Polyamide membranes play a pivotal role in energy-efficient separation technologies, such as water purification and resource recovery, owing to their ability to regulate ion transport through mechanisms like steric exclusion, dielectric exclusion, and Donnan exclusion. Among these, Donnan exclusion is critical for selective ion transport; however, discrepancies between theoretical predictions and experimental results have hindered a comprehensive understanding of this mechanism. This study represents a fundamental investigation into the electrochemical behavior of polyamide membranes, utilizing the molecular Layer-by-Layer (mLbL) assembly method to precisely control membrane thickness, morphology, and chemical structure. By tuning charge density and electrolyte concentration, we explore the correlation between impedance behavior and the Donnan exclusion mechanism. While this research is grounded in fundamental electrochemistry, its insights are highly relevant for industrial applications, particularly in the design of advanced separation membranes for environmental applications such as heavy metal removal from wastewater and lithium recovery from brines. This study bridges the gap between theoretical models and experimental observations, offering valuable guidance for the development of next-generation membranes that address both scientific challenges and practical engineering needs in sustainable technologies.
