Volume 129, 2005
From the journal:

Faraday Discussions

Interaction forces between oil–water particle interfaces—Non-DLVO forces

Raymond R. Dagastine,b   Tam T. Chau,b   D.Y.C. Chan,c   Geoffrey W. Stevensb  and  Franz Grieser*a  

* Corresponding authors

a School of Chemistry, Particulate Fluids Processing Center, University of Melbourne, Parkville, Victoria 3010, Australia
E-mail: franz@unimelb.edu.au
Fax: 61-3-93475180
Tel: 61-3-83446476

b Department of Chemical Engineering and Biomolecular Engineering, Particulate Fluids Processing Center, University of Melbourne, Parkville, Victoria 3010, Australia

c Department of Mathematics and Statistics, Particulate Fluids Processing Center, University of Melbourne, Parkville, Victoria 3010, Australia

Abstract

The interaction force between a rigid silica sphere and a butyl or octyl acetate droplet was measured in an aqueous environment using atomic force microscopy (AFM). The force measurements were performed without added stabilizers and the observed force behavior was found to be dependent on the type of inorganic electrolyte present, where the interfacial tension was constant over the electrolyte concentration range used. Force measurements in the presence of sodium nitrate showed repulsion at all concentrations. Force measurements in the presence of calcium nitrate or sodium perchlorate exhibited an initial repulsion followed by an attraction resulting in a mechanical instability in the AFM cantilever, termed jump-in. The force behavior observed was independent of the water solubility of the organic liquid, in that the same force–distance characteristics were obtained for slightly water soluble butyl acetate and the water sparingly soluble octyl acetate droplets. Modeling of the drop profile during particle–droplet interactions for this type of AFM measurement showed that the force–distance data for the sodium nitrate system obeys typical DLVO interactions. The disagreement between the DLVO predictions for the sodium perchlorate and calcium nitrate systems is attributed to a specific ion effect at the liquid–liquid interface, which gives rise to an attraction force that is greater than the electrostatic double layer repulsion over the length scale of 5 to 10 nm.

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Article information

DOI
https://doi.org/10.1039/B405750C
Article type
Paper
Submitted
20 Apr 2004
Accepted
28 May 2004
First published
05 Oct 2004

Faraday Discuss., 2005,129, 111-124

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Interaction forces between oil–water particle interfaces—Non-DLVO forces

R. R. Dagastine, T. T. Chau, D.Y.C. Chan, G. W. Stevens and F. Grieser, Faraday Discuss., 2005, 129, 111 DOI: 10.1039/B405750C

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