A continuum approach to predicting electrophoretic mobility reversals

At concentrated electrolytes, the ion-ion electrostatic correlations effect is considered an important factor in electrokinetics. In this paper, we compute, in theory and simulation, the dipole moment for a spherical particle (charged, dielectric) under the action of an alternating electric field using the modified continuum Poisson-Nernst-Planck (PNP) model by Bazant et al. (Phys. Rev. Lett. 106, 2011).1 We investigate the dependency of the dipole moment in terms of the frequency and its variation with such quantities like zeta potential, electrostatic correlation length, and double layer thickness. With thin electric double layers, we develop simple models through performing an asymptotic analysis to the modified PNP model. We also present numerical results for an arbitrary Debye screening length and electrostatic correlation length. From the results, we find a complicated impact of electrostatic correlations on the dipole moment. For instance, with increasing the electrostatic correlation length, the dipole moment decreases and reaches a minimum, and then it goes up. This is because of initially decreasing of surface conduction and its finally increasing due to the impact of ion-ion electrostatic correlations on ion’s convection and migration. Also, we show that in contrast to the standard PNP model, the modified PNP model can qualitatively explain the data from the experimental results in multivalent electrolytes.

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“…Indeed, this model was able to predict the electro-osmotic flow reversal near a flat surface 50 and electrophoretic mobility reversal. 51 …”

Section: Introductionmentioning

confidence: 99%

On the Impact of Electrostatic Correlations on the Double-Layer Polarization of a Spherical Particle in an Alternating Current Field

Alidoosti

Zhao

2018

Langmuir

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“…Recently Stout and Khair [31] modeled this mobility reversal using a modified Poisson equation proposed by Bazant et al [32], and the predictions agreed with experiments with mobility reversals in multivalent electrolytes. On the other hand, for the three high LaCl 3 concentration cases, charge inversion occurs and positive mobilities are observed in experiments.…”

Section: Electrolytementioning

confidence: 58%

Electrophoretic mobility of spherical particles in bounded domain

Liu

Pennathur

Meinhart

2016

Journal of Colloid and Interface Science

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“…The present model also reproduces the asymptotic behavior of the electrophoretic mobility for low surface potentials. Note that, previous studies that accounted for ionic correlation effects, failed to capture this limiting behavior of electrophoretic mobility at such low surface potentials . For the trivalent electrolyte

z_{+} : z_{-} = 3 : 1

scenario (case 2: LaCl 3 ), the quantities related to Yukawa potential were chosen as

σ_{n}^{'} = - 0.04 normaln m^{- 2}

κ^{' - 1} = 0.5 nm

and

l_{n} = 2.1 nm

.…”

Section: Resultsmentioning

confidence: 99%

Solvent‐mediated nonelectrostatic ion–ion interactions predicting anomalies in electrophoresis

et al. 2017

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We study the effects of solvent-mediated nonelectrostatic ion-ion interactions on electrophoretic mobility of a charged spherical particle. To this end, we consider the case of low surface electrostatic potential resulting in the linearization of the governing equations, which enables us to deduce a closed-form analytical solution to the electrophoretic mobility. We subsequently compare our results to the standard model using Henry's approach and report the changes brought about by the nonelectrostatic potential. The classical approach to determine the electrophoretic mobility underpredicts the particle velocity when compared with experiments. We show that this issue can be resolved by taking into account nonelectrostatic interactions. Our analysis further reveals the phenomenon of electrophoretic mobility reversal that has been experimentally observed in numerous previous studies.

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A continuum approach to predicting electrophoretic mobility reversals

Cited by 41 publications

References 38 publications

On the Impact of Electrostatic Correlations on the Double-Layer Polarization of a Spherical Particle in an Alternating Current Field

On the Impact of Electrostatic Correlations on the Double-Layer Polarization of a Spherical Particle in an Alternating Current Field

Electrophoretic mobility of spherical particles in bounded domain

Solvent‐mediated nonelectrostatic ion–ion interactions predicting anomalies in electrophoresis

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