Shapes and dynamics of miscible liquid/liquid interfaces in horizontal capillary tubes
Stevar, M.S.P. and Vorobev, A. (2012) Shapes and dynamics of miscible liquid/liquid interfaces in horizontal capillary tubes. Journal of Colloid and Interface Science (doi:10.1016/j.jcis.2012.06.053).
We report optical observations of the dissolution behaviour of glycerol/water, soybean oil/hexane, and isobutyric acid (IBA)/water binary mixtures within horizontal capillary tubes. Tubes with diameters as small as were initially filled with one component of the binary mixture (solute) and then immersed into a solvent-filled thermostatic bath. Both ends of the tubes were open, and no pressure difference was applied between the ends. In the case of glycerol/water and soybean oil/hexane mixtures, we managed to isolate the dissolution (the interfacial mass transfer) from the hydrodynamic motion. Two phase boundaries moving from the ends into the middle section of the tube with the speeds ( and d are the coefficient of diffusion, time and the diameter of the tube, respectively) were observed. The boundaries slowly smeared but their smearing occurred considerably slower than their motion. The motion of the phase boundaries cannot be explained by the dependency of the diffusion coefficient on concentration, and should be explained by the effect of barodiffusion. The shapes of the solute/solvent boundaries are defined by the balance between gravity and surface tension effects. The contact line moved together with the bulk interface: no visible solute remained on the walls after the interface passage. Changes in temperature and in the ratio between gravity and capillary forces altered the apparent contact angles. The IBA/water system had different behaviour. Below thecritical (consolute) point, no dissolution was observed: IBA and water behaved like two immiscible liquids, with the IBA phase being displaced from the tube by capillary pressure (the spontaneous imbibition process). Above the critical point, two IBA/water interfaces could be identified, however the interfaces did not penetrate much into the tube.
|Keywords:||liquid/liquid interface, dissolution rate, binary mixture, non-Fickian diffusion, barodiffusion, dynamic surface tension, spontaneous imbibition, capillary tube|
|Subjects:||Q Science > QC Physics
T Technology > TP Chemical technology
|Divisions:||Faculty of Engineering and the Environment > Engineering Sciences
|Date Deposited:||02 Jul 2012 10:58|
|Last Modified:||04 Jul 2012 13:13|
|Contributors:||Stevar, M.S.P. (Author)
Vorobev, A. (Author)
|Date:||28 June 2012|
|RDF:||RDF+N-Triples, RDF+N3, RDF+XML, Browse.|
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