Surface Properties Of Aqueous Solutions Research Articles

Surface Properties of Aqueous Solutions of Mixtures of Sodium Dodecyl Sulphate and Linalool under Equilibrium and Dynamic Conditions

The effect of the concentration and of the composition of mixtures of a traditional surfactant sodium dodecyl sulphate (SDS) and of linalool (LL), a volatile fragrance with surface-active properties, on the surface tension of their aqueous solutions has been studied. Surface tension was measured both under equilibrium and under dynamic conditions of the surface formation (in a time range of 20 ms to 20 s), as well as during evaporation of solutions. It has been shown that under equilibrium conditions the individual surfactants and their mixtures exhibit similar surface activity. On the contrary, under dynamic conditions LL decreases surface tension faster in comparison to SDS, so that the surface tension of mixed solutions is determined by adsorption of LL. A synergetic effect on the decreasing of the surface tension at high surfactants concentration is observed both under dynamic and under equilibrium conditions. Upon evaporation of droplets of mixed solutions at a time interval of about minutes, the composition of the adsorption layer changes as a result of desorption of LL into the gas phase, so that the surface tension is determined by the adsorption of the second component—SDS.

Study of surface properties of aqueous solutions of sodium dodecyl sulfate in the presence of hydrochloric acid and heavy metal ions

The surface properties (equilibrium and kinetic studies) and adsorption characteristics of sodium dodecyl sulfate (SDS) at the liquid−air interface were presented. The effects of hydrochloric acid and heavy metal ions addition on some surface properties of SDS were studied. The equilibrium surface tension and critical micelle concentration (CMC) were obtained. Moreover, the adsorption parameters were calculated using the Szyszkowski equation. The kinetics of SDS adsorption was examined, and the diffusion coefficients as well as the micellar dissociation constant were calculated. As it was found both hydrochloric acid and heavy metal ions decrease the CMC values in all presented cases. The dynamic surface tension of the systems under discussion decreases with the increasing time and the higher the decrease is, the higher the surfactant concentration is. The SDS adsorption is controlled by diffusion. The value of diffusion coefficients decreases with the increasing surfactant concentration.

Dynamic surface properties of poly(methylalkyldiallylammonium chloride) solutions

Dynamic surface properties of aqueous solutions of cationic polyelectrolytes poly(hexylmethyldiallylammonium chloride) (PHMDAAC) and poly(butylmethyldiallylammonium chloride) (PBMDAAC) differ significantly from the properties of the solutions of other charged homopolymers, for example, sodium poly(sterenesulfonate) (PSS) and poly(dimethyldiallylammonium chloride) (PDMDAAC). At the same time, the obtained results are in agreement with the predictions of the theory of the dilational surface viscoelasticity of polymer solutions. The dynamic surface elasticity of PHMDAAC solutions increases monotonically with the surface age up to about 30 mN/m while the increase of the solution ionic strength results in non-monotonic kinetic dependencies and in low values (<5 mN/m) of the surface elasticity close to equilibrium. The surface activity of PBMDAAC is much lower and the deviations of the surface elasticity from zero exceed error limits only slightly in the investigated concentration range (≤0.2 wt%).

Behavior of thin liquid films from aqueous solutions of a pulmonary surfactant in presence of corticosteroids

Therapeutic pulmonary surfactants are currently investigated in clinical medicine as corticosteroids delivery vehicles into the lung. The influence of the corticosteroids Budesonide and Beclometasone dipropionate on the surface properties of aqueous solutions of the therapeutic surfactant preparation Curosurf® has been studied using the black foam film and the wetting film methods. The measurements of probability W for black foam film formation versus surfactant concentration C indicated that the two characteristics of black foam film stability – critical concentration Cc and threshold concentration Ct – for Curosurf® mixtures with 3μg/cm3 corticosteroids practically coincide with the values for Curosurf® alone. The disjoining pressure/black film thickness isotherms for mixtures of Curosurf®+corticosteroids are slightly shifted to larger film thicknesses compared to isotherm of Curosurf® alone. The measurements of wetting film thickness and wetting contact angles showed that the hydrophobization of SiO2-solid surface by mixtures of Curosurf®+corticosteroids is slightly smaller than the hydrophobization due to Curosurf® only. Budesonide and Beclometasone dipropionate equally influence the wetting behaviour of the Curosurf® solutions. These results indicate that the addition of corticosteroids does not alter significantly the surface properties of the therapeutic pulmonary surfactant.

Parameter Interpretation and Reduction for a Unified Statistical Mechanical Surface Tension Model.

Surface properties of aqueous solutions are important for environments as diverse as atmospheric aerosols and biocellular membranes. Previously, we developed a surface tension model for both electrolyte and nonelectrolyte aqueous solutions across the entire solute concentration range (Wexler and Dutcher, J. Phys. Chem. Lett. 2013, 4, 1723-1726). The model differentiated between adsorption of solute molecules in the bulk and surface of solution using the statistical mechanics of multilayer sorption solution model of Dutcher et al. (J. Phys. Chem. A 2013, 117, 3198-3213). The parameters in the model had physicochemical interpretations, but remained largely empirical. In the current work, these parameters are related to solute molecular properties in aqueous solutions. For nonelectrolytes, sorption tendencies suggest a strong relation with molecular size and functional group spacing. For electrolytes, surface adsorption of ions follows ion surface-bulk partitioning calculations by Pegram and Record (J. Phys. Chem. B 2007, 111, 5411-5417).

How do temperature and chemical structure affect surface properties of aqueous solutions of carboxylic acids?

• The surface properties of binary systems of aqueous–organic acid calculated. • The activity coefficients of components have been calculated by UNIFAC methods. • The interaction energy values were calculated by using LWW model. • The U 12 –U 11 value shows same behavior for studied systems with rising temperature. • The relative Gibbs adsorption increases with increasing the length of carboxylic acid chain. Surface properties of binary mixtures of organic acids (formic, acetic, propanoic and butanoic acids) with water have been calculated by surface tension data at various temperatures (293.15–323.15) K. The surface tension data over the whole mole fraction range are correlated by the Li et al. (LWW) model, then the interaction energy between organic acids and water have been calculated with the results of this model. Also, adsorption isotherms of binary aqueous solutions of organic acids are determined using Gibbs adsorption equation with experimental data found in the literature and using the UNIFAC group contribution method. The values of adsorption for mixtures of organic acids/water increases with increasing the alkyl chain length of organic acid at different temperatures. Finally, the results have been discussed in terms of surface concentration and lyophobicity using the extended Langmuir (EL) isotherm. The results provide information on the molecular interactions between unlike molecules that exist at the surface and the bulk.

Aggregation Behavior and Micellar Properties of Sodium Salts of Naphthenic Acid Mixtures

AbstractThe aim of this study was to investigate micellar and self‐assembly properties of four sodium salts of naphthenic acid mixtures by determination and comparative analysis of their critical micelle concentration values at seven different temperatures ranging from 10 to 40 °C using spectrofluorophotometric measurements. It was concluded that fractions having the lowest percentage of aliphatic structures give the least flexible micelles due to sterically rigid structure of cyclic side chains, what makes them difficult to pack in the micellar core. Additionally, surface properties of aqueous solutions of investigated mixtures were studied by the determination of the maximum surface excess, Γmax and the minimum area per surfactant molecule (Amin) values.

Salt-free catanionic surface active ionic liquids 1-alkyl-3-methylimidazolium alkylsulfate: Aggregation behavior in aqueous solution

A series of salt-free catanionic surface active ionic liquids (SAILs), 1-alkyl-3-methylimidazolim alkyl sulfates (denoted as [Cnmim][CmSO4], n=6, 8, 10; m=12 and n=4; m=10, 14) were synthesized by an ion exchange reaction and their surface properties in aqueous solution were examined systematically by surface tension, fluorescence and electrical conductivity measurements. As catanionic surfactants, these SAILs exhibit notably higher surface activity, compared to the cationic or anionic analogues. Increment in both cationic and anionic alkyl chain lengths for [Cnmim][CmSO4] can both improve the amphiphilic character remarkably. This can be ascribed to cooperative interactions as formation of catanionic pairs between alkyl-substituted imidazolium cations and alkyl sulfate anions. The negative micellization Gibbs free energy values prove that the micellization of all the 1-alkyl-3-methylimidazolim alkyl sulfates investigated is a spontaneous process. Any additional CH2 group makes the micellization process easier regardless if it is on a cation or an anion. When keeping the total carbon atom number constant, we find that the [Cnmim][CmSO4] molecules with greater asymmetric alkyl chains display superior surface activity. This work indicates that the self-assembly of these imidazolium-based salt-free catanionic SAILs can be tailored by adjusting the mismatch of alkyl chains. These SAILs are expected to have potential applications in the fields of colloidal and interface and nanomaterial synthesis.

Micellization and surface properties of aqueous solutions of binary mixtures of tween-80 and bromide cetyltrimethylammonium

The physicochemical properties of solutions of mixtures of cationic (cetiltrimethylammonum bromide) and nonionic (polyoxyethylene (20) sorbitan monooleate) surfactant, i.e., Tween-80, have been studied. The critical concentration of micellization, adsorption at the interface of a mixture of surfactants solution/air, and the minimum area occupied by a surfactant molecule have been determined. It was shown that, in the whole region of ratios between surfactants, sinergic effects are observed for both micellization and for the process of adsorption at the interface of a mixture of surfactants solution/air. The results obtained have been analyzed according to the regular solution theory (RST).

Thermodynamic studies on mixed micellization of amphiphilic drug amitriptyline hydrochloride and nonionic surfactant Triton X-100

In the present work, we report the surface properties and mixed micellization of a tricyclic antidepressant drug amitriptyline hydrochloride (AMT) with nonionic surfactant poly(ethylene glycol) t-octylphenyl ether (TX-100) using surface tension measurements. The surface properties in aqueous solution of AMT drug in the absence and presence of TX-100 are presented. The critical micelle concentration (cmc), maximum surface excess concentration at the air/water interface (Γmax) and the minimum area per surfactant molecule at the air/water interface (Amin) parameters are evaluated. Γmax increases and cmc as well as Amin decrease with increasing concentration (mole fraction) of the additive (TX-100). We also report the thermodynamics of AMT in the absence and presence of TX-100 and evaluated Gibbs energies (viz., at air/water interface (Gmin(s)), the standard Gibbs energy change of micellization (ΔmicG0), the standard Gibbs energy change of adsorption (ΔadsG0), the excess free energy change of micellization (ΔGexm)).

Synthesis and surface properties of aqueous solutions of chitosan derivatives and ethylene oxide sulfonic acids

The synthesis and surface properties of aqueous solutions of salts of chitosan and di-, tri-, and oligo(ethylene oxide) sulfonic acids are described. It is shown that, unlike chitosan acetate solutions, the solutions of chitosan oligo(ethylene oxide) sulfonate feature a pronounced surface activity and good foamforming properties; this makes the latter compounds candidates for use in foam technologies of fiber and textile finishing.

Effect of temperature on the behavior of surface properties of alcohols in aqueous solution

The influence of temperature on the behavior of surface properties of aqueous solutions has often been used to obtain information about solute structural effects on water. In this work, we present experimental results for surface tension of aqueous solutions of n-pentanol, n-hexanol, n-heptanol, and n-octanol at T = (283.15, 288.15, 293.15, 298.15, 303.15, and 308.15) K at several concentrations. The results were used to evaluate the limiting experimental slopes of surface tension with respect to mole fraction and the hydrophobicity constant of the Connors model at each temperature. The thermodynamic behavior of aqueous alcohol solutions is discussed in terms of the effect of the hydrocarbon chain on water structure. The temperature dependence of the limiting slopes of surface tension with respect to mole fraction, as well as the hydrophobicity constant derived from surface measurements, is interpreted in terms of alcohol hydration.

Sorption of Alkyl Benzyl Dimethyl Ammonium Compounds by Activated Sludge

The adsorption isotherms on activated sludge from wastewater treatment plants and the surface properties in aqueous solution of alkyl benzyl dimethyl ammonium compounds have been investigated. Langmuir and Freundlich adsorption isotherms described satisfactorily the equilibrium adsorption of these cationic surfactants on activated sludge. Adsorption on sludge as well as the affinity of these compounds to be adsorbed in the liquid/gas interface increased with increasing the alkyl chain length in the cationic surfactant molecule. Water hardness decreased the critical micelle concentration values of the alkyl benzyl dimethyl ammonium homologues tested and the extent of their sorption to activated sludge.

Association of cationic surfactants to humic acid: Effect on the surface activity

Surface properties of aqueous solutions of mixtures of humic acid, HA, and a series of cationic surfactants, C n TAB, have been studied. For a fixed amount of HA, the concentration of surfactant at which micelle-like aggregates are formed, cac, were determined. The log(cac) varies with the number of carbon atoms in the surfactant alkyl chain in a way similar to that shown by the log(cmc) of the pure surfactants. The addition of small amounts of C n TAB to an aqueous solution of HA has a huge effect on the surface tension decrease of water. This enhancement of the surface activity exhibited by mixtures of HA and C n TAB is explained in terms of the efficiency and effectiveness of surface adsorption. These parameters were determined by measuring the values of pC 20, and the excess surface concentration Γ, respectively. The values of the standard free energy of adsorption, Δ G ad ° , were also determined as a function of the surfactant chain length, and from this relation the contribution by methylene group was determined.

Dynamic Surface Tensions of Fluorous Surfactant Solutions

AbstractDynamic surface properties of aqueous solutions of cationic fluorous surfactant CF3CF2CF2O(CF(CF3)CF2O)2CF(CF3)CONH(CH2)3N+(C2H5)2CH3I‐ (abbrev. FC‐4 ) were reported. The critical micelle concentration (cmc) (3.6×10‐5 mol/L) and equilibrium surface tensions γeq were measured by Krüss K12 tension apparatus. Dynamic surface tension γ(t) was measured in the range of 15 ms to 200 s using the MBP tensiometer. The surface excess Γ, as a function of concentration, was obtained from equilibrium tensiometry using the Gibbs equation. Data from these experiments were combined to analyze the γ(t) decays according to the asymptotic Ward and Tordai equation. The results show that at the initial adsorption stage, the dynamic surface tension data were all consistent with this diffusion‐controlled mechanism, and at the end of the adsorption process, there were some evidences for an adsorption barrier, suggesting a mixed diffusion‐controlled adsorption mechanism. Using measured quantities, the barrier strength was estimated as between 25 and 35 kJ/mol at 25 °C. The surface pressure plays an important role in contributing to the barrier.

Dynamic Surface Properties of Sodium Poly(styrenesulfonate) Solutions

We present experimental results on the dynamic surface properties of aqueous solutions of sodium poly(styrenesulfonate). The dynamic surface elasticity at frequencies from 0.01 up to 500 Hz and at concentrations exceeding 0.1 wt % proved to be significantly higher than the corresponding data for solutions of nonionic polymers. Another peculiarity consisted in extremely slow changes of the surface properties with time. The addition of salt did not lead to significant changes of the surface elasticity, which was in disagreement with the expectation from the SCF theory. The obtained results can be explained if one assumes aggregate formation in the surface layer.

Surface properties of aqueous solutions of l-leucine

The surface tension, σ, of solutions of l-leucine (CH 3) 2CHCH 2CH(NH 2)COOH in water, as well as in aqueous solutions of NaOH and HCl were measured in the temperature range between 278 and 308 K using the Wilhelmy plate method. l-Leucine was found to be a very weak surfactant, which can be understood if assuming strong interactions of this solute with the water structure. Striking differences were observed in the surface entropy of l-leucine solutions in water, 0.5 M HCl and 0.5 M NaOH. Moreover, surface activity of the solute is much lower than that supposed taking into account the hydrophobicity of this amino acid. It was concluded that the observed phenomena are caused by the water structure changes close to the side chain of leucine, caused by enforced hydrophobic hydration, i.e. formation of clathrate-like hydrates.

Untypical surface properties of aqueous solutions of 1,5-pentanediol

The surface tensions σ of aqueous solutions of 1,5-pentanediol were measured in the temperature range between 278 and 338 K using Wilhelmy plate method. They exhibit, in a wide range of concentrations, the S-shaped temperature dependencies with a region of positive d σ/d T, never reported before. The results were interpreted in terms of specific interactions of molecules adsorbed at the interface. Increasing surface concentration of diol molecules forming an interface causes their rearrangement, which microscopic structure strongly depends on temperature, most possibly agglomeration or formation of micelles.

Association and surface properties of diblock copolymers of ethylene oxide and DL‐lactide in aqueous solution

AbstractDiblock copolymers of ethylene oxide and DL‐lactide (EmLn copolymers) were prepared by sequential anionic polymerisation and characterised by gel permeation chromatography (GPC) and 13C NMR. Their association and surface properties in aqueous solution were studied by surface tension and dynamic and static light scattering. Comparison of the critical micelle concentrations (cmc) and micelle association numbers (Nw) of the EmLn copolymers with published values for oxyethylene/oxybutylene (EmBn) copolymers indicated a slightly lower hydrophobicity for a lactide unit: i.e. L ≃ 0.75B. The temperature dependence of the cmc of copolymer E42L12 was analysed to obtain a standard enthalpy of micellisation ΔmicH0 ≈ 40 kJ · mol−1.

Surface Properties of Aqueous Solutions of Some Quaternary Ammonium Salts

It has been shown that the studied chlorine containing unsaturated quaternary ammonium salts (QAS) are micelle forming surfactants. Their colloid-chemical properties have been discussed on the grounds of their structural pecularities.