Impact of carbon dioxide on the surface tension of 1-hexanol aqueous solutions

Surface tension and adsorption kinetics of amphiphiles in aqueous solutions: The role of carbon chain length and temperature

Surface tension and adsorption behavior of mixtures of diacyl glycerol arginine-based surfactants with DPPC and DMPC phospholipids

This paper describes the effect of temperature on the surface tension and adsorption kinetics of 1-hexanol aqueous solutions. The experiments were performed in a closed chamber where both liquid and vapor phases coexisted, and the surface tension was influenced by a combination of liquid and vapor phase adsorption. The surface tension of 1-hexanol aqueous solutions at steady-state was found to decrease upon an increase in temperature, and a linear relationship was observed between them. The modified Langmuir equation of state and the modified kinetic transfer equation were used to model the experimental data of the steady-state and dynamic (time-dependent) surface tension, respectively. The equilibrium constants and adsorption rate constants were evaluated through nonlinear regression for temperatures ranging from 10 to 35 °C. From the steady-state modeling, the equilibrium constants for adsorption from vapor phase and liquid phase were found to increase with temperature. From the dynamic modeling, the adsorption rate constants for adsorption from vapor phase and liquid phase were found to increase with temperature too. Small deviations from the experimental data have been observed in the dynamic modeling. These deviations may be due to the experimental errors or more likely the limitations of the model used.

A homologous series of surfactins containing β‐hydroxy fatty acids having 13, 14, or 15 carbon atoms were isolated from the supernatant of Bacillus subtilis strain S499 cultures. Their surface‐active properties at the air‐water interface were then evaluated. Dynamic surface tension data were analyzed by the relaxation function γt=γm+(γo−γm)/[1+(t/t*)n]. Based on various parameters t*, n, vmax, γm calculated from this equation, the dynamic surface properties of surfactin were found to depend on both bulk concentration and hydrophobic character of the alkyl chain. At low concentrations of surfactin, the dynamic surface tension (γd) decreased with increasing carbon atom number of the surfactin alkyl chain (n=13 to 15). However, at high concentrations, the maximum decrease of 41‐4 was achieved by surfactin‐C14. In contrast, more strongly hydrophobic alkyl chains in surfactins always enhanced their ability in reducing the equilibrium surface tensions and their aptitude in forming micelles.

Dynamic and equilibrium surface tension of aqueous surfactant and polymeric solutions

Adsorption kinetics of the partially dissociated ionic surfactants: The effect of degree of dissociation

<p>The surface tension (ST) of xylem sap at the water-air interface is a crucial phenomenon, influencing many physiological events such as air seeding and embolism, by which xylem vessels become air-filled and cease to function. Refilling of embolized, may relies on sap’s surface activity at the interface. It is commonly assumed that the ST of xylem sap is equal to the ST of pure water (72 mN/m). However, xylem sap is a complex solution and consists of surface-active molecules that may adsorb and accumulate at the water-air interface and thereby reduce the ST of water as a function of their aqueous concentration. However, when a new water-air interface is formed, equilibrium ST is not reached instantaneously. Specifically, amphiphilic molecules are kinetically adsorbed and undergo orientation at the interface following diffusion from the bulk solution. Dynamic ST of xylem sap and liquid-solid interactions, describing the surface phenomena of the xylem of vascular plants is currently not fully understood. This is mainly due to a lack of quantitative knowledge on the rate and extent of dynamic and equilibrium ST of sap. In this regard, the main objective of this study is to quantify the dynamic and equilibrium ST of xylem sap as a function of their aqueous concentration. We extracted xylem sap from lemon trees and measured ST as a function of time using the pendant drop technique. The dynamic ST data were analyzed using empirical and diffusion-control mathematical models which adequately described the exponential-like decay of the ST as a function of time. The results showed reduced ST of water in the xylem sap, indicating significant surface activity, reaching equilibrium ST values as low as 42 mN/m. The rate of ST decay was higher in high sap concentration and reduced in diluted one. The results of dynamic and equilibrium ST and the corresponding model will be presented and their implications for xylem hydraulic functioning will be discussed.</p><p> </p><p>Keywords: Dynamic surface tension, Equilibrium surface tension, Diffusion, Xylem sap.</p><p> </p>

We report the use of UV light to control the dynamic surface tensions of mixed surfactant systems containing sodium dodecyl sulfate, SDS, and 4,4‘-bis(trimethylammoniumhexyloxy)azobenzene bromide, BTHA. The light influences the dynamic surface tension of these solutions by driving the isomerization of the azobenzene moiety from cis to trans. By combining use of the du Nouy ring, maximum bubble pressure, and Wilhelmy plate methods to measure dynamic and equilibrium surface tensions, the dynamic surface tension of an illuminated aqueous solution of these surfactants is demonstrated to be up to 25 mN/m lower than the dynamic surface tension of a solution not previously exposed to UV light. In contrast, the equilibrium surface tensions of these solutions change by less than 2 mN/m upon illumination. Measurements of quasi-elastic and static light scattering from these mixed surfactant solutions support our hypothesis that illumination influences the dynamic surface tension through its effect on the state of ag...

A Novel Fast Technique for Measuring Dynamic Surface and Interfacial Tension of Surfactant Solutions at Constant Interfacial Area

The dynamic surface tension (DST) data and biochemical parameters (BCP) of animal blood have been obtained. A strong positive correlation was found for goats between σ1, σ2, σ3 (DST) and sodium levels (BCP), λz (DST)—with the levels of lipid and sodium (BCP); whereas a strong negative correlation was found for goats between σ3 (DST) and the level of total protein and chloride (BCP), λz (DST)—with the level of albumin (BCP). A strong positive correlation was found for horses between σ1, σ2, σ3 (DST) and lipid levels (BCP); λ0 (DST)—the level of chloride (BCP); λz (DST)—the level of albumin and chloride (BCP). A strong negative correlation was found for horses between σ1 (DST) and sodium level (BCP); σ2, σ3 (DST) and chloride level (BCP); λ0 (DST) and lipid level (BCP). Some moderate and weak correlations of different types were also found, but these have less importance for practical usage. The particular correlations between BCP and DST data of the same serum samples allowed DST data to be checked directly at the farm, and requiring the use of more expensive and time-consuming biochemical analysis only in cases of high necessity for a particular animal.

Dynamic surface tension and surface rheology of biological liquids

Traditionally, surfactant bulk solutions in which dynamic surface tension (DST) measurements are conducted using the pendant-bubble apparatus are assumed to be quiescent. Consequently, the transport of surfactant molecules in the bulk solution is often modeled as being purely diffusive when analyzing the experimental pendant-bubble DST data. In this Article, we analyze the experimental pendant-bubble DST data of the alkyl poly (ethylene oxide) nonionic surfactants, C12E4 and C12E6, and demonstrate that both surfactants exhibit "superdiffusive" adsorption kinetics behavior with characteristics that challenge the traditional assumption of a quiescent surfactant bulk solution. In other words, the observed superdiffusive adsorption behavior points to the possible existence of convection currents in the surfactant bulk solution. The analysis presented here involves the following steps: (1) constructing an adsorption kinetics model that corresponds to the fastest rate at which surfactant molecules adsorb onto the actual pendant-bubble surface from a quiescent solution, (2) predicting the DST behaviors of C12E4 and C12E6 at several surfactant bulk solution concentrations using the model constructed in step 1, and (3) comparing the predicted DST profiles with the experimental DST profiles. This comparison reveals systematic deviations for both C12E4 and C12E6 with the following characteristics: (a) the experimental DST profiles exhibit adsorption kinetics behavior, which is faster than the predicted fastest rate of surfactant adsorption from a quiescent surfactant bulk solution at time scales greater than 100 s, and (b) the experimental DST profiles and the predicted DST behaviors approach the same equilibrium surface tension values. Characteristic (b) indicates that the cause of the observed systematic deviations may be associated with the adsorption kinetics mechanism adopted in the model used rather than with the equilibrium behavior. Characteristic (a) indicates that the actual surfactant bulk solution in which the DST measurement was conducted, most likely, cannot be considered to be quiescent at time scales greater than 100 s. Accordingly, the observed superdiffusive adsorption behavior is interpreted as resulting from convection currents present in a nonquiescent surfactant bulk solution. Convection currents accelerate the surfactant adsorption process by increasing the rate of surfactant transport in the bulk solution. The systematic nature of the deviations observed between the predicted DST profiles and the experimental DST behavior for C12E4 and C12E6 suggests that the nonquiescent nature of the surfactant bulk solution may be intrinsic to the experimental pendant-bubble DST measurement approach. To validate this possibility, we identified generic features in the experimental DST data when DST measurements are conducted in a nonquiescent surfactant bulk solution, and the DST measurements are analyzed assuming that the surfactant bulk solution is quiescent. An examination of the DST literature reveals that these identified generic features are quite general and are observed in the experimental DST data of several other surfactants (decanol, nonanol, C10E8, C14E8, C12E8, and C10E4) measured using the pendant-bubble apparatus.

Solubility determination of surface-active components from dynamic surface tension data

Adsorption of Globular Proteins at the Air/Water Interface as Measured via Dynamic Surface Tension: Concentration Dependence, Mass-Transfer Considerations, and Adsorption Kinetics

An examination of the short-time approximation for mixed-controlled adsorption