Hydrophobicity Of Solid Surface Research Articles

Foam, emulsion and wetting films stabilized by polyoxyalkylated diethylenetriamine (DETA) polymeric surfactants

This review explores three (A, B, C) polyoxyalkylated diethylenetriamine (DETA) polymeric surfactants belonging to the group of star-like polymers. They have a similar structure, differing only in the number of polymeric branches (4, 6 and 9 in the mentioned order). The differences in these surfactants' ability to stabilize foam, o/w/o and w/o/w emulsion and wetting films are evaluated by a number of methods summarized in Section 2. Results from the studies indicate that differences in polymeric surfactants' molecular structure affect the properties exhibited at air/water, oil/water and water/solid interfaces, such as the value of surface tension, interfacial tension, critical micelle concentration, degree of hydrophobicity of solid surface, etc. Foam, emulsion and wetting films stabilized by such surfactants also show different behavior regarding some specific parameters, such as critical electrolyte concentration, surfactant concentration for obtaining a stable film, film thickness value, etc. These observations give reasons to believe that model studies can support a comprehensive understanding of how the change in polymeric surfactant structure can impact thin liquid films properties. This may enable a targeted design of the macromolecular architecture depending on the polymeric surfactants application purpose.

Control of static and dynamic hydrophobicity of solid surface and its application

Control of static and dynamic hydrophobicity of solid surface and its application

Understanding weathering of oil sands ores by atomic force microscopy

AbstractEffect of weathering on colloidal interactions between bitumen and oil sands solids was studied by atomic force microscopy (AFM). The change in bitumen chemistry due to weathering was found to have a negligible effect on the interactions of bitumen with solid particles. However, the increase in solid surface hydrophobicity due to ore weathering reversed the long‐range interaction forces between bitumen and solids from repulsive to attractive with a corresponding increase in adhesion force. The measured force profiles between bitumen and various solids can be well fitted with the extended DLVO theory by considering an additional attractive force. The attractive long‐range force and increased adhesion force make the separation of bitumen from solids more difficult and the attachment of fine solids on liberated bitumen easier, thereby leading to poor bitumen liberation and lower aeration efficiency. Such changes account for the observed poor processability of the weathered ores. © 2009 American Institute of Chemical Engineers AIChE J, 2009

動的撥水性評価のための転落挙動解析システムの開発

動的撥水性評価のための転落挙動解析システムの開発

Effect of surface hydrophobicity on the adhesion of S. cerevisiae onto modified surfaces by poly(styrene-ran-sulfonic acid) random copolymers

The hydrophobicity of solid surfaces has been regarded as a controlling factor in microbial adhesion phenomena. In this study, the surface hydrophobicity was modified by coating with a poly(styrene-ran-sulfonic acid) random copolymer (PS- x-SA, charge density ( x): 0–15.3%), and the adhesion rate, J 0, of S. cerevisiae performed with a direct observation technique. The results indicated that the degree of sulfonation of PS- x-SA greatly influenced the hydrophobicity of substrates and the adhesion of yeast cells. The J 0 of PS- x-SA substrates were gradually decreased as increasing charge density. The interactions between cells and substrates explained by the XDLVO theory, predicted that the decrease of J 0 as increasing charge density was not due to the increase of electric double layer repulsion, but mainly due to the hydrophobic acid–base interactions. Also, it predicted that microbial adhesions of PS- x-SA were mostly reversible, while some of PS and PS-5.1-SA adhered cells were hardly removed. Based on these results, XDLVO theory was effective for predicting adhesion phenomena of S. cerevisiae onto the PS- x-SA-coated substrates.

Oil Detachment from Solid Surfaces in Aqueous Surfactant Solutions as a Function of pH

Effective removal of oil from metal surfaces utilizing aqueous solutions depends on the appropriate selection of surfactant(s) and pH conditions. In the experiments described in this paper, the detachment of oil droplets from a solid surface in aqueous surfactant solutions was studied and the variation in droplet shape, particularly contact angle, and the time required for droplet detachment were measured. In parallel, tests of oil removal from solid surfaces in an industrial ultrasonic bath were conducted under conditions similar to drop-detachment tests. Consistent trends were found in both types of tests; that is, conditions for which droplets detach more quickly correspond to conditions of greater oil removal in an ultrasonic bath. At high pH, faster drop-detachment (and oil removal) kinetics were observed when the oil−water interface was negatively charged (per ζ-potential measurements). In contrast, at low-pH conditions, faster kinetics were observed when the solid−liquid interface was positively charged. The pH effect is consistent with a mechanistic model in which electrostatic interactions and solid-surface hydrophobicity changes due to surfactant adsorption onto solid surfaces under various pH conditions are considered. This study also demonstrated that single-drop-detachment tests and/or ζ-potential measurements are useful as simple, timesaving screening methods for selecting promising conditions for specific cleaning applications.