scholarly journals Interfacially-Adsorbed Particles Enhance the Self-Propulsion of Oil Droplets in Aqueous Surfactant

2021 ◽  
Author(s):  
Seong Ik Cheon ◽  
Leonardo Batista Capaverde Silva ◽  
Aditya Khair ◽  
Lauren Zarzar
Keyword(s):  
Surface Coverage ◽  
Particle Surface ◽  
Surfactant Solution ◽  
Interfacial Area ◽  
Droplet Surface ◽  
Symmetrical Distribution ◽  
Oil Water ◽  
Particle Visualization ◽  
Anionic And Cationic Surfactants ◽  
Intermediate Surface

We have demonstrated that adsorption of silica nanoparticles at the interface of a solubilizing oil droplet in surfactant solution can significantly accelerate the droplets’ self-propulsion speed. Using fluorescent particle visualization, we correlated the degree of particle surface coverage on bromodecane droplets to the droplet speed in TX surfactant. Slowest speeds were found at the lowest and highest surface coverages and the fastest speeds were achieved at intermediate surface coverages of about 40%. The particle-assisted propulsion acceleration was further demonstrated in nonionic, anionic, and cationic surfactants and a range of oils with varying solubilization rates. We propose that particles at the droplet interface hinder solubilization by displacing oil-water interfacial area, providing asymmetry in the distribution of oil-filled micelles along the droplet surface and accelerating Marangoni flow. We describe a fluid-mechanical model to rationalize the effect of the particles by considering the effect of a non-symmetrical distribution of solubilized oil at the droplet surface. Approaches by which to modulate the distribution of solubilization across droplet interfaces may provide a facile route to tuning active colloid speeds and dynamics. <br>

Interfacially-Adsorbed Particles Enhance the Self-Propulsion of Oil Droplets in Aqueous Surfactant

2020 ◽  
Author(s):  
Seong Ik Cheon ◽  
Leonardo Batista Capaverde Silva ◽  
Aditya Khair ◽  
Lauren Zarzar
Keyword(s):  
Surface Coverage ◽  
Particle Surface ◽  
Surfactant Solution ◽  
Interfacial Area ◽  
Droplet Surface ◽  
Symmetrical Distribution ◽  
Oil Water ◽  
Particle Visualization ◽  
Anionic And Cationic Surfactants ◽  
Intermediate Surface

We have demonstrated that adsorption of silica nanoparticles at the interface of a solubilizing oil droplet in surfactant solution can significantly accelerate the droplets’ self-propulsion speed. Using fluorescent particle visualization, we correlated the degree of particle surface coverage on bromodecane droplets to the droplet speed in TX surfactant. Slowest speeds were found at the lowest and highest surface coverages and the fastest speeds were achieved at intermediate surface coverages of about 40%. The particle-assisted propulsion acceleration was further demonstrated in nonionic, anionic, and cationic surfactants and a range of oils with varying solubilization rates. We propose that particles at the droplet interface hinder solubilization by displacing oil-water interfacial area, providing asymmetry in the distribution of oil-filled micelles along the droplet surface and accelerating Marangoni flow. We describe a fluid-mechanical model to rationalize the effect of the particles by considering the effect of a non-symmetrical distribution of solubilized oil at the droplet surface. Approaches by which to modulate the distribution of solubilization across droplet interfaces may provide a facile route to tuning active colloid speeds and dynamics. <br>

scholarly journals Interfacially-Adsorbed Particles Enhance the Self-Propulsion of Oil Droplets in Aqueous Surfactant

2020 ◽  
Author(s):  
Seong Ik Cheon ◽  
Leonardo Batista Capaverde Silva ◽  
Aditya Khair ◽  
Lauren Zarzar
Keyword(s):  
Surface Coverage ◽  
Particle Surface ◽  
Surfactant Solution ◽  
Interfacial Area ◽  
Droplet Surface ◽  
Symmetrical Distribution ◽  
Oil Water ◽  
Particle Visualization ◽  
Anionic And Cationic Surfactants ◽  
Intermediate Surface

We have demonstrated that adsorption of silica nanoparticles at the interface of a solubilizing oil droplet in surfactant solution can significantly accelerate the droplets’ self-propulsion speed. Using fluorescent particle visualization, we correlated the degree of particle surface coverage on bromodecane droplets to the droplet speed in TX surfactant. Slowest speeds were found at the lowest and highest surface coverages and the fastest speeds were achieved at intermediate surface coverages of about 40%. The particle-assisted propulsion acceleration was further demonstrated in nonionic, anionic, and cationic surfactants and a range of oils with varying solubilization rates. We propose that particles at the droplet interface hinder solubilization by displacing oil-water interfacial area, providing asymmetry in the distribution of oil-filled micelles along the droplet surface and accelerating Marangoni flow. We describe a fluid-mechanical model to rationalize the effect of the particles by considering the effect of a non-symmetrical distribution of solubilized oil at the droplet surface. Approaches by which to modulate the distribution of solubilization across droplet interfaces may provide a facile route to tuning active colloid speeds and dynamics. <br>

Particles in monolayers and thin liquid films

Surfactants ◽  
2019 ◽  
pp. 467-500
Author(s):  
Bob Aveyard
Keyword(s):  
Free Energy ◽  
Particle Surface ◽  
Line Tension ◽  
Liquid Films ◽  
Thin Liquid Films ◽  
Fluid Interfaces ◽  
Free Energy Of Adsorption ◽  
Three Phase ◽  
Oil Water ◽  
Particle Adsorption

Small particles can adsorb strongly at fluid interfaces and form monolayers which can be studied using a Langmuir trough. For sufficiently large particles the monolayers can be viewed microscopically. The driving force for particle adsorption is the concomitant removal of fluid/fluid interface. For very small adsorbed particles, the free energy of forming the three-phase contact line around particles (hence the line tension) may also contribute significantly to the free energy of adsorption. Adsorption can be enhanced by having areas of particle surface with different wettability (Janus particles). Monolayers have structures dependent on lateral interactions between particles; for particles at the oil/water interface, electrical repulsion through oil is often the dominant interaction, which can give rise to highly ordered monolayers. Adsorbed particles can either inhibit or facilitate the formation of stable thin liquid films, depending on particle wettability.

Effect of enzyme molecules covering of oil–water interfacial area on the kinetic of oil hydrolysis

2008 ◽  
Vol 139 (3) ◽  
pp. 540-548 ◽  
Author(s):  
Sulaiman Al-Zuhair ◽  
K.B. Ramachandran ◽  
Masitah Hasan
Keyword(s):  
Interfacial Area ◽  
Oil Water ◽  
Enzyme Molecules ◽  
Oil Hydrolysis

scholarly journals Surface Tension of Surfactant-Containing, Finite Volume Droplets

2020 ◽  
Author(s):  
Bryan Bzdek ◽  
Rachael Miles ◽  
Jussi Malila ◽  
Hallie Boyer ◽  
Jim Walker ◽  
...  
Keyword(s):  
Surface Tension ◽  
Climate Models ◽  
High Surface ◽  
Particle Surface ◽  
Volume Ratio ◽  
Droplet Surface ◽  
Submicron Particles ◽  
Cloud Droplets ◽  
Droplet Shape ◽  
Size Dependent

&lt;p&gt;Surface tension influences the fraction of atmospheric particles that become cloud droplets. Recent field studies have indicated that surfactants, which lower the surface tension of macroscopic solutions, are an important component of aerosol mass. However, the surface tension of activating aerosol particles is still unresolved, with most climate models assuming activating particles have a surface tension equal to that of water. For surfactants to be relevant to particle activation into cloud droplets, multiple parameters must be considered. First, the concentration of surfactant in the initial particle must be sufficiently large that surface tension depression is maintained during activation, despite the dilution that occurs as water condenses onto the particle. Second, the high surface to volume ratio of micron and submicron particles necessitates partitioning a larger fraction of the surfactant molecules to the particle surface than in a typical solution, resulting in a depletion of the bulk concentration and an increase in the surface tension relative to a bulk sample. Third, the timescale for establishing equilibrium at the droplet surface must be known. The interplay of these parameters highlights the necessity of direct measurements of picolitre droplet surface tension.&lt;/p&gt;&lt;p&gt;This presentation will describe two cutting-edge approaches we have developed to directly measure the surface tension of microscopic droplets. In the first approach, ejection of ~20 &amp;#181;m radius surfactant-containing droplets from a dispenser excites oscillations in droplet shape that can be used to retrieve the droplet surface tension on microsecond timescales. These measurements allow investigation of surfactant partitioning timescales in aerosol and, crucially, test the assumption that droplet surfaces are generally in their equilibrium state. In the second approach, the coalescence of ~8 &amp;#181;m radius droplets is investigated. Coalescence excites droplet shape oscillations which again permit quantification of droplet surface tension. We demonstrate that surfactants can significantly reduce the surface tension of finite sized droplets below the value for water, consistent with recent field measurements. This surface tension reduction is droplet size dependent and does not correspond exactly to the macroscopic solution value. A new monolayer partitioning model confirms the observed size dependent surface tension arises from the high surface-to-volume ratio in finite-sized droplets and enables predictions of aerosol hygroscopic growth. This model, constrained by the laboratory measurements, is consistent with a reduction in critical supersaturation for activation and a 30% increase in cloud droplet number concentration, in line with a radiative cooling effect larger than current estimates assuming a water surface tension by 1 W&amp;#183;m&lt;sup&gt;-2&lt;/sup&gt;. The results imply that one single value for surface tension cannot be used to predict the activated aerosol fraction.&lt;/p&gt;

scholarly journals Reversible adsorption of proteins at the oil/water interface I. Preferential adsorption of proteins at charged oil/water interfaces

1946 ◽  
Vol 133 (870) ◽  
pp. 121-121
Keyword(s):  
Sodium Chloride ◽  
Isoelectric Point ◽  
Interfacial Area ◽  
Ammonium Bromide ◽  
Water Interface ◽  
Oil Droplets ◽  
Water Emulsion ◽  
Oil In Water ◽  
Alkaline Side ◽  
Oil Water

The behaviour of positively and negatively charged oil-in-water emulsions, stabilized with hexadecyl trimethyl ammonium bromide and sodium hexadecyl sulphate respectively in the presence of protein solutions has been studied. Under certain conditions proteins will adsorb to a charged oil/water interface. When finely dispersed oil-in-water emulsion was used to provide this oil/water interface, adsorption of protein resulted in flocculation of the oil droplets. Flocculation of emulsion on the addition of protein is pH conditioned and occurred on the acid side of the isoelectric point of the protein with negatively charged and on the alkaline side with positively charged oil globules. No flocculation occurred on the alkaline side of the isoelectric point with a negative emulsion or the acid side with a positive emulsion. The amount of protein required to cause maximum clarification of the subnatant fluid corresponded with that needed to give a firmly gelled protein monolayer at the interface, namely, 2∙5 mg. of protein/sq. m. of interfacial area. With that amount of protein the flocculated oil globules remained discrete and no coalescence or liberation of free oil occurred. If only 1 mg. of protein/sq. m. of interfacial area was added, flocculation was followed by rapid coalescence of oil globules and liberation of free oil. If smaller amounts still were used, no visible change in the dispersion of the oil droplets could be seen macroscopically. With greater amounts than 2∙5 mg. /sq. m. of interfacial area, up to ten times the monolayer concentration was adsorbed to the interface. Sodium chloride affected the flocculation range, and instead of the clear-cut change-over between the positive and negative interfaces at the isoelectric point of the protein, overlapping occurred. 5% sodium chloride shifted the flocculation point about 1 unit of pH . The addition of sodium chloride also altered the point of maximum clarification. Thus with haemoglobin the maximum clarification point was shifted from 2∙5 to 1∙7 mg. /sq. m. of interfacial area by the addition of 1% sodium chloride. The adsorption of protein on to charged oil/water interfaces was reversible. This was best demonstrated with haemoglobin. Thus, haemoglobin was adsorbed at pH 5∙0 to a negative emulsion—the red floccules were washed and transferred to a buffer at pH 10. The haemoglobin was released and the emulsion was redispersed. The effect of adsorption and desorption on the structure of the protein molecule has been studied with haemoglobin. By solubility and colour tests it was shown that the haemoglobin molecule was changed to parahaematin by adsorption and subsequent desorption from a charged oil /water interface. Molecular weight and shape determinations were carried out on the desorbed protein. Two proteins have been separated by this adsorption mechanism. This was demonstrated on a mixture of album in and haemoglobin. Some applications of the flocculation technique are indicated and the significance of the phenomena described are discussed.

Investigation of the specific interfacial area of a palm oil–water system

2004 ◽  
Vol 79 (7) ◽  
pp. 706-710 ◽  
Author(s):  
Sulaiman Al-Zuhair ◽  
Kadathur B Ramachandran ◽  
Masitah Hasan
Keyword(s):  
Palm Oil ◽  
Water System ◽  
Interfacial Area ◽  
Specific Interfacial Area ◽  
Oil Water

The Effects of Third Substances at the Particle/Surface Interface in Compressor Fouling

2017 ◽  
Author(s):  
Nicola Aldi ◽  
Nicola Casari ◽  
Devid Dainese ◽  
Mirko Morini ◽  
Michele Pinelli ◽  
...  
Keyword(s):  
Gas Turbine ◽  
Environmental Conditions ◽  
Particle Surface ◽  
Particle Diameter ◽  
Surfactant Solution ◽  
Solid Particles ◽  
Normal Velocity ◽  
Plant Design ◽  
Inorganic Matter ◽  
Starting Point

Since the beginning of the 1950s, manufacturers and operators have struggled to understand, reduce and eliminate compressor fouling and its effects on gas turbine operation. Several devices (inertial separators, barriers, filters, etc.) and strategies (on-line and off-line washing, manual cleaning, etc.) have been adopted in order to limit and/or eliminate the foulants which stick to the compressor blade and vane surfaces. The state of the power plant design and installation and environmental conditions determine the rate of fouling and, in turn, gas turbine performance losses. The types of contaminant (organic or inorganic), their concentration and their ability to stick are variable depending on the weather conditions. Desert, tropical, rural, and off-shore conditions are characterized by different foulants with different characteristics which determine compressor fouling. In this paper, an analysis of the influence of third substances at the particle/surface interface is presented. The analysis is carried out on two different compressor rotors, transonic and subsonic. Firstly, a sensitivity analysis is proposed related to the particle diameter and foulant mixture in order to highlight the influence of air humidity due to environmental conditions or the pressure drop after the filtration stages. The effects of a water electrolytic solution (generated by the presence of inorganic matter) and a water surfactant solution (used in the case of washing) are also considered. In this case, the properties of the mixture substance (solid particles bound by a liquid film) are considered. Secondly, using previous numerical analyses (particle-laden flow with a Eulerian-Lagrangian approach) as a starting point, the variation in particle sticking ability is evaluated against the presence of third substances (water solutions and oily substances) and the particle kinematic characteristics using a sticking model based on an energy balance equation. The results show the influence of the third substance on particle sticking capability using a susceptibility-to-fouling criterion. Particularly in the presence of humid conditions, sticking capability increases with respect to dry conditions, even though the major effects are due to the mixture viscosity and not only to the presence of liquid water. The sticking capability of the mixture varies according to particle diameter as a function of the particle normal velocity. The results are presented in order to easily quantify the effects of the presence of a third substance at the particle/surface interface according to the type of liquid phase involved in the sticking process.

scholarly journals Reversible adsorption of proteins at the oil/water interface I. Preferential adsorption of proteins at charged oil/water interfaces

1945 ◽  
Vol 184 (996) ◽  
pp. 102-115 ◽  
Keyword(s):  
Sodium Chloride ◽  
Isoelectric Point ◽  
Interfacial Area ◽  
Ammonium Bromide ◽  
Water Interface ◽  
Oil Droplets ◽  
Water Emulsion ◽  
Oil In Water ◽  
Alkaline Side ◽  
Oil Water

The behaviour of positively and negatively charged oil-in-water emulsions, stabilized with hexadecyl trimethyl ammonium bromide and sodium hexadecyl sulphate respectively in the presence of protein solutions has been studied. Under certain conditions proteins will adsorb to a charged oil/water interface. When finely dispersed oil-in-water emulsion was used to provide this oil/water interface, adsorption of protein resulted in flocculation of the oil droplets. Flocculation of emulsion on the addition of protein is pH conditioned and occurred on the acid side of the isoelectric point of the protein with negatively charged and on the alkaline side with positively charged oil globules. No flocculation occurred on the alkaline side of the isoelectric point with a negative emulsion or the acid side with a positive emulsion. The amount of protein required to cause maximum clarification of the subnatant fluid corresponded with that needed to give a firmly gelled protein monolayer at the interface, namely, 2·5 mg. of protein/sq.m, of interfacial area. With that amount of protein the flocculated oil globules remained discrete and no coalescence or liberation of free oil occurred. If only 1 mg. of protein/sq.m, of interfacial area was added, flocculation was followed by rapid coalescence of oil globules and liberation of free oil. If smaller amounts still were used, no visible change in the dispersion of the oil droplets could be seen macroscopically. With greater amounts than 2·5 mg./sq.m, of interfacial area, up to ten times the monolayer concentration was adsorbed to the interface. Sodium chloride affected the flocculation range, and instead of the clear-cut change-over between the positive and negative interfaces at the isoelectric point of the protein, overlapping occurred. 5 % sodium chloride shifted the flocculation point about 1 unit of pH. The addition of sodium chloride also altered the point of maximum clarification. Thus with haemoglobin the maximum clarification point was shifted from 2·5 to 1·7 mg./sq.m. of interfacial area by the addition of 1 % sodium chloride. The adsorption of protein on to charged oil/water interfaces was reversible. This was best demonstrated with haemoglobin. Thus, haemoglobin was adsorbed at pH 5·0 to a negative emulsion— the red floccules were washed and transferred to a buffer at pH 10. The haemoglobin was released and the emulsion was redispersed. The effect of adsorption and desorption on the structure of the protein molecule has been studied with haemoglobin. By solubility and colour tests it was shown that the haemoglobin molecule was changed to parahaematin by adsorption and subsequent desorption from a charged oil/water interface. Molecular weight and shape determinations were carried out on the desorbed protein. Two proteins have been separated by this adsorption mechanism. This was demonstrated on a mixture of albumin and haemoglobin. Some applications of the flocculation technique are indicated and the significance of the phenomena described are discussed.

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