@MMMs (M3). The underwater oil contact angle (UWOCA) of with hexane, gasoline, dichloromethane and petroleum ether was 165°, 167°, 164° and 135°, respectively. The air/water contact angle (WCA) of M3 was 42°, which is lower than that of M1 (63°). It is important to note that M3 demonstrated a high rejection of different oil-in-water emulsions with <300 nm oil droplets (>90 %) and an improved pure water permeance of 62 LMH bar−1 compared to 44 LMH bar−1of M1. M3 also exhibited double the antifouling rates of M1 hence corroborating wettability and surface charge results. In summary, our current study provides an available tuning approach to engineering membranes for the treatment of oil-in-water emulsions containing nano-sized oil droplets.

Electro-Enhanced Rapid Separation of Nanosized Oil Droplets from Emulsions Via the Superhydrophilic Micro-Sized Pore Membrane

Electro-Enhanced Rapid Separation of Nanosized Oil Droplets from Emulsions Via the Superhydrophilic Micro-Sized Pore Membrane

Robust zirconia ceramic membrane with exceptional performance for purifying nano-emulsion oily wastewater

While membrane-based oil-water separation has been widely explored, using conventional membranes to treat oily wastewaters remains practically challenging especially when such wastewaters contain more stable nano-sized oil droplets and are of high oil content, and harsh chemical conditions. Herein, we report a novel protocol of efficiently separating both synthetic and real oil nano-emulsions via specially designed robust zirconia membranes. The best-performing zirconia membrane, fabricated at low sintering temperature, has relatively uniform sub-100 nm pores and is underwater superoleophobic. Such zirconia membranes possess not only outstanding separation performance under long-term operation but robust structural stability at harsh conditions. At different cross-flow velocities, a combined model of intermediate pore blocking and cake filtration dominated membrane fouling behavior. Specifically, at high pH value (especially > pH(IEP)), membrane fouling was effectively mitigated due to a dominant role of electrostatic repulsion interaction at membrane–oil interface. Compared with conventional and commercial ceramic membranes, our zirconia membrane is the first reported in literature that can effectively reject nano-sized oil droplets (∼18 nm) with over 99% rejection. Moreover, the zirconia membrane has also been challenged with real degreasing wastewater with very high oil content (∼4284 mg L–1) and pH (∼12.4) and delivered consistently high separation performance over many operation cycles.

Spider silk bioinspired superhydrophilic nanofibrous membrane for efficient oil/water separation of nanoemulsions

Membrane separation has been acknowledged as an effective strategy to treat oily emulsions based on size-sieving. For separating nanoemulsions, smaller membrane pores are required to reject nano-sized oil droplets; however, the permeate flux would be significantly restrained. Herein, bioinspired by spider silk, a novel superhydrophilic electrospun nanofibrous membrane with spindle-knotted structures (SK-ENM) was constructed for highly efficient separation of nanoemulsions. The special spindle-knotted structures were constructed with 3–3.5 wt% polyacrylonitrile utilizing electrospinning based on Rayleigh instability. The prepared SK-ENM possessed a highly porous structure with a mean pore size of 0.634 μm, and strong superhydrophilicity/underwater superoleophobicity with rich micro/nano-hierarchical structures. For separating the surfactant-stabilized paraffin-in-water nanoemulsion with a mean droplet size of 325.7 nm, the oil rejection, permeate flux, and flux recovery rate were 95.68%, 1143.3 LMH/bar, and 99.98%, respectively. Thus, the SK-ENM with larger pores achieved both high oil rejection and high permeate flux for separating nano-sized oil droplets, which is a breakthrough achievement in overcoming the limitations of size-sieving. This could be attributed to the directional migration and coalescence of nano-sized oil droplets on spindle-knotted structures driven by Laplace force, which was calculated to be 8.7 × 10-8N. Meanwhile, the resulting large oil droplets were proved to be rejected by the superhydrophilic nanofibrous membrane with negligible fouling. This study provides insights into the design of novel functional superhydrophilic membranes for separation of emulsions. The as-prepared SK-ENM can be effectively applied to treating various nanoemulsions and complex oily wastewater in practical.

Two-step droplet formation in monodisperse nanodroplet generation in quenched hydrothermal solution as revealed by spontaneous transformation of nanodroplets to swollen micelles in octane‑in‑water nanoemulsions

HypothesisMonodisperse nanodroplet generation in quenched hydrothermal solution (MAGIQ) is a newly developed bottom-up process for preparing nanoemulsions. In this process, homogeneous solutions of oil in supercritical water are quenched by adding cold water containing a surfactant to induce rapid phase-separation, during which oil molecules self-assemble to form nano-sized oil droplets. The droplet size in MAGIQ is known to be influenced by the interplay of the phase‐separation dynamics, coalescence kinetics of the droplets, and adsorption kinetics of the surfactant on the droplet surface; however, the primary stages of the droplet formation are still elusive. ExperimentsOctane‑in‑water nanoemulsions containing 0.5, 1, and 3 vol% octane were prepared by the MAGIQ method. Their ripening was studied by dynamic light scattering, and the phase diagram was established. FindingsThe nanoemulsions containing 0.5 and 1 vol% octane transformed to thermodynamically stable microemulsions containing swollen micelles, whereas the nanoemulsion containing 3 vol% octane underwent Ostwald ripening. The initial formation of the nano-sized droplets in the former was ascribed to a unique mechanism of droplet formation in MAGIQ—the droplets are first formed by the phase separation of homogeneous binary solutions of oil in supercritical water and then stabilized upon surfactant adsorption.

Cineole-containing nanoemulsion: Development, stability, and antibacterial activity

1,8-cineole is a monoterpene commonly used by the food, cosmetic, and pharmaceutical industries owing to its flavor and fragrances properties. In addition, this bioactive monoterpene has demonstrated bactericidal and fungicidal activities. However, such activities are limited due to its low aqueous solubility and stability. This study aimed to develop nanoemulsion containing cineole and assess its stability and antibacterial activity in this context. The spontaneous emulsification method was used to prepare nanoemulsion (NE) formulations (F1, F2, F3, F4, and F5). Following the development of NE formulations, we chose the F1 formulation that presented an average droplet size (in diameter) of about 100 nm with narrow size distribution (PdI <0.2) and negative zeta potential (∼ – 35 mV). According to the analytical centrifugation method with photometric detection, F1 and F5 formulations were considered the most stable NE with lower droplet migration velocities. In addition, F1 formulation showed high incorporation efficiency (> 80 %) and TEM analyses demonstrated nanosized oil droplets with irregular spherical shapes and without any aggregation tendency. Antibacterial activity assessment showed that F1 NE was able to enhance the cineole action against Staphylococcus aureus, Enterococcus faecalis, and Streptococcus pyogenes. Therefore, using a simple and reproducible method of low energy emulsification we designed a stable nanoemulsion containing 1,8-cineole with improved antibacterial activity against Gram-positive strains.

(Invited) Mulling over Nanoemulsions: Interfacial Molecular Structure, Stabilization and Assembly

Nanoemlusions are finding numerous applications in the fields of pharmaceuticals, food production, materials synthesis and cosmetics. With the search for broader and improved usage of these unique droplets comes the need to better understand the molecular interactions at the surface that lead to their stabilization. This presentation will focus on our most recent efforts to understand the molecular assembly and structuring present at an oil-water droplet surface that contributes to the stabilization of these nano-sized oil droplets in water, and similarly sized water droplets in oil. The studies are a combination of spectroscopic and thermodynamic measurements coupled with theoretical simulations.

Phase inversion emulsification of different vegetable oils using surfactant mixture of cremophor EL and lipase-synthesized glucose monooleate

A sugar-fatty acid ester, named glucose monooleate (GluO) was synthesized using commercial immobilized lipase B from Candida antarctica. A preparation of oil-in-water (O/W) emulsion using a combination of non-ionic surfactant mixture, i.e., GluO and Cremophor EL (CrEL), and different vegetable oils, i.e., coconut, sunflower, olive, palm and jojoba oils through phase inversion emulsification (PIE) was investigated. A baseline formulation was carried out to obtain an optimal ratio of surfactant-to-oil (S:O) and Cremophor EL-to-Glucose monooleate (CrEL:GluO) with coconut oil as the carrier oil. GluO proves to be an effective co-surfactant when a high amount of oil was incorporated. At 60:40 of S:O and CrEL:GluO, coconut and sunflower oil were emulsified into nano-sized oil droplets with the sizes (in diameter) of 36 ± 1.5 nm (PDI = 0.17 ± 0.05) and 42 ± 1.3 nm (PDI = 0.18 ± 0.07), respectively. In contrast, olive, palm and jojoba oils produced coarse emulsions with larger oil particles with the sizes of 238 ± 22, 295 ± 41 and 312 ± 63 nm, respectively. Furthermore, at 60:40 of S:O and CrEL:GluO, up to 0.98 mg of β-carotene (≈0.03% of total emulsion weight) can be encapsulated within coconut oil droplets of the O/W system with an average size below 100 nm. The emulsification process was investigated through Fourier-transform infrared (FTIR) spectroscopy, small-wide angle X-ray (SWAX) and optical polarizing microscopy (OPM) analyses. Possible effects of the surfactant mixture (CrEL-GluO) and different vegetable oils on the emulsion preparation were also discussed.

Enhanced oil recovery performance of gemini surfactant-stabilized nanoemulsions functionalized with partially hydrolyzed polymer/silica nanoparticles

Nanoemulsion flooding is a novel route to enhanced recovery of petroleum resources over conventional water-flood by effective detachment and mobilization of residual oil trapped within rock-pores. In this article, we conducted experimental investigations to test the functionality of robust nanoemulsions comprising of gemini surfactant/polymer/silica nanoparticle assemblies; and explained mechanistic behavior of nanoemulsion-assisted oil displacement on a molecular scale. The presence of nano-sized oil droplets was confirmed by light scattering and CryoTEM imaging. Pseudoplastic behavior of nanoemulsions was identified, and viscous activation energies were determined using Arrhenius modeling. Viscoelasticity studies confirmed that elastic modulus dominated over viscous modulus, indicating that deforming forces do not exceed inter-droplet repulsions and interfacial stresses. Hence, nanoemulsion (oil) droplets retain their structural integrity under varying shear conditions. Core-flooding experiments showed that enhanced oil recoveries (EOR) of nanoemulsions improved over conventional aqueous fluids to 21–27% range of original oil in place (OOIP).

Consolidated bile-based vesicles/self-nanoemulsifying system (CBBVs/SNES) as a solution for limitations of oral delivery of vesicular dispersions: In-vitro optimization and elucidation of ex-vivo intestinal transport mechanisms

The oral delivery of bile-based vesicles (BBVs) has been limited by their poor physical stability, low drug load and slow absorption rate. The novel consolidated bile-based vesicles/self-nanoemulsifying system (CBBVs/SNES) combines the advantages of vesicular and self-nanoemulsifying systems (SNES). This work aimed to prepare physically stable CBBVs/SNES loaded with the full dose of amlodipine besylate (AB) as model drug. AB-loaded BBVs dispersion was optimized using Box-Behnken design and evaluated for particle size distribution, encapsulation efficiency and solubilization efficiency. AB-loaded CBBVs/SNES was prepared by mixing the vesicles of the optimized BBV with Labrafil-based SNES that gave the highest drug solubility. AB-loaded CBBVs/SNES was evaluated for particle size, Polydispersity index (PDI) and in vitro release. When diluted in GIT fluids, consolidated system spontaneously emulsifies forming nanosized oil droplets and in-situ formed mixed micelles. The formation of nanosized mixed micelles (<100 nm) was confirmed by transmission electron microscopy and particle size analysis (PS; 106.8 ± 17.60 nm and PDI; 0.20 ± 0.01). The developed CBBVs/SNES showed enhanced physical stability when stored for 3 months at 2–8 °C. The ex-vivo transport study confirmed that the developed CBBVs/SNES improved the drug transport about 3.8 folds in comparison to the reconstituted vesicular dispersion through offering three pathways of transport (in-situ formed mixed micelles uptake, nanoemulsion droplet uptake and vesicular uptake). The various offered transport pathways and the improvement of drug load and physical stability propose that CBBVs/SNES administered via the oral route could therefore be promising in oral delivery of vesicular systems. In-vivo studies is presently investigated.

Gemini surfactant/polymer/silica stabilized oil-in-water nanoemulsions: Design and physicochemical characterization for enhanced oil recovery

The present study deals with the synthesis and characterization of oil-in-water nanoemulsion systems for application in enhanced oil recovery (EOR). Nanoemulsions stabilized by N,N′-bis((dimethyltetradecyl)-1,6-hexanediammonium bromide) gemini surfactant (14-6-14 GS), partially hydrolyzed poly-acrylamide (PHPA) polymer and/or silica (SiO2) nanoparticle were synthesized by ultrasonication technique. Nanoparticles strengthen the mechanical barrier (electrostatic repulsion + steric hindrance) at oil-aqueous interfaces, resulting in increased ionic strength and droplet stability. Dynamic light scattering (DLS) results confirmed the formation of nano-sized (<500 nm) oil droplets within bulk emulsion phase. Kinetic stabilities of nanoemulsions were investigated by zeta potential and phase behavior analyses. Surface tension of surfactant-stabilized nanoemulsions increased with PHPA addition. However, silica particles improved adsorption ability of surfactant-polymer-nanoparticle (SPN) systems, causing decrease in surface tension. Rheological experiments were conducted as screening experiment at different temperatures to identify pseudoplastic character, and flow parameters were fitted using the Power law model. Contact angle studies showed that nanoemulsions alter the wetting characteristics of rock from intermediate-wet to favorable water-wet condition. Core-flooding studies revealed tertiary oil recovery percentage of 26.25% of original oil in place (OOIP) by chemical injections of {14-6-14 GS + PHPA + SiO2} nanoemulsions, after conventional water-flooding.

Formation and surface-stabilizing contributions to bare nanoemulsions created with negligible surface charge

The stabilization of nanoemulsions, nanosized oil droplets dispersed in water, is commonly achieved through the addition of surfactants and polymers. However, nanoemulsions in the absence of emulsifiers have been observed to acquire a significant negative charge at their surface, which ultimately contributes to their stability. While the source of this negative charge is disputed to this day, its presence is taken as an inherent property of the aqueous-hydrophobic interface. This report provides a look at the molecular structure and bonding characteristics of bare aqueous-hydrophobic nanoemulsion interfaces. We report the creation of bare nanoemulsions with near zero surface charge, which are marginally stable for several days. The process of creating these low-charge nanoemulsions (LCNEs) required rigorous cleaning procedures and proper solvent storage conditions. Using vibrational sum-frequency scattering spectroscopy, we measure the structure and bonding of the interfacial aqueous and hydrophobic phases. The surfaces of these LCNE samples possess a measurable free OH vibration, not found in previous studies and indicative of a clean interface. Tuning the nanoemulsion charge through addition of anionic surfactants, modeling potential surface-active contaminants, we observe the free OH to disappear and a reorientation of the interfacial hydrophobic molecules at micromolar surfactant concentrations. Notably, the free OH vibration provides evidence for stronger dispersion interactions between water molecules and the hydrophobic phase at the LCNE surface compared with similar planar water-alkane interfaces. We propose the stronger bonding interactions, in addition to an ordered interfacial aqueous layer, contribute to the delayed droplet coalescence and subsequent phase separation.

A review on antifungal activity and mode of action of essential oils and their delivery as nano-sized oil droplets in food system.

An escalated demand of minimally processed food and increased negative perception for synthetic preservative has led to a lookout for a natural preservative. Essential oils (EOs) are volatile and aromatic secondary metabolites of plants that have been tapped mainly for its flavour and fragrances and various biological properties such as antimicrobial and antioxidant. The constituents and antifungal potential of EOs have been reported widely in the present scientific literature. Moreover, the current scientific research dealing with the mode of action of EOs on fungal spores and mycelial cells are very scarce, unlike bacteria. The antimicrobial efficacy of EO in real food system may alter due to interaction with food matrix components. Besides, minimum alteration in sensory qualities while retaining its maximum activity is the most sought-after criteria for food preservation with EOs. If the oil is applied in excess to have better antimicrobial activity, it may end up having an unacceptable organoleptic impact on the food. Appropriate edible delivery systems of EOs as an emulsion is a probable approach to retain the maximum efficacy of EOs in the food system. Nano-emulsification of EO could increase its bioactivity due to increased bioavailability in the food matrix. The basis of this review is to provide an overview of current knowledge about the antifungal properties and antifungal mode of action of EOs, and to recognize the application of EO as nano-sized oil droplets in the food system.

Dual functional membrane with multiple hierarchical structures (MHS) for simultaneous and high-efficiency removal of dye and nano-sized oil droplets in water under high flux

Dual functional membranes with super-wetting and adsorption capacity have drawn great attentions owing to their good application prospect in the treatment of mixed wastewater containing oil and dyes. Despite recent development in such functional membranes, there are still some obstacles need to be resolved. The one is how to further improve the dye adsorption capacity to realize the high-efficiency removal of dye under high permeation flux. The other is to improve the rejection towards nano-sized oil droplets in water. Herein, with porous polypropylene (PP) membrane as substrate, we show that constructing multiple hierarchical structures (MHS) on membrane surface is an effective way to solve the above mentioned problems. The MHS prepared by low-cost tannic acid, 3-Aminopropyltriethoxysilane (APTES), and polyethyleneimine (PEI) are composed of rough layer, nanospheres, and nano nodes with abundant amine groups. On the one hand, the MHS can endow the membrane with high adsorptive capacity (480 mg g−1 toward methyl blue). On the other hand, the MHS can also decrease the pore size of the membrane, making it suitable for separation of nano-sized oil droplets. Moreover, the MHS can also render the membrane superhydrophilicity and excellent anti-oil-adhesion properties. Thanks to these advantages derived from MHS, the obtained dual functional membrane can realize high-efficiency and simultaneous removal of high concentrated dye (10–50 ppm, removal efficiency>95%) and nano-sized oil droplets (about 50–300 nm, oil rejection>99%) from mixed wastewater under high flux (1680 L m−2 h−1). Considering the significantly enhanced performance, as well as the facile and cost-effective process, the as-prepared functional membrane with MHS has good application prospects. Besides, a new insight on the influence of hydrodynamic conditions on membrane fouling during emulsion separation is also proposed, which may guide better design of anti-fouling membranes.