Electrokinetic sweeping of colloids at a reactive magnesium oxide interface

Abstract

Investigating the electrokinetic (EK) response in the vicinity of interfaces has regained interest due to the development of new membrane based processes for energy harvesting or soil depollution. However, the case of reactive interfaces, ubiquitous in these processes, remains scarcely explored. Here we experimentally investigate the EK response of a model interface between an aqueous electrolyte and a bulk MgO crystal surface (100), for different pH. For that purpose, we use a lab-scale non invasive method to monitor the zeta potential of the interface versus time, by confocal fluorescent particle tracking. An unexpected motion of the particles, repelled and then attracted again by the interface is observed. We attributed this motion to the surface reactivity, inducing ion concentration gradients perpendicular to the interface and subsequent diffusiophoresis of the charged particle. Accordingly, we could describe at a semi-quantitative level the particle dynamics by solving numerically the Poisson–Nernst–Planck equations to establish concentration profile in the system and subsequent diffusiophoretic motion. These experiments open the way to the characterization of both the EK response and the reaction rate in the vicinity of reactive interfaces.

Graphical abstract: Electrokinetic sweeping of colloids at a reactive magnesium oxide interface

Supplementary files

Article information

Article type
Paper
Submitted
18 Jun 2021
Accepted
08 Sep 2021
First published
09 Sep 2021
This article is Open Access
Creative Commons BY-NC license

Soft Matter, 2021, Advance Article

Electrokinetic sweeping of colloids at a reactive magnesium oxide interface

L. Fu, C. Ybert, O. Bonhomme, L. Joly and A. Biance, Soft Matter, 2021, Advance Article , DOI: 10.1039/D1SM00908G

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