Anionic Cationic Adsorption Films Research Articles

Properties of anionic–cationic adsorption films:: Part 2

The composition and mutual interactions of the components in anionic–cationic adsorption films have been determined by using a regular solution model for the mixed monolayers. Equimolar mixtures containing sodium nonylsulfonate and decyl- or dodecylpyridinium chloride or bromide have been investigated. The ionic strength of the solutions has been fixed by addition of appropriate amount of inorganic electrolyte (NaCl, NaBr, NaI). It has been found that an increase of the ionic strength and change of the inorganic electrolyte from sodium chloride through bromide to iodide results in a weakness of mutual attraction of the adsorbed components which indicates that these interactions have a mainly electrostatic character. The ionic strength of the solution and the kind of the inorganic electrolyte also distinctly influence the composition of mixed adsorption films. This effect is greater the more different the surface activity is of the mixture components.

Properties of Anionic–Cationic Adsorption Films in the Presence of Inorganic Electrolytes, 2

The composition and mutual interaction of the components in anionic–cationic adsorption films have been determined by using a regular solution model for the mixed monolayers. Equimolar mixtures of surfactants that differ markedly in their surface activity (decylpyridinium chloride and sodium butylsulfonate) have been investigated. A marked asymmetry of the composition of mixed adsorption films, as well as mutual attraction of the adsorbed components (negative values of surface interaction parameter β) have been found in these systems. The effect of the ionic strength and kind of the inorganic electrolyte on the surface interactions is similar, as in the case of mixtures of decylpyridinium chloride and sodium alkylsulfonates with hydrocarbon chains longer than the butyl ones that were previously investigated.

Properties of anionic–cationic adsorption films

The regular solution model for mixed monolayers was used to calculate the composition of the anionic–cationic adsorption films and parameters characterizing the mutual interactions between their components. The surfactants forming the mixed monolayers were decylpyridinium chloride and sodium hexylsulfonate. The monolayers under investigation were all adsorbed from equimolar solutions of surfactants. The results obtained show that the composition of the anionic–cationic adsorption films is dependent on the concentration and the kind of inorganic electrolyte present in the solution. The values of surface interaction parameter β, being all negative, show that the adsorbed components attract mutually. It has been observed that the strength of the attraction mentioned is also dependent on the factors given above for the composition of mixed adsorption films. It has also been established that the system examined here behaves, both qualitatively and quantitatively, in very similar manner to the previously investigated mixture of decylpyridinium chloride and sodium octylsulfonate, i.e. of surfactants with the same difference in length of the hydrocarbon chains as examined in this work.

Properties of Anionic–Cationic Adsorption Films in the Presence of Inorganic Electrolytes

The composition and mutual interaction of the components in anionic–cationic adsorption films have been determined by using to the mixed monolayers a regular solution model. The effect of the inorganic electrolyte concentration and kind on the properties of monolayers adsorbed from solutions containing decylpyridinium chloride and sodium decylsulfonate in concentration ratios varying over a wide range has been investigated. The calculations have been performed both neglecting and taking into consideration the effect of surface interactions on the partial molar areas of surfactants in the mixed monolayer. It has been found that although calculation results are very different, all conclusions concerning the effect of the solution composition are almost the same in both cases.

Influence of Inorganic Electrolyte Concentration on Properties of Anionic–Cationic Adsorption Films

The composition and mutual interaction of the components in mixed adsorption films have been determined on the basis of the results of surface tension measurements obtained for solutions of single anionic and cationic surfactants with hydrocarbon chains of the same length (sodium decylsulfonate and decylpyridinium chloride) and their mixtures. An equation analogous to one derived on the basis of a regular solution model, however without the controversial assumption that the excess entropy of mixing is zero, has been used in calculations. Investigations have been made for mixtures of different compositions and for different concentrations of added inorganic electrolyte (NaCl).

Effect of Inorganic Electrolyte Concentration on Anionic-Cationic Adsorption Films: 4. Dodecylpyridinium Bromide + Sodium Octylsulfonate + Sodium Bromide

The effect of sodium bromide concentration on the simultaneous adsorption of dodecylpyridinium bromide and sodium octylsulfonate on the free surface of their aqueous solutions has been investigated. The composition of the mixed films adsorbed from equimolar solutions has been evaluated on the basis of the Gibbs adsorption equation and by using the regular solution model, it has been stated that this composition depends on the surface tension value and the concentration of added inorganic electrolyte. The same factors influence the value of the surface interaction parameter β; negative values indicate a strong attraction between the adsorbed components. The concentration ratio of both surfactants in the solution significantly influences the composition of anionic-cationic adsorption films and the mutual interactions of their components. A distinct difference in the effects of NaBr and NaCl on the properties of the mixed monolayers has been also found.

Effect of inorganic electrolyte concentration on anionic-cationic adsorption films. Part 3: Dodecylpyridinium chloride + sodium octylsulfonate + sodium chloride

Abstract The effect of sodium bromide concentration on the simultaneous adsorption of dodecylpyridinium bromide and sodium octylsulfonate on the free surface of their aqueous solutions has been investigated. The composition of the mixed films adsorbed from equimolar solutions has been evaluated on the basis of the Gibbs adsorption equation and by using the regular solution model, it has been stated that this composition depends on the surface tension value and the concentration of added inorganic electrolyte. The same factors influence the value of the surface interaction parameter β; negative values indicate a strong attraction between the adsorbed components. The concentration ratio of both surfactants in the solution significantly influences the composition of anionic-cationic adsorption films and the mutual interactions of their components. A distinct difference in the effects of NaBr and NaCl on the properties of the mixed monolayers has been also found.

Effect of the molar ratio of surfactants in the solution on the composition and mutual interactions in anionic—cationic adsorption films

The composition and mutual interactions of the components in anionic—cationic films adsorbed from solutions of composition varying over a wide range have been calculated by using a regular solution model of the mixed monolayer on the basis of surface tension measurements. Mixtures of surfactants of similar surface activity (sodium decylsulfonate and decylpyridinium chloride) as well as those differing markedly in their surface activity (dodecylpyridinium chloride and sodium octylsulfonate), containing a large excess of inorganic electrolyte (0.1 M NaCl), have been investigated. Both types of mixtures show negative deviations from ideal behavior. The attractive interaction between adsorbed components is strongest in the case of adsorption from solutions containing equimolar amounts of both surfactants. This interaction is stronger in the case of mixtures of surfactants containing hydrocarbon chains of the same length. Over a wide composition range these mixtures form mixed films of almost equimolar composition. However, in the case of mixtures of surfactants differing in their surface activity, mixed adsorption films are formed which consist predominantly of the component with the longer hydrocarbon chain even if its content in the solution is very small. The composition of mixed monolayers and the mutual interactions between their components are dependent on the surface tension in a significant way,

Effect of Inorganic Electrolyte Concentration on Anionic-cationic Adsorption Films

Effect of Inorganic Electrolyte Concentration on Anionic-cationic Adsorption Films

Application of the regular solution model to anionic-cationic adsorption films

The composition and mutual interactions of the components in anionic-cationic adsorption films have been calculated by using a regular solution model of the mixed monolayers. The components of the mixtures investigated were sodium alkylsulfonates and alkylpyridinium halides. It has been stated that the composition of monolayers adsorbed from equimolar solutions is close to that obtained on the basis of the Gibbs surface excesses and is dependent on the surface tension value (the degree of surface coverage), the difference in the surface activity of the components (except for the solutions in pure water) as well as the concentration and type of added inorganic electrolyte. The same factors influence the value of the interaction parameter β, for which negative values indicate a strong attraction between the components in the mixed monolayers.

Effect of inorganic electrolyte concentration on anionic-cationic adsorption films Part 1. Decylpyridinium chloride + sodium octylsulphonate + sodium chloride

The effect of NaCl on simultaneous adsorption of decylpyridinium chloride (R10PyCl) and sodium octylsulphonate (R8SO3Na) on the free surface of their aqueous solutions has been examined. The surface excess of each component was determined on the basis of a suitable form of the Gibbs adsorption equation. The ionic strength effect on the adsorption of particular components of mixtures, as well as on the composition of anionic-cationic films adsorbed from equimolar solutions, is small. This is due to little difference in surface activity of surfactants investigated.

Effect of inorganic electrolyte type on anionic—cationic adsorption films

The effect of inorganic electrolyte type (NaCl, NaBr, NaI) on the composition of anionic—cationic films adsorbed from solutions containing alkylsulphonate (R m SO 3 −) and alkylpyridinium (R n Py +) ions has been investigated. The surface excess of each component has been determined by using a from of the Gibbs adsorption equation appropriate to the results of surface tension measurements. It has been found that the replacement of NaCl by NaBr has almost no effect on the mixed monolayer composition, whereas the replacement of NaCl by NaI gives a considerable effect — the largest one occurring for films having a resultant cationic character ( n &>; m). On applying the integral adsorption isotherm based on Butler's equation to the results of surface tension measurements. Δ G values have been calculated for anionic—cationic surfactant adsorption. It has been found that, contrary to cationic monolayers investigated earlier, mixed adsorption films are actually insensitive to the inorganic electrolyte type, which indicates a substantial reduction of the resultant electric charge.

Effect of the ionic strength of the solution on the composition of anionic-cationic adsorption films: octylpyridinium chloride/sodium dodecylsulfonate

Effect of the ionic strength of the solution on the composition of anionic-cationic adsorption films: octylpyridinium chloride/sodium dodecylsulfonate

Thermodynamic characteristics of anionic—cationic adsorption films based on a butler-type equation, II

It was stated that the simplified form of an integral adsorption isotherm based on the Butler's equation and derived previously (D. Góralczyk and B. Waligóra J. Colloid Interface Sci. 82, 1 (1981)), describes satisfactorily the surface behavior of the solutions containing equimolar amounts of anionic and cationic surfactants with various surface ativity only within the range of great surface pressures. On the other hand, in the case of a small degree of surface coverage, deviation appear due to the presence of excess of ions with longer alkyl chain in the mixed adsorption film. The values of Δ G of adsorption for anionic—cationic surfactants are within the limits of experimental error equal to the sum of the values characteristic for single ionic substances being components of the mixture. The presence of adsorption film influences on the water structure in the surface layer which causes nonzero values of Δ G H2 O .

Thermodynamic characteristics of anionic—cationic adsorption films based on a butler-type equation

An attempt has been made to interpret the results of measurements of the surface tension of solutions containing equimolar amounts of anionic and cationic surfactants with hydrocarbon chains of the same length by a simplified form of the integral adsorption isotherm based upon Butler's equation. In the case of mixtures of surfactants with relatively short hydrocarbon chains ( n k = n a = 8 or 10) this isotherm satisfactorily describes the experimental results, which makes possible the calculation of the values of the Gibbs free energy of adsorption for water and for anionic-cationic surfactants. Deviations observed in the case of mixtures of surfactants with longer alkyl chains ( n k = n a = 12) are probably caused by the strong interaction of adsorbed ions or by the lack of ideality of solutions.

Thermodynamic characteristics and composition of anionic-cationic adsorption films

On the basis of surface tension measurements carried out at fixed ionic strength (0.1 M) at different temperatures, the changes of standard thermodynamic functions ( ΔG o , ΔS o , and ΔH o ) have been calculated for the adsorption from solutions containing equimolar quantities of decylpyridinium chloride and sodium alkylsulfonates with different lengths of the hydrocarbon chain. Applying the Gibbs adsorption equation, the surface excess values have also been calculated for both types of surface-active ions which are adsorbed from solutions containing equimolar quantities of anionic and cationic detergents. It has been found that in the case of mixtures of detergents of different hydrocarbon chain lengths, the adsorption films are enriched in the more surfaceactive component, which is particularly marked at low surface coverage.