Microemulsion Solution Research Articles

DISPLACEMENT OF OIL BY MICELLAR SOLUTION WITH NANOPARTICLES FROM POROUS MODEL WITH CORE MATERIAL

Enhanced oil recovery (EOR) techniques play an important role in maintaining oil production worldwide. These methods are given special attention due to the constant decline in the availability of oil resources. One type of EOR is the tertiary method - a chemical method that involves the use of synthetic substances for mining. Liquid flooding in the presence of a surfactant is a common chemical EOR, and microemulsions belong to these systems. The injection of the microemulsion rim reduces the interfacial tension between the crude oil and the formation fluid, which results in the mobilization of a significant portion of the residual oil. Recently, the possibility of simultaneous use of nanoparticles and chemicals to increase the efficiency of the processes of increasing oil recovery has been considered. In this work, nanoparticles participate in the role of microemulsion stabilization, and their joint effect on the displacement capacity of oil from the bulk model of a porous medium is also analyzed. The work is aimed at studying the effect of adding silicon oxide nanoparticles to a microemulsion solution, which is an agent for displacing viscous oil from a bulk porous medium. In the experiment, laboratory studies of oil displacement by various compositions, including surfactants, salt, alcohol and nanoparticles, were carried out on two types of bulk models assembled from glass beads and quartz sand, phase saturations were determined at different points in time, and displacement capacity graphs were built. The oil displacement study was carried out for six liquids: water, mineralized water, nanofluid, aqueous solution with surfactant, also a solution for microemulsion without and with the addition of nanoparticles. It has been found that the effect of adding nanoparticles to the microemulsion composition in the case of bulk models consisting of glass beads leads to a slight increase in the volume of displaced oil. In the case of bulk models consisting of core material, an increase in residual oil saturation is observed, which is associated with adsorption of particles on the surface of core material.

Assessment of hemostatic ability of biomaterial based on chitosan and Eclipta prostrata L. extract

The biomaterials based on chitosan and Eclipta prostrata L. extract have been prepared by microemulsion method and solution method (with and without sodium tripolyphosphate (STPP) as a cross-linking agent). The main component in Eclipta prostrata L. extract is flavonoid groups. The structure of the chitosan/extract biomaterials was studied by infrared spectroscopy. The chitosan/extract biomaterial using STPP cross-linker appeared an absorption band at 1152 cm−1 attributed to the vibrations of C–O–P bonds, which proved that chitosan has crosslinked with STPP. The morphology of the biomaterials was investigated by the dynamic light scattering technique and field emission scanning electron microscopy. The obtained results showed that the particle size of the chitosan/extract biomaterials prepared by microemulsion method and solution method with STPP ranged from 68.06 nm to 1484 nm, with an average particle size of 304.9–1019 nm. The microemulsion method produced biomaterials with much smaller average particle size than the solution method using cross-linkers. The hemostatic ability of the biomaterials was better than that of the control sample based on the time of blood clotting formation and glomerular aggregation ability. The sample with the ratio of E. prostrata L. extract: chitosan of 1:30 had the lowest hemostasis time (6 min 46 s) and its glomerular aggregation rate after 5 min was 13.05%. This indicated that the biomaterials based on chitosan and E. prostrata L. extract are promising for application in biomedicine as hemostatic materials.

Robust Scale Dissolver Mitigates Mixed-Scale Issue in South China Sea

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 211187, “Tackling Mixed-Scales Issue in an Oil Field Using a Novel Robust Scale Dissolver,” by Nora Aida Ramly, Luky Hendraningrat, SPE, and Latief Riyanto, SPE, Petronas, et al. The paper has not been peer reviewed. _ The evaluation of a recently developed robust solid dissolver (RSD), from the laboratory phase through pilot deployment, is presented in the complete paper. Based on laboratory tests, the RSD can dissolve mixed scales completely in 24 hours at well temperatures while experiencing no incompatibility issues with production chemicals and all pumping and wireline components. The RSD was developed based on the total organic system that can prevent corrosion and is compatible with hydrocarbon. The RSD was piloted at oil Well 1 in Field PN and successfully removed mixed scales, allowing the well’s revival. Introduction Solid scale deposition is one of the most frequent flow-assurance issues both in subsurface and at the surface. The scale can be classified as organic (wax or asphaltenes), inorganic (calcites, sulphates, sulfides, halites, carbonates, and oxides), soap-related (naphthenates and carboxylates), gas-related (hydrates), or mixed scales. Scale occurrence, quantity, and severity mainly are determined by mineralogy, water chemistry, reservoir pressure and temperature, and the flow characteristics of the producing fluid in the well. Furthermore, scale formation is exacerbated by higher pH conditions and a higher water-cut environment, as would be expected in oil fields where water is to be injected for pressure maintenance. The most common type of scales found in Malaysian oil fields are organic and inorganic scales. The operator’s previously deployed scale-dissolving chemical in its fields only could cater to a single type of scale treatment at a time, which was ineffective for dissolving mixed scales simultaneously. Another method is the use of a mechanical solution using a coiled tubing unit (CTU). Removal mechanically by CTU in tubulars is a successful method in removing hard barite scales, but the cost is high and the method requires several days of production deferment. An improved and cheaper mixed-scale removal approach was needed to clean out mixed-scale issues in more-challenging brownfields. The RSD technology was developed for wellbore cleanout caused by mixed scale based on a stable microemulsion solution consisting of acid and solvent components. The solution was proposed to dissolve both organic and inorganic scales simultaneously in the near-wellbore area and tubing string of an oil well. The very small droplet size formed by the surfactant system and solvent is a significant advantage of using microemulsion and can allow penetration even in tight formations with small pore throats and promotes more-uniform surface coverage because of the increased interfacial area of the droplets. Previous studies have reported that the microemulsion can be pumped without causing a significant increase in pumping pressure.

Emulsion electrospinning of zein or gelatin-pectin with carotenoid from watermelon

Zein and gelatin-pectin nanofibers including carotenoid microemulsion were fabricated by emulsion electrospinnig. The microemulsion and feed solution properties, fiber morphology, carotenoid compounds and encapsulation efficiency were determined. The particle size ranges of microemulsion were narrow (190–206 nm) with homogeneous distribution. A low PDI value (0.251±0.02) showed a uniform size distribution. The zein solution properties except viscosity decreased with addition of the microemulsion, while all solution properties decreased for the gelatin-pectin solution. Scanning electron micrograph images showed that the addition of the microemulsion along with solvents significantly affected the electrospinning process, fiber diameter and morphology. As the microemulsion concentration increased, fiber production became more difficult or fiber could not be obtained. Electrospinability was better for zein solutions than the blend of gelatin-pectin solution. The highest encapsulation efficiency (%79.74) was achieved with zein nanofibers including the mixture of acetic acid:ethanol:water (30:40:30) and 40% microemulsion. In addition, gelatin-pectin nanofibers with 30% microemulsion were relatively obtained more smooth and thinner diameter, while the nanofibers had lowest encapsulation efficiency. Accordingly, the zein nanofibers and pectin-based nanofibers may be used as carrier vehicles for microemulsion containing bioactive compounds. They may be as a promising material in fortified foods and pharmaceuticals.

Essential Oil Microemulsions Inactivate Antibiotic-Resistant Bacteria on Iceberg Lettuce during 28-Day Storage at 4 °C.

The objective of this study was to investigate the antimicrobial activities of essential oil-based microemulsions in the wash water against Escherichia coli O157:H7 and Pseudomonas fluorescens on Iceberg lettuce. Evaluated wash microemulsions included oregano oil, lemongrass oil, and cinnamon oil, along with a plant-based emulsifier for improved solubility. Iceberg lettuce was inoculated for 2 min with E. coli O157:H7 (6.0 log CFU/g) or P. fluorescens (6.0 log CFU/g) and then dip-treated in a phosphate buffered saline (PBS) control, 50 ppm chlorine, 3% hydrogen peroxide treatment or a 0.1%, 0.3%, or 0.5% microemulsion solution. Treated leaves were stored at 4 °C, and analyzed for surviving bacteria on days 0, 3, 7, 10, 14, 21, and 28. Efficacies of the antimicrobials were concentration and storage-time dependent. There was a 1.26–4.86 log CFU/g reduction in E. coli O157:H7 and significant reductions (0.32–2.35 log CFU/g) in P. fluorescens during storage at days 0–28 (p < 0.05). The 0.1% oregano oil microemulsion resulted in the best visual appeal in Iceberg leaves inoculated with E. coli O157:H7 and showed better improvement in the quality of the Iceberg leaves inoculated with spoilage bacteria P. fluorescens. The results suggest that 0.5% cinnamon and 0.3% oregano oil treatments have the potential to provide natural, eco-friendly, and effective alternatives to chemicals for the decontamination of leafy greens, eliminating E. coli O157:H7 and P. fluorescens.

Electrochemical analysis of ferrocene in bicontinuous microemulsions using β- cyclodextrin modified monolayer graphene electrodes

• The reduction peak of ferrocene increased significantly by modifying β-CD in BME. • Modification density of β-CD on a monolayer graphene exceeds a coverage of 0.5. • Small water domains around β-CD forms a concentration field for ferrocenium ions. A monolayer graphene electrode modified with β-cyclodextrin (β-CD) was produced via a one-step reaction using an originally synthesized pyrene derivative of β-CD (py-β-CD). A py-β-CD-modified graphene electrode with a high modification density exceeding a coverage of 0.5 was obtained. Using this electrode, the electrochemical behaviors of water-insoluble ferrocene (Fc) and of a water-soluble ferrocene derivative in a bicontinuous microemulsion (BME) solution, consisting of a phosphate buffer (pH = 7.4), sodium dodecyl sulfate (SDS), 2-butanol, and toluene, were analyzed to investigate the effects of β-CD modification on the redox reactions of these species. In the reduction reaction of water-insoluble Fc, almost no peak was observed for the unmodified graphene electrode, whereas a high peak current increase was observed for the β-CD-modified electrode. The mechanism of the increase in the peak current of the reduction reaction can be derived from many small water domains formed around the β-CD molecules on the graphene surface. These water domains form many oil–water interfaces on the surface of the graphene electrode, which act as an [Fc] +1 concentration field by interacting with SDS.

Development and Evaluation of Ceftazidime Loaded Microemulsion for Parenteral Drug Delivery System

The goal of this study was to develop a parenteral microemulsion formulation of Ceftazidime antibiotics. The ceftazidime sparingly soluble in organic solvent like ethanol, DMSO, and dimethyl formamide were determined. For biological experiment, organic solvent- free aqueous solutions of ceftazidime (hydrate) are prepared by directly dissolving the crystalline compound in aqueous buffer. The peudo ternary phase diagrams of oil, surfactant, cosurfactants (Butanol/ Isopropyl alcohol mixture) and water were constructed to identify boundaries for microemulsion existence. Ceftazidime microemulsion particle size, solution viscosity and conductivity were evaluated. The microemulsion stability and haemolytic activity were examined after dilution in 5% dextrose solution for injection to 1 mg/mL ceftazidime. In vitro haemolysis studies indicated that Ceftazidime microemulsions were well tolerated by erythrocytes. The novel microemulsion formulation of Ceftazidime was developed that is suitable for parenteral administration. This new formulation could potentially have less vehicle-associated side effects that current commercial formulation of Ceftazidime based on Cremophor® EL and isopropyl alcohol solution.

An experimental and field case study to evaluate the effects of shut-in on well performance

There is still debate on how shutting fractured wells for a period of time can affect the well performance. In this study, we combined two approaches to better understand the effects of shut-in time on well performance. First, we analyzed flowback and post-flowback production data from a horizontal well drilled in the Montney Formation, which was fractured with water containing a microemulsion (ME) additive. After the shut-in time for 7 months, the oil and solution gas rates significantly increased by 750% and 671%, respectively. However, the free gas rate decreased by 95% in 65 days, before it started to build up again to exceed the values at the start of the production. Second, we performed a series of imbibition oil-recovery, dynamic liquid-liquid contact angle, and interfacial tension measurements to investigate how the interplay of (i) capillary suction and (ii) osmotic pressure affects oil production from core plugs during the counter-current imbibition tests. Combined analyses of field and laboratory results suggest that the increase in oil production rate after the shut-in period is due to combined effects of (i) free-gas dissolution into the oil (ii) capillary imbibition of fracturing water containing ME solution into the rock matrix driven by wettability alteration and osmotic pressure, and (iii) reduction in phase trapping near fracture face due to interfacial tension reduction.

A pore-scale study of foam-microemulsion interaction during low tension gas flooding using microfluidics- secondary recovery

The most commonly used methods for secondary oil recovery have been waterflood and immiscible gas flood. However, these methods leave behind substantial amount of residual oil. Past laboratory scale Low-Tension-Gas (LTG) coreflooding experiments have shown secondary oil recovery up to 80% OOIP (Original Oil in Place) for low permeability (sub 10mD) reservoirs. LTG flooding combines the well-known concepts of Surfactant EOR, where a surfactant solution is injected to lower oil-water IFT to ultra-low values (10−3 dyne/cm), and Foam EOR, where foam is generated in-situ by the co-injection of gas to provide mobility control to the oil displacement. While past LTG coreflooding experiments for secondary recovery have demonstrated promising oil recovery, the exact pore-scale mechanisms involved during secondary LTG flooding are yet to be studied. The most important questions to be addressed are the oil-displacement mechanisms in equilibrated and non-equilibrated microemulsion systems (Winsor Type I and Type III), the impact of foam on the microemulsion equilibration, and the overall oil recovery value and rate as functions of these factors. The study was conducted in a borosilicate water-wet micromodel with a porous network reflective of actual rock pore network. Alternate slugs of microemulsion/surfactant solution and gas were injected into the micromodel to re-create secondary LTG flooding on the pore-scale. Unique oil displacement flow mechanisms were identified for Type I and Type III microemulsion systems. Oil displacement flow mechanisms also varied depending on whether the injected liquid was equilibrated microemulsion or non-equilibrated surfactant solution. Oil-in-water macroemulsions were characteristic of non-equilibrated Type I systems, and water-entrained macroemulsions were characteristic of non-equilibrated Type III systems. Foam generated in-situ was observed to improve microemulsion equilibrium rate and oil recovery rates for secondary LTG flooding.

Direct Electrochemical Hydrogenation of Naphthalene to Decalin at Pt and Pt-Ru Alloy Electrodes in Liquid Phase

Decalin has been recognized as one of organic chemical hydrides, which can be obtained by reversible hydrogenation reaction of naphthalene in the presence of a catalyst. However, because naphthalene is solid under the ambient conditions, the naphthalene/decalin system has been hardly turned to practical use for the hydrogen storage so far. Recently, we have, for the first time, demonstrated a direct electrochemical hydrogenation of toluene to methylcylcohexane at Pt electrodes in a microemulsion solution at room temperature [1]. In a microemulsion system, a hydrophobic organic compound and water (or hydrated ion, e.g. proton) can be supplied simultaneously to an electrode surface, and can react together with electron transfers. Thus, any solid organic compounds that form a microemulsion solution with water can react electrochemically with proton at lower temperatures than their melting or boiling points. In the present study, direct electrochemical hydrogenation of naphthalene was investigated by employing the microemulsion technique with Pt and Pt-Ru electrocatalysts sputtered on a Ti sheet. Author has, for the first time, achieved a high Faraday efficiency and selectivity for the naphthalene/decalin conversion under a galvanostatic condition at 60°C.Thin Pt-Ru alloy or pure Pt were prepared on a Ti sheet by RF-sputtering a Pt target with or without Ru target. The composition of the alloys was controlling by varying exposed target area ratio, and analyzed by X-ray photoelectron spectroscopy. Microemulsion electrolytes were prepared from naphthalene, a sulfuric acid solution and two surfactants by mixing and sonicating. All the electrochemical measurements were performed with an H type cell at 60°C. A platinum black and a reversible hydrogen electrode were employed as the counter electrode and reference electrode, respectively. The working electrode was immersed into a microemulsion solution while the counter electrode into a sulfuric acid solution. After the electrolysis, products were analyzed and quantified by gas chromatography (GC) with a flame ionization detector for calculating the Faraday efficiency and selectivity. Toluene was employed as internal standard for quantitative GC analysis.Fig. 1 shows cyclic voltammograms (CVs) at a Pt/Ti electrode taken in 1 M sulfuric acid (black) and a naphthalene-containing microemulsion electrolyte (red) at sweep rate of 1 mV/s. In the sulfuric acid solution, the Pt/Ti electrode exhibited a characteristic reversible hydrogen adsorption wave below 0.3 V. In contrast, the hydrogen adsorption feature completely disappeared from the CV in the microemulsion electrolyte presumably due to an adsorption of naphthalene on the Pt surface. However, reduction current appeared below ca. 0.2 V and steeply increased below 0.05 V. This can be explained by a partial reduction and desorption of the adsorbed naphthalene molecules[2] and subsequent bulk hydrogenation reaction on the vacant sites. It should be pointed out that the steep reduction current was observed at more positive potential than the hydrogen evolution reaction, suggesting a Langmuir-Hinshelwood type reaction with underpotential-deposition (UPD) hydrogen on the electrode surface.The GC analysis after a constant-current electrolysis at 2 mA cm-2 for 150 min revealed the formation of cis- and trans- decalin via10-electron transfer as well as tetralin via 4-electron transfer. In comparison between the isomers, cis-decalin was the dominant species presumably due to a flat orientation of the adsorbed naphthalene molecule [2], which reacted with UPD hydrogens via the Langmuir-Hinshelwood type mechanism. Surprisingly, the Fraday efficiency for the naphthalene/decalin conversion and selectivity for dacalin/tetralin was much improved at a Pt-Ru/Ti electrode, up to 48% and 93%, respectively. These improvements might be ascribed to change in the adsorption energy of naphthalene on the Pt site due to alloying with Ru, or change in the adsorption site to Ru.Reference[1] M. Wakisaka and M. Kunitake, Electrochem. Commun. 64 (2016) 5.[2] S.-L. Yau, Y-G. Kim, and K. Itaya, J. Phys. Chem. B 101 (1997) 3547. Figure 1

Microemulsion synthesis of anhydrous calcium sulfate nanowhiskers with calcium acetate solution and its surface structure stable and crystal phase evolution after modification

Methods obtaining gypsum whiskers via calcining dihydrate or hemihydrate gypsum perform high energy consumption. It also performs potential environmental impacts. New methods with energy-saving, high-efficiency, and environmentally friendly perform great challenges, which aim at fabricating gypsum whiskers even nanowhiskers. In this study, we used high-concentration calcium acetate solution and dilute sulfuric acid to fabricate anhydrite calcium sulfate nanowhiskers with microemulsion solution at room temperature. For further research on regulation and modification of its surface, calcium sulfates were modified by silicone quaternary ammonium salt and fatty acid methyl ester sulfonate in order to study their surface structure and crystal evolution during modification. After characterization, it indicated that the phase of calcium sulfate transmitted from anhydrite phase into dihydrite phase with a slight change on the surface layers. Benefiting from stability and activity properties of calcium sulfate nanowhiskers after modified, the compressive strength of cement paste with only 1% calcium sulfates performed increased absolutely 10.1% and 4.3% at conservation age of 3 days and 28 days.

Stability Test of Nanostructured Lipid Carriers-Loaded Mefenamic Acid prepared by Microemulsion Technique

The objectives of this study were to prepare the nanostructured lipid carriers (NLCs)-loaded mefenamic acid and to study the particle size and zeta potential of the NLCs-loaded mefenamic acid after storage in refrigerator (approximately 2 – 4°C) for 7 days. The preparation method of NLCs-loaded mefenamic acid used the microemulsion technique. All compositions were vigorously mixed with vertex method to obtained the clear microemulsion solution. Tween®80 (surfactant) and 1 – butanol (co – surfactant) were mixed at the ratio of 3:2 to use as the surfactant mixture. Then, it was dispersed in cold water (approximately 2 – 4°C) at different ratio, and the droplet size was reduced by a homogenizer at 6, 000 rpm for 5 minutes and sonicator for 30 minutes to form the NLCs-loaded mefenamic acid. The prepared NLCs-loaded mefenamic acid were kept in refrigerator (approximately 2 – 4°C) for 7 days. After that, the solutions were tested the particle size and zeta potential. The particle size and zeta potential of NLCs-loaded mefenamic acid after storage were in the range of 160-310 nm and -4.00 to -19.00 mV, respectively. It was found that the F4 formula was the best to prepare the NLCs-loaded mefenamic acid. F4 formula composed of the 1%w/w mefenamic acid, 10%w/w water, 80%w/w surfactant, and 10%w/w capric triglyceride, and the dilution ratio was 1:25.

Synthesis of Rh nanoparticles encapsulated in ZSM-5 and its application for methanol to olefin over acid sites with simultaneous production of hydrogen over Rh

Metal-loaded zeolites possess metal and solid acid catalysis and therefore can be applied for complex reactions where different reactions proceed on different type of active sites. The optimization of each active sites, such as amount and strength of active sites, are indispensable to improve the yield of the desired product in complex reaction. On the other hand, in metal-loaded zeolite catalysts, the acid site amount is still difficult to be controlled independently because metal particles may be located on the acid sites, leading to the decrease in the acidity. To realize independent control of the each active sites of metal-loaded zeolite, we herein synthesized Rh nanoparticles encapsulated in ZSM-5 catalysts (Rh@ZSM-5) in a water-in-oil microemulsion solution by modifying the synthesis method for metal nanoparticles encapsulated in zeolite in our previous literature. In this method, the formation of metal nanoparticles encapsulated in amorphous silica was followed by the transformation of amorphous silica into zeolite and thus the amounts of solid acid and metal active sites are expected to be controlled independently. Rh@ZSM-5 was found to possess Rh nanoparticles inside of zeolite and the metal particle size and the amount of the solid acid sites were almost independent of the Rh loadings. Reaction of methanol over Rh@ZSM-5 was carried out to elucidate the bifunctional catalysis and its effect on the product selectivity. During the methanol conversion over Rh@ZSM-5, methanol to olefin reaction over solid acid sites and methanol decomposition over Rh metal proceeded in parallel. Rh@ZSM-5 exhibited the larger yield of propylene and butenes than ZSM-5. It could be because that hydrogen atoms produced in situ over Rh@ZSM-5 effectively inhibited the formation of aromatic intermediates to produce ethylene and aromatic compounds.

Mono-Dispersed Microspheres Locally Assembled on Porous Substrates Formed through a Microemulsion Approach.

A cost-effective, simple, and time-saving method to fabricate mono-dispersed periodic microsphere structures on substrates with patterned sites is very meaningful due to their significance on various biological studies. Herein, a simple and facile method to fabricate mono-dispersed microsphere arrays on porous substrates was developed. The mixture of polystyrene and an organic stabilizer solution which contains aqueous solution, fabricated through shaking, was applied to prepare microemulsion solution. An ordered porous structure was produced by spreading and evaporating the solvent of microemulsion on a glass slide, accompanied by the enrichment of didodecylamine in the cavities. The porous cavities were further modified with polyacrylic acid and poly(diallyldimethylammonium chloride) which could immobilize the microspheres. The charged microspheres were incorporated into the cavities by an electrostatic interaction with the oppositely charged polyelectrolytes. The positive polyelectrolytes with abundant charges as well as a suitable content and dimension of microspheres, ensured the formation of mono-dispersed and ordered arrays. Considering that other charged particles were universally suitable for the present strategy, the reported approach opened an efficient way for the preparation of microsphere-based materials.

Mass and Momentum Transfer Considerations for Oil Displacement in Source Rocks Using Microemulsion Solutions

Existing strategies for hydrocarbon extraction have been designed primarily based on macroscopic properties of fluids and rocks. However, recent work on tight formations and source rocks (such as shale) revealed that the fluid properties and phase change of the hydrocarbons stored in the lower end of the pore size distribution inside the organic nanopores deviate significantly from their bulk phases in the large pores. The cause for such deviations is primarily the presence of strong fluid-wall molecular interactions in the nanopore. Organic nanopores, in source rock, store more hydrocarbons than those pores in a conventional reservoir for the same pore volume because nanopore confined hydrocarbons are more compacted and denser than the bulk phase. However, the recovery factor from these pores were reported to be considerately lower. Surfactants, introduced in the form of micelle or microemulsion, have the potential to increase the recovery. Whereas the transport behavior of micelles and their adsorption on solid walls are well-established, the role of microemulsion on the recovery of hydrocarbons under confinement remains poorly understood. In this work, molecular dynamics (MD) simulations were employed to investigate the two-phase flow in kerogen nanopores containing oil, water, and a microemulsion droplet. A slit-shaped pore was modeled representing the organic nanopore, and a mixture of hydrocarbon was chosen to represent the oil phase. Initially, the microemulsion droplets containing nonionic surfactant dodecylhepta(oxyethylene)ether (C12E7), swollen with solvent (d-limonene), were introduced to the water phase. We showed that the droplets were dispersed under the strong molecular interactions existing in the nanopore space. Subsequently, both the solvent and the surfactant components played essential roles in displacing the oil phase. The surfactant molecules were deposited at the interface between the aqueous phase and the oil, thereby reducing the interfacial tension. The solvent molecules, originally solubilized in a microemulsion droplet, penetrated the oil film near the pore walls. Those solvent molecules were exchanged with the adsorbed oil molecules and transformed that portion of oil into free oil for enhanced recovery. In addition, we considered the Couette flow of water near the organic wall with a film of oil, and found that the oil phase, which consisted of free and adsorbed molecules, could be mobilized by the viscous force caused by the flowing water. Hence, the chemicals introduced by the water mobilized both the free oil and a portion of adsorbed oil inside the oil-wet pores. However, there existed a slip at the oil/water interface which inhibited the momentum transfer from the water phase to the oil phase. When the surfactants were present at the interface, they acted as a linker that diminished the slip at the interface, hence, allowing the momentum transfer from the water phase to the oil phase more effectively. As a result, the fractional flow of oil increased due to the presence of both the surfactant and the solvent. At the final part, we extended our study from a single channel to three-dimensional (3D) kerogen pore network, where the pore sizes were less than or equal to 7 nm. The MD results showed that the dispersed microemulsion droplets also mobilized and displaced the oil present within the kerogen pore network. The results of this work are important for our understanding of flow and displacement under confinement and its application to oil recovery from source rocks.

New bioanalytical microemulsion Electrokinetic chromatography method for the simultaneous determination of Trifluridine with its metabolites and Tipiracil in rat plasma: Application to pharmacokinetic studies

A Microemulsion Electrokinetic Chromatography method coupled with diode array detector (MEEKC-DAD) was developed for the first time and found to be efficient, sensitive, and selective for the simultaneous analysis of Trifluridine (FTD), and its metabolites 5-(trifluoromethyl) uracil (FTY) and 5-carboxy-2′-deoxyuridine (5CDU), and Tipiracil (TIP) in rat plasma. Sample pre-treatment involved a simple protein precipitation from plasma using acetonitrile. The separation was achieved using a fused silica capillary (65 cm total length, 55 cm effective length and 50 µm i.d.) and a microemulsion solution consisted of 1.66% sodium dodecyl sulfate (SDS), 0.91% heptane, 6.61% 1-butanol, and 90.72% borate buffer (20 mM, pH 9.5). Electrophoretic separation was carried out at 20 °C and 20 kV. The samples were injected for 40 s at 20 mbar and detected simultaneously at 205 nm. The electrophoretic parameters indicated that the developed MEEKC-DAD method permitted complete resolution of the analytes within 13 min. The developed method was fully validated according to the FDA guidelines for bioanalytical method validation. The method was linear in the range 200–4000 ng/ml for FTD, FTY, 5CDU, and 100–1000 ng/ml for TIP. The intra/inter-day accuracy and precisions were ≤4% for all drugs. Extraction recovery and stability were also assessed and were within acceptable range. After being validated, the method was applied for the determination of the studied drugs in plasma samples collected from rats injected intraperitoneally with a combination of FTD and TIP. The results obtained were used to study the pharmacokinetics of FTD with its metabolite and TIP in rat plasma.

Experimental Investigation into the Screening of New Surfactant Flowback Aids and Statistical Interpretation of Their Imbibing Capacity for Selected Core Substrates

AbstractSpontaneous imbibition is a pervasive part of many natural and industrial processes. As an inherent feature of fluid transport in porous media, it is a driver for oil recovery. Understanding spontaneous imbibition and leveraging surface science is fundamental for fluid recovery; specifically, the role of the surfactant in the imbibition processes and the potential to alter capillarity and wettability of reservoir rock. Surfactant success relies on the understanding of the factors governing the interfacial phenomena among crude oil, and formation properties under reservoir conditions. Developing a methodology coupling chemical performance with analytical techniques, and statistical interpretation of core/surfactant/oil interactions, can help establish workflows to advance new chemistries and enhance oil recovery. This article discusses a study of flowback aids formulated as microemulsions corresponding to the thermodynamically stable Winsor Type IV solutions. Neat formulated microemulsions, when dosed at field treatment concentrations, provide either oil‐in‐water droplet microemulsions or nanoemulsions. The solvency potential was measured, and the Kauri‐butanol (Kb) value was determined. Parameters such as critical micelle concentration (CMC) and interfacial tension (IFT) were determined to characterize microemulsion solutions. These systems were tested using either in the column flow test with formation material sieved to match mineral grain size, or sandstone cores of various permeabilities. The results indicate that surfactant‐based flow‐enhancing aids are desirable for improved oil recovery when compared to the control fluid. The statistical analysis of core‐fluid interaction includes an ANOVA followed by assumption evaluations and model interpretation, which demonstrates that the core permeability term, followed by the surfactant term, has the highest contribution whereas oil has no statistical significance to the model.

Spontaneous and Flow-Driven Interfacial Phase Change: Dynamics of Microemulsion Formation at the Pore Scale.

The dynamic behavior of microemulsion-forming water-oil-amphiphiles mixtures is investigated in a 2.5D micromodel. The equilibrium phase behavior of such mixtures is well-understood in terms of macroscopic phase transitions. However, what is less understood and where experimental data are lacking is the coupling between the phase change and the bulk flow. Herein, we study the flow of an aqueous surfactant solution-oil mixture in porous media and analyze the dependence of phase formation and spatial phase configurations on the bulk flow rate. We find that a microemulsion forms instantaneously as a boundary layer at the initial surface of contact between the surfactant solution and oil. The boundary layer is temporally continuous because of the imposed convection. In addition to the imposed flow, we observe spontaneous pulsed Marangoni flows that drag the microemulsion and surfactant solution into the oil stream, forming large (macro)emulsion droplets. The formation of the microemulsion phase at the interface distinguishes the situation from that of the more common Marangoni flow with only two phases present. Additionally, an emulsion forms via liquid-liquid nucleation or the Ouzo effect (i.e., spontaneous emulsification) at low flow rates and via mechanical mixing at high flow rates. With regard to multiphase flow, contrary to the common belief that the microemulsion is the wetting liquid, we observe that the minor oil phase wets the solid surface. We show that a layered flow pattern is formed because of the out-of-equilibrium phase behavior at high volumetric flow rates (order of 2 m/day) where advection is much faster than the diffusive interfacial mass transfer and transverse mixing, which promote equilibrium behavior. At lower flow rates (order of 30 cm/day), however, the dynamic and equilibrium phase behaviors are well-correlated. These results clearly show that the phase change influences the macroscale flow behavior.

AKTIVITAS ANTIBAKTERI DARI DESAIN MIKROEMULSI MINYAK ATSIRI KAYU MANIS

&lt;span class="fontstyle0"&gt;This research focused on the study of the capability of cinnamon essential oil as antibacterial&lt;br /&gt;agent, when it is made as a microemulsion solution. The study occupied further research on&lt;br /&gt;specific type, concentration, and amount of emulsifier needed to make the cinnamon essential&lt;br /&gt;oil miscible in water without causing destruction in its antibacterial activity. Four different&lt;br /&gt;emulsifiers were tested, namely Tween 20, Tween 80, soya lechitin, and carboxymethyl cellulose&lt;br /&gt;(CMC) to stabilize the essential oil in water. The emulsifiers were used at 2% w/w, while the&lt;br /&gt;essential oil concentrations were varied at 0.5%, 1%, and 1.5%. In this study, the antibacterial&lt;br /&gt;activity of the microemulsion solution of cinnamon essential oil was tested against two types of&lt;br /&gt;pathogenic bacteria commonly found in foods, namely Staphylococcus aureus and Escherichia&lt;br /&gt;coli. Among the four types of emulsifiers, which are used, CMC showed the best results as an&lt;br /&gt;emulsifier. The results of this study indicated that microemulsion solution has antibacterial&lt;br /&gt;activity best is a combination between the CMC and the essential oil of cinnamon&lt;/span&gt;

Quality by Design approach for an in situ gelling microemulsion of Lorazepam via intranasal route

The present study illustrates the application of the concept of Quality by Design for development, optimization and evaluation of Lorazepam loaded microemulsion containing ion responsive In situ gelator gellan gum and carbopol 934. A novel approach involving interactions between surfactant and polymer was employed to achieve controlled drug release and reduced mucociliary clearance. Microemulsion formulated using preliminary solubility study and pseudo ternary phase diagrams showed significantly improved solubilization capacity of Lorazepam with 54.31±6.07nm droplets size. The effect of oil to surfactant/cosurfactant ratio and concentration of gelling agent on the drug release and viscosity of microemulsion gel (MEG) was evaluated using a 32 full factorial design. The gel of optimized formulation (MEG1) showed a drug release up to 6h of 97.32±1.35% of total drug loaded. The change in shear-dependent viscosity for different formulations on interaction with Simulated Nasal Fluid depicts the crucial role of surfactant-polymer interactions on the gelation properties along with calcium ions binding on the polymer chains. It is proposed that the surfactant-polymer interactions in the form of a stoichiometric hydrogen bonding between oxyethylene and carboxylic groups of the polymers used, provides exceptional ME stability and adhesion properties. Compared with the marketed formulation, optimized MEG showed improved pharmacodynamic activity. Ex vivo diffusion studies revealed significantly higher release for MEG compared to microemulsion and drug solution. MEG showed higher flux and permeation across goat nasal mucosa. According to the study, it could be concluded that formulation would successfully provide the rapid onset of action, and decrease the mucociliary clearance due to formation of in situ gelling mucoadhesive system.