Interaction forces between oil-water particle interfaces: non-DLVO forces

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Dagastine, Raymond R.

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Interaction forces between oil-water particle interfaces: non-DLVO forces

Please use this identifier to cite or link to this item: http://hdl.handle.net/1959.3/190504

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Title: Interaction forces between oil-water particle interfaces: non-DLVO forces
Author(s): Dagastine, Raymond R.; Chau, Tam T.; Chan, D. Y. C.; Stevens, Geoffrey W.; Grieser, Franz
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.
Publication type: Journal article
Source: Faraday Discussions, Vol. 129 (2005), pp. 111-124
Publication year: 2005
FOR Code(s): 0306 Physical Chemistry (Incl. Structural)
Keyword(s): Acetic acid; Aqueous solution; Atomic force microscopy; Calcium; Calcium derivative; Electricity; Electrolyte; Force; Inorganic compound; Liquid; Molecular interaction; Oil; Prediction; Silicon dioxide; Sodium nitrate; Sodium perchlorate; Solubility; Stabilizing agent; Water
Publisher: Royal Society of Chemistry
ISSN: 1359-6640
Publisher URL: http://dx.doi.org/10.1039/b405750c
Peer reviewed