Adsorption Of Anionic Surfactants Research Articles

Electrophoretic Effects of the Adsorption of Anionic Surfactants to Poly(dimethylsiloxane)-Coated Capillaries

Poly(dimethylsiloxane) (PDMS) is one of the most convenient materials to construct capillary electrophoresis microchips. Even though PDMS has many advantages, its use is often limited by its hydrophobicity. Although it is well-known that the surface properties of PDMS can be modified by anionic surfactants, very little is known regarding the driving forces or the electrophoretic consequences of the adsorption of anionic surfactants. In this work, the adsorption of alkyl surfactants on PDMS was studied by performing electroosmotic flow (microEOF) measurements. In order to mimic the behavior of PDMS microchannels, fused-silica capillaries were coated with PDMS and used for the microEOF measurements. This approach allowed using standard CE instrumentation and provided significant advantages over similar experiments performed on microchips. The change in the microEOF in the presence of surfactants was correlated to the surfactant adsorbed amount which, plotted versus surfactant concentration, gives an adsorption isotherm. The adsorption isotherms were obtained using alkyl surfactants with different chain lengths and head groups. According to our results, the interaction of alkyl surfactants with the PDMS surface is determined by a combination of hydrophobic and electrostatic interactions, where the former is more significant than the latter. The affinity of each surfactant for the PDMS surface was calculated by fitting the adsorption profiles with a Langmuir equation and, in the case of single-charged surfactants, correlated to the corresponding cmc value.

Controlling the Electrophoretic Mobility of Single-Walled Carbon Nanotubes: A Comparison of Theory and Experiment

The electrophoretic mobilities of single-walled carbon nanotubes (SWNTs) in agarose gels subjected to negatively charged covalent functionalization and noncovalent anionic surfactant adsorption are compared using a simplified hydrodynamic model. Net charges are calculated on the basis of estimated friction coefficients for cylindrical rodlike particles. The effects of functionalization with negatively charged 4-hydroxybenzene diazonium and anionic sodium cholate are quantified and compared with model predictions. The adsorption of Na+ counterions into the nonionic surfactant layer adsorbed on SWNTs (Triton-X-405) is shown to induce a positive charge and reverse the mobility under select conditions. This effect has not been identified or quantified for nanoparticle systems and may be important in the processing of these systems.

Effect of anionic surfactants on synthesis and self-assembly of silica colloidal nanoparticles

Effects of the anionic surfactants, sodium dodecyl sulfate and sodium oleate, on the formation and properties of silica colloidal nanoparticles were investigated. At a concentration of ∼ 1 × 10 −3 M , adsorption of anionic surfactants increased particle size, monodispersity, and negative surface charge density of synthesized silica particles. As uniformity of particle size and particle–particle interactions increase, colloidal photonic crystals readily self-assemble without extensive washing of the synthesized silica nanoparticles. The photonic crystals diffract light in the visible region according to Bragg's law. The assembled colloidal particle arrays exhibit a face-centered cubic structure in dried thin films. This study offers a new approach for producing ordered colloidal silica thin films.

Adsorption of anionic surfactants onto sepiolite

Anionic surfactants constitute the main ingredients of detergents and a number of surfactant formulations used in a spectrum of diverse industries. The aim of this study is to examine the amenability of natural sepiolite to the adsorption of anionic surfactants, sodium dodecylsulfate (SDS) and sodium dodecylbenzenesulfonate (SDBS). Adsorption isotherms exhibit three regions with distinctly different slopes. The first region is characterized by the complexation of anionic surfactants with Mg 2+ ions at the octahedral sheet or hydrogen bonding between the oxygen groups of anionic head groups of surfactant and H + of the bound or zeolitic water. The Mg 2+ ions released from sepiolite leads to the precipitation of magnesium salt of surfactant in the second region. The third region marks both the beginning of plateau region and micellar dissolution of the precipitate. The effect of temperature on surfactant adsorption for SDS/sepiolite system was utilized to calculate such thermodynamic parameters as the free energy of adsorption ( Δ G ads ° ) and the heat of adsorption ( Δ H ads ° ). The low value of Δ H ads ° (1.87 kJ/mol) is an evidence for the physical adsorption of anionic surfactants onto sepiolite. The relatively large value of entropic contribution ( − T Δ S ads ° ) indicates that the adsorption of anionic surfactants onto sepiolite is entropically governed.

Effect of ionic surfactants on bauxite residues suspensions viscosity

Measurement of the rheological property of bauxite residue sample received from an Australian alumina refinery, treated with a number of cationic and anionic surfactant in laboratory has been carried out using a Brookfield viscometer for the assessment of the effect of surfactants on the residue viscosity. Sodium laurate, prepared with an excess of sodium hydroxide, was found to be effective while direct addition of anionic surfactants (lauric acid and sodium laureth sulphate) and cationic (cetyl trimethyl ammonium bromide) produce only moderate effect on the red mud suspension apparent viscosity at 65 °C. The experimental data appear to confirm the crucial role of the cation sodium in the process of adsorption of anionic surfactants on the flocculated red mud particles.

Wettability alteration and spontaneous imbibition in oil-wet carbonate formations

Alkaline/surfactant flooding has been widely tested for its ability to improve oil recovery, but little effort has been made toward understanding the controlling mechanisms and variables. This paper investigates the effect of electrolyte concentration, surfactant concentration and water/oil ratio on wettability, phase behavior, and displacement from a narrow gap. Wettability of calcite can be altered to about intermediate-wet to preferentially water-wet with alkaline/surfactant systems. Anionic surfactant adsorption can be significantly reduced in the presence of sodium carbonate.

Electroacoustic characterization of electrokinetics in concentrated pigment dispersions: 3-Cyano-4-(4′-butanesulfonamidophenyl)-5-furylidene-furan-2-one

The surface and colloid chemistry of organic pigment dispersions have largely been ignored in the literature, although organic pigments play a crucial role in classical and ink jet printing and imaging. This paper presents detailed measurements of an aqueous dispersion of the title compound, prepared without added surfactant, and examines the adsorption of various anionic surfactants via electrokinetic sonic amplitude (ESA) measurements. Quantitative adsorption data are compared with adsorption isotherms obtained via phase separation methods and are found to be in good agreement. Determination of saturation monolayer adsorption is significantly faster and more convenient using ESA measurement technology. However, some of the surfactants examined exhibited multilayer or partial multilayer adsorption. A surfactant modeled after the title compound was synthesized and exhibited particularly effective stabilization, although the adsorption appears slightly weaker than the classical surfactants studied. The intrinsic negative surface charge observed in aqueous dispersion of the title compound was identified as due to mechanicochemical activation of surface molecules to hydrolyze the furanone ring to the α-cyano maleic acid moiety. Electrophoretic mobility measurements as a function of volume fraction at various ionic strengths indicate that increasing electrophoretic mobility magnitudes accompanying increasing NaCl concentrations were due to preferential adsorption of chloride to the particle surfaces.

Adsorption of Polycation and Anionic Surfactant onto Iron Surfaces and the Inhibition of Carbon Dioxide Corrosion

The adsorption process of two polycations (pDADMAC and C‐PAM) with different charge densities has been investigated using the quartz crystal microbalance technique with dissipation monitoring (QCM‐D). The effect of the charge density of the polycation, the NaCl concentration, and the complexation with an anionic surfactant are addressed in this work. X‐ray photoelectron spectroscopy and atomic force microscopy were utilized to analyze the adsorbate with respect to the film coverage and film structure. The corrosion‐inhibiting performance of the films on high‐purity iron in a CO2 saturated brine, at 25°C, 1 bar CO2, and pH 4, was investigated by the linear polarization resistance technique. It was found that the polycations adsorbed onto the iron surface, but the corrosion rate of 1 mm yr−1 was not lowered. However, the polycations formed a complex with an anionic surfactant, and such films showed excellent inhibition performance. Both films, of pDADMAC/SDS and of C‐PAM/SDS, lowered the corrosion rate of iron below 0.01 mm yr−1. The SDS concentration was below the cmc. It is believed that the SDS adsorbed into the preadsorbed polycation film, forming a complex structure resulting in a hydrophobic and dense film.

Ultrafiltration of oil-in-water emulsions with ceramic membranes: Influence of pH and crossflow velocity

The effect of pH and crossflow velocity on the ultrafiltration of a model metalworking o/w emulsion was studied. The emulsion was prepared using a vegetable oil as the base oil and a mixture of anionic and non-ionic surfactants as emulsifiers. Experiments were carried out using Carbosep ® tubular ceramic membranes with two different cut offs (50 and 300 kDa) in a transmembrane pressure range of 0.05–0.4 MPa. Concentration polarization was observed at low crossflow velocities. Zeta potential and droplet size distribution measurements showed that properties of the o/w emulsion are not affected by pH. However, both permeate flux and chemical oxygen demand (COD) retention decreased drastically at low pH values, since membranes become positively charged and adsorption of anionic surfactants onto the membrane surface takes place, making it more hydrophobic and causing flux decline and surfactant monomers permeation through the membrane. The resistance-in-series (RIS) model was applied in order to ascertain the main resistances to the permeate flux. COD retentions higher than 92% were achieved for all the operating conditions with both membranes.

Adsorption of anionic and nonionic surfactant mixtures from synthetic detergents on soils

Adsorption of anionic surfactant (sodium dodecylbenzenesulfonate, SDBS) and nonionic surfactant (an alcohol ethoxylates with 12 carbons and 9 oxyethyl groups, A 12E 9) mixtures, widely used as the major constituents of synthetic detergents in China and become the most common pollutants in the environment, on soils was conducted to investigate the behavior of mixed surfactants in soils. The effects of addition order and mixing ratios of two surfactants, associated with pH and ion strength in solutions, on adsorptions were considered. The results show that saturated adsorption amount of SDBS and A 12E 9 on soils decreased respectively when A 12E 9 was added into soils firstly compared with that secondly, possibly resulting from the screening of A 12E 9 to part adsorption sites on soils and the hydrocarbon chain–chain interactions between SDBS and A 12E 9. The adsorption of SDBS and A 12E 9 on soils was enhanced each other at pre-plateau region of isotherms. At plateau region of isotherms, the adsorption of SDBS on soils decreased with the increase of molar fraction of A 12E 9 in mixed surfactant solutions, while that of A 12E 9 increased except the molar ratio of SDBS to A 12E 9 0.0:1.0. With the increase of pH in mixed surfactant solutions, adsorption amount of SDBS and A 12E 9 on soils decreased, respectively. The reduction of ion strength in soils resulted in the decrease of adsorption amount of SDBS and A 12E 9 on soils, respectively.

Separation characteristics of charged ultrafiltration membranes modified with the anionic surfactant

Separation characteristics of charged ultrafiltration membranes (UF) premodified with the anionic surfactant—sodium dodecylsulfate—were studied. We investigated the membranes characterized by the irreversible adsorption of the anionic surfactant: negatively charged membranes PA-100 − with the pore radius of 5.7–9.0 nm and also membranes PA-10 with the pore radius of 2.9–5.8 nm having a small positive charge on the surface. Objects of investigation also included unmodified PA-100 − and PA-10 ultrafiltration membranes and nanofiltration membranes OFMN-P, OPMN-K, and OPMN-KM 3. We have established that due to the modification of UF membranes with the anionic surfactant their surface properties and pore structure undergo changes. The presented data indicate that the value of adsorption of the anionic surfactant affects the separation characteristics of modified membranes. Our investigations have shown that volume flow and Na + retention coefficient of modified ultrafiltration membranes PA-10 featuring the maximum anionic surfactant adsorption are commensurable with the separation characteristics of nanofiltration membranes at much lower working pressures.

Removal of Disperse Dyes from Water Using Surfactant Treated Alumina

An alumina surface was modified by adsorption of an anionic surfactant, sodium dodecyl sulfate (SDS). Typical S-shaped isotherm of surfactant on alumina was observed. The adsorption of Disperse Red-11, Disperse Blue-26 and Disperse Red-156 on alumina and surfactant treated alumina has been investigated. The enhancement in adsorption of these disperse dyes on surfactant treated alumina is observed, which may be attributed to their solubilization in surfactant aggregates formed at the solid/liquid interface. The effect of pH on adsorption has been studied. The adsorption is greatly influenced by pH of the medium. The applicability of the Langmuir model and the Dual-Mode sorption model (DSM) were tested for equilibrium data.

Regularities of the Two-Layer Adsorption of Anionic Surfactant and Cationic Polyelectrolyte on the Fused Quartz Surface

The adsorption of sodium dodecyl sulfate (SDS) on the quartz capillary surface that was preliminarily covered with a layer of cationic polyelectrolyte (CPE) is studied. The charge sign change of the modified quartz surface and subsequent increase of negative surface charge observed upon the adsorption of SDS indicate the formation of the second adsorption layer composed of surfactant molecules. It is shown that the surfactant layer is stronger attached to the surface at a higher charge of the CPE adsorption layer. Upon the formation of the surfactant layer on a looser CPE adsorption layer, the desorption of SDS molecules decreases, which can be associated with the partial penetration of these molecules into the CPE layer.

Adsorption and intercalation of anionic surfactants onto layered double hydroxides—XRD study

Layered double hydroxides (LDH) with brucite like structure was modified with various anionic surfactants containing sulfonate, carboxyl, phosphonate and sulfate end group through ion-exchange method. XRD reports indicated that the sulfonate group containing surfactants led to an adsorption process whereas the sulfate, carboxyl and phosphonate group containing surfactant led to an intercalation process. This can be evidenced from the change in basal spacing of LDH. The presence of anionic surfactants in the LDH was supported by FTIR spectroscopy. The FTIR spectrum indicated that complete removal of carbonate anion from the inter layer space of LDH is very difficult. The phosphonate intercalated HT showed less thermal stability than pristine LDH.

Kinetics of Adsorption of Anionic, Cationic, and Nonionic Surfactants

The kinetics of adsorption of anionic, nonionic, and cationic surfactants on a cellulose-water interface were investigated. The effects of monovalent, divalent, and a mixture of mono- and divalent salts on the adsorption kinetics of anionic surfactant were also investigated. The cellulose surface is shown to have dual sites of hydrophobic and hydrophilic nature. It is shown that anionic and nonionic surfactant molecules mostly adsorb on the hydrophobic site while cationic surfactant molecules mostly adsorb on the hydrophilic site. A simple model based on two-site adsorption is developed to describe the kinetics of adsorption. The values of rate constants are determined by using the experimental data and are compared with those reported in the literature. The rate constants show that the rates of adsorption of sodium dodecylbenzenesulfonate (NaDBS) and polyethoxylated tert-octylphenol (TX-100) are same and cetyltrimethylammonium bromide is higher than NaDBS and TX-100 at the cellulose-water interface.

Adsorption of Anionic Surfactant on Alumina and Reuse of the Surfactant-Modified Alumina for the Removal of Crystal Violet from Aquatic Environment

The adsorption characteristics of sodium dodecyl sulfate (SDS), an anionic surfactant on neutral alumina were studied in detail. Alumina was found to be an efficient adsorbent for SDS and could be used for the removal of SDS from its highly concentrated (several thousand ppm) solution. The equilibrium time found was 2 h. Though the removal efficiency was low (∼65%) at neutral pH, but in slightly acidic condition and in the presence of NaCl the efficiency could be increased dramatically (up to >98%). The adsorption isotherm study showed distinct four regions. The effects of various other parameters such as adsorbent dose, time, and the presence of different ions (Cl- NO- 3, SO2- 4, and Fe3+), and nonionic surfactant on the SDS adsorption were also studied. It was observed that the adsorption capacity was increased due to the presence of these ions in general. After the adsorption of SDS on alumina, the surfactant-modified alumina (SMA) was used for the removal of crystal violet (CV), a well-known cationic dye from aquatic environment. The kinetic studies showed that 1 h shaking time was sufficient to achieve the equilibrium. The removal of CV followed the second order kinetics. Studies were conducted to see the effects of adsorbent dose and initial CV concentration on the removal of CV using SMA. The pH was maintained at 6.7 ± 0.1. SMA was found to be very efficient, and ∼99% efficiency could be achieved under optimised conditions for the removal of CV when present even at a high concentration (200 ppm). To test whether the removal of CV was possible from real water using SMA, the adsorption study was conducted using CV spiked samples using distilled water, tap water, and synthetically prepared wastewater. It was interesting to note that the removal efficiency was even better for tap water and much better for wastewater when compared to that using distilled water. Desorption of both SDS and CV from the SMA surface was possible using 1 M sodium hydroxide solutions.

Adsorption of cationic–anionic surfactant mixtures on activated carbon

This paper reported the adsorption of cationic–anionic surfactant mixtures, such as octyltriethylammonium bromide/sodium dodecylbenzenesulfonate (OTEAB/SDBS) and dodecylpyridinium chloride/sodium octanesulfonate (DPC/SOS), on activated carbon (AC) in deionized water and in mineralized water systems. The AC surface chemistry was characterized by X-ray photoelectron spectroscopy and ζ-potential determinations. It was observed that in deionized water solution, the addition of SOS obviously promoted the adsorption of DPC, while the existence of OTEAB increased the adsorption of SDBS first and then decreased that slightly with increasing SDBS concentration. In mineralized water solution, the addition of cationic (anionic) surfactants reduced the adsorption of anionic (cationic) surfactants. It was shown that the adsorption of the surfactants on the AC was predominated mainly by the hydrophobic interaction between AC surface and surfactants because of the low oxygen content and very low ζ-potential on the AC surface. There might exist synergism between cationic and anionic surfactants when adsorbing on AC in deionized water due to the electrostatic interaction between oppositely charged surface active ions. Such synergism might be greatly weakened when a large number of inorganic salts exist owing to the “screen” effect of the counter ions of the salt on the electrostatic attraction of oppositely charged surface active ions.

Adsorption of anionic and non-ionic surfactants on a cellulosic surface

The adsorption of an anionic surfactant, sodium dodecylbenzenesulfonate (NaDBS) and a non-ionic surfactant, Triton X-100 (TX-100) has been studied on cellulose surfaces with and without the presence of electrolytes by using both spectrophotometric and titrametric methods. The adsorption isotherms are identified with four different regimes for both surfactants. Two important phenomena reflected in the adsorption isotherms are the steep increase in adsorption due to hemimicellisation below the critical micelle concentration (CMC) and the decrease in the adsorption above the CMC. Adsorption of anionic surfactant, NaDBS gets enhanced in presence of monovalent (K +) or bivalent (Ca 2+) cation while for non-ionic surfactant, TX-100 there is no such enhancement in adsorption in presence of salt.

Adsorption of organic compounds onto polyelectrolyte immobilized-surfactant aggregates on cellulosic fibers

The adsorption of anionic surfactants with different hydrophobic chain lengths onto cellulose fibers pretreated with a cationic polyelectrolyte has been investigated. Five steps are involved in the adsorption process, which was ascribed to the formation of monolayer and bilayer surfactant aggregates. Electrostatic interaction between the residual surface charges followed by hydrophobic interaction among the alkyl chains are considered the main factors in the adsorption process. The adsorption of the anionic surfactant was found to greatly enhance the retention of organic compounds onto the polyelectrolyte-treated cellulose. The coadsorption phenomenon, which was dependent on the saturation level of the adsorbed surfactant, has been explained in terms of the accumulation of the organic solute on the hydrophobic core generated by the adsorbed layer.

Confinement-Induced Phase Behavior and Adsorption Regulation of Ionic Surfactants in the Aqueous Film between Charged Solids

Self-consistent field theory for adsorption and association is utilized to calculate the adsorption of an ionic surfactant (C16P3+) to two identical, negatively charged, slightly hydrophobic solids separated by a thin film and immersed in an infinite reservoir of aqueous 1:1 electrolyte. This theory explicitly accounts for short-ranged “chemical” forces as well as electrostatic and polarization forces. A change in the separation between the solids leads to a change in interaction energy, which leads to a change in both the amount and the organization of the adsorbed surfactant (proximal adsorption). When the separation between the solids is much greater than the thickness of the adsorbed layers, the general features of the proximal adsorption can be predicted from the adsorption at infinite separation; the adsorption depends on whether each surface is above or below the charge compensation point (ccp). At the ccp, the net charge of the solid plus the adsorbed surfactant is zero. There are few other ions a...