Thinning of a vertical free draining aqueous film incorporating colloidal particles

Tan, Su N., Yang, Yujie and Horn, Roger G. 2010, Thinning of a vertical free draining aqueous film incorporating colloidal particles, Langmuir, vol. 26, no. 1, pp. 63-73, doi: 10.1021/la9021118.

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Title Thinning of a vertical free draining aqueous film incorporating colloidal particles
Author(s) Tan, Su N.
Yang, Yujie
Horn, Roger G.
Journal name Langmuir
Volume number 26
Issue number 1
Start page 63
End page 73
Total pages 11
Publisher American Chemical Society
Place of publication Washington, D. C.
Publication date 2010
ISSN 0743-7463
Summary The drainage under gravity of a vertical foam film formed on a wire frame has been investigated. Dual-wavelength optical interferometry was used so that unambiguous fringe order assignments could be made, enabling absolute film thicknesses to be calculated with confidence. Films were stabilized by nonionic polypropylene glycol surfactant. Halfmicrometer silica particles with varying degrees of hydrophobicity were added to the film-forming liquid to investigate their effect on film drainage rate and stability. Hydrophilic particles had little or no effect, while hydrophobic particles slowed the drainage of the film and caused a minor increase in film lifetime, from ∼10 to ∼30 s. In both the hydrophilic and hydrophobic cases the films ruptured when they reached a thickness of ∼2 particle diameters. Particles of intermediate hydrophobicity had the most significant effect, increasing film lifetime by an order of magnitude over that for hydrophilic particles. The intermediate particles allowed films to thin down to a thickness less than the particle diameter, indicating that particles bridge across the entire film. This did not occur with more hydrophobic particles even though they were embedded in each of the two film surfaces. These results correlate well with previous literature on particle-laden foams. The film thickness and drainage measurements allow drainage mechanisms for the different particles to be identified, thus providing a mechanistic explanation for the observation by several previous authors that foams formed in the presence of particles, for example during mineral processing, have the greatest stability when the particles are of intermediate hydrophobicity.
Notes First published online 3rd November 2009
Language eng
DOI 10.1021/la9021118
Field of Research 030603 Colloid and Surface Chemistry
091404 Mineral Processing/Beneficiation
Socio Economic Objective 840399 First Stage Treatment of Ores and Minerals not elsewhere classified
HERDC Research category C1.1 Refereed article in a scholarly journal
Copyright notice ©2009, American Chemical Society
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