Dilute Surfactant Research Articles

Equilibrium Contact Angle and Adsorption Layer Properties with Surfactants.

The three-phase contact line of a droplet on a smooth surface can be characterized by the Young equation. It relates the interfacial energies to the macroscopic contact angle θe. On the mesoscale, wettability is modeled by a film-height-dependent wetting energy f( h). Macro- and mesoscale descriptions are consistent if γ cos θe = γ + f( ha), where γ and ha are the liquid-gas interface energy and the thickness of the equilibrium liquid adsorption layer, respectively. Here, we derive a similar consistency condition for the case of a liquid covered by an insoluble surfactant. At equilibrium, the surfactant is spatially inhomogeneously distributed, implying a nontrivial dependence of θe on surfactant concentration. We derive macroscopic and mesoscopic descriptions of a contact line at equilibrium and show that they are consistent only if a particular dependence of the wetting energy on the surfactant concentration is imposed. This is illustrated by a simple example of dilute surfactants, for which we show excellent agreement between theory and time-dependent numerical simulations.

A review of shampoo surfactant technology: consumer benefits, raw materials and recent developments.

Surfactants form the core of all shampoo formulations, and contribute to a wide range of different benefits, including cleansing, foaming, rheology control, skin mildness and the deposition of benefit agents to the hair and scalp. The purpose of this review was to assist the design of effective, modern, shampoo surfactant technologies. The mechanisms through which surfactants help deliver their effects are presented, along with the appraisal techniques through which surfactant options can be tested and screened for product development. The steps that should be taken to select the most appropriate blend of surfactants are described, and useful information on the most widely used surfactants is provided. The review concludes with an examination of recent developments in 'greener' surfactants, 'sulphate-free' technologies and structured liquid phases for novel sensory properties and for suspending benefit agents.

A Novel Method with Dilute Surfactant Flooding by Considering the Effect of Time and Temperature on Crude Oil Aging, Experimental Study on Heavy Oil of Bangestan

Wettability alteration has been a sophisticated issue for scientists and reservoir engineers since early 20th century; thus, many investigations have been carried out to determine wettability and enhance it to ideal conditions, which leads to improvement in oil recovery. Dilute surfactant flooding has been approved as one of the noteworthy methods in chemical flooding. Several petroleum reservoirs were recognized as suitable nominees for surfactant/water flooding when screening criteria were established. Surfactant flooding was applied to mobilize the trapped oil in reservoirs. The key mechanism to enhance oil recovery by surfactant flooding was defined as rock wettability alteration. Experimental investigations into the impact of aging and temperature on wettability alteration were performed. Subsequently, core flooding test of surfactant was performed to define the effect of thinned cationic surfactant slug with cyclic 7 days technique (Multi-slug injection) on displacement sweep efficiency in the carbonate core of Bangestan reservoir with its heavy oil reservoir. Moreover, contact angle and interfacial tension (IFT) measurements were made to gain the supplementary information for a surfactant/waterflooding. The best concentration of C19TAB was determined by measuring interfacial tension values of the crude oil in contact with surfactant solutions prepared in synthetic brackish water. Results displayed a decrease in residual oil saturation by changing the contact angle and IFT reduction between oil and water. Moreover, aging was known as a significant constraint to change the wettability index to make similar oil-wet condition. Besides, laboratory experiments verified that the influence of wettability alteration was higher than IFT reduction.

Effect of inorganic and organic counterions on interfacial properties of oleic acid-based gemini surfactants

We studied the effect of counterion species of oleic acid-based gemini surfactants with carboxylate headgroups. Adsorption and self-aggregation properties were investigated by static surface tension, pyrene fluorescence, dynamic light scattering and phase diagram measurements. We found that, in the case of inorganic counterions (Li+, Na+, K+, and Cs+), a decreased ion size leads to a decreased critical micelle concentration (cmc) as well as a decreased area per surfactant molecule adsorbed at the air/aqueous solution interface (Acmc). The smaller inorganic counterions (hard acid) can interact with the carboxylate headgroups (hard base), and hence reduce the head-to-head electrostatic repulsion. The smaller counterions also induced the lower phase transition concentration from an optically isotropic solution (L1) phase to a hexagonal liquid crystal (H1) phase. In the case of organic counterions (monoethanolamine (MEA) and diethanolamine (DEA)), the micellization behavior was predominantly affected by the hydrophobicity of the counterions, whereas the hydrated ion size was a key parameter determining the molecular packing at the air/solution interface. In addition, we found a structural transformation from larger aggregates to smaller ones (micelles) to occur for the organic counterion systems at dilute surfactant concentrations.

Microdroplet Generation with Dilute Surfactant Concentration in a Modified T-Junction Device

Emulsions with very low surfactant concentration or without surfactant are highly required in many fields. Microfluidics have proven to be a promising emulsion preparation method. However, for the fresh interface formation during microfluidic droplet generation, excessive amounts of surfactant are also demanded to speed up surfactant transfer and drive low interfacial tensions. Here we present a newly designed capillary embedded T-junction microdevice to intensify surfactant mass transfer for microdroplet generation. Within the device, surfactant molecules are concentrated onto the tip of the droplet breakup very fast by hydrodynamic forces, leading to extremely low dynamic IFTs temporarily. Microdroplets as small as 15 μm are generated with surfactant concentrations significantly lower than their CMC values, when the concentrations of SDS, Tween 20, and F68 are only 0.05 wt % (1/6 CMC), 0.20 wt % (4/7 CMC), and 0.20 wt % (2/3 CMC) individually. The novel method would be promising in fields of biocompatib...

Dynamics of falling droplet and elongational properties of dilute nonionic surfactant solutions with drag-reducing ability

The dynamics of the falling droplet through a nozzle for dilute nonionic surfactant (oleyl-dimethylamine oxide, ODMAO) aqueous solutions with viscoelastic and drag-reducing properties were investigated at different concentrations of ODMAO solutions Cs = 500, 1000, and 1500 ppm by weight. The effects of the flow rate and tube outer diameter on the length of the filament, which was the distance between the tube exit and the lower end of a droplet at the instant when the droplet almost detached from the tube, were clarified by flow visualization measurements by a high-speed video camera. Two types of breaking-off processes near the base of the droplet and within the filament were classified by the Ohnesorge number Oh and the Weber number We. In the regime of the higher Oh and We, the length of the filament became drastically larger at Cs = 1000 and 1500 ppm, whose high spinnability represented the strong viscoelasticity of ODMAO solutions. In the case where the filament was broken up near the lower end of the neck and thinning in time, the thinning of the diameter of the filament was measured by a light-emitting diode micrometer. As for the elasto-capillary thinning of dilute nonionic surfactant solutions, the initial necking process was similar to that of Newtonian fluids and then followed the exponential thinning like polymer solutions. The apparent elongational viscosity of the dilute nonionic surfactant solution was evaluated in the elasto-capillary thinning regime, in which the elongation rate was almost constant. At Cs = 1000 and 1500 ppm, the Trouton ratio, which was the ratio of the apparent elongational viscosity to the shear viscosity, was found to be several orders of magnitude larger than that of Newtonian fluids, while the shear viscosity measured by the capillary viscometer was almost the same order of the Newtonian fluids. The higher elongational property would be closely related to the higher drag-reducing ability of dilute nonionic surfactant solutions.

Dynamic network modeling of displacement and oil recovery in dilute surfactant flooding

ABSTRACT Dynamic network model, validated by comparing with the previous studies, is presented for investigating pore-scale displacement and oil recovery in dilute surfactant flooding (DSF), which is an economically enhanced oil recovery (EOR) technology. The objective is to study the effects of water/oil interfacial tension (IFT), injection rate, and oil viscosity on oil recovery in DSF and the corresponding water flooding (WF). The results indicate that oil recovery increased with the reduction of IFT and the increase of the viscosity ratio. Displacement patterns also reveal that relatively large sweep efficiency can be achieved by using DSF.

Adsorption Behavior of Fatty Alcohol Ether Sulfonate at Different Interfaces

AbstractThe equilibrium surface tension, dynamic surface tension, and interfacial tension (IFT) of fatty alcohol ether sulfonates (CmEnSO) were measured to investigate their adsorption behavior. The effect of NaCl and CaCl2 concentrations on the IFT was also studied. The results showed that the number of EO units has no significant effect on the critical micelle concentration (CMC) and CMC decreases with increasing the length of the hydrophobic group. The surface tension at the CMC increases with the increase of the number of EO units and the length of the hydrophobic group. At dilute surfactant concentration, the adsorption process for CmEnSO is controlled by diffusion; at higher concentration, it becomes a mixed diffusion‐kinetic adsorption mechanism. The IFT between CmEnSO solution and dodecane remains around 10−1 mN/m over a wide range of electrolyte concentrations (NaCl concentration from 25 to 210 g/L, CaCl2 concentration from 0.1 to 10 g/L).

Turbid and transparent shear-induced structures in dilute cationic surfactant solutions

The advection of shear-induced structures (SISs) was visualized for cationic dilute surfactant solutions in a rectangular channel flow and an impinging wall jet. The SISs visualized here were transparent and distinguished as the macroscopic dark structures in contrast to the background light-scattering micelles. The SIS phase was separated from the solution and behaved like an elastic gel. In the rectangular channel flow, the threadlike SISs of centimeter order length appeared to be aligned in the direction of the flow, and the average thread length was increased with the Reynolds number and turbulent drag reduction. Although the origin of the threadlike SISs was not clear in the fully developed rectangular channel, the impinging flow developed in the streamwise direction and revealed the growing process of the SISs. The viscoelastic solution with equimolar counterions rolled up the wall SIS layer in the impinging flow, and built the cylindrical sheet-like SIS. In contrast, the solution with excess counterions presented the generation of a transparent gel-like SIS from a turbid wall shear layer, and produced a ring-like SIS. The shapes of the phase-separated SISs were dependent on both flow geometry and fluid viscoelasticity.

Study on Flow Characteristics of Dilute Polymer and Surfactant Solutions

Study on Flow Characteristics of Dilute Polymer and Surfactant Solutions

Analysis of an organized turbulent structure using a pattern recognition technique in a drag-reducing surfactant solution flow

This work presents the investigation for an organized turbulent structure in a drag-reducing flow of dilute surfactant solution by utilizing a particle image velocimetry system to perform the pattern recognition technique on a trajectory in four quadrants of streamwise and wall-normal velocity fluctuations. The pattern recognition is added to a new algorithm in order to directly capture the spatial rotation motion. The Reynolds number based on the channel height and bulk mean velocity was set to 1.5×104. Surfactant solution with a weight concentration of 150ppm was employed and the drag reduction rate was 65%. In the drag-reducing flow, we observe increased frequencies of occurrence of the flow events that correspond to a meandering motion in the wall-normal direction of the high-and low-speed regions. Three findings from investigation of the ensemble-averaged Reynolds shear stress and vortex structure are as follows: (i) the Reynolds shear stress in the large fluctuation range occurs in the narrow region; (ii) Size, strength, arrangement and inclination in the spatial vortex structure in the drag-reducing flow differ from those of the water; and (iii) all trajectory contributions for the wall friction coefficient decrease. Finally, we interpreted that the viscoelasticity characterizing the viscoelastic stress and relaxation time in rheological properties of the flow changes specific elementary vortex for the drag-reducing flow, and the trajectories of each flow pattern change drastically.

The effects of interfacial tension, injection rate, and permeability on oil recovery in dilute surfactant flooding

ABSTRACTSurfactant flooding as a potential enhanced oil recovery technology in depleted reservoirs after water flooding has been documented for several decades and has attracted extensive attention. This research explored the effect of interfacial tension among crude oil and surfactant, injection rate, and permeability on oil recovery in dilute surfactant flooding. The results indicated that the additional oil recovery increased with the reduction of the interfacial tension and the increase of the permeability. The additional oil recovery increased and later decreased with the increase of injection rate. The research is instructive for surfactant flooding application for enhanced oil recovery.

Adsorption kinetics of the ionic surfactant decanoic acid

The adsorption kinetics of ionic surfactant decanoic acid was examined. Dynamic and equilibrium surface tensions (ST) were measured using a video-enhanced pendant bubble tensiometer. The equilibrium ST data and the complete ST relaxation profiles were compared with theoretical profiles predicted by both non-ionic and ionic models. The quasi-equilibrium approach was used in the ionic model to describe the electric field in the electrical double layer. Both non-ionic and ionic generalized-Frumkin models predict the equilibrium and dynamic ST data very well. Using the ionic model, a comparison between the dynamic ST data and the theoretical ST profiles gave a diffusivity of 5.5×10−6cm2/s. The adsorption of decanoic acid onto the air–water interface was determined to be diffusion controlled. Dynamic surface properties (Γ and ψs), the electrical potential ψ(r, t) in the double layer, and the double layer thickness λ(C, t) were also evaluated. It was found that the surface charge density increases very quickly at the early stages (∼1s) of the surfactant adsorption process. Additionally, the electrical surface potential data implied that the surface charge density becomes significantly stronger at very dilute surfactant concentrations, where π is less than 1mN/m.

Study on the adsorption and aggregation of dilute gemini surfactant solutions

ABSTRACTAs a function of temperature in aqueous solutions, the adsorption and aggregation of N,N’-bis (tetradecyl dimethyl)-1,2-dibromide-ethanediyl ammonium salt (GS14-2-14) and N,N’-bis (hexadecyl dimethyl)-1,2-dibromide-ethanediyl ammonium salt (GS16-2-16), were researched with drop-volume technique and conductometry, respectively. The results of surface tension measurements, which were analyzed by originally developed thermodynamic equations, illustrate that GS14-2-14 has a better surface activity and arranges more tightly in the adsorbed film than GS16-2-16. The data of conductivity were used to find critical micelle concentration (cmc) and counterion binding degree of micelle (β). Thermodynamic parameters of micellization were also obtained from the temperature dependence of cmc values. From the study, it is discovered that the micellization process is spontaneous and exothermic in nature and it is mainly driven by entropy.

The effect of oil properties on oil recovery in dilute surfactant flooding

ABSTRACTIn this study, five different simulated oils were obtained, and their viscosities and interfacial tension between simulated oil and surfactant aqueous solution were measured. The core displacement experiments were carried out to explore the effect of oil properties on oil recovery in dilute surfactant flooding. Single-core experimental results indicated that a relatively low oil/water interfacial tension level might have a bigger contribution to improve oil recovery, despite a favorable mobility control being of importance. Parallel cores experimental results illustrated that the higher the permeability contrast, the lower the oil/water interfacial tension that was required to mobilize the low-permeability core.

Dynamic and Energy Analysis on the Viscosity Transitions with Increasing Temperature under Shear for Dilute CTAC Surfactant Solutions

Quite dilute CTAC/NaSal surfactant solution system (0.78–3.13 mmol/L) has been investigated with increasing temperature under shear for the first time. The experimental temperature range is very wide (10–60 °C) and astride the Krafft point (TK). Even at a temperature 8 °C lower than TK, the solution can remain in a transparent and homogeneous metastable state, due to the temperature-induced formation of higher ordered self-assemblies. Different shear rates induce very different assembly transitions for the same solution with same temperature increasing rate (r). A special “two peaks” phenomenon appears under the following conditions: concentration of 1.25–2.50 mmol/L, shear rate of 5 s–1 and r of 0.0033–0.0333 °C/s. An equation is established to describe the relations between the change in rodlike micelle size with time (dR/dt) and the combined effects of shear and temperature. It can be found that either effect of shear or temperature has two aspects on dR/dt, therefore, the micellar size actually depends on the “matching-degree” of the two effects under our experimental conditions. Besides, the total free energy change in the surfactant solution system is analyzed to study the simultaneous effects of shear and temperature from energy viewpoint.

Dynamic wetting failure in surfactant solutions

The influence of insoluble surfactants on dynamic wetting failure during displacement of Newtonian fluids in a rectangular channel is studied in this work. A hydrodynamic model for steady Stokes flows of dilute surfactant solutions is developed and evaluated using three approaches: (i) a one-dimensional (1D) lubrication-type approach, (ii) a novel hybrid of a 1D description of the receding phase and a 2D description of the advancing phase, and (iii) an asymptotic theory of Cox (J. Fluid Mech., vol. 168, 1986b, pp. 195–220). Steady-state solution families in the form of macroscopic contact angles as a function of the capillary number are determined and limit points are identified. When air is the receding fluid, Marangoni stresses are found to increase the receding-phase pressure gradients near the contact line by thinning the air film without significantly changing the capillary-pressure gradients there. As a consequence, the limit points shift to lower capillary numbers and the onset of wetting failure is promoted. The model predictions are then used to interpret decades-old experimental observations concerning the influence of surfactants on air entrainment (Burley & Kennedy, Chem. Engng Sci., vol. 31, 1976, pp. 901–911). In addition to being a computationally efficient alternative for the rectangular geometries considered here, the hybrid modelling approach developed in this paper could also be applied to more complicated geometries where a thin air layer is present near a contact line.

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.

Surfactant with and without bronchoalveolar lavage in an experimental model of meconium aspiration syndrome.

To assess the effect of surfactant administration, preceded or not by bronchoalveolar lavage (BAL) with dilute surfactant, on pulmonary function in experimental severe meconium aspiration syndrome. Twenty-one newborn pigs received 20% meconium in saline intratracheally and were randomly allocated to one of three groups: I, control; II, surfactant only (poractant alfa, 200 mg/kg); or III, dilute surfactant BAL followed by 125 mg/kg surfactant. Arterial blood gases (ABGs), lung compliance, and resistance were assessed. Thirty minutes after treatment, mean PaO2 (mm Hg) increased to 72 in group I, to 106 in group II and to 172 in group III (P=0.01). After 3 h, mean PaO2 (mm Hg) was 70 in group I, 95 in group II and 198 in group III (P<0.01). After 6 h, it was 79 in group I, 110 in group II, and 217 in group III (P=0.01). From the 30-min point onward, there were significant differences among treatment groups in all other parameters and at every point of assessment, except for compliance and resistance 3 h after treatment. BAL with dilute surfactant, followed by an additional dose of surfactant, produced significant improvements in ABGs and pulmonary mechanics as compared with a single dose of surfactant.

Equilibrium and dynamic surface tension properties of salt-free catanionic surfactants with different hydrocarbon chain lengths

The equilibrium and dynamic surface tension properties of a series of 1:1 salt-free catanionic surfactants (alkyltrimethylammonium decanoate) were investigated; and, the influence of the length of hydrocarbon chain of cationic part (carbon number of 10, 12, 14, 16, 18, respectively) on the surface properties was discussed. The plot of the logarithm of the critical aggregation concentration (cac) against the carbon number showed a linear decrease with an increase in chain length. On the basis of the slope of this plot, it was found that the variation of cac with the chain length is smaller for salt-free catanionic surfactants (C+n–C−10) than that for single anionic or cationic surfactants. The surface tension at the cac was quite low, much lower than that of single cationic or anionic surfactants at cmc. At dilute surfactant concentration, the adsorption process is diffusion-controlled adsorption; at higher concentration (above cac), it became the mixed diffusion-kinetic mechanism. The diffusion rate of the monomer for the salt-free catanionic surfactants was lower than that of conventional cationic or anionic surfactants, due to a larger molecular size. Furthermore, it was confirmed that the kinetic energy of adsorption at the gas/solution interface decreased with an increase in the hydrocarbon chain length.