Study Of Surfactant Adsorption Research Articles

In-Situ AFM Studies of Surfactant Adsorption on Stainless Steel Surfaces during Electrochemical Polarization

Corrosion inhibitors are one of the best practices to prevent the far-reaching negative impacts of corrosion on ferrous alloys. A thorough understanding of their corrosion-inhibiting effects is essential for a sustainable economy and environment. Anionic surfactants are known to act efficiently as corrosion inhibitors. Here, we present that in-situ atomic force microscopy (AFM) measurements can provide deep insights into the adsorption and inhibition mechanism of surfactants on stainless steel surfaces during local corrosion. These include the configuration of surfactant molecules on the surface and how the microstructure of the stainless steel surface influences the inhibition process. Three different anionic surfactants, namely palm kernel oil (PKO), linear alkylbenzene sulfonate (LAS), and fatty alcohol ether sulfate (FAES), were investigated on a titanium-stabilized ferritic stainless steel (1.4510) in NaCl solution. For PKO, the results show random adsorption of bi- and multilayer whereas LAS and FAES adsorb only as local corrosion occurs. Thereby, LAS accumulates only locally and especially at the titanium precipitates of the 1.4510 and FAES forms a densely packed monolayer on the surface. This leads to better corrosion inhibiting properties for LAS and FAES compared to PKO.

New Insights into Surfactant Adsorption Estimation in Carbonates under Harsh Conditions Using Surface Complexation Modeling

Summary Several laboratory experiments demonstrated that the use of sodium hydroxide could increase the solution pH and reduce the adsorption of anionic surfactants. However, a better understanding of rock-oil-brine interactions and their effect on surfactant adsorption during alkaline-surfactantpolymer (ASP) flooding is needed for realistic and representative estimations of surfactant adsorption levels. Therefore, this study presents a novel approach to capture these interactions and better predict their effect on surfactant adsorption as well as effluent concentrations of surfactant and various aqueous species using the Phreeqc simulator. Currently, surface complexation models (SCMs) consider rock-brine, oil-brine, and surfactant-brine reactions. In this work, four new surface complexation reactions with intrinsic stability constants that honor oil-surfactant interactions have been proposed for the first time and then validated against experimental data reported in the literature. In addition, we analyzed the effect of various parameters on surface adsorption under harsh conditions of high temperature and high salinity using the proposed SCM. The results showed that the developed surfactant-based SCM is capable of estimating surfactant adsorption and its concentration in the effluent during chemical floods. The model was validated against two sets of ASP corefloods from the literature including single-phase and two-phase dynamic surfactant adsorption studies. The findings highlighted that oil-surfactant surface complexation reactions are important and should be captured for a more representative and accurate estimation of surfactant adsorption during chemical flooding. Moreover, the detailed and comprehensive analysis showed that surfactant adsorption increased and its concentration in the effluent decreased with the increase in temperature of the chemical flood. The latter shows that the adsorption process is endothermic and it is more of chemisorption as opposed to physio-adsorption. It was also showed that a decrease in water total salinity decreases the surfactant adsorption on the rock surface, which is related to the increase in the repulsive forces between the rock surface and adsorbed species. Additionally, with the increase in surfactant concentration in the chemical flood, surfactant concentration in the effluent increases, with a slight increase in surfactant adsorption. This slight increase in adsorption can be neglected compared with the injected and produced masses of the surfactant that are proportional. Moreover, the effect of sulfate spiking is significant where the increase in sulfate concentration reduces the surfactant adsorption. Furthermore, it is worth highlighting that the lowest surfactant adsorption levels were achieved through injected water dilution; less than 0.1 mg/g of rock. This is the first study to test a novel formulation of SCM considering the oil-surfactant effect on surfactant adsorption properties. The proposed framework to estimate surfactant adsorption is conducted for high-temperature and high-salinity reservoir conditions. Thus, it could be used in numerical reservoir simulators to estimate oil recovery due to wettability alteration by chemical flooding in carbonates, which will be investigated in our future work. The surfactant adsorption mechanisms during chemical flooding are very case-dependent and hence, the findings of this study cannot be generalized.

Exploration of the Adsorption Kinetics of Surfactants at the Water-Oil Interface via Grand-Canonical Molecular Dynamics Simulations.

It is well-known that surfactants tend to aggregate into clusters or micelles in aqueous solutions due to their special structures, and it is difficult for the surfactant molecules involved in the aggregation to move spontaneously to the oil-water interface. In this article, we developed a new grand-canonical molecular dynamics (GCMD) model to predict the saturated adsorption amount of surfactant with constant concentration of surfactant molecules in the bulk phase, which can prevent surfactants aggregating in the bulk phase and get the atomic details of the interfacial structural change with increase of the adsorption amount through a single GCMD run. The adsorption of anionic surfactant sodium dodecyl sulfate (SDS) at the heptane-water interface was studied to validate the model. The saturated adsorption amount obtained from the GCMD simulation is consistent with the experimental results. The adsorption kinetics of SDS molecules during the simulation can be divided into three stages: linear adsorption stage, transition adsorption stage, and dynamic equilibrium stage. We also carried out equilibrium molecular dynamics (EMD) simulations to compare with GCMD simulation. This GCMD model can effectively reduce the simulation time with correct prediction of the interfacial saturation adsorption. We believe the GCMD method could be especially helpful for the computational study of surfactant adsorption under complex environments or emulsion systems with the adsorption of multiple types of surfactants.

From Surface Tension to Molecular Distribution: Modeling Surfactant Adsorption at the Air–Water Interface

Surfactants are centrally important in many scientific and engineering fields and are used for many purposes such as foaming agents and detergents. However, many challenges remain in providing a comprehensive understanding of their behavior. Here, we provide a brief historical overview of the study of surfactant adsorption at the air-water interface, followed by a discussion of some recent advances in this area from our group. The main focus is on incorporating an accurate description of the adsorption layer thickness of surfactant at the air-water interface. Surfactants have a wide distribution at the air-water interface, which can have a significant effect on important properties such as the surface excess, surface tension, and surface potential. We have developed a modified Poisson-Boltzmann (MPB) model to describe this effect, which we outline here. We also address the remaining challenges and future research directions in this area. We believe that experimental techniques, modeling, and simulation should be combined to form a holistic picture of surfactant adsorption at the air-water interface.

Experimental investigation, binary modelling and artificial neural network prediction of surfactant adsorption for enhanced oil recovery application

Throughout the application of enhanced oil recovery (EOR), surfactant adsorption is considered the leading constraint on both the successful implementation and economic viability of the process. In this study, a comprehensive investigation on the adsorption behaviour of nonionic and anionic individual surfactants; namely, alkyl polyglucoside (APG) and alkyl ether carboxylate (AEC) was performed using static adsorption experiments, isotherm modelling using (Langmuir, Freundlich, Sips, and Temkin models), adsorption simulation using a state-of-the-art method, binary mixture prediction using the modified extended Langmuir (MEL) model, and artificial neural network (ANN) prediction. Static adsorption experiments revealed higher adsorption capacity of APG as compared to AEC, with sips being the most fitted model with R2 (0.9915 and 0.9926, for APG and AEC respectively). It was indicated that both monolayer and multilayer adsorption took place in a heterogeneous adsorption system with non-uniform surfactant molecules distribution, which was in remarkable agreement with the simulation results. The (APG/AEC) binary mixture prediction depicted contradictory results to the experimental individual behaviour, showing that AEC had more affinity to adsorb in competition with APG for the adsorption sites on the rock surface. The adopted ANN model showed good agreement with the experimental data and the simulated adsorption values for APG and AEC showed a decreasing trend as temperature increases. Simulating the impact of binary surfactant adsorption can provide a tremendous advantage of demonstrating the binary system behaviour with less experimental data. The utilization of ANN for such prediction procedure can minimize the experimental time, operating cost and give feasible predictions compared to other computational methods. The integrated workflow followed in this study is quite innovative as it has not been employed before for surfactant adsorption studies.

Electrochemically Assisted Deposition of Calcite for Application in Surfactant Adsorption Studies

The ability to study the adsorption behavior of surfactant species is of interest in the field of enhanced oil recovery (EOR), especially pertaining to alkaline surfactant flooding. In this work, a...

An Experimental Study of Surfactant Alternating CO2 Injection for Enhanced Oil Recovery of Carbonated Reservoir

Core flooding experiments were conducted with the objective of evaluating near miscible surfactant alternating CO2 injection and the effect of surfactant concentrations on gas-oil and water displacements in porous media. The core samples were provided from a low permeability mixed wet oil reservoir at 156 °F and 1900 psia. In addition, very few studies of surfactant adsorption on carbonate minerals have been conducted. Hence, the surfactant adsorption on carbonate rock was determined by core flooding and crushed tests. It was found that for the crushed rock, the required equilibrium time is approximately five hours, while it is more than four days for the flow-through tests. Hysteresis effects demonstrated that the irreducible water saturations were 5 to 10% higher than the initial connate water saturation after drainage cycles during 5000 ppm surfactant solution. Furthermore, near-miscible surfactant alternating CO2 injection process led to a 4-17% increase in the recovery factor in comparison to water alternating gas process.

In‐situ spectroscopic study of surfactant adsorption onto hematite from binary mixtures and the effect of inorganic ions

Attenuated total reflectance Fourier transform infrared (ATR‐FTIR) spectroscopy has proven to be a powerful tool for surfactant adsorption studies. In many practical applications, surfactant mixtures and waters with different chemistry are employed, which significantly complicates adsorption studies. In this work, we investigate the effect of calcium and carbonate ions, frequently found in natural waters, on the co‐adsorption of sodium dodecylbenzenesulfonate (SDBS) and a non‐ionic primary alcohol ethoxylate (NEODOL 25–7) onto hematite at pH 8 and 10.5 using ATR‐FTIR spectroscopy. Adsorption of SDBS was affected by pH and the presence of inorganic ions to a greater extent than the adsorption of NEODOL 25–7. A larger amount of SDBS was adsorbed at pH 8 than at pH 10.5 in all the experiments. The effect of co‐adsorbing ions on the amount of SDBS adsorbed was significant only at pH 10.5 and not at pH 8. Calcium ions promoted adsorption of SBDS onto hematite, whereas addition of carbonate decreased the amount of SDBS adsorbed. In the presence of both calcium and carbonate ions, calcium carbonate precipitate was formed on the hematite surface, promoting accumulation of NEODOL 25–7 at the surface. NEODOL 25–7 was found to have a strong effect on the hydrophilicity of the hematite film when adsorbed in combination with SDBS. A more hydrophilic surface was obtained upon adsorption of the surfactants in the presence of sodium chloride, film dispersion occurred in the presence of calcium chloride, and a less hydrophilic surface was obtained in the presence of both calcium chloride and sodium carbonate. Copyright © 2014 John Wiley & Sons, Ltd.

A comparative study of surfactant adsorption by clay minerals

Abstract The adsorption of surfactants from aqueous solutions in porous media is essential in enhanced oil recovery (EOR) from oil reservoirs. Surfactant loss that is due to adsorption by the reservoir rocks weakens the efficiency of the chemical slurry that is injected and decreases the oil–water interfacial tension (IFT). This project investigated the effect of the mineralogical composition of adsorbents on adsorption. The experiments were conducted in batches. Adsorbents were composed of various combinations of quartz sand and clay minerals at various percentages and were exposed to nonionic and anionic surfactants. The amount of surfactant that was adsorbed was quantified by subtracting the concentration of surfactants after adsorption from the initial concentration. We observed a direct relationship between the adsorption of the nonionic surfactant and the amount of clay minerals in the adsorbents as the amount of surfactant that was adsorbed by the adsorbents increased when the percentage of clay minerals in adsorbents increased (from 5% to 20% in the mixture). The rank order of adsorption power of clay minerals for the nonionic surfactant was montmorillonite⪢illite>kaolinite. Adsorption of the anionic surfactant by all adsorbents was negligible.

Molecular behavior of ionic and nonionic surfactants in saline medium

The aim of this study was to investigate the molecular behavior of ionic and nonionic surfactants at different salt concentrations. The nonionic surfactants used in this work were nonylphenol 20 EO, nonylphenol 100 EO, lauryl alcohol 10 EO, and lauryl alcohol 23 EO, being EO the number of ethene oxide groups. The ionic surfactants were synthesized through saponification reactions using the following vegetable oils: coconut oil and castor oil. The cmc (critical micelle concentration) of each surfactant was determined using surface tension measurements at different surfactant and salt concentrations. The study of surfactant adsorption, using the Gibbs equation with factor n = 1 for nonionic surfactants and n = 2 for ionic ones, allowed to obtain the packing area per surfactant molecule, the surface excess, and the Gibbs free energy of micellization. The obtained results were compared and discussed in view of the hole of the type of surfactant and electrolyte influence. From the obtained results, it can be concluded that the ionic surfactants, due to electrostatic repulsion between ionic head groups, showed higher cmc values than those obtained for nonionic ones. When salt ions were added to the ionic surfactant solution, the cmc values were decreased due to the existence of electrostatic interactions between the ionic head groups of these molecules with the electrolytes. For nonionic surfactants, the increasing ethoxylation degree, the hydrophilic portion of surfactant molecule, and electrolyte addition diminishes cmc values. Concerning to the Gibbs free energy of micellization, the obtained results showed that the adsorption process was spontaneous for all studied surfactants, but it was thermodynamically more favorable for nonionic ones.

Adsorption of ethoxylated cationic surfactants on self-assembled monolayers of alkanethiols on gold using surface plasmon resonance detection

Adsorption of a series of ethoxylated cationic surfactants at model surfaces of alkanethiol self-assembled monolayers was studied by the surface plasmon resonance technique. Model surfaces were tailor-made by choosing alkanethiols or mixtures of alkanethiols with methyl, hydroxyl, carboxyl, and trimethylammonium groups in terminal position. The ethoxylated and quaternized cationic surfactants having from 2 to 18 oxyethylene units, showed a decrease in adsorbed amount with increasing oxyethylene chain length for both hydrophobic and hydrophilic surfaces. On a negatively charged surface, containing carboxylate groups, the surfactant with only two oxyethylene groups adsorbed strongly due to electrostatic attraction and the adsorption increased with increasing amount of surface carboxylate groups. This work shows the usefulness of self-assembled alkanethiols on gold as a tool for performing surfactant adsorption studies on surfaces with variable hydrophobicity and charge.

A Comparative Study of Surfactant Adsorption on Model Surfaces Using the Quartz Crystal Microbalance and the Ellipsometer

The nature of hexaethylene glycol mono- n-tetradecyl ether (C 14EO 6) layers adsorbed onto different model surfaces was systematically investigated by means of QCM-D (quartz crystal microbalance-dissipation) and ellipsometry. The amount of non-ionic surfactant adsorbed is determined both at hydrophilic and hydrophobic surfaces. In particular, the substrates employed were hydrophilic silica, hydrophobized silica (using dimethyldichlorosilane), and hydrophobized gold surfaces (using 10-thiodecane and 16-thiohexadecane). It was shown that the frequency shift obtained from the QCM-D experiments results in an overestimation of the adsorbed mass. This is attributed to two different effects, viz. water that is coupled to the adsorbed layer due to hydration of the polar region of the surfactant and second water that for other reasons is trapped within the adsorbed layer. Furthermore, from the ellipsometry data the adsorbed layer thickness is determined. By combining the thickness information and the dissipation parameter (obtained from the QCM-D experiments), we note that the dissipation parameter is insufficient in describing the viscoelastic character of thin surfactant films.

Microcalorimetry and ellipsometry in surfactant adsorption studies

The applications of calorimetric and ellipsometric methods to the understanding of adsorption phenomena occurring at the solid/liquid interface are presented. Gas adsorption calorimetry and immersion calorimetry can be used to characterise powdered adsorbents in terms of surface area, surface energy and pore size distribution, whereas adsorption from solution calorimetry is well suited to follow in situ the building steps of the surfactant adsorbed layer. On the other hand, ellipsometry allows the adsorption isotherms as well as the thickness of the adsorbed layer to be determined on well defined flat surfaces. Some applications for surfactant studies are reviewed and a recent result, obtained in the case of the adsorption of a cationic surfactant below its Kraft temperature onto silica, is presented.

Study of surfactant adsorption onto electropolymerized o-phenylenediamine film by using a capacitive sensing method

A capacitive sensing device has been designed by using electropolymerized o-phenylenediamine (PPD) film as an isolating layer and has been applied successfully to study the adsorption of Tween 80 onto the PPD film surface. The PPD was prepared with a cyclic voltammetry method and the thickness of the PPD film was estimated as about 110 ± 10 nm. The properties of the PPD insulating film were characterized with an electrochemical impedance method. The results show that the equivalent circuit model of this device is Randles type. The adsorption process of Tween 80 onto the PPD film was detected with the electrochemical impedance method. The result implies that the adsorption model of Tween 80 onto the PPD film appeared as pseudo Langmuir type and the adsorption equilibrium constant was 213.87 (dm3 g−1). We expect that the capacitive sensor will be a useful tool for investigation of interface action.

Comparison between wettability gradients made on gold and on Si/SiO 2 substrates

We have previously shown that wettability gradients on Si/SiO 2 can be used to analyze in detail the interactions of surfactants and proteins with the vast number of different surface properties that a gradient represents. We have also shown that the interactions of surfactants can be used to characterize the surface. In this report we discuss a new kind of wettability gradient that is composed from alkanethiols on gold. Surfactant and protein adsorption phenomena are investigated and compared with analogous experiments made on gradients prepared from chlorosilanes on Si/SiO 2 substrates. Surfactant adsorption studies were used to investigate the surface properties. Through their electrostatic interactions negatively charged groups on the surface could be detected and through their hydrophobic interactions defects in the surface layer resulting in hydrophobic groups could be detected. The alkanethiol gradient had at the extreme OH-side an advancing contact angle to water between 30 and 40°. Still this surface had a lower adsorbed amount of fibrinogen compared to a (completely wetting) silica surface covered with negatively charged and uncharged silanol groups, indicating that the fibrinogen molecules also interacts electrostatically through their positively charged amino acid residues. This shows that the amount of fibrinogen adsorbed is not solely dependent on the surface hydrophilicity.

Influence of the Dielectric Constant of the Media on Oxide Stability in Surfactant Solutions

The influence of the dielectric constant of the suspension on the colloidal stability of alumina in the presence of surfactant was investigated. Colloid stability measurements were supplemented with electrokinetic, conductivity, and surfactant adsorption studies. Studies with physadsorbed sodium dodecyl sulfate were performed in the presence of different volume percents of short chain alcohols or dioxane in order to vary the dielectric constant of the suspension. It was observed that the surfactant adsorption decreased with the dielectric constant of the media. At 50 vol % of different alcohols, the addition of surfactant could not reverse the alumina charge and restabilize coagulated particles. To understand the influence of lower dielectric constant on surfactant adsorption at the surface or in the second layer, (hydrophilic head pointing toward the solution), alumina and silica particles were chemically precoated with dodecyl chains. The addition of anionic surfactant suspended such hydrophobic particl...

Quartz Crystal Microbalance and Surface Plasmon Resonance Study of Surfactant Adsorption onto Gold and Chromium Oxide Surfaces

The adsorption of two nonionic surfactants on hydrophobic gold and hydrophilic chromium oxide surfaces from aqueous solution has been investigated using a quartz crystal microbalance (QCM) and surface plasmon resonance (SPR). Adsorption isotherms for a nonyl phenol ethoxylate with average ethylene oxide chain length of 9 (N9) on gold and for octaethylene glycol monododecyl ether (C12E8) on both gold and chromium oxide surfaces have been measured by QCM. Isotherms for N9 and C12E8 on the gold surface can be described by Langmuir adsorption, while that of C12E8 on the chromium oxide surface was S-type. Complementary SPR experiments of C12E8 adsorption onto gold suggest that the resonance frequency change of the QCM crystal in solution with adsorbed C12E8 (at saturation coverage) is 80% greater than that predicted by the Sauerbrey equation for air measurements. This implies a 2.08 Hz/ng change for the QCM in contact with aqueous solution. This calibration factor was used to calculate the saturated surface coverage for the surfactants (and hence area per surfactant) at the solid/liquid interface. These data are in good agreement with those reported in the literature for N9 and C12E8 adsorbed onto various hydrophobic and hydrophilic surfaces. © 1995, American Chemical Society. All rights reserved.

The study of surfactant adsorption by specular neutron reflection

The specular reflection of neutrons is now a well-established technique for the study of surfactant adsorption at the air-liquid interface. In combination with isotopic substitution it provides a powerful method for determining adsorbed amounts and the surface/interfacial monolayer structure. The application of the technique for the determination of adsorption isotherms will be described, with particular emphasis on multi-component systems. Recent results for nonionic and mixed nonionic-cationic surfactants will be discussed, and compared with theoretical predictions.

Static and dynamic light scattering study of fluorinated polymer colloids with a crystalline internal structure

The light scattering properties of polymer colloids made of polytetrafluoroethylene with added copolymers are described in some detail. The particles possess a partially crystalline internal structure which makes them optically anisotropic, and consequently gives rise to a strong depolarized component in the scattered light intensity. We present a complete theory of static and dynamic light scattering which includes the effects of polycrystallinity, of optical polydispersity, and of interparticle interactions. We also discuss applications to surfactant adsorption studies, to sedimentation experiments and to fractal aggregation processes

Adsorption of anionic and amphoteric foam-forming surfactants on different rock types

Surfactant adsorption studies carried out with surfactants suitable for mobility control by foams in gas-flooding enhanced oil recovery are described. The extent of adsorption of three surfactants (an anionic surfactant, a betaine, and a sulfobetaine) is measured on four types of rock representing reservoir materials (berea sandstone, Indiana limestone, Baker dolomite and quartz) from three brines (a sodium chloride solution and two synthetic reservoir brines with different concentrations of total dissolved solids). This allows the assessment of the effects of surfactant type, rock type, brine salinity and the presence of divalent cations on surfactant adsorption. In order to probe into adsorption mechanisms, an attempt is made to correlate adsorption levels with rock surface charges. Adsorption of the anionic surfactant on sandstone and dolomite is significantly lower than that of both amphoterics, while adsorption of the amphoterics on limestone is similar to or lower than adsorption of the anionic surfactant. The presence of divalent cations increases the adsorption of the anionic surfactant and the betaine on sandstone and limestone, but has very little effect on the adsorption of the sulfobetaine on all rocks, or on the adsorption of all three surfactants on dolomite. The effect of the total dissolved solids concentration in the brine on adsorption is different for different surfactant/rock combinations. A correlation of surfactant adsorption with rock surface charge shows that adsorption of the anionic surfactant is consistent with an electrostatic mechanism of adsorption. Adsorption of both amphoteric surfactants occurs through a complex interplay of mechanisms, some of which can be suggested from the observed trends.