Surface concentration polarization induces fouling processes accompanied by changes in the resistance of a semipermeable membrane, but the connection between these two phenomena has not yet been evaluated. Here, we propose to connect them by introducing the concept of pH equivalent (pHeq), which is used to describe the electrical properties of a polarized membrane surface in terms of a pH value at which a membrane is conditioned. First, the resistance and capacitance of polyamide thin-film membranes conditioned at different pH were evaluated ex situ using electrical impedance spectroscopy (EIS), which decreases and increases in proportion with increasing pH when the pH exceeds the pKa of the ionization of carboxyl groups. Filtration of 0.1 mM Fe(III) chloride solution in dead-end mode was then conducted as a model reaction for the fouling process. The occurrence of concentration polarization in the early stage indeed led the capacitance and the resistance at the membrane/electrolyte interface to a pHeq similar to that of an alkaline-like environment, while no significant decline in flux or rejection was observed. In addition to being responsible for the formation of Fe(OH)₃ in fouling, this high pHeq is also likely the bridge connecting the electrical characteristics of the membrane to macroscopic observations (flux and rejection) based on the electroviscous consideration.

表面浓度极化引起结垢过程，伴随着半透膜电阻的变化，但是这两种现象之间的联系尚未得到评估。在这里，我们建议通过引入pH当量（pHeq）的概念来连接它们，该概念用于根据膜被调节到的pH值来描述偏振膜表面的电性能。首先，将电阻和在不同的pH调节聚酰胺薄膜膜的电容进行了评价易地使用电阻抗光谱法（EIS），当pH值超过羧基离子化的pKa时，pH值会随着pH值的增加而减少和增加。然后以死端模式过滤0.1 mM的Fe（III）氯化物溶液，作为污垢过程的模型反应。早期发生的浓度极化确实确实导致了膜/电解质界面处的电容和电阻达到类似于碱性环境的pHeq，而未观察到通量或截留率显着下降。除了负责形成Fe（OH）₃ 在结垢时，这种高pHeq可能也是基于电粘性考虑将膜的电特性与宏观观察结果（通量和排斥率）联系起来的桥梁。