Increasing Surfactant Concentration Research Articles

Interactions of Surfactants with Biomimetic Membranes. 1. Ionic Surfactants

AbstractWhen impregnated with esters of fatty acids, nitrocellulose filters can be used as a biomimetic membrane. They are easy to make, cheap, and may be used not only as an imitation of biological membranes but also as a sensor to characterize surfactant interactions with dirty fabric. These impregnated filters when fixed in a thermostatically controlled chamber separated into two compartments that contain stirred aqueous solutions by the filter, may be considered as a simple model of a laundry machine. The results revealed that the addition of ionic surfactants into one of the solutions led to the formation of transmembrane electrical potential that is proportional to the logarithm of surfactant concentration. Thus, our biomimetic membranes can be used as electrochemical sensors to detect and measure surfactant concentration. When concentration is near the critical micelle concentration (CMC), a new phenomenon was observed, i.e., spontaneous oscillations of both transmembrane potential and transmembrane current, which mimics the opening and closing of aqueous channels in biological membranes. A further increase of surfactant concentration les to a sharp 100‐fold decrease of transmembrane electrical resistance and the disappearance of any transmembrane voltage. This effect, explained by the washing out of fatty acids from the pores, may be used for screening and development of new detergents.

Strong Modulation of Short Wind Waves and Ka-Band Radar Return Due to Internal Waves in the Presence of Surface Films. Theory and Experiment

Strong variability of Ka-band radar backscattering from short wind waves on the surface of water covered with surfactant films in the presence of internal waves (IW) was studied in wave tank experiments. It has been demonstrated that modulation of Ka-band radar return due to IW strongly depends on the relationship between the phase velocity of IW and the velocity of drifting surfactant films. An effect of the strong increase in surfactant concentration was revealed in convergent zones, associated with IW orbital velocities in the presence of a “resonance” surface steady current, the velocity of which was close to the IW phase velocity. A phenomenological model of suppression and modulations in the spectrum of small-scale wind waves due to films and IW was elaborated. It has been shown that backscatter modulation could not be explained by the modulation of free (linear) millimeter-scale Bragg waves, but was associated with the modulation of bound (parasitic) capillary ripples generated by longer, cm–dm-scale waves—a “cascade” modulation mechanism. Theoretical analysis based on the developed model was found to be consistent with experiments. Field observations which qualitatively illustrated the effect of strong modulation of Ka-band radar backscatter due to IW in the presence of resonance drift of surfactant films are presented.

Abstract P-38: Tunable Soft Networks of Wormlike Micelles and Clay Particles

Background: Over the past few decades, there has been a great deal of interest in the aqueous self-assembly of surfactant molecules into giant wormlike micelles (WLMs). These cylindrical aggregates undergo reversible breakdown processes and in favorable cases can grow up to few tens of micrometers that is comparable with the length of high molecular weight polymer. The viscoelastic properties of WLMs can be easily modified by different additives like salts or polymers. A new emerging research area consists of tuning the WLM solution properties by inorganic nanoparticles. It suggests, in particular, the use of networks of entangled WLMs as a matrix for producing soft nanocomposites with different kinds of embedded nanoparticles that are promising for controlled release, template synthesis, and oilfield applications. These materials can combine adaptive rheological properties of the WLM matrix and the functionality of nanofiller. Methods: Rheometry and cryo-transmission electron microscopy were combined to investigate the structure and properties of mixed WLMs of zwitterionic oleylamidopropyl dimethyl betaine and anionic sodium dodecyl sulfate surfactants and platelike particles of bentonite clay. Results: This system demonstrates the formation of giant linear long-lived WLMs, which even at extremely low surfactant concentrations reach a sufficient length to entangle with each other and form a temporally persistent network. The stability of these micelles can be due to electrostatic attraction between the headgroups of the anionic and zwitterionic surfactants and favorable volume/length hydrophobic ratio in the surfactant mixture. At increasing surfactant concentration, the long-lived linear micelles transform into fast-breaking branched micelles. Stable viscoelastic suspensions of clay particles in semi-dilute solutions of WLM were elaborated. They represent a novel type of soft nanocomposite with the tunable matrix. Structural studies revealed that the clay is dispersed in a dense network of entangled WLM in the form of 100-nm tactoids. Rheological investigations demonstrated that clay particles can induce an increase of viscosity and relaxation time by up to one order of magnitude. The effect of the clay becomes more pronounced with increasing content of anionic surfactant, when the micelles become branched. This behavior was explained by the stabilization of micelle-nanoclay junction points due to the screening of the repulsion between positively charged fragments of zwitterionic head groups by added anionic surfactant. Conclusion: The pronounced effect of nanoparticles on the viscoelasticity of the network formed by branched WLMs was observed for the first time. The nanoparticles-WLM junctions were confirmed by cryo-TEM data. The elaborated systems are of interest for many industrial applications.

Investigation on Hydrate Growth at the Oil-Water Interface: In the Presence of Wax and Surfactant.

Natural gas hydrates can readily form in deep-water-oil production processes and pose a great threat to subsea pipeline flow assurance. The usage of surfactants and hydrate antiagglomerants is a common strategy to prevent hydrate hazards. In water/wax-containing oil systems, hydrate coexisting with wax could lead to more complex and risky transportation conditions. Moreover, the effectiveness of surfactants and hydrate antiagglomerants in the presence of wax should be further evaluated. In this work, for the purpose of investigating how wax and surfactants could affect hydrate growth at the oil-water interface, a series of microexperiments was conducted in an atmospheric visual cell where the nucleation and growth of hydrates took place on a water droplet surrounded by wax-containing oils. On the basis of the experimental phenomena observed using a microscope, the formation of a hydrate shell by lateral growth, the collapse of a water droplet after hydrate initial formation, and the formation of hollow-conical hydrate crystals were identified. These experimental phenomena were closely related to the concentration of wax and surfactant used in each case. In addition, it was shown that the effectiveness of the surfactant could be weakened by wax molecules. Moreover, there existed a critical wax content above which the effectiveness of the surfactant was greatly reduced and the critical wax content gradually increased with increasing surfactant concentration. This work could provide guidance for hydrate management in wax-containing systems.

Interaction of Bis-Guanidinium Acetates Surfactants with Bovine Serum Albumin Evaluated by Spectroscopy

Abstract The interactions between cocopropane bis-guanidinium acetates, tallowpropane bis-guanidinium acetates with bovine serum albumin (BSA) in an aqueous solution were studied by fluorescence and circular dichroic spectroscopy measurements. The aim of the study was to elucidate the influence of the hydrophilic group and the length of the hydrophobic chain of these surfactants on the mechanism of binding to BSA. The results revealed that for both surfactants, at low concentrations, the Stern–Volmer plots had an upward curvature and at high concentrations, the quenching efficiency was decreased with increase in surfactant concentration. Different thermodynamics parameters demonstrated the existence of hydrogen bond and van der Waals force which acting as binding forces. Static quenching was observed among the protein and surfactant. The conformation of BSA was changed at higher surfactant concentrations as shown by synchronous fluorescence and CD spectroscopy. This work reveals the mechanism and binding characteristics between guanidine surfactants and protein, and provided the basis for further applications of surfactants.

Cobalt removal from an industrial effluent by foam fractionation

In this study, the removal of cobalt from an effluent was investigated probably for the first time by foam fractionation. Foam fractionation is considered as a green method because of its friendly nature, high removal efficiency, costs effectiveness and non-hazardous nature. Sodium dodecyl sulfate (SDS) was used as an anionic surface-active agent and the effect of gas flow rate, the initial concentrations of surfactant and cobalt and pH on the cobalt removal efficiency was investigated. The results showed that by increasing surfactant concentration and gas flow rate, the cobalt removal efficiency would be improved however, the cobalt concentration in foamate would decrease at high gas flow rates. High gas flow rates generally produce dilute foamate. Drainage of the interstitial bulk fluid that is entrapped between the foam bubbles has a key importance in the normal performance of the foam fractionation operation. Experiments showed that the well-drained foams are low in volume and high in Co2+ leading to an easier separation of their ingredients that usually follows. The efficiency reached the highest when cobalt feed concentration was about 1 mg/L, but dropped gradually in higher concentrations. By increasing pH to around 5, high removal efficiency was achieved and then decreased again. The optimum conditions for high cobalt removal efficiency were obtained when SDS concentration was about 100 mg/L and the initial cobalt concentration was below and close to 1 mg/L. The results of experiments revealed that the amount of cobalt removed per unit weight of SDS was higher for low [SDS]/[Co2+] ratios. They also showed that the air–liquid interface coverage by surface excess solute ions would not be more that 5% of the total area. Under optimum conditions for cobalt removal pH value and gas flow rate were found to be around 5 and 9 L/h, respectively. Under these conditions the removal efficiency was shown to be 99.4%.

Novel epigallocatechin gallate-based polyether surfactants: Synthesis, characterization and demulsification properties

Natural polyphenols such as tannins, procyanidins, and cardanol are widely used in the field of surface chemistry. To further explore the application of the other natural polyphenols, epigallocatechin gallate (EGCG) derived from green tea was employed. EGCG is an ideal choice to achieve a hyperbranched surfactant. A precursor (EGA) was first obtained by the reaction among the EGCG, formaldehyde, and tetraethylenepentamine (TEPA). EGA surfactants were synthesized in the high-pressure kettle by anionic polymerization with EGA, propylene oxide (PO) and ethylene oxide (EO). The good consistency between the designed PO/EO ratios of EGA surfactants and the theoretical values were proved by 1H NMR spectra. The increase of micelle size with the increase of surfactant concentration and NaCl concentration was observed both by dynamic light scattering and TEM. Result shows EGA surfactants with higher absolute value of ∆G°ads and high interfacial activity have potential demulsification applications. As a result, toward aging oil emulsions of the South China Sea Oilfield, the surfactants exhibited excellent demulsification performance. The dehydration ratio reached 94.3% at a low concentration of 100 mgL−1 for 100 min at 70°C, while the commercial demulsifier SP169 only reached 86.9%. This emulsion could be dehydrated completely at even higher temperature at 80°C as well as higher dosage in 150 mgL−1. Meanwhile, the demulsification ratios of crude oil emulsions and aging oil emulsions produced from Bohai Oilfield reached 94.0% and 95.0%, respectively. Coming from the waste oil after demulsification, aging oil emulsions have more additives than crude oil emulsions, therefore the former is more stable. In addition to the above high interfacial activity, this excellent demulsification performance may result from the assistance of polyphenol structure and multiple branches of EGA surfactants. The demulsification of three above emulsions demonstrated that although there exist great differences in properties of emulsions, EGA surfactants exhibit the universality of efficient demulsification.

An Advanced Material with Synergistic Viscoelasticity Enhancement of Hydrophobically Associated Water‐Soluble Polymer and Surfactant

In order to prepare materials with controllable properties, changeable microstructure, and high viscoelasticity solution with low polymer and surfactant concentration, a composite is constituted by adding surfactant (sodium dodecyl sulfate, SDS) to hydrophobically associated water-soluble polymer (abbreviated as PAAC) solution. The viscoelasticity, aggregate microstructure, and interaction mechanism of the composite are investigated by rheometery, Cryo-transmission electron microscopy (Cryo-TEM), and fluorescence spectrum. The results show that when the mass ratio of polymer to surfactant is 15:1, the viscosity of the composite reaches the maximum. The viscosity of the composite system increases hundredfold. The viscosity plateau under dynamic shear is generated. The composite has the properties of high viscoelasticity, strong shear thinning behavior, and good salt tolerance, and temperature resistance. The maximum viscosity of the composite is shown at the salinity of 20000mg L-1 . In addition, there is no phase separation in the composite with the increase of polymer and surfactant concentration, which indicates the good stability of the system. It is proposed a method to obtain a high viscoelasticity solution by adding surfactants without wormlike micelles to a hydrophobically associated water-soluble polymer solution.

Synergistic Effect of Binary Surfactant Mixtures in Two-Phase and Three-Phase Systems.

Cationic alkyltrimethylammonium bromides (CnTAB, with n = 8, 12, 16, 18) and their mixtures with n-octanol as a nonionic surfactant were chosen as a model system to study the synergistic effect on foamability (two-phase system) and floatability (three-phase system) of quartz in the presence of binary mixtures of ionic/nonionic surfactants. The foam height of one-component solutions and binary mixtures and floatability of quartz particles were characterized as a function of the surfactant concentration and the number of carbons (n) in the alkyl chain of CnTAB. The experimental results of foamability and floatability measurements in one-component and mixed solutions revealed the synergistic effect, causing a significant enhancement in the foam height and recovery of quartz. In the presence of n-octanol, the height of foam increased remarkably for all CnTAB solutions studied, and this effect, whose magnitude depended on the CnTAB hydrophobic tail length, could not be justified by a simple increase in total surfactant concentration. A similar picture was obtained in the case of flotation response. The mechanism of synergistic effect observed in mixed CnTAB/n-octanol solutions was proposed. The discussion was supported by molecular dynamics simulations, and the probable mechanism responsible for synergism was discussed. In addition, an analysis allowing accurate determination of the concentration regimes, where the synergistic effect can be expected, was given. It was shown that for the two-phase system, the n-octanol molecule preadsorption at the liquid/gas interface causes an increase in CnTAB adsorption coverage over the level expected from its equilibrium value in the one-component solution. In the case of the three-phase system, the synergistic effect was related to the ionic surfactants serving as an anchor layer for n-octanol, which, in water/n-octanol solution (one-component system), do not adsorb on the surface of quartz.

Effect of anionic and non-anionic surfactants on the adsorption density

Surfactant adsorption is one of the crucial issues in surfactant flooding to enhance the oil recovery factor. In this paper, we investigated the profound impact of two different surfactants on the carbonate rocks adsorption density in different temperatures. According to the results of this experiment, carbonate rocks adsorption density increased with the increase of surfactant concentrations. Higher surfactants’ concentration, adsorption density had reached a plateau after 7 hours. Furthermore, temperature increase has caused to reduce the adsorption density for all surfactant concentration. The maximum adsorption density is about 50 mg/g at 20 Besides, polyacrylamide addition would decrease the adsorption density.

Effect of surfactants on the transport of polyethylene and polypropylene microplastics in porous media

The transport of microplastics in porous media is attracting increasing attention. However, to date, research is limited to polystyrene microplastics. Meanwhile, surfactants can promote solid dispersion to form a stable suspension, possibly allowing microplastics to migrate when attached to a surfactant, which would increase the scope and degree of microplastic pollution, further endangering human health and the stability of the ecological environment. Therefore, in this study, the transport behavior of microplastics in porous media was explored in the presence of surfactants. Herein, polyethylene (PE) and polypropylene (PP) were evaluated while dispersed by two ionic surfactants: cationic surfactant-cetyltrimethylammonium bromide (CTAB) and anionic surfactant-sodium dodecylbenzenesulfonate (SDBS). The influence of different factors (surfactant concentration, ionic strength, pH, flow rate, and multivalent cations) on the transport of microplastics in porous media was explored via quartz sand packed-column experiments. Our experimental results show that the transport abilities of PE and PP increased with increasing surfactant concentration when the surfactant concentration was less than the critical micelle concentration (CMC). In the presence of CTAB and SDBS, physicochemical factors had different effects on the transport of microplastics mainly by controlling Zeta potential, advection diffusion and CMC. The mobility of PE and PP decreased with increasing ionic strength, cation valence and pH, and decreasing flow rate. However, the mobility of PE and PP under CTAB is much greater than that of PE and PP under SDBS, because quartz sand can absorb more CTAB molecules through electrostatic attraction to weaken the collision between microplastics and quartz sand. Further, the transport ability of PP was greater than that of PE under all conditions considered. Notably, the Extended-Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory formed by adding osmotic, elastic, and hydrophobic force could well described the migration behavior of microplastics in CTAB and SDBS well. This research highlights that surfactant has a significant impact on the transport ability of microplastics, and provides a comprehensive understanding of the migration and fate behaviors of microplastics affected by surfactants, which is necessary to prevent and reduce the environmental hazards of microplastics.

Effect of in Situ Formed Emulsions on Enhanced Extra-Heavy Oil Recovery by Surfactant Flooding

Thermochemical flooding is becoming more popular nowadays as a subsequent EOR method after thermal recovery in extra-heavy oil reservoirs. During this process, in-situ emulsions could happen due to interfacial active components existing in heavy crude oil. The enhanced oil recovery is inevitably related with the formation of emulsions, which is one of the main mechanisms and deserves a thorough study. Also, the features of relative permeability curves during thermochemical flooding should be investigated further, because they are very important but usually are difficult to obtain since physical reactions could happen.Based on core-flooding experiments, combined with careful observation of produced crude oil emulsion morphology, this paper compared and analyzed the features of relative permeability curves and displacement efficiency at different conditions, and the mechanisms of extra-heavy oil production by surfactant displacement is then investigated. The surfactant used are provided by the oilfield at a varied mass fraction of 0.1%, 0.2% and 0.3% and under temperature of 100, 150 and 180 °C. The relative permeability data were processed with JBN method.The experimental results show that both the oil and water relative permeability increase as the temperature increases. As surfactant concentration increases, the relative permeability of the aqueous phase decreases as opposite to oil. The ultimate recovery increased with the increase of temperature and surfactant concentration. Except for the oil viscosity reduction by surfactant, it is interesting to note that the formation of crude oil emulsions (mainly O/W emulsions) are observed to be positively impacting the oil recovery factor. As surfactant concentration increases, larger size of dispersed phase in the emulsions were observed in the effluent corresponding to a higher oil recovery factor. This work is of great significance for heavy oil research and field development.

Studies on influence of characteristics of surfactant and foam on foam concrete behaviour

This paper describes an extensive laboratory-based investigation conducted to evaluate the relative performance of foam produced with two different synthetic surfactants namely Sodium lauryl sulphate (SLS) and Nonylphenol ethoxylate (NPE) along with an additive Carboxymethyl cellulose sodium salt (CMC) for use in foam concrete. The different essential characteristics of foam and surfactants such as initial foam density, foam stability, average bubble size and viscosity of surfactant solution are investigated in the present study through systematic experimental design based on response surface methodology. Further, based on studies on microstructure of foam concrete, it is found that selection of surfactant and CMC concentration have significant influence on foam characteristics and hence on the air void size distribution of foam concrete. In addition, the dependence of the compressive strength and water permeation characteristics of foam concrete on the air void size parameters of concrete is also investigated. Experimental outcomes indicate that increase in surfactant concentration from 3% to 6% results in 24%–44% reduction in median air void diameter in concrete which eventually led to 29%–37% enhancement in compressive strength of foam concrete mixes. In the same line, addition of CMC to surfactant solution enhances viscosity of surfactant solution significantly and thereby results in improvement of foam microstructure, concrete air void microstructure and eventually improves compressive strength of foam concrete. Further, improved microstructure with smaller air voids in foam concrete with NPE + CMC results in 10%–25% relatively higher compressive strength than SLS + CMC foam concrete mixes.

Effect of trace amounts of ionic surfactants on the zeta potential of DPPC liposomes

Surfactants are commonly found in today's world as an essential component of cleaning detergents, cosmetics and drug delivery systems. They can penetrate into lipid membranes, thus changing their properties. The aim of this paper is to compare the effect of addition of small amounts of cationic (DTAB) and anionic surfactants (SDS) with the same alkyl chain length on the zeta potential of DPPC liposomes with their influence on the corresponding DPPC monolayers. It was found that the addition of ionic surfactants with an initial concentration in the solution equal to 2.3, 4.5 and 9.1 μM to the liposome suspension changes their electrokinetic potential significantly. These changes increase with the increasing surfactant concentration and are greater for the anionic surfactant. This indicates the incorporation of surfactants into the structure of liposomes. Based on the analysis of π-area isotherms of DPPC monolayers it was proved that the ionic surfactant molecules are irreversibly integrated into the DPPC monolayer.

Design and Optimization of Febuxostat-loaded Nano Lipid Carriers Using Full Factorial Design.

This work aims to develop nanostructured lipid carriers (NLCs) to improve the oral bioavailability of febuxostat (FEB). High shear homogenization, a well-known technique, followed by bath sonication with slight modifications was used to prepare FEB-loaded NLCs using oleic acid as liquid lipid and stearic acid as solid lipid. A total of 3² full factorial design was utilized to examine the effect of 2 independent variables, namely, X1 (liquid to solid lipid ratio) and X2 (surfactant concentration) on the Y1 (particle size) and Y2 (% entrapment efficiency) of the drug. The prepared NLCs were evaluated for particle size, polydispersity index, zeta potential, and (%) entrapment efficiency. The drug's highest solubility was found in the stearic (solid lipid) and oleic acid (liquid lipid), which were further chosen for NLC preparation. Result of the present study showed an increase in entrapment efficiency and a decrease in particle size with the increase in liquid lipid to solid lipid ratio. With increased surfactant concentration, a small particle size is observed. The optimized formulation's particle size and (%) entrapment efficiency was found to be 99 nm and 80%, respectively. The formulations' zeta potential and polydispersity index were found within the range. Compared to plain drug suspension, the optimized formulation showed higher drug release, which may be due to the presence of the higher amount of liquid lipid. The particles shown in the transmission electron microscopy were round in shape and have smooth surface. Stability studies showed that the NLC formulation can be stored for a longer time period under room condition. FEB-loaded NLC were successfully prepared using full 3² factorial design, and can be further used for oral delivery of FEB for gout treatment.

Contrastive Study of the Foaming Properties of N-Acyl Amino Acid Surfactants with Bovine Serum Albumin and Gelatin.

A detailed study on the foamability, foam stability, foam liquid-carrying capacity, and foam morphology of two N-acyl amino acid surfactants with bovine serum albumin (BSA) and gelatin were performed by foam scanning. The results showed that the foamability of the mixed system increased gradually and then tended to be stable with increasing surfactant concentration. The foamability of the high-concentration BSA system was stronger than that of the low-concentration BSA system. The foamability and foam stability of sodium N-lauroyl phenylpropanoic acid (N-C12P)/BSA were better than those of sodium N-lauroyl propylamino acid (N-C12A)/BSA, and the foamability and foam stability of N-C12A/gelatin was better than those of N-C12P/gelatin. The liquid-carrying capacity of the foam initially increased and then decreased with increasing time, and the maximum liquid-carrying capacity increased with increasing surfactant concentration. When the concentration of the surfactant was 8 mM, the drainage rate of N-C12A/protein was higher than that of N-C12P/protein. The morphology of the bubble gradually changed from spherical to polyhedron and the number of bubbles gradually decreased with time increasing. Differences in surfactant structure and protein type had an important effect on the number and area of foam.

Static and flow behaviors of supercritical CO2 foam stabilized with betaine surfactant for mobility control application

Aiming at improving the stability of Supercritical CO2 (SC-CO2) foam in high temperature and salinity reservoirs, a kind of betaine surfactant, Hexadecyl Hydroxypropyl Sulfo Betaine (HHSB), was screened to stabilize SC-CO2 foam. The properties of SC-CO2 foam were improved at elevated temperature and pressure. The effects of surfactant concentration, temperature, pressure and salinity on film drainage rate were measured to explore the stability of SC-CO2 foam. The results showed that an increase of surfactant concentration, pressure and salinity can decrease film drainage rate and enhance the foam stability, which was attributed to the increase of surfactant adsorption at the gas–liquid interface. The performance of SC-CO2 foam formed by HHSB was improved and the tolerant temperature was up to 100 °C. 1-D core flooding experiments indicated that compared with Coinjection of Surfactant and Gas (CSG) method the SC-CO2 foam generated through Surfactant-Alternative-Gas (SAG) method had lower foam strength but better in-depth migration capacity. The high temperature and pressure 3-D sand showed that in Water-Alternative-Gas (WAG) case CO2 broke early through the high permeability layers. In SAG case, SC-CO2 foam can improve the macroscopic sweep efficiency by reducing the CO2 mobility.

Study of the inhibition effect of a new cationic surfactant on mild steel corrosion in a 1 M HCl solution

6-(2,3-dioxoindolin-1-yl)-N,N,N-trimethylhexan-1-ammonium bromide 3, a cationic surfactant, was synthesized and characterized by different spectroscopic techniques (nuclear magnetic resonance and High-resolution mass spectrometry (1H NMR, 13C NMR, and HRMS)). The effect of the cationic surfactant on the corrosion of mild steel in a 1 M HCl solution at temperatures between 298°K and 328°K has been assessed using the weight loss method and various electrochemical techniques (potentiodynamic polarization and electrochemical impedance spectroscopy (EIS)). The results of this study showed that the synthesized surfactant is an efficient corrosion inhibitor for mild steel in 1 M HCl. The inhibition efficiency reached 92.98% after 6 h of immersion at 298 K using a concentration of 1 mM. Both kinetic and thermodynamic parameters of the corrosion and inhibition process were investigated. As surfactant concentration increases, the corrosion inhibition efficiency (IE%) increases. Besides, it was found that the cationic surfactant adsorption on the surface of the mild steel followed the Langmuir isotherm. Also, electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization measurements showed that the inhibitor was considered as a mixed inhibitor with an anodic dominant character.

Use of saponin foam reinforced with colloidal particles as an application to soil remediation: Experiments in a 2D tank

Foam can be used to achieve environmental remediation in case of contamination caused by light non aqueous phase spills. However, when it comes in contact with oily pollutants, foam becomes weaker and its life time is greatly reduced. Such weakening can be dampened by using silica particles -together with saponin surfactant- which were shown to reinforce foam in bulk and 1D sandpack experiments. Here is addressed both foam propagation in a 2D porous media when buoyancy and gravity interfere, and foam behaviour when in contact with floating oil. Therefore, macroscopic foam displacement, and specific liquid and gas phases behaviours were studied in a 2D-tank. A piston-like displacement was observed during foam propagation in the absence of oil, while foam liquid phase was influenced by gravity and did not propagate homogeneously on entire tank height. In the presence of oil, foam was partly destroyed, which increased the local permeability of gas and created new preferential paths for gas flow. This effect was partially avoided via a surfactant concentration increase, but solid colloidal particles turned out to be a more efficient stabilizing agent, by significantly increasing foam strength and its oil-tolerance.

Experimental study of combined microemulsion/brine flooding to EOR in carbonate reservoirs

The application of Enhanced Oil Recovery (EOR) methods is essential to promoting increase in the oil recovery where the conventional recovery methods unsuccessful. Numerous studies have demonstrated that microemulsion and surfactant systems injection can change the properties of fluids and increase the oil recovery. In this work, flooding tests were carried out combining brine and microemulsion in different proportions and schemes of injection. Microemulsion systems constituted by: Ultramine 200, n-butanol, kerosene and water were obtained and characterized by measurements of droplet diameter, surface tension, interfacial tension (IFT), and viscosity. The surfactant concentration in the microemulsion was evaluated on the oil recovery through flooding experiments. This study also evaluated how surface and interfacial tensions influence crude oil recovery (29° API). Results demonstrate that the oil recovery increases with the increase in surfactant concentration in the microemulsion. However, that increase is significant only up to 9 wt%, reaching an additional 21% oil recovery of the original oil in place (OOIP). This research recommends chemical method to EOR tests by combined injection from microemulsion and brine. The chemical action of microemulsion system results in a miscible phase, promotes oil mobilization, improve brine flooding, and increase the oil recovery.