The influence of the sublayer on the surface dilatational modulus

Wantke, K. D.; Örtegren, Jonas; Fruhner, H.; Andersen, A.; Motschmann, H.

doi:10.1016/j.colsurfa.2004.11.046

Cited by 25 publications

(21 citation statements)

References 20 publications

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“…High values of surface viscoelasticity can potentially lead to the suppression of marginal regeneration and a reduced rate of foam film drainage [24][25][26] and coalescence [3,12] therefore, a good correlation between the liquid film or foam stability and the surface viscoelasticity has been found [27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42]. If the enhanced viscoelasticity is developed on airwater interface during foam generation (at surface ages < 1s), foamability can also be enhanced.…”

Section: Surface Viscoelasticitymentioning

confidence: 99%

Foamability of sodium dodecyl sulfate solutions: Anomalous effect of dodecanol unexplained by conventional theories

Wang

Nguyen

Farrokhpay

2016

Colloids and Surfaces A: Physicochemical and Engineering Aspect

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This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. • Antifoam efficacy of DOH and decreased bubble surface potential explain the decreased foamability of pre-CMC SDS-DOH solutions.• Complex effect of surfactant mixtures on foamability is demonstrated.4 AbstractConventional theories indicate that surfactant solutions with low surface tension, fast adsorption kinetics, and high interfacial viscoelasticity increase foamability. These theories are applicable to single surfactants of pre-CMC. Here, we examine whether these theories are applicable for surfactant mixtures. Specifically, we investigated the foamability of sodium dodecyl sulfate (SDS)-dodecanol (DOH) solutions. We found that the foamability of SDS-DOH solutions exhibited 'anomalies' that were unexplained by conventional theories. The remarkable decrease in the foamability of SDS solutions caused by the addition of DOH could not be easily explained by the theories of surface tension and surface viscoelasticity.Instead, we proposed alternative mechanisms to resolve these unexpected results. Below the DOH solubility limit, the replacement of SDS molecules by DOH molecules at the air-water interface results in a reduced surface potential, leading to a lower foamability. The antifoam effects of DOH droplets can account for the reduced foamability above this limit. This paper highlights the complex effect of surfactant mixtures on foamability.

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Section: Surface Viscoelasticitymentioning

confidence: 99%

Foamability of sodium dodecyl sulfate solutions: Anomalous effect of dodecanol unexplained by conventional theories

Wang

Nguyen

Farrokhpay

2016

Colloids and Surfaces A: Physicochemical and Engineering Aspect

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“…A good correlation between the liquid film or foam stability and the surface viscoelasticity has been reported [60,[62][63][64][65][66][67][68][69][70][71][72][73][74][75][76][77][78]. However, questions remain unanswered: Is the good correlation between film stability and surface rheology indicative of a similar correlation with foam stability?…”

Section: Surface Viscoelasticity and Foam Propertiesmentioning

confidence: 97%

Effects of reagents and solid particles on drainage and stability of liquid film, foam and froth

Wang¹

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The objective of this study is to explore the interrelated mechanisms governing foam drainage and stability by modeling the foam column kinetics, measuring the interfacial properties of the air-water interface and conducting forced drainage experiments. Studies on foams are usually divided into four length scales: (i) a gasliquid interface (molecular scale), (ii) a liquid film (nanometer scale), (iii) a bubble (millimeter scale), and (iv) a foam (meter scale). Although much progress has been made in each length scale, the correlation between the different length scales remains poorly understood and quantified. The present study seeks to address this problem. In many industrial processes, such as froth flotation and foam fractionation, careful control of the foam or froth stability is required to optimize the process performance. Therefore, an understanding of the correlation between the different length scales is of paramount interest for industrial applications. The present study can be divided into three different parts: (1) foam column kinetics, (2) mechanisms governing foamability and foam stability, and (3) foam drainage in the presence of solid particles.The first part models foam column kinetics to predict the evolution of foam growth, liquid fraction, the transport of liquid and gas in growing foams and foam collapse by analogy with chemical kinetics. First, a modeling framework was formulated to categorize the foam or froth growth models into zeroth, first and second order, according to the dependence of the foam collapse rate on the foam volume or height.Then, a novel kinetic model was developed based on the mass balance of gas and liquid in the foam column to simulate the foam column kinetics. Finally, the simulation results were compared with the reported experimental data. Good agreement between model predictions and published experimental results confirms the validity of the analogy between foam column kinetics and reaction kinetics.Mechanisms governing the foamability and foam stability are crucial to understanding foam behaviors. The foamability and foam stability of surfactant blend and surfactant solutions in different electrolyte concentrations were examined to elucidate the different mechanisms that collectively determine foamability and foam stability. The foam growth kinetic model developed in the previous section was also applied here. First, the foamability of sodium dodecyl sulfate (SDS)-dodecanol (DOH) IIsolutions was investigated to test the conventional theories that apply to a single surfactant of pre-critical micelle concentration (CMC). The remarkable decrease in the foamability of SDS solutions caused by the addition of DOH could not be easily explained by the theories of surface tension and surface viscoelasticity. Instead, alternative mechanisms were proposed. Second, findings regarding the foamability of SDS-DOH solutions were extended to froth flotation, that is, the effect of a nonpolar collector (diesel oil) on the foamability of frother solutions (methyl isobutyl ca...

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“…(6.12) and (6.14), the measured elasticity modulus should then become equal to the Gibbs elasticity of the surface. However, significant deviations from Gibbs elasticity have been reported even at high frequencies which have been attributed to the effect of subsurface adsorption layer (Wantke et al, 2005) or the compressibility of surfactant layer (Kovalchuk et al, 2005). Here, we used the directly measured dilatational elasticity instead of Gibbs elasticity since it provides a better estimation of the surface elasticity under dynamic surface conditions.…”

Section: Tlf Drainage Kineticsmentioning

confidence: 99%

“…Their SHG measurements on the surface of an oscillating bubble provided experimental evidence for the proposed extended surface model (Örtegren et al, 2004). Later on, they discussed their findings in the framework of the Guggenheim convention (Wantke et al, 2005 …”

Section: Guggenheim Model Of Fluid -Liquid Interfacesmentioning

confidence: 99%

“…It would, however, be informative and helpful to know how the geometry of adsorption could affect the physicochemical properties of interfaces and how one could experimentally distinguish between the Gibbs and the Guggenheim models of fluid interfaces. There are only a few papers in the literature to date that have addressed this issue (Wantke et al, 2001;Wantke et al, 2005). Chapter 5 presented an example of how the monolayer adsorption could arouse controversy over the Gibbs analysis of the surface tension data.…”

Section: Introductionmentioning

confidence: 99%

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Molecular insights of adsorption and structure of surfactants and inorganic ions at fluid – liquid interfaces

Shahir¹

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Traditional approaches to studying fluid -liquid interfaces include the macroscopic measuring of interfacial properties such as surface tension and matching the collected data against adsorption models. This method is capable of producing valuable data about the thermodynamics of adsorption and has been widely used by the community to extract information about the adsorption of thousands of different surface-active molecules. Nonetheless, this methodology cannot produce any molecular-level information about the microscopic structure of adsorption layers and interfaces.As a result, the molecular origins of many interfacial phenomena remained unknown until the advent of surface-sensitive techniques such as computer simulation and non-linear spectroscopy.The new insights provided by these methods have challenged the traditional views about the origins of some interfacial phenomena and promise modification of classical theories which were developed to explain these phenomena.In general, this thesis aims to study the interfacial structure and adsorption of ionic surfactants, some surface-active alcohols as model nonionic surfactants including, n-pentanol, methyl isobutyl carbinol (MIBC) and n-hexanol and inorganic salts including LiCl, NaCl and CsCl at both microscopic and macroscopic levels. The employed methodology involves a combination of traditional adsorption modelling with some macroscopic measurements and sum frequency generation (SFG) spectroscopy, which is capable of distinguishing between bulk and interfacial molecules. Using SFG spectroscopy, the interfacial structure of adsorption layers and the composition of interfaces were investigated in detail and independently of the bulk solution.Specifically, the surface saturation of solutions of MIBC was identified directly using SFG spectroscopy and was then compared to equilibrium surface tension data to find that surface tension surprisingly continued to decrease even after full surface saturation. This is in contradiction to the traditional view that all surfactants adsorb at the outermost adsorption monolayer. Because of the limited surface area of the topmost adsorption monolayer, its full saturation is considered as the end of the adsorption process. This view is based on the notion of Gibbs dividing plane, which is usually taken as being equal to the physical adsorption monolayer in a surfactant solution. The postsaturation surface tension decrease, therefore, cannot be explained by the Gibbs convention. A different adsorption geometry, which considers the under-monolayer adsorption of alcohols, was proposed based on the Guggenheim extended interface model. In Chapter 5, a recent controversy about the applicability of the famous Gibbs adsorption isotherm to the analysis of surface tension data was addressed with regards to the new concept of under-monolayer adsorption. The results showed that the linearity of a surface tension plot is not necessarily indicative of a fully saturated ii surface. The same adsorption geometry was also proposed for t...

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The influence of the sublayer on the surface dilatational modulus

Cited by 25 publications

References 20 publications

Foamability of sodium dodecyl sulfate solutions: Anomalous effect of dodecanol unexplained by conventional theories

Foamability of sodium dodecyl sulfate solutions: Anomalous effect of dodecanol unexplained by conventional theories

Effects of reagents and solid particles on drainage and stability of liquid film, foam and froth

Molecular insights of adsorption and structure of surfactants and inorganic ions at fluid – liquid interfaces

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