Colloid vibration potential and the electrokinetic characterization of concentrated colloids

Abstract

Subjecting charged colloidal particles to a compressional sound wave gives rise to a periodic polarization of the ionic atmosphere surrounding the particles. This periodic polarization causes each particle to act as a vibrating dipole resulting in an alternating voltage, termed the colloid vibration potential (CVP), between any two points in space separated by a phase distance other than an integral multiple of the wavelength and normal to the propagation direction. The present work shows that the CVP is analogous in many respects to the Dorn effect (sedimentation potential) and reflects the same intrinsic phenomena where double-layer relaxation is the dominant process. Both Smoluchowski's theory of the Dorn effect and Enderby's treatment of a charged particle in a sound field are reviewed. Expressions are presented showing the relationship of the CVP to the f potential for dilute colloids. It is also shown how the theory can be extended to particle concentrations as high as 50% by volume using the Levine et al. cell model theory. An apparatus for making electrokinetic measurements using continuous wave ultrasonics is described in detail Data are presented comparing mobilities obtained from CVP measurements and microelectrophoresis. Data are also shown for the dependence of the CVP on particle concentration and compared to predictions based on the proposed modifications using the cell model theory. Also included are data showing the versatility and advantages of acoustical electroki * Author to whom all correspondence should be addressed.

Measurement and Interpretation of Electrokinetic Phenomena (IUPAC Technical Report)

“…The problem of considering the effect on the electroacoustic signal of hydrodynamic or electrostatic interactions between particles in concentrated suspensions was first theoretically tackled [96] by using the cell model of Levine and Neale [97,98] to provide a solution that was claimed to be valid for U CV measurements on concentrated systems (see [87] for a discussion on the validity of such approach in the high-frequency range). It is possible to deal with concentrated systems at high frequency without using cell models in the case of near neutrally buoyant systems (where the relative density compared to water is in the range 0.9-1.5) using a procedure developed by O'Brien [99,100].…”

Cell Model of the Direct Current Electrokinetics in Salt-Free Concentrated Suspensions: The Role of Boundary Conditions

“…[1][2][3][4][5][6][7][8][9][10][11][12][13] The electrokinetic properties of these systems are key factors in processing techniques and quality control.…”

Electrokinetics of Concentrated Suspensions of Spherical Colloidal Particles with Surface Conductance, Arbitrary Zeta Potential, and Double-Layer Thickness in Static Electric Fields

“…However, in a great number of practical situations, suspensions are usually more concentrated than those typically considered as dilute, so some theoretical approaches to the issue of concentrated suspensions, including electrophoresis (16), sedimentation (17,18), electrical conductivity (19), and electroacoustic phenomena (20)(21)(22), to mention just a few, have been published in the past few decades. The majority of them have in common the use of cell models (23,24), to account for particle-particle interactions.…”