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Titre du Document
Evolution of water-in-oil emulsion controlled by droplet-bulk ion exchange: acoustic, electroacoustic, conductivity and image analysis
Auteur(s)
DUKHIN A. ; GOETZ P.
Résumé
Water-in-kerosene emulsion stabilized with SPAN surfactant exhibits a slow transition (on scale of hours) from an emulsion to a mini-emulsion state. We continuously monitor this transition in the relatively concentrated samples (5 vol.% water), without dilution, using acoustic, electroacoustic and conductivity measurements. Continuous stirring prevents sedimentation. We confirm our measurements with microscopic image analysis and by comparing with a stable water-in-car oil microemulsion stabilized with AOT. Acoustic measurements yield information about the droplet size evolution in time. The original droplets, having a size of about 0.4 μm, slowly coalesce into larger droplets. After 10 h the droplet size has increased to about 5 μm. At this point a mini-emulsion fraction appears with a droplet size of only 25 nm and the droplet size distribution becomes bimodal. It takes another 24 h for the emulsion droplets to completely transform into a mini-emulsion state. The conductivity exhibits a rapid change during the first 10 h of emulsion coalescence, but the rate becomes much slower as the mini-emulsion fraction begins to grow. Electroacoustic measurements shows that the original emulsion droplets carry a substantial surface charge, which we are able to calculate using Shilov's theory for overlapped DLs. The measured electroacoustic signal gradually decays with time. In the final state the mini-emulsion droplets generate practically no electroacoustic signal and appear uncharg
Editeur
Elsevier
Identifiant
ISSN : 0927-7757
Source
Colloids and surfaces. A, Physicochemical and engineering aspects A. 2005, vol. 253, n° 1-3, pp. 51-64 [14 pages] [bibl. : 16 ref.]
Langue
Anglais
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