“…4, 5, 6, and 7 the data obtained for the non-ionic surfactants C 11 DMPO, C 13 DMPO, C 10 EO 8 , C 12 EO 5 , Tr-45, Tr-100, and C 14 EO 8 are summarised, based on the results reported in [39–46, 48, 58, 59, 83–93]. It is seen that for almost all surfactants a good agreement exists between the fitting results of the drop profile and bubble profile analysis data by the Frumkin isotherm using the parameters given in the Table 1.Fig.…”
Section: Resultsmentioning
confidence: 99%
“…5Surface tension isotherms for C 10 EO 8 and C 12 EO 5 , data from [49, 87–89]Fig. 6Surface tension isotherms for Triton X45 and X100, data taken from [58, 83]Fig. 7Surface tension isotherms for C 14 EO 8 , data from [40, 48, 65]
…”
Section: Resultsmentioning
confidence: 99%
“…The realistic values of the diffusion coefficients indicate that a diffusion-governed adsorption mechanism can be applied for the description of these surfactant systems.Fig. 13Dynamic surface tension isotherms for aqueous surfactant solutions, experimental data from [39, 43, 58, 76] ( symbols ) and theoretical predictions ( curves )
…”
Section: Resultsmentioning
confidence: 99%
“…To calculate the dynamic surface tensions, the diffusion controlled adsorption model based on Fick’s equation was employed [58]. The diffusion of the surfactant in a drop of radius R is governed by Fick’s law.…”
Section: Methodsmentioning
confidence: 99%
“…For ethoxylated surfactants, however, especially those with large ethoxylated head groups and hydrocarbon chains, the Frumkin model oversimplifies the adsorption behaviour and the so-called reorientation model provides a better description of the interfacial layer. The main assumption in this model is that the adsorbed surfactants can have two orientations (subscripts 1 and 2) [58]. The resulting equation of state reads:where is the average molar area with being the surface coverage, and being the total adsorption.…”
Surface tension and dilational viscoelasticity of solutions of various surfactants measured with bubble and drop profile analysis tensiometry are discussed. The study also includes experiments on the co-adsorption of surfactant molecules from a solution drop and alkane molecules from saturated alkane vapor phase. Using experimental data for 12 surfactants with different surface activities, it is shown that depletion due to adsorption of surfactant from the drop bulk can be significant. An algorithm is proposed quantitatively to take into consideration the depletion effect which is required for a correct description of the co-adsorption of alkanes on the solution drop surface and the correct analysis of experimental dynamic surface tension data to determine the adsorption mechanism. Bubble and drop profile analysis tensiometry is also the method of choice for measuring the dilational viscoelasticity of the adsorbed interfacial layer. The same elasticity moduli are obtained with the bubble and drop method only when the equilibrium surface pressures are sufficiently small (Π < 15 mN m−1). When the surface pressure for a surfactant solution is larger than this value, the viscoelasticity moduli determined from drop profile experiments become significantly larger than those obtained from bubble profile measurements.
“…4, 5, 6, and 7 the data obtained for the non-ionic surfactants C 11 DMPO, C 13 DMPO, C 10 EO 8 , C 12 EO 5 , Tr-45, Tr-100, and C 14 EO 8 are summarised, based on the results reported in [39–46, 48, 58, 59, 83–93]. It is seen that for almost all surfactants a good agreement exists between the fitting results of the drop profile and bubble profile analysis data by the Frumkin isotherm using the parameters given in the Table 1.Fig.…”
Section: Resultsmentioning
confidence: 99%
“…5Surface tension isotherms for C 10 EO 8 and C 12 EO 5 , data from [49, 87–89]Fig. 6Surface tension isotherms for Triton X45 and X100, data taken from [58, 83]Fig. 7Surface tension isotherms for C 14 EO 8 , data from [40, 48, 65]
…”
Section: Resultsmentioning
confidence: 99%
“…The realistic values of the diffusion coefficients indicate that a diffusion-governed adsorption mechanism can be applied for the description of these surfactant systems.Fig. 13Dynamic surface tension isotherms for aqueous surfactant solutions, experimental data from [39, 43, 58, 76] ( symbols ) and theoretical predictions ( curves )
…”
Section: Resultsmentioning
confidence: 99%
“…To calculate the dynamic surface tensions, the diffusion controlled adsorption model based on Fick’s equation was employed [58]. The diffusion of the surfactant in a drop of radius R is governed by Fick’s law.…”
Section: Methodsmentioning
confidence: 99%
“…For ethoxylated surfactants, however, especially those with large ethoxylated head groups and hydrocarbon chains, the Frumkin model oversimplifies the adsorption behaviour and the so-called reorientation model provides a better description of the interfacial layer. The main assumption in this model is that the adsorbed surfactants can have two orientations (subscripts 1 and 2) [58]. The resulting equation of state reads:where is the average molar area with being the surface coverage, and being the total adsorption.…”
Surface tension and dilational viscoelasticity of solutions of various surfactants measured with bubble and drop profile analysis tensiometry are discussed. The study also includes experiments on the co-adsorption of surfactant molecules from a solution drop and alkane molecules from saturated alkane vapor phase. Using experimental data for 12 surfactants with different surface activities, it is shown that depletion due to adsorption of surfactant from the drop bulk can be significant. An algorithm is proposed quantitatively to take into consideration the depletion effect which is required for a correct description of the co-adsorption of alkanes on the solution drop surface and the correct analysis of experimental dynamic surface tension data to determine the adsorption mechanism. Bubble and drop profile analysis tensiometry is also the method of choice for measuring the dilational viscoelasticity of the adsorbed interfacial layer. The same elasticity moduli are obtained with the bubble and drop method only when the equilibrium surface pressures are sufficiently small (Π < 15 mN m−1). When the surface pressure for a surfactant solution is larger than this value, the viscoelasticity moduli determined from drop profile experiments become significantly larger than those obtained from bubble profile measurements.
Spilling breaking waves in the presence of light‐wind and surfactants are studied experimentally in a wind‐wave tank. The breaking waves are mechanically generated with a single wave maker motion that produces a weak spilling breaker in clean water without wind. Separate experiments are performed with the same wave maker motion at different low wind speeds in clean water and in water with various concentrations of Triton X‐100 (soluble surfactant). The crest profiles of the waves along the center plane of the tank are measured with a laser‐induced fluorescence (LIF) technique that utilizes a high‐speed camera. In clean water with wind speeds lower than 2.3 m/s (the minimum wind speed of wind‐generated waves for clean water in our tank), the breaking of the waves is initiated with a similar bulge‐capillary‐waves pattern on the forward face of the wave crest as reported in Duncan et al. (1999). When the wind speed is above 3 m/s, wind waves are generated. The wind waves strongly affect the breaking process of the mechanically generated waves. It is found that the bulge‐capillary‐waves pattern is independent of the wind, but is dramatically affected by surfactants. The slope of the back face of the wave crest decreases with increasing wind speed. At the moment of incipient breaking, the distances between the leading edge of the bulge (called the toe) and the highest point of the wave crest in all cases are linearly proportional to the surface wind drift. After the fluid in the bulge slides down the front face of the wave, the maximum horizontal distance of the toe away from the crest increases as the wind speed increases.
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