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Issue 32, 2008
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Electroacoustic and ultrasonic attenuation measurements of droplet size and ζ-potential of alkane-in-water emulsions: effects of oil solubility and composition

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Abstract

The effects of oil solubility and composition on the zeta potential and drop size of oil-in-water emulsions stabilised by sodium dodecyl sulfate (SDS) were studied by electroacoustics and ultrasonic attenuation. The ζ-potentials of toluene and alkane emulsions were found to decrease (be less negative) as the water solubility of the dispersed oil phase increased. The ζ-potentials also depended on the composition of mixed oils, becoming more negative with increasing mole fraction of an insoluble oil (hexadecane). As the water solubility of the dispersed oil phase increased, the conductance within the Stern layer relative to the diffuse layer (Kis/Kds) increased, which is interpreted as due to the displacement of the shear plane further into the diffuse layer. The shear plane was calculated to increase from ∼0.50 nm at the insoluble oil–water interface (hexadecane) to ∼2.5 nm at a soluble oil–water interface of toluene. The lowering of the ζ-potentials of the soluble oils is ascribed to the shift of the shear plane into the diffuse layer, resulting in a more diffuse interface. The total surface conductance of the mixed oils was related to the log of the oil solubility and decreased from ∼7 × 10−9 Ω−1 to 3 × 10−9 Ω−1 with increasing oil solubility from hexadecane to toluene, respectively. The lower surface conductance at the soluble oil–water interface is attributed to a reduction in the dielectric constant of the water inside of the shear plane, caused by the presence of the soluble oil.

Graphical abstract: Electroacoustic and ultrasonic attenuation measurements of droplet size and ζ-potential of alkane-in-water emulsions: effects of oil solubility and composition

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Article information


Submitted
06 May 2008
Accepted
26 Jun 2008
First published
09 Jul 2008

Phys. Chem. Chem. Phys., 2008,10, 4843-4852
Article type
Paper

Electroacoustic and ultrasonic attenuation measurements of droplet size and ζ-potential of alkane-in-water emulsions: effects of oil solubility and composition

A. M. Djerdjev and J. K. Beattie, Phys. Chem. Chem. Phys., 2008, 10, 4843
DOI: 10.1039/B807623E

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