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ID: 337823.0, MPI für Dynamik komplexer technischer Systeme / Physical and Chemical Foundations of Process Engineering
Concentration Polarization and Nonequilibrium Electroosmotic Slip in Dense Multiparticle Systems
Authors:Nischang, I.; Reichl, U.; Seidel-Morgenstern, A.; Tallarek, U.
Language:English
Date of Publication (YYYY-MM-DD):2007
Title of Journal:Langmuir
Volume:23
Issue / Number:18
Start Page:9271
End Page:9281
Review Status:Peer-review
Audience:Experts Only
Abstract / Description:Electrical field-induced concentration polarization (CP) and CP-based nonequilibrium electroosmotic slip are studied in fixed beds of strong cation-exchange particles using confocal laser scanning microscopy (CLSM) and the macroscopic electroosmotic flow (EOF) dynamics. A key property of the investigated fixed beds is the coexistence of quasi-electroneutral macroporous regions between the micrometer-sized particles and the ion-permselective (here, cation-selective) intraparticle mesopores with a mean size of 10 nm. The application of an external electrical field to the particles induces depleted and enriched CP zones along their anodic and cathodic interfaces, respectively, by the local interplay of diffusive and electrokinetic transport. The intensity and dimension of the CP zones depend on the applied electrical field strength and the fluid-phase ionic strength. With increasing field strength a limiting current density through a particle is approached, meaning that charge transport locally through a particle becomes controlled by the dynamics in the adjoining extraparticle convective-diffusion boundary layer (depleted CP zone). In this regime a nonequilibrium electrical double layer can be induced electrokinetically in the depleted CP zone and intraparticle pore space, resulting in nonlinear EOF in the interparticle macropore space. The local CP dynamics analyzed by CLSM is successfully correlated with the onset of nonlinearity in the macroscopic EOF dynamics. We further demonstrate that multiparticle effects arising in fixed beds (random close packings) of ion-permselective particles modulate significantly the local pattern of CP and intensity of the nonequilibrium electroosmotic slip with respect to the undisturbed single-particle picture.
External Publication Status:published
Document Type:Article
Communicated by:Andreas Seidel-Morgenstern
Affiliations:MPI für Dynamik komplexer technischer Systeme/Bioprocess Engineering
MPI für Dynamik komplexer technischer Systeme/Physical and Chemical Foundations of Process Engineering
External Affiliations:Institut für Verfahrenstechnik, Otto-von-Guericke-Universität Magdeburg, Universitätsplatz 2, 39106 Magdeburg, Germany
Identifiers:URL:http://dx.doi.org/10.1021/la700691k
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