Stability mechanism of W/O crude oil emulsion stabilized by polymer and surfactant

Rational design and fabrication of an alkali-induced O/W emulsion stabilized with cellulose nanofibrils (CNFs): implication for eco-friendly and economic oil recovery application

In this work, an alkali-induced oil in water (O/W) emulsion stabilized with cellulose nanofibrils (CNFs) was proposed to advance the development of enhanced oil recovery (EOR) approaches. The reactive species in the crude oil were first determined by FT-ICR MS. Subsequently, direct measurements of emulsion rheology, morphology, drop size distribution, and interfacial tensions (IFTs) were performed. Particular interest was placed on the stability and variation of the average drop diameter of the emulsions to reveal the underlying stabilizing mechanisms. The results showed that the introduction of L-CNFs (containing lignin segment) and CNFs could significantly prohibit the coalescence of drops and thus improve the stability of the emulsions. L-CNFs and CNFs were irreversibly absorbed at the oil-water interface forming a solid "armor" on the drops with 63.1% of the oil-water interface being covered by CNFs. This finally led to the generation of highly stable O/W emulsions. This work demonstrated the potential of CNFs as promising "green" interface stabilizers for emulsion flooding EOR particularly for in situ surfactant generation scenarios.

Improved Stability of Polyglycerol Polyricinoleate-Substituted Nanostructured Lipid Carrier Cholecalciferol Emulsions with Different Carrier Oils

Cholecalciferol, also known as vitamin D₃ , is a recognized therapeutic agent for treatment of bone diseases and cancer. However, instability and poor bioavailability have been major challenges for delivering Vitamin D₃ . The objective of this study was to formulate improved nanostructured lipid carrier (NLC) vitamin D₃ emulsions. We tested the effect of different carrier oils and the use of a solid lipid nanoparticle emulsifier, polyglycerol polyricinoleate (PGPR) on the stability of the vitamin D₃ emulsions. In contrast to the control that used glyceryl monostearate (GMS) the PGPR substitution resulted in relatively small particle sizes (0.30 to 0.43 μm), with high absolute value of zeta potentials (39.5 to 67.8 mV) and high encapsulation efficiency (85.2% to 90.4%). The stability of the NLC emulsions against environmental stresses was evaluated under varying conditions of ionic strength, pH, freeze-thaw cycles, and storage at different temperatures. Although NLC emulsions were stable at high ionic strengths, they were found to be unstable at low pH (<3), which led to aggregation and coalescence of emulsion droplets. In case of freeze-thaw stress, although relatively stable compared to control NLC, the PGPR substituted groups exhibited a slight increase in particle size and a decrease in zeta potential when the cycle was repeated five times. Additionally, we found that PGPR-substituted emulsions showed higher liquid dispersion stability than controls at 25 and 65 °C. Thus, we have formulated a modified NLC vitamin D₃ emulsion that can be widely used in the food industry. PRACTICAL APPLICATION: Vitamin D₃ , an essential micronutrient, is often added as supplements in food products and beverages for added health benefits. However, the stability of vitamin D₃ emulsions that are used in the preparation of such products has been a major concern. We have developed a modified emulsion that has improved stability against environmental stresses. We believe, in future, this formulation can be efficiently used in the food industry.

Nanoparticle-induced ion-sensitive reduction in decane-water interfacial tension

The synergistic effect of ions and nanoparticles on the interfacial tension is of great significance for extensive applications in interface-related industrial processes. However, its mechanisms are still unclear owing to a lack of understanding on the interaction between nanoparticles/ions at the interface. Here, we employ the molecular dynamics method to explore the synergistic effect of ions and nanoparticles on reducing the decane-water interfacial tension and reveal the dominant role of the three-phase contact angle and the interaction between nanoparticles. The results show that the reduction of interfacial tension is sensitive to cation species and temperature. The stronger hydration of cations induces an increased three-phase contact angle, weakening the interaction between nanoparticles and water molecules at the interface. Hence, the virial term of interfacial tension decreases. Meanwhile, the potential of mean force between nanoparticles at the interface indicates that the order of interaction strength between nanoparticles for different cations is Ca2+ > Mg2+ > Na+. The strong interaction between nanoparticles restricts the motion of nanoparticles and water molecules at the interface, inducing a reduced kinetic energy term of interfacial tension. Therefore, the interfacial tension decreases after adding the nanoparticles. Besides, as temperature rises, the difference in the adsorption ability of nanoparticles on water molecules causes a falling interfacial tension with a characteristic stage.

Application of α-amylase as a novel biodemulsifier for destabilizing amphiphilic polymer-flooding produced liquid treatment

The performance and de-emulsification mechanism of α-amylase, a novel environmental friendly biodemulsifier in petroleum industry, was investigated at room temperature. The effects of α-amylase on the viscosity of amphiphilic polymer solution and de-emulsification rate were studied by changing the concentration of α-amylase, temperature and salinity. Polymer molecular weight, Zeta potential, interfacial film strength and interfacial tension were measured to investigate the de-emulsification mechanism of α-amylase. The results show that α-amylase is an efficient biodemulsifier to increase the de-emulsification rate of amphiphilic polymer emulsions. Hydrolysis of α-amylase to amphiphilic polymers destroys the structure of the amphiphilic polymer, thereby reduces the viscosity and the interfacial film strength of the system. Once de-emulsification is completed, the lower layer, i.e. the emulsified layer, will be clear. Thus, α-amylase can be applied as an effective de-emulsifier for amphiphilic polymer-stabilized O/W emulsion.

Efavirenz Dissolution Enhancement IV-Antisolvent Nanocrystallization by Sonication, Physical Stability, and Dissolution

Efavirenz is a fundamental drug in the HIV therapy; however, it has a low bioavailability due to low water solubility. Particle nanonization should enhance its dissolution and therefore its bioavailability. Nanocrystallization is a promising technique for preparing drug nanocrystals. A solution containing efavirenz (EFV) and methanol was added to an aqueous solution of particle stabilizers, under sonication. The adequate polymer stabilizer and its concentration and drug load were evaluated. Particle size and zeta potential of suspensions were measured. Nanosuspensions were freeze-dried and the resulting powder was characterized by some techniques, with special attention to dissolution. Particle size and zeta potential analysis showed that HMPC and PVP were the most suitable polymers. All samples prepared with these stabilizers had nanosized particles and proper zeta potential; however, sedimentation and particle growth were detected with Turbiscan™. Time-related destabilization occurred when the lowest polymer concentration of 20% was used. SEM analysis of the dried powder shows film formation for suspensions with 40% of polymer and particle aggregation in samples with less polymer. Dissolution profiles of samples were higher than EFV raw material, although the lower the polymer concentration, the higher the dissolution.

The Effect of pH on the Properties of a Cationic Bitumen Emulsifier

Surfactants used in road surface treatments have an optimal application pH value which is an important condition for applications, otherwise stable bitumen emulsions with high solid contents are impossible to achieve. Therefore, a wide range of pH values were employed to investigate its effect on the bitumen/water interfacial properties of a cationic bitumen emulsifier. It is shown that interfacial tension and dilatational modulus have correlations with pH value. The lowest value of interfacial tension declined with the decrease of pH value. The strong acid system has the highest dilatational modulus while this modulus of the neutral system is the lowest. Compared with the neutral system, the maximum of the dilatational modulus also appears in the acid or alkaline system at a relatively low concentration. Physical properties of bitumen emulsions, including storage stability and Zeta potential, show the same changing rule as the interfacial rheology.

Interfacial adsorption of pH-responsive polymers and nanoparticles

Using dissipative particle dynamics (DPD), we model the interfacial adsorption of pH-responsive polyelectrolytes and polyelectrolyte-grafted nanoparticles (PNPs) at a planar water-oil interface. The electrostatic interactions in the presence of the dielectric discontinuity across the interface are modeled by exploiting the Groot method, which uses an iterative method to solve the Poisson equation on a uniform grid with distributed charge. We reveal the effects of the pH and salinity of the aqueous solution and the length of the polyelectrolyte on the adsorption behavior of weak polyelectrolytes. The adsorption kinetics is monitored via the trajectory of the center of mass of the polyelectrolyte in the direction normal to the interface. The residence time at the interface and the pair correlation function between the polyelectrolyte and the oil are measured to quantitatively characterize the adsorption. Similar to the weak polyelectrolytes, the influences of pH, salinity and grafted chain length on the adsorption of an individual PNP are explored. Our results show that by grafting polyelectrolytes, the interfacial behavior of the nanoparticles can be tuned by changing the pH and salinity of the solution, which is dictated by the contact angle, the pair correlation function between the particles and the oil, the desorption energy, and the particle morphology at the interface. We also observe that the electrostatic-driven variations in the interfacial activity and morphology of the PNPs are not sensitive to the length of the grafted polyelectrolytes.

The enhanced stability and biodegradation of dispersed crude oil droplets by Xanthan Gum as an additive of chemical dispersant

It is necessary for chemical dispersant to disperse oil effectively and maintain the stability of oil droplets. In this work, Xanthan Gum (XG) was used as an environmentally friendly additive in oil dispersant formulation to enhance the stability and biodegradation of dispersed crude oil droplets. When XG was used together with chemical dispersant 9500A, the dispersion effectiveness of crude oil in artificial sea water (ASW) and the oil droplet stability were both greatly enhanced. In the presence of XG, lower concentration of 9500A was needed to achieve the effective dispersion and stabilization. In addition to the enhancement of dispersion and stabilization, it was found that the biodegradation rate of crude oil by bacteria was dramatically enhanced when a mixture of 9500A and XG was used as a dispersant. Because of the low environmental impact of XG, this would be a potential way to formulate the dispersant with lower toxicity.

Study on the stabilization mechanism of crude oil emulsion with an amphiphilic polymer using the β-cyclodextrin inclusion method

The β-cyclodextrin inclusion method to investigate crude oil emulsions stabilized by amphiphilic polymers is proposed.

Effect of magnesium salt concentration in water-in-oil emulsions on the physical properties and microstructure of tofu

The aim of this research was to prepare water-in-oil (W/O) emulsions encapsulating different concentrations of magnesium chloride (MgCl2) and to investigate the effect of W/O emulsions on the physical properties and microstructure of tofu. The results showed that the stability of W/O emulsions improved as the concentrations of polyglycerol polyricinoleate (PGPR) and MgCl2 increased. Dynamic viscoelastic measurements indicated that gelation time decreased with increasing MgCl2 concentration in W/O emulsions, suggesting a more rapid reaction between magnesium ions and protein molecules. As the concentration of MgCl2 in W/O emulsions increased, the yield and water content of tofu decreased, while the protein and crude fat contents and hardness values increased. At a concentration of 2.0M MgCl2 in W/O emulsion, the WHC and microstructure of the tofu samples were optimal. The variations in the physical properties of tofu were attributed to the concentration of magnesium ions and the coagulation rate.

Investigation into the adsorption of partially hydrolyzed polyacrylamide onto in situ formed magnesium hydroxide particles

Robust, fast method treating wastewater containing HPAM and the detailed adsorption mechanism of HPAM onto in situ formed Mg(OH)₂ was proposed.

Effects of interfacial tension and emulsification on displacement efficiency in dilute surfactant flooding

This study provides an investigation on the effect of interfacial tension (IFT) and emulsification on displacement efficiency in dilute surfactant flooding.

Effect of Tween 40 and Tween 60 on the Properties of a Cationic Slow-Set Emulsifier

The properties of a cationic slow-set emulsifier named INDULIN SBT in the absence and presence of Tween 40 and Tween 60 is investigated in this paper. After adding Tween 40 and Tween 60, the interfacial tension and dilatational modulus of SBT have remarkable changes. Compared with the pure SBT system, the interfacial properties of the mixed surfactant systems are improved obviously, especially if the ratio of the mixtures is 1 : 1. The Zeta potentials are also the lowest with favorable storage stability in these systems. At suitable ratios, synergistic adsorption may take place, resulting in remarkable enhanced interfacial properties. The combination of SBT and Tween 40 as well as Tween 60 could be used as surfactant mixtures applied in asphalt emulsions.

Interfacial sciences in unconventional petroleum production: from fundamentals to applications

With the ever increasing demand for energy to meet the needs of growth in population and improvement in the living standards, in particular in developing countries, the abundant unconventional oil reserves (about 70% of total world oil), such as heavy oil, oil/tar sands and shale oil, are playing an increasingly important role in securing global energy supply.

Solution properties and phase behavior of a combination flooding system consisting of hydrophobically amphoteric polyacrylamide, alkyl polyglycoside and n-alcohol at high salinities

Application of polymer/surfactant (SP) combination flooding technique is attracting considerable interest in enhanced oil recovery (EOR).