Adsorption Of Cationic Surfactants Research Articles

Electrosorption of amphiphilic surfactants at the mercury-solution interface and its influence on the stability of thin liquid films

The adsorption of non-ionic, anionic and cationic surfactants on a stationary mercury electrode from aqueous solutions of a supporting electrolyte is discussed with respect to phase transformations in the adsorption monolayer, the determination of adsorption parameters and outer Helmholtz potentials. Investigations of the stability of thin liquid films, formed from solutions of these surfactants between a mercury electrode and a hydrogen bubble reveal certain peculiarities. The latter are explained by the assumption of the existence, in some cases, of a hydrophobic component of the of the disjoining pressure in the films, with the estimation of the corresponding hydrophobic force constant.

Surfactant Adsorption by Zeolite: Hemimicelle Formation and Cooperative Adsorption

Adsorption of cationic surfactants on zeolites was measured potentiometrically by use of surfactant cation selective electrode. The surfactants used were dodecyltrimethylammonium bromide (DTAB) and tetradecyltrimethylammonium bromide (TTAB). Analysis of the binding isotherms indicates non- or less cooperative nature in the surfactant binding by zeolite. This fact suggests a difficulty of aggregation of bound surfactant ions like hcmimicclIe. On the other hand, fluorescence probing study by use of pyrene (Py) clearly indicated a formation of hydrophobic microenvironment even at a very small amount of bound surfactant. Probing study by 1-pyrenylaldehyde (PyA), however, indicated a gradual growth of hydrophobic nature of the microenvironment. The latter fact is consistent with the inference from the binding isotherm. Pyrene absorbed on zeolite is inferred to induce clustering of surfactant ions.

Adsorption of Cationic Surfactants to Keratin Powder

The adsorption of cationic surfactans onto keratin powder was studies to determine differences in alkyl chain length (C10C18). The adsorption isotherms of C10C14 cationics were of the Langmuir-type. Those of C16 and C18 cationics showed much stronger interaction with keratin powder than those of C10C14 cationics. Irreversible adsorption was also observed in the former. The kinetic frictional coefficient of keratin powder-adsorbed C10C18 cationics was measured. For C16 and C18 cationics, the values were less than those of C10C14 cationics. The amount of saturated adsorption, the sum of both hydrophobic and irreversible adsorption, increased in the order : C14>C16, C18>C12>C10.The antibacterial capacity of cationic surfactants against Staphylococcus aureus was assessed and interactions between cationic surfactants and ovalbumin were studied. The results in each case were found to be related to saturated adsorption. C14 showed the highest activity toward Staphylococcus aureus, ovalbumin and keratin powder regarless of the type of protein.

A theoretical interpretation of cationic surfactant adsorption of mica, monitored by electron spectroscopy for chemical analysis: effects of the surface energetic heterogeneity of mica

A theoretical interpretation of cationic surfactant adsorption of mica, monitored by electron spectroscopy for chemical analysis: effects of the surface energetic heterogeneity of mica

Flow adsorption calorimetry of surfactants as a function of temperature, salinity, and wettability

Surfactant adsorption and the enthalpy thereof have been evaluated using flow adsorption calorimetry. This technique permits the simultaneous determination of both the quantity and the enthalpy of adsorption. Temperature, salinity, surfactant type, and the wettability of the adsorbent surface were all shown to have an effect on both the amount of and the enthalpy of adsorption. In general, there was a decrease in adsorption as temperature increased and an increase in adsorption as salinity increased, up to a maximum. Similarly, the molar enthalpy of adsorption increased with increasing temperature and decreased with increasing salinity. The molar enthalpy of adsorption for all surfactant types was higher for oil-wet than for water-wet material. A Langmuir isotherm adequately described the adsorption of cationic surfactant on an oil-wet surface for all temperatures and salinities reported in this study.

Selective adsorption of cationic surfactants on crosslinked poly(p-hydroxystyrene)

Cross-linked poly(p-hydroxystyrene) (PHSresin) was found to be an excellent and selective adsorbent for cationic surfactants in aqueous solution. Its adsorption capacity was remarkably higher than those observed with cation-exchange resins and porous resins not possessing an ion-exchange functional group. In addition, its adsorption capacity was not reduced by the presence of hydrochloric acid, sodium hydroxide, or sodium chloride and other inorganic salts. Elution of the adsorbed surfactants from PHS resin was easily accomplished by treatment with methanol, and the resin was effectively regenerated, in sharp contrast to adsorption on conventional cation-exchange resins. Cationic surfactants were concentrated into about 10 wt% solution in methanol

A Thermodynamic Study of Adsorption of Cationic Surfactants from their Aqueous Solutions onto Oxide Surfaces: Theoretical Description of Adsorption Isotherms and Heats of Adsorption

AbstractExcept for the region of very low surface coverages, the adsorption of cationic surfactants from their aqueous solutions onto negatively charged oxide surfaces is governed by the competition between monolayer‐like and bilayer‐like surfactant aggregates formed on the solid surface. That adsorption mechanism combines, thus, the features of both ion and polymer adsorption, and yet is influenced strongly by the energetic heterogeneity of the surfaces of the real oxides. — Starting from that adsorption model a theoretical approach is developed, making a quantitative description of experimental adsorption isotherms and heats of adsorption possible. Illustrative calculations are presented for DTAB adsorption on silica gel.

Mixed adsorption of cationic and anionic surfactants from aqueous solution on silica gel

The adsorption of dodecyltrimethylammonium bromide (DTAB), dodecylpyridinium bromide (DPB), sodium dodecylbenzenesulfonate (SDBS) and sodium dodecyl sulfate (SDS) from their single aqueous solutions and DTAB—SDBS and DPB—SDS binary mixed solutions on silica gel at 25°C has been investigated. The results show that the individual cationic surfactants can be adsorbed strongly onto the silica gel, but no significant adsorption of anionic surfactants can be detected. However, in the mixed systems, the adsorption amounts of both the cationic and anionic surfactant ions are enhanced, and the excess adsorption of cationic surface-active ions is exactly equal to the adsorption of anionic surface-active ions. Thus, it is reasonable to suggest that the excess adsorption of cationic and anionic surface-active ions is in the form of ion-pairs.

A zeta-potential model for ionic surfactant adsorption on an ionogenic hydrophobic surface

Adsorption of ionic surfactants on a hydrophobic surface (i.e., Nuclepore track-etched polycarbonate membranes, Nuclepore Corp., Pleasanton, CA 94566) is investigated using electrokinetics. Zeta potentials computed from streaming-potential measurements are used in conjunction with an ionogenic surface charge model to characterize, for the first time, the electrical nature of these membranes. The polycarbonate surface exhibits a low, negative surface charge density (ca. a maximum magnitude of 0.2 μC/cm 2) and is ionogenic in nature in that the charge develops by the hydrolysis of discrete carboxylic surface groups with an average p K s of 3.92. Electron spectroscopy for chemical analysis (ESCA) confirms the presence of carboxylic groups on the surface. Streaming-potential measurements are also made for the adsorption of cationic surfactants (alkyltrimethylammonium bromides) and an anionic surfactant (sodium dodecyl sulfate) as a function of solution pH, ionic strength, and surfactant concentration. The ionogenic model for the membrane surface is extended to include Langmuir specific adsorption of the surfactants in the submonolayer region. Agreement between the proposed surfactant adsorption model and the new zeta-potential data is excellent over the range of pH and surfactant concentration studied. The standard free energy of adsorption for dodecyltrimethylammonium bromide is found to be −7.9 RT with a maximum adsorption site density of 4.9 × 10 16 sites/m 2. Likewise, the standard free energy for adsorption for sodium dodecyl sulfate is −8.6 RT with a maximum adsorption density of 1.3 × 10 16 sites/m 2. These results, derived from electrokinetic measurements, are in good accord with accepted values (1–4).

The Effect of Multilayer Adsorption of Cationic Surfactants on the Electrodeposition of Cobalt

It has been shown that the addition of the surfactant tetrabutylammonium perchlorate (TBAP) causes a periodic increase and decrease in the rate of deposition of cobalt as the concentration of surfactant is increased. This is interpreted as another example of the effect on the rate of surface reactions of the formation of alternating hydrophobic‐hydrophilic surfaces caused by Langmuir‐Blodgett type films on metals.

ζ-Potential and Surface Adsorbability of Styrene/Acrylamide Copolymer Latices in Aqueous Solutions of N-Alkylpyridinium Bromides

To study the surface adsorption of cationic surfactants on hydrophilic polymer latices, ζ-potentials of styrene/acrylamide [P (St/AAm) ] copolymer latices were measured in aqueous solutions of alkylpyridinium bromide (abbr. APB, CnH2n+1NC5H5Br;n=12: DPB, n=14: TPB, n=16: HPB). The thickness Δ of the AAm layer on the P(St/AAm) latex surface determined by viscosity and the distance t from the Stern layer to the slipping plane in the electirical double layer on the latex surface increased with AAm the fraction. It thus appears that the hydration layer is present on the surface of P(St/AAm) latices. The sign of the ζ-potential of the latex changed from negative to positive with increasing concentration of surfactant and the amount of surfactant adsorbed on latices decreased with increasing the thickness of PAAm layer. The surfactant adsorption increased with the hydrocarbon chain length of APB in the order, HBP>TPB >DPB. These results can be explained on the basis of electrostatic attractive force and hydrophobic interaction. The negative value of free energy of adsorption ΔG for surfactant on a latex decreased with increasing thickness of the PAAm layer and increased with chain length of the surfactant. The large positive value of entropy of adsorption ΔS indicates the importance of entropic interactions and the formation of hydrophobic bonds as driving forces for adsorption of the surfactant on a letex surface. It is concluded that the adsorbability of a surfactant onto P(St/AAm) latices is less than that on the PS latex, since hydrophilic poly-AAm layer is present on the surface of P(St/AAm) latices.

ζ-Potential and Surface Adsorbability of Styrene/Acrylic Acid Copolymer Latices in Aqueous Solutions of N-Alkylpyridinium Bromides

To study the surface adsorption of cationic surfactants on hydrophilic polymer latices, the ζ-potentials of styrene/acrylic acid [P(St/AA)] copolymer latices were measured in aqueous alkyl pyridinium bromide solutions (abbr. APB, CnH2n+1 NC5H5Br ; n=12 : DPB, n=14 : TPB, n=16 : HPB) and compared with those of polystyrene (PS), styrene/2-hydroxyethyl methacrylate copolymer [P(St/HEMA)] and styrene/acrylamide copolymer [P St/AAm] latices. Surface charge density (σ) was proportional to the amount of acrylic acid (AA) used in the copolymeation. σ for P(St/AA) latices increased with pH. The distance t from the Stern layer riz to slipping plane in the electrical double layer increased with the AA fraction. Hydrous poly acrylic acid (PAA)layers thus appear to be present on the surfaces of P(St/AA)latices. PAA layer thickness is less than that of poly-HEMA or poly-AAm layers. The amount of surfactant adsorbed per unit area of a latex was calculated from the ζ-potential value. The sign of the ζ-potential of a latex changed from negative to positive with increase in surfactant concentration. Surf actant adsorption increased with APB hydrocarbon chain length in the order, HPB>TPB>DPB. These results can be explained by elctrostatic attractive force and hydrophobic interaction. The amount of surfactant adsorbed on P(St/AA) latices was less than an the PS latex, equal to that on P(St/HEMA) and P St/AAm5 latices and larger than that on the P(St/AAm10) latex. The negative value of free energy of adsorption ΔG for a surfactant on a latex decreased with PS>P(St/HEMA)-P(St/AAm5)-P(St/AA5)>P(St/AAm10). The large posltlve value of enttopy of adsorption ΔS indicates the importance of entropic interactions and the formation of hydrophobic bonds as the driving force for adsorption of a surfactant on a latex surface. Steric prevention by a PAA layer may be less than that by poly-HEMA and poly-AAm layers.

Adsorption of cationic surfactants on muscovite mica as quantified by means of ESCA

A novel method for a quantitative determination of surfactant adsorption on the muscovite mica basal plane by means of ESCA is reported. The known three-dimensional chemical structure of mica, especially the number of exchangeable ions on the molecularly smooth surface, is utilized as an internal standard. Results obtained with this method for dimethyldioctadecylammonium ion adsorption are shown to yield a quantitative agreement with transfer ratios measured using a Langmuir—Blodgett technique. Adsorption isotherms of primary alkylammonium ions on the basal plane of muscovite mica am characterized by a first cooperative adsorption step occurring at low surfactant concentrations. At higher solution concentrations a further, much slower increase in the surface density of adsorbed molecules is observed. The relevance of these results for the understanding of flotation and contact angles is briefly discussed.

The zeta potential arising from cationic surfactant adsorption in non-aqueous dispersions of carbon black

The effect of counterion size of the cationic surfactants CTAC, CTAB and CTAS on the sign and magnitude of the zeta potential on Austin black dispersions in n-heptane and benzene were investigated. Zeta potentials were determined using single-particle microelectrophoresis. Velocities were measured at the stationary levels; all the conditions for true electrophoresis were satisfied. The measured electrophoretic mobilities were converted to zeta potentials using the Hückel equation, corrected for relaxation effects. Results for n-heptane dispersions and a series on quaternary ammonium salts differing only in the size of the counterions, indicated a dependence on the sign and magnitude of the zeta potential on the nature of the counterion. The smallest counterion (chloride) gave negative zeta potentials, while the larger counterions yielded positive zeta potentials which increased with increasing size of the counterions. Similar trends were observed with the benzene dispersions. An ion-induced surface dipole mechanism was postulated to explain the observed phenomena.

Mixed adsorption of nonionic and cationic surfactants on silica gel and methylated silica gel

The adsorption of ethoxylated octyl phenols Triton X-100 (TX100) and Triton X-305 (TX305) and cetyltrimethylammonium bromide (CTAB) from their single and mixed aqueous solutions on silica gel and methylated silica gel at 25°C has been investigated. The adsorption from mixed solutions of CTAB-TX100 or CTAB-TX305 on silica gel exhibits a synergistic effect at low concentrations and an antagonistic effect at high concentrations, but the effects are less pronounced for the latter system. It is suggested that the synergistic effect is due to the additional interaction between the hydrocarbon chains of adsorbed TX molecules and adsorbed CTA + ions. The antagonistic effect, which occurs at high concentrations, is believed to result from the formation of mixed micelles in the bulk solution. In contrast with that on the silica gel, the adsorption from mixed solution of TX100-CTAB on methylated silica gel shows no synergistic effect at low concentrations since the CTA + ion is not adsorbed. At high concentrations, although the adsorption of TX100 is obviously depressed in the presence of CTAB, the adsorption of CTA + ion becomes significant in the presence of TX100. It is suggested, as above, that the decrease in the adsorption of TX100 is due to the formation of TX100-CTA + mixed micelles in the bulk solution. At high concentrations of TX100, some CTA + ions may be incorporated into the adsorbed TX100 layer by the hydrophobic interaction between neighbouring hydrophobes (surface solubilization). However, the results show that neither TX305 or CTAB are adsorbed onto methylated silica gel either from their respective single solution or from their mixed solution.

Adsorption Mechanism of a Cationic Surfactant on Textiles in Excess Anionic Surfactant Solution

Many studies have been carried out on the mechanism of the adsorption of anionic and cationic surfactants on textiles. The case of cationic and anionic surfactants used in combination has also been reported. In such a case, the cationic surfactant is treated as a dispersion and when used with excess anionic surfactant solution, it is not adsorbed on textiles. In the present research, it was found that if a cationic surfactant is used as a corpuscle (fine solid, over 10 μm) in the presence of excess anionics, adsorption on to various textiles becomes possible.For an understanding of this phenomenon, the work of adhesion (Wa) between an anionic/cationic surfactant complex and the surface of a textile was calculated, measuring the contact angle of 2 liquids with the complex by Wu's equation. Wa and the amount of adsorbed cationic surfactant on textiles were found to show a very close correlation.Thus, in an excess anionic surfactant solution, an anionic/cationic surfactant complex is apparently formed on the surface of a corpuscle of a cationic surfactant, and the work of adhession between this complex and each textile is related to the adsorption (or deposition) of a cationic surfactant on textiles.

Electrical aspects of the adsorption of ionic surfactants on coal measured by the mean electrophoretic mobility as a function of sample dilution

A dilution method is proposed as a means of studying the adsorption of cationic surfactants on coal. Only the electrical part of the adsorption is observed. It is shown that particle charge increases with surfactant concentration, and some irreversibility occurs because the mobilities of states of high dilution depend on initial surfactant concentrations as well. The magnitude of the adsorption is different for different cations. A comparison of measurements on dilution with surfactant solution and distilled water supports the mechanism of particle charge arising from preferential cation adsorption.

ζ-Potential and Surface Adsorbability of Styrene/2-Hydroxyethyl Methacrylate Copolymer Latex in Aqueous Solutions of N-Alkylpyridinium Bromides

To study surface adsorption of cationic surfactants on a hydrophilic polymer latex, ζ-potential of styrene/2-hydroxyethyl methacrylate [P (St/HEMA)] copolymer latex was measured in aqueous solutions of alkyl pyridinium bromides (abbr. APB, CnH2n+1NC5H5Br; n=12 : DPB, n=14 : TPB and n=16 : HPB). Hydrophobic polystyrene (PS) latex was used as the reference sample. The amount of surfactant adsorbed per unit area of the latex was calculated from the ζ-potential value. With increasing concentration of surfactant, the sign of the ζ-potential of the latex changed from negative to positive and the amount of surfactant adsorbed increased. The surfactant adsorption increased with the hydrocarbon chain length of APB in the order HPB > TPB > DPB. These results can be explained by electrostatic bonds and the van der Waals force between the latex and surfactant. The amount of surfactant adsorbed on the P (St/HEMA) latex was less than that on the PS latex. The free energy of adsorption ΔG for a surfactant on a latex was calculated from parameters such as the slope of the ζ-log Cs (Cs : the concentration of surfactant) curve. The negative value of ΔG increased with chain length of the surfactant. Also this value on the P (St/HEMA) latex was less than that on the PS latex. The large positive value of the entropy of adsorption ΔG indicates the importance of entropic interactions and the formation of hydrophobic bonds as driving forces for adsorption of the surfactant on the latex surface. The ΔG for P (St/HEMA) latex had a smaller positive value than that for PS latex. It is concluded that the adsorbability of surfactant on P (St/HEMA) latex is lower than that on the PS latex, since hydrophilic poly-HEMA layer is present on the surface of the P (St/HEMA) latex.

Dewatering of a fuel grade peat with surfactants. Adsorption and electrokinetics

The influence of surfactants on the dewatering of a highly decomposed fuel peat was studied. Dewatering was effected by pressing at 2.06 MPa, for 2.5 min, with either a cationic surfactant, anionic surfactant or an inorganic electrolyte. The adsorption of the cationic surfactant on the peat and its effect on the zeta potential of the peat were measured. For the normally negatively-charged peat, adsorption of cationic surfactant leads to charge reversal at a surfactant concentration that is pH dependent. The anionic surfactant did not improve dewatering, while the cationic surfactant and the multivalent inorganic salt did. There is an optimum value for the amount of additive and this optimum dosage is found to occur at concentrations where the electrokinetic potential of the peat is near zero.

Adsorption of Cationic Surfactants on Phospholipid Membranes and Its Contributions to Membrane-Surface Potential

Abstract The adsorption behavior of cationic surfactants (alkyltrimethylammonium ions) on the phospholipid (phosphatidylethanolamine) membranes has been studied by means of interfacial electrostatic measurements, i.e., the surface potential of the monolayer and the zeta potential of the vesicles, in order to elucidate the balance between hydrophobic and electrostatic interactions. The data have been analyzed in terms of the interfacial electrochemical concept; these analyses have revealed that the hydrophobic interaction of a surfactant with the phospholipid membrane is the main motive force for adsorption and there is a critical alkyl-chain length to promote the surfactant adsorption. Furthermore, it was found that the electrostatic interactions between the surfactant and the phospholipid membrane, and among the surfactants themselves, also play a role in their adsorption.