Unravelling the fouling behavior of anion-exchange membrane (AEM) by organic solute of varying characteristics

Abstract

Organic fouling is a major obstacle in various ion-exchange membrane based electrochemical systems. Particularly, the correlation between the main characteristics of organic solute and fouling of anion-exchange membrane (AEM) is still controversial. Herein, AEM fouling by four target charged organic solutes of distinct charge, hydrophobicity, molecular weight and solute size was explored in electrodialysis, evaluated using three fouling indicators (i.e., transition time, transmembrane migration, and membrane resistance). Sodium dodecyl sulfate (SDS) compared to the other three much larger organic solutes induced immediate rising of transmembrane electrical potential (TMEP), i.e., transition time approximating zero. Surprisingly, all organic solutes penetrated across the nano-scaled membrane, supported by the total organic carbon (TOC) content of concentrate. Then, in each fouling case, membrane impedance analysis highlighted that the resistance of membrane bulk (Rm) was dominant compared to those of the interfaces and external fouling layer, thus suggesting occurrence of severe internal fouling. Finally, correlation analysis using R language demonstrated that the electronegativity and hydrophobicity of organic solutes were highly responsible for AEM fouling (contribution >70%) under each evaluation regime, thus being more important than molecule weight and size. These results bring an insight about the relative importance of and can be useful for developing future more appropriate anti-fouling strategies for ion-exchange membranes subjected to organic fouling.