Electrokinetic sweeping of colloids at a reactive magnesium oxide interface,Soft Matter

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Electrokinetic sweeping of colloids at a reactive magnesium oxide interface
Soft Matter ( IF 2.9 ) Pub Date : 2021-09-09 , DOI: 10.1039/d1sm00908g
Li Fu ₁ , Christophe Ybert ₁ , Oriane Bonhomme ₁ , Laurent Joly _{1,

2} , Anne-Laure Biance ₁

Affiliation

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.

中文翻译：

反应性氧化镁界面处胶体的电动扫描

由于新的基于膜的能量收集或土壤净化过程的发展，研究界面附近的电动 (EK) 响应重新引起了人们的兴趣。然而，在这些过程中无处不在的反应界面的情况仍然很少被探索。在这里，我们通过实验研究了水性电解质和块状 MgO 晶体表面 (100) 之间模型界面对不同 pH 值的 EK 响应。为此，我们使用实验室规模的非侵入性方法来监测界面的 zeta 电位与时间，通过共聚焦荧光粒子跟踪。观察到粒子的意外运动，被界面排斥然后再次吸引。我们将这种运动归因于表面反应性，诱导垂直于界面的离子浓度梯度和随后的带电粒子的扩散电泳。因此，我们可以通过数值求解 Poisson-Nernst-Planck 方程来在半定量水平上描述粒子动力学，以建立系统中的浓度分布和随后的扩散泳运动。这些实验为表征反应界面附近的 EK 响应和反应速率开辟了道路。

更新日期：2021-09-15

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