scholarly journals Adhesion of emulsified oil droplets to hydrophilic and hydrophobic surfaces – effect of surfactant charge, surfactant concentration and ionic strength

Soft Matter ◽  
2018 ◽  
Vol 14 (26) ◽  
pp. 5452-5460 ◽  
Author(s):  
Janneke M. Dickhout ◽  
J. Mieke Kleijn ◽  
Rob G. H. Lammertink ◽  
Wiebe M. de Vos
Keyword(s):  
Ionic Strength ◽  
Shear Flow ◽  
Surfactant Concentration ◽  
Flow Cell ◽  
Hydrophobic Surfaces ◽  
Oil Droplets ◽  
Emulsified Oil ◽  
Hydrophilic And Hydrophobic Surfaces

Using a novel flow cell technique to study the adhesion of oil droplets to a surface under shear flow.

scholarly journals Membrane Filtration of Anionic Surfactant Stabilized Emulsions: Effect of Ionic Strength on Fouling and Droplet Adhesion

2019 ◽  
Vol 3 (1) ◽  
pp. 9 ◽  
Author(s):  
Janneke Dickhout ◽  
Rob Lammertink ◽  
Wiebe de Vos
Keyword(s):  
Ionic Strength ◽  
Anionic Surfactant ◽  
Membrane Fouling ◽  
Flow Cell ◽  
Cellulose Membrane ◽  
Oil Droplets ◽  
Flux Decline ◽  
Cake Layer ◽  
The Impact ◽  
Cellulose Surface

Membranes hold great potential to be used for the successful treatment of oily waste water, but membrane fouling leads to substantial decreases in performance. Here we study the impact of ionic strength on membrane fouling from an emulsion stabilized by the anionic surfactant sodium dodecyl sulfonate (SDS). For this we use a unique combinatorial approach where droplet adhesion to a cellulose surface in a flow cell is compared to membrane fouling (flux decline) on a cellulose membrane. In the initial membrane fouling stages droplet adhesion dominates. While the flow cell demonstrates a high number of droplets adhering especially at high ionic strengths (100 mM NaCl), the strongest flux decline is observed at intermediate (10 mM NaCl) ionic strength. This suggests that the fouling mechanism must be different, with pore blocking expecting to dominate at intermediate ionic strength. At the later fouling stages the porosity of the cake layer plays a key role in the flux reduction. At low ionic strength, oil droplets repel each other strongly and an open, more permeable, cake layer is formed. However at higher ionic strength, a screening of charge interactions leads to a lower porosity and thereby a lower flux. This leads to a clear trend: with a higher ionic strength a higher flux decline is observed. Flux recovery is high at all ionic strengths, in line with the observation in the flow cell that oil droplets can easily be sheared of a cellulose surface at all ionic strengths. This work thus highlights the critical effect of the ionic strength on membrane fouling by anionically stabilized emulsions. Moreover it shows how the use of an optical flow cell can provide key insights to help explain observations in more standard membrane fouling experiments.

Influence of pressure-dependent surface viscosity on dynamics of surfactant-laden drops in shear flow

2018 ◽  
Vol 858 ◽  
pp. 91-121 ◽  
Author(s):  
Zheng Yuan Luo ◽  
Xing Long Shang ◽  
Bo Feng Bai
Keyword(s):  
Shear Flow ◽  
Simple Shear ◽  
Surfactant Concentration ◽  
Constitutive Law ◽  
Simple Shear Flow ◽  
Drop Surface ◽  
Shear Surface ◽  
Surface Viscosity ◽  
Principal Axes ◽  
Surfactant Transport

We study numerically the dynamics of an insoluble surfactant-laden droplet in a simple shear flow taking surface viscosity into account. The rheology of drop surface is modelled via a Boussinesq–Scriven constitutive law with both surface tension and surface viscosity depending strongly on the surface concentration of the surfactant. Our results show that the surface viscosity exhibits non-trivial effects on the surfactant transport on the deforming drop surface. Specifically, both dilatational and shear surface viscosity tend to eliminate the non-uniformity of surfactant concentration over the drop surface. However, their underlying mechanisms are entirely different; that is, the shear surface viscosity inhibits local convection due to its suppression on drop surface motion, while the dilatational surface viscosity inhibits local dilution due to its suppression on local surface dilatation. By comparing with previous studies of droplets with surface viscosity but with no surfactant transport, we find that the coupling between surface viscosity and surfactant transport induces non-negligible deviations in the dynamics of the whole droplet. More particularly, we demonstrate that the dependence of surface viscosity on local surfactant concentration has remarkable influences on the drop deformation. Besides, we analyse the full three-dimensional shape of surfactant-laden droplets in simple shear flow and observe that the drop shape can be approximated as an ellipsoid. More importantly, this ellipsoidal shape can be described by a standard ellipsoidal equation with only one unknown owing to the finding of an unexpected relationship among the drop’s three principal axes. Moreover, this relationship remains the same for both clean and surfactant-laden droplets with or without surface viscosity.

Proteolytic degradation of fibrinogen layers adsorbed on hydrophilic and hydrophobic surfaces

1990 ◽  
Vol 44 ◽  
pp. 51-60 ◽  
Author(s):  
Stefan Welin-Klintström ◽  
Maude Wikström ◽  
Agneta Askendal ◽  
Hans Elwing ◽  
Ingemar Lundström ◽  
...  
Keyword(s):  
Proteolytic Degradation ◽  
Hydrophobic Surfaces ◽  
Hydrophilic And Hydrophobic Surfaces

scholarly journals Compositional and Temperature Effects on the Rheological Properties of Polyelectrolyte–Surfactant Hydrogels

Polymers ◽  
2019 ◽  
Vol 11 (5) ◽  
pp. 927 ◽  
Author(s):  
Jiří Smilek ◽  
Sabína Jarábková ◽  
Tomáš Velcer ◽  
Miloslav Pekař
Keyword(s):  
Ionic Strength ◽  
Rheological Properties ◽  
Surfactant Concentration ◽  
Background Electrolyte ◽  
Effect Of Temperature ◽  
Physical Interactions ◽  
Chain Conformations ◽  
Oppositely Charged ◽  
Electrolyte Ph ◽  
Positively Charged

The rheological properties of hydrogels prepared by physical interactions between oppositely charged polyelectrolyte and surfactant in micellar form were studied. Specifically, hyaluronan was employed as a negatively charged polyelectrolyte and Septonex (carbethopendecinium bromide) as a cationic surfactant. Amino-modified dextran was used as a positively charged polyelectrolyte interacting with sodium dodecylsulphate as an anionic surfactant. The effects of the preparation method, surfactant concentration, ionic strength (the concentration of NaCl background electrolyte), pH (buffers), multivalent cations, and elevated temperature on the properties were investigated. The formation of gels required an optimum ionic strength (set by the NaCl solution), ranging from 0.15–0.3 M regardless of the type of hydrogel system and surfactant concentration. The other compositional effects and the effect of temperature were dependent on the polyelectrolyte type or its molecular weight. General differences between the behaviour of hyaluronan-based and cationized dextran-based materials were attributed to differences in the chain conformations of the two biopolymers and in the accessibility of their charged groups.

scholarly journals Forces involved in bacterial adhesion to hydrophilic and hydrophobic surfaces

Microbiology ◽  
2008 ◽  
Vol 154 (10) ◽  
pp. 3122-3133 ◽  
Author(s):  
Niels P. Boks ◽  
Willem Norde ◽  
Henny C. van der Mei ◽  
Henk J. Busscher
Keyword(s):  
Bacterial Adhesion ◽  
Hydrophobic Surfaces ◽  
Hydrophilic And Hydrophobic Surfaces
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