Data underlying Mismatch and Mix: Making use of Electrokinetic Aspects of Spacers for Intensified Electrodialysis

s enElectrodialysis (ED) processes are limited in terms of practical current densities due to the emergence of concentration boundary layers. A great deal of research has focused on methods to promote mixing of these boundary layers, particularly through developing new spacer materials. Spacers are crucial to the performance of electrodialysis stacks, forming the flow channels between membranes and leading to hydrodynamic mixing that can reduce mass transport limitations. The conventional treatment of spacers in electrodialysis has focused on characterizing the hydrodynamic mixing resulting from spacer geometry and assessing how this impacts the overall stack resistance. In this work, we explore the electrokinetic aspect of spacer performance: how does the electric-field bending induced by polymeric spacers give rise to electro-osmotic mixing and how can we enhance this effect by increasing the surface charge of conventional spacer materials? In order to understand these effects, we carried out an experimental study to characterize the ED performance of a lab-scale stack using spacers with different surface charge densities, achieved through polyelectrolyte adsorption on the spacers. Our results show that in the limiting current regime, substantial increases in the current density or reductions in power consumption can be achieved when making use of this enhanced mixing due to electro-osmosis. We also explain this enhancement through the use of a simplified theoretical model to highlight the potential of utilizing electrokinetic mixing from spacers in electrodialysis.<br>

电渗析（Electrodialysis, ED）过程受限于浓度边界层的形成，实际电流密度难以进一步提升。已有大量研究致力于开发促进此类边界层混合的方法，尤其是通过研发新型间隔物（spacer）材料。间隔物对电渗析堆的性能至关重要：其可在膜之间形成流道，并通过流体动力学混合降低传质限制。传统电渗析领域对间隔物的研究多聚焦于表征间隔物几何结构引发的流体动力学混合效应，并评估其对电渗析堆整体内阻的影响。本研究聚焦于间隔物性能的电动学维度：聚合物间隔物引发的电场弯曲如何催生电渗混合，以及我们能否通过提升传统间隔物材料的表面电荷来强化这一效应？为明晰上述效应，本研究开展了实验探究：通过在间隔物表面吸附聚电解质，制备了不同表面电荷密度的间隔物，并以此表征实验室规模电渗析堆的ED性能。研究结果表明，在极限电流工况下，利用电渗引发的强化混合效应，可显著提升电流密度或降低能耗。本研究还通过简化理论模型对该强化效应进行了解释，以凸显利用间隔物电动混合效应提升电渗析性能的应用潜力。