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Effect of Geometry on Electrokinetic Characterization of Solid Surfaces.

Kumar, Abhijeet and Kleinen, J. and Venzmer, Joachim and Gambaryan-Roisman, Tatiana (2017):
Effect of Geometry on Electrokinetic Characterization of Solid Surfaces.
In: Langmuir, pp. 7556-7568, 33, (30), ISSN 0743-7463,
DOI: 10.1021/acs.langmuir.7b00344,
[Online-Edition: http://dx.doi.org/10.1021/acs.langmuir.7b00344],
[Article]

Abstract

An analytical approach is presented to describe pressure-driven streaming current (Istr) and streaming potential (Ustr) generation in geometrically complex samples, for which the classical Helmholtz−Smoluchowski (H−S) equation is known to be inaccurate. The new approach is valid under the same prerequisite conditions that are used for the development of the H−S equation, that is, the electrical double layers (EDLs) are sufficiently thin and surface conductivity and electroviscous effects are negligible. The analytical methodology is developed using linear velocity pro files to describe liquid flow inside of EDLs and using simplifying approximations to describe macroscopic flow. At first, a general expression is obtained to describe the Istr generated in different cross sections of an arbitrarily shaped sample. Thereafter, assuming that the generated Ustr varies only along the pressure-gradient direction, an expression describing the variation of generated Ustr along the sample length is obtained. These expressions describing Istr and Ustr generation constitute the theoretical foundation of this work, which is first applied to a set of three nonuniform cross-sectional capillaries and thereafter to a square array of cylindrical fibers (model porous media) for both parallel and transverse fiber orientation cases. Although analytical solutions cannot be obtained for real porous substrates because of their random structure, the new theory provides useful insights into the effect of important factors such as fiber orientation, sample porosity, and sample dimensions. The solutions obtained for the model porous media are used to device strategies for more accurate zeta potential determination of porous fiber plugs. The new approach could be thus useful in resolving the long-standing problem of sample geometry dependence of zeta potential measurements.

Item Type: Article
Erschienen: 2017
Creators: Kumar, Abhijeet and Kleinen, J. and Venzmer, Joachim and Gambaryan-Roisman, Tatiana
Title: Effect of Geometry on Electrokinetic Characterization of Solid Surfaces.
Language: English
Abstract:

An analytical approach is presented to describe pressure-driven streaming current (Istr) and streaming potential (Ustr) generation in geometrically complex samples, for which the classical Helmholtz−Smoluchowski (H−S) equation is known to be inaccurate. The new approach is valid under the same prerequisite conditions that are used for the development of the H−S equation, that is, the electrical double layers (EDLs) are sufficiently thin and surface conductivity and electroviscous effects are negligible. The analytical methodology is developed using linear velocity pro files to describe liquid flow inside of EDLs and using simplifying approximations to describe macroscopic flow. At first, a general expression is obtained to describe the Istr generated in different cross sections of an arbitrarily shaped sample. Thereafter, assuming that the generated Ustr varies only along the pressure-gradient direction, an expression describing the variation of generated Ustr along the sample length is obtained. These expressions describing Istr and Ustr generation constitute the theoretical foundation of this work, which is first applied to a set of three nonuniform cross-sectional capillaries and thereafter to a square array of cylindrical fibers (model porous media) for both parallel and transverse fiber orientation cases. Although analytical solutions cannot be obtained for real porous substrates because of their random structure, the new theory provides useful insights into the effect of important factors such as fiber orientation, sample porosity, and sample dimensions. The solutions obtained for the model porous media are used to device strategies for more accurate zeta potential determination of porous fiber plugs. The new approach could be thus useful in resolving the long-standing problem of sample geometry dependence of zeta potential measurements.

Journal or Publication Title: Langmuir
Volume: 33
Number: 30
Divisions: 16 Department of Mechanical Engineering
16 Department of Mechanical Engineering > Institute for Technical Thermodynamics (TTD)
Profile Areas
Profile Areas > Thermo-Fluids & Interfaces
Date Deposited: 28 Aug 2017 16:12
DOI: 10.1021/acs.langmuir.7b00344
Official URL: http://dx.doi.org/10.1021/acs.langmuir.7b00344
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