Dynamic Interfacial Tension Research Articles

The reactive wetting kinetics of interfacial tension: a reaction-limited model

The variation of dynamic interfacial tension has been measured and explained on the basis of a new reaction-limited model.

Mixtures of Quillaja saponin and beta-lactoglobulin at the oil/water-interface: Adsorption, interfacial rheology and emulsion properties

Aim of the present study was to investigate the interfacial properties of mixed films of Quillaja saponins (QS) and beta-lactoglobulin (β-LG) at the oil/water-interface. It was hypothesized that due to the differences in the physical characteristics of the dispersed phase molecular interactions and film characteristics at the oil/water interface substantially differ from the air/water-interface. Furthermore QS/β-LG-interactions will affect stability of emulsions in a concentration-dependent manner. Oscillating drop experiments were performed with subsequent analysis of raw data (Lissajous-plots) to discover non-linear behavior upon compression and expansion. Interfacial shear rheology as well as dynamic interfacial tension and two-fluid needle experiments were performed to comprehensively characterize interfacial properties of mixtures of QS/β-LG. Finally, emulsions were prepared and their stability, oil droplet size and ζ-potential were determined. It became obvious that QS dominates the interfacial film in a binary mixture as indicated by dynamic interfacial tension and dilational rheology. Strain stiffening was observed for mixed QS/β-LG interfacial layers upon dilational expansion at an amplitude above 2.8%. Intermolecular interactions increased in mixtures of QS/β-LG as indicated by shear rheology. Emulsion experiments showed extensive aggregation of oil droplets in QS/β-LG-emulsions with high content of β-LG. Aggregation of oil droplets increased velocity of creaming and after 7days a distinct creaming layer was visible. Changes in dispersity were influenced by concentration and ratio of QS and β-LG.

Study on interfacial properties of Imidazolium ionic liquids as surfactant and their application in enhanced oil recovery

Enhanced oil recovery is a tertiary method for recovering oil trapped in porous rock of the reservoir. This oil becomes trapped in porous media because of capillary forces. The reduction of these forces by surfactants is an important aspect of enhanced oil recovery. The development of ionic liquid−based surfactants has gained significant interest in their use as cationic surfactants in analytical methods and separations. In the current study, functionality of long chain imidazolium ionic liquids as surfactants have been investigated by measuring, dynamic interfacial tension of water/oil system and their ability to reduce IFT under harsh conditions of salinity and temperature. In the present study, an advantage of 1-hexadecyl-3-methyl imidazolium bromide (C16mimBr) over traditional cationic surfactant (CTAB) has been highlighted. The efficiency of both (C16mimBr & CTAB) in recovering additional oil when used in an EOR process has been found out by conducting lab-scale core flooding experiments. Also, small Poly (dimethylsiloxane), (PDMS) microchannels have been prepared and moduled as oil filled porous structures in the reservoir. Microscopic images of surfactant solutions flowing through these channels have been recorded to find out whether they form emulsions while flowing. The experiments revealed that C16mimBr is more efficient in reducing interfacial tension between water/oil system and thus recovering more entrapped oil than traditional cationic surfactant CTAB. The results obtained here reflect high interfacial activity, high oil solubility due to the formation of emulsions and stability under harsh reservoir conditions for the IL in consideration.

A novel perspective on emulsion stabilization in steam crackers

Fouling issues in steam crackers may arise due to a number of reasons, including emulsion formation in the quench water tower. Freeze-drying according to a protocol developed in-house was used to extract species potentially capable of stabilizing emulsions from process water sampled from a quench tower. Such species were subsequently fractionated into solubility classes: water soluble, and soluble in organic solvents (polar and apolar). Liquid chromatography/mass spectrometry analyses indicated differences in the chemical composition of these fractions, with molecules bigger and richer in oxygen in the fraction soluble in polar organic solvents compared to those detected in the water soluble fraction. Bottle tests demonstrated that the interfacial material soluble in polar organic solvents was the most effective in stabilizing water-in-gasoline and gasoline-in-water emulsions. When the water soluble fraction was added to these stable emulsions it acted as demulsifier, with the most marked effects observed at low pH. In the absence of the water soluble fraction emulsion stability was largely pH-independent. The role of electrostatic forces in emulsion stabilization was investigated by conducting zeta potential measurements. With the organic soluble fraction only added to the oil phase and at pH 5.5, emulsions were stable and the zeta potential was close to zero, proving that electrostatic forces did not play a role in stabilizing this system. With the water soluble fraction added to the water phase and at alkaline pH, emulsions were stable and the zeta potential was negative, suggesting that electrostatic stabilization mechanisms cannot be discounted in the presence of the water soluble fraction. Scanning Electron Microscopy (SEM)/Energy Dispersive X-Ray Spectroscopy (EDX) were used to probe the morphology and elemental composition of the Langmuir-Blodgett films extracted from the gasoline-water interface. SEM images highlighted the presence of particles at the gasoline-water interface, suggesting Pickering stabilization mechanisms. Dynamic interfacial tension measurements showed that the decrease of the interfacial tension measured for gasoline-water interfaces upon addition of interfacial material was relatively low and similar for all fractions, supporting this hypothesis. SEM/EDX data further reveal the strong correlation between interfacial film composition and emulsion stability, with high densities of particles containing sulfur and iron associated with significant emulsion stability. The compressional visco-elastic moduli of interfacial films were determined using a pulsating drop rheometer. Measurements were done at pH 5.5 and 8.5, with the individual solubility fractions added. Film rigidity was similar with all fractions, indicating that it did not dictate the differences in their stabilizing properties.

Synthesis, Characterization and Properties of N‐Alkyl‐N,N‐di(2‐hydroxyethyl) Amine Oxides

AbstractN‐Dodecyl‐N,N‐di(2‐hydroxyethyl) amine oxide (C12DHEAO) and N‐stearyl‐N,N‐di(2‐hydroxyethyl) amine oxide (C18DHEAO) were synthesized with N‐alkyl‐diethanolamine and hydrogen peroxide. Their chemical structures were confirmed using 1H‐NMR spectra, mass spectral fragmentation and FTIR spectroscopic analysis. It was found that C12DHEAO and C18DHEAO reduced the surface tension of water to a minimum value of approximately 28.75 mN m−1 at concentration of 2.48 × 10−3 mol L−1 and 32.45 mN m−1 at concentration of 5.21 × 10−5 mol L−1, respectively. The minimum interfacial tension (IFTmin) and the dynamic interfacial tension (DIT) of oil–water system were measured. When C18DHEAO concentration was in the range of 0.1–0.5%, the IFTmin between liquid paraffin and C18DHEAO solutions all reached the ultra‐low interfacial tension. Furthermore, their foam properties were investigated by Ross‐Miles method, and the height of foam of C12DHEAO was 183 mm. It was also found that they showed strong emulsifying power.

Online measurements of surface tensions and viscosities based on the hydrodynamics of Taylor flow in a microchannel.

This paper demonstrates an online measurement technique which can measure both surface tension and viscosity for confined fluids in microfluidic systems. The surface tension and viscosity are determined by monitoring the liquid film thickness deposited in a microchannel based on the hydrodynamics of Taylor flow. Measurements were carried out for pure liquids and binary aqueous liquid mixtures. The results agreed well with reference data and theoretical models. This novel method has considerable potential for measuring dynamic interfacial tension of complex mixtures. Furthermore, it offers opportunity for integrating property measurement with two-phase flow in microchannel, opening new lines of applications.

Properties and Performance of Newly Developed Demulsifiers in Oil Sands Froth Treatment

Chemical demulsification with EO-PO block copolymers is widely employed to treat bitumen froth in oil sands operations. In this effort, the relation between demulsifier properties and demulsification efficiency was explored using three EO-PO block copolymer demulsifiers, DMO A, DMO B, and DMO C. The EO-PO block copolymers were categorized by their relative solubility number (RSN) and dynamic interfacial tension (IFT). The dewatering and solids removal efficiencies of EO-PO block copolymer demulsifiers were in the order DMO C > DMO B > DMO A from 0 to 50 ppm dosage at 30 min settling time. DMO C also showed superior performance with lower hydrocarbon losses to the underflow as compared to demulsifiers DMO A and DMO B at all the dosages studied. The direct correlation was observed between the RSN values and dewatering/solids removal performance while the IFT does not correlate to the dewatering/solids removal efficacy of the EO-PO block copolymer demulsifiers. The influence of operating conditions such as pH and mixing was also studied on dilbit dewatering, solids removal efficiency, and naphtha/bitumen losses to underflow. The decrease in pH by addition of acidic chemistry in the presence of demulsifier was not assisting to enhance demulsifier performance. The results also showed that over- or undermixing are pushing more hydrocarbons to the underflow due to the existence of unresolved bitumen emulsion.

Silica nanoparticles cationic surfactants interaction in water-oil system

The aim of this experimental study is to get insight into the combined interfacial and bulk properties of silica nanoparticles and CTAB cationic surfactant mixture in water/oil systems. The study is focused on low surfactant/nanoparticle ratios to avoid extra free surfactants in the bulk. Surfactant concentration was fixed at 9.0×10−2mM, (0.1 CMC) and the nanoparticle concentration varied between 0 and 5wt.%. Drop profile analysis tensiometry (PAT) was utilized to measure the equilibrium and dynamic interfacial tension at water/heptane interface. To comprehend the layer structure of nanoparticle-surfactant complex at the interface, the interfacial rheology was also studied using drop oscillation experiments. The formation of the surfactant-nanoparticle complex layer at the drop surface and its different structures were explained using surface pressure vs. drop surface area curves and the standard deviations of experimental drop profiles from Young-Laplace equation during large compression/expansion cycles. The results demonstrate significant changes in the standard deviation at the onset of closed-packed state of surfactant-nanoparticle complex collapse. This illustrates the formation of irregular adsorbed layer (multilayer formation). The number of surfactant-nanoparticle complexes at drop surface was calculated by accurately assessing the surface coverage at the maximum packing of particles at the interface. For the studied concentration range, surfactant-nanoparticle complexes demonstrate surface activity higher than similar surfactant concentration, however with slower dynamics of adsorption. Elasticity measurements during large compression/expansion path can also provide more details about the structure of mono-/multi-layer formation.

Effect of spacer length on the interfacial behavior of N,N′-bis(dimethylalkyl)-α,ω-alkanediammonium dibromide gemini surfactants in the absence and presence of ZnO nanoparticles

In this paper the interfacial behavior of aqueous solutions of cationic gemini surfactants of the, N,N′-bis(dimethylalkyl)-α,ω-alkanediammoniumdibromide type (known as the 12-s-12 series), in the absence and presence of ZnO nanoparticles was studied. Equilibrium and dynamic interfacial tension between n-decane and aqueous surfactant solutions were investigated. It was concluded that the synergistic effect between surfactants and nanoparticles increases the surfactant efficiency with respect to reducing the interfacial tension. Moreover, the magnitude of the effect of ZnO nanoparticles on the interfacial tension decreases with increasing length of the spacer group in the gemini surfactant structure. Dynamic studies illustrate that the migration mechanism of gemini surfactants (regardless of the presence of ZnO) from the bulk to the interface was controlled by both diffusion and adsorption. The effect of spacer length on the contact angle and emulsion stability both with and without nanoparticles was also studied.

Investigation of effects of salinity, temperature, pressure, and crude oil type on the dynamic interfacial tensions

The main objectives of this study are to determine the influence of crude oil type, salinity, temperature and pressure on the dynamic interfacial tension (DIFT) of crude oil based on the experiments and modeling approaches. DIFT is also modeled using dynamic adsorption models, mono-exponential decay model as well as empirical equations. The results showed that when temperature increases, unlike deionized water which inversion phase temperature was observed, the equilibrium IFT of crude oils/sea water increases due to reduction of surface excess concentration of natural surfactants at the fluid/fluid interface as a dominant mechanism.

Destabilization of Emulsion Formed During Aqueous Extraction of Peanut Oil: Synergistic Effect of Tween 20 and pH

AbstractTo destabilize the emulsion formed during aqueous extraction processing (AEP) of peanuts, Tween and Span series surfactants (Tween 20, Tween 80, Span 20, and Span 80) were used alone or in combination to break the emulsion. Results indicate that only Tween surfactants had a pronounced demulsifying effect that was dependent on Tween concentration and system pH. When 1.2 wt% Tween 20 aqueous solution was used for oil extraction at pH 10.0, the highest free oil yield was achieved at 76.1 %, which was similar to the oil recovery of using proteases as a destabilization agent. The results obtained using a model emulsion system containing peanut oil and Tween 20/peanut protein isolates (PPI) showed that when Tween 20 and PPI coexisted in extraction medium at pH 10.0, the dynamic interfacial tension and droplet size distribution curves were very similar to those when Tween 20 was used alone, suggesting that Tween 20 dominated at the interface, instead of PPI. Destabilization of the model emulsions relied on three important factors: inclusion of Tween 20 at the initial mixing stage, high pH, and a gentle mixing speed. A synergistic destabilization mechanism of using Tween 20 at high pH during AEP was proposed. The discovery of Tween 20 as an effective demulsifier significantly contributes to the development of AEP of oilseeds.

Both-branch amphiphilic polymer oil displacing system: Molecular weight, surfactant interactions and enhanced oil recovery performance

Hydrophobically modified polyacrylamidepolymers were synthesized by an aqueous micellar copolymerization, the N-benzyl-N-n-hexadecyl acrylamide being used as hydrophobic comonomer. The effect of the molecular weight (MW) and surfactant interactions on the rheological properties and oil-water interfacial activity were studied. The results indicate that increasing MW, the critical aggregation concentration of amphiphilic polymer will be decreased, and the network structural strength increased, which was measured by fluorescent probes, DLS and electron microscope. Mixing with the surfactant, sodium dodecyl sulfate (SDS), the solution viscosity increased at first and decreased later on with increasing the ratio of SDS concentration, and the dynamic interfacial tension between oil and water can be reduced by two orders of magnitude compared to the polymer solution only. The result of enhance oil recovery performance of the polymer/surfactant compound system is that it can significantly reduce the residual oil saturation due to the synergistic effect of the increasing viscosity and surface activity. The overall recovery efficiency was raised by 10–25% OOIP compared to the baseline polymers.

Effect of Sodium Carbonate on the Cloud Point in Alkyl Ether/Brine Systems: Apparent Relation with Dynamic Interfacial Tension Minimum

AbstractThe effect of Na2CO3 on the cloud point in Na2CO3/surfactant/brine was investigated using two series of nonionic surfactants, C13EOx and C17EOx. The cloud point, Tcp, was found to decrease linearly with increasing Na2CO3 concentration. This was attributed to Na+ and particularly to CO32−salting‐out effect. The slope a = dTcp/d[Na2CO3] became more and more negative as the degree of ethoxylation is increased, suggesting that the higher the number of ethylene oxide (EO) groups the stronger is the cloud point depression for a given increment in Na+and CO32−ions in solution. This was also illustrated by the linear variation of ΔTcp = Tcp,0 − Tcp,[Na2CO3] with the surfactant degree of ethoxylation.

The effect of ethoxylated nonyl phenols on the interfacial tension between crude oil and water

ABSTRACTIn this study, the effect of ethoxylated nonyl phenols with ethoxy group numbers 4 and 9 (nonyl phenol 4 and nonyl phenol 9), were investigated on the interfacial tension between crude oil and water. The interfacial tensions decreased significantly in a concentration range of 0–1.25 g.l–1. By increasing sodium chloride concentration, the time which was required to reach equilibrium interfacial tension was reduced. Therefore, sodium chloride affected the dynamic interfacial tension. However, ethoxylated nonyl phenols resisted against change of salinity. The effect of mixed surfactants on the decreasing of the interfacial tension was more than an individual surfactant, because of the synergism. The most effective mixture of a two surfactants system was observed when mass ratio of nonyl phenol 9 and nonyl phenol 4 was 0.5.

Study on synthesis and performance of lignin polyether sulfonate surfactants for enhanced oil recovery

ABSTRACTLignin polyether sulfonate surfactants with lipophilic groups of different polymerization degree were synthesized and the dynamic interfacial tension (IFT) between solutions of these surfactants prepared with brine and two kinds of oil from Daqing and Huabei Oilfields were measured, respectively. The results showed that the surfactants were effective to lower the IFT between brine and the two kinds of oil. The structures of synthesized surfactants were analyzed by Fourier transform infrared spectroscopy. The contents and hydrophilic–lipophilic balance values of lignin polyether sulfonates were studied to evaluate the basic physicochemical properties of synthesized surfactants.

Mixed adsorption mechanism for the kinetics of BLG interfacial layer formation at the solution/tetradecane interface

The adsorption kinetics of β-lactoglobulin (BLG) at the water/tetradecane (W/TD) interface as studied by drop profile analysis tensiometry is significantly controlled by the diffusional transport in the aqueous solution bulk. However, due to the contact with the hydrophobic oil phase the protein molecules change their conformation in order to adapt to the interfacial environment. This conformational change can be expressed via the adsorption activity constant. The analysis of the dynamic interfacial tensions leads to much lower activities at short adsorption times and low surface coverages. This allows to conclude that in the early stage of the adsorption layer formation the structure of the BLG adsorption layer at the W/TD interface is similar to that at the water/air (W/A) interface.

Mixtures of saponins and beta-lactoglobulin differ from classical protein/surfactant-systems at the air-water interface

Interactions between surfactants and proteins have been intensively studied in the past because their interactions in food and cosmetic products can tremendously alter the product properties. Recent studies have shown that Quillaja saponins (QS) have very different interfacial properties in comparison to common low-molecular weight surfactants. It was reported that QS forms highly elastic interfacial films, adsorbs more slowly to the interface and cannot as easily be classified as an ionic or non-ionic surfactant. However, the mechanism of interaction between QS and proteins like beta-lactoglobulin (β-LG) is still to be understood. For this purpose the present study aimed to explore the interactions between Quillaja saponin and beta-lactoglobulin in the bulk and at the air/water-interface. At this purpose, interfacial properties were characterized with dynamic interfacial tension, short-term adsorption, shear and dilational oscillation experiments and the results were compared to foam properties. To study molecular interactions fluorescence quenching was analyzed and sequential two-fluid needle experiments were performed to get more insights on depletion of β-LG by QS.The presence of β-LG lowered the dilational viscoelasticity of the mixed films. Although the interfacial film was weakened by β-LG the dilational elasticity was still very high and did not result in reduced foam stability. Interfacial shear results suggest that QS and β-LG can interact at the interface probably through hydrogen bonds and/or hydrophobic interactions. We determined 1.7 binding sites on β-LG in the bulk which are accessible for complex formation for QS by fluorescence quenching experiments. The findings of this work can contribute to a better understanding of the properties of complex systems with mixtures of natural surfactants and proteins.

Effect of Different Surfactants on the Interfacial Behavior of the n-Hexane-Water System in the Presence of Silica Nanoparticles.

This paper presents the effect of negatively charged silica nanoparticles (NPs) on the interfacial tension of the n-hexane-water system at variable concentrations of four different surfactants, viz., an anionic surfactant, sodium dodecyl sulfate (SDS), a cationic surfactant, cetyltrimethylammonium bromide (CTAB), and two nonionic surfactants, Tween 20 and Triton X-100 (TX-100). The presence of negatively charged silica nanoparticles is found to have a different effect depending on the type of surfactant. In the case of ionic surfactants, SDS and CTAB, silica NPs reduce the interfacial tension of the system. On the contrary, for nonionic surfactants, Tween 20 and TX-100, silica NPs increase the interfacial tension. The increasing/decreasing nature of the interfacial tension in the presence of NPs is well supported by the calculated surface excess concentrations. The diffusion kinetic control (DKC) and statistical rate theory (SRT) models are used to understand the behavior of dynamic interfacial tension of the surfactant-NP-oil-water system. The DKC model is found to describe the studied surfactant-NP-oil-water systems more aptly.

Two new quantitative technical criteria for determining the minimum miscibility pressures (MMPs) from the vanishing interfacial tension (VIT) technique

In this paper, two new quantitative technical criteria are developed to determine the minimum miscibility pressures (MMPs) from the vanishing interfacial tension (VIT) technique: the linear correlation coefficient (LCC) criterion and the critical interfacial thickness (CIT) criterion. Six series of dynamic interfacial tension (IFT) tests for the dead and live light crude oil–CO2 systems are conducted under different test conditions. The MMP is determined when the LCC is smaller than 0.990 or the interfacial thickness is smaller than 1.0nm for the first time. The determined respective MMPs of 12.9MPa and 13.2MPa for the dead and live light crude oil–CO2 systems from the VIT technique agree well with the MMPs of 12.4–12.9MPa for the former system from the coreflood tests and fairly well with 15.2–15.4MPa for the latter system from the slim-tube tests. In addition, the specific effects of three experimental factors on the determined MMPs are studied by applying the two new quantitative technical criteria: (a) the initial vs. equilibrium IFTs; (b) the oil composition; and (c) the initial gas–oil ratio (GOR). The measured initial other than equilibrium IFTs are found to be sufficiently accurate to determine the MMP from the VIT technique. This is because the pendant oil drops used in the dynamic IFT tests are so small that they can be saturated with CO2 almost instantaneously. The live light crude oil pre-saturated with CH4-dominated hydrocarbons has a slightly higher MMP in comparison with the dead light crude oil. Moreover, the initial GOR effect on the MMP is found to be negligible in a lower GOR range (1:1–10:1 in volume) or in a large CO2 concentration range (31.76–94.69mol%). It becomes pronounced in a higher GOR range (200:1–4000:1 in volume) or in an extremely small range of high CO2 concentrations (98.79–99.99mol%).

Emulsion stability of surfactant and solid stabilized water-in-oil emulsions after hydrate formation and dissociation

Hydrates are ice-like crystalline compounds that can cause plugging of crude oil pipelines. Stable water-in-oil emulsions aid in preventing hydrate particle agglomeration and hydrate plug formation in crude oil pipelines. The type of stabilizers present in water-in-crude oil emulsions also influences hydrate formation. Therefore, the effect of hydrate formation and dissociation on the stability of water-in-oil emulsions stabilized using either surfactants or solid particles was investigated. In addition, the difference in the effect of hydrate formation and dissociation on water-in-oil emulsions stabilized using solid particles of varying hydrophobicity was investigated. Furthermore, the effect of hydrate formation and dissociation on droplet size of the water-in-oil emulsions was quantified. The results showed that, the water-in-oil emulsions stabilized using moderately hydrophobic solid particles resisted emulsion destabilization, after hydrate formation and dissociation, unlike water-in-oil emulsions that were stabilized using either surfactants or highly hydrophobic solid particles. Also, after hydrate dissociation, for surfactant stabilized emulsions, the droplet size of water in the residual emulsion increased by more than 85% as compared to the droplet size before hydrate formation. On the contrary, for solid stabilized emulsions, no significant change in the droplet size of the residual emulsion was observed after hydrate dissociation as compared to the water-in-oil emulsion before hydrate formation. A conceptual mechanism was proposed to explain the observed difference in the stability of solid stabilized water-in-oil emulsions when subjected to hydrate formation and dissociation. Additionally, dynamic interfacial tension measurements were carried out to explain the difference in the initial droplet size of solid stabilized and surfactant stabilized water-in-oil emulsions.