Unveiling the adsorption mechanism of organic foulants on anion exchange membrane in reverse electrodialysis using electrochemical methods

This study investigates the fouling of anion exchange membrane by organic foulants in fresh water, which is one of the causes of performance degradation of reverse electrodialysis (RED). Three organic foulants, namely sodium alginate (SA), humic acid (HA), and sodium dodecylbenzene sulfonate (SDBS) are selected and the behavior of adsorption fouling of the selected organic foulants is monitored, analyzed and identified using physicochemical (ion exchange capacity (IEC), water uptake (WU)) and electrochemical (permselectivity, electrochemical impedance spectroscopy (EIS), j-V and j-P plots) methods. Compared to the pristine membrane, the resistance of anion exchange membrane increases and the selective permeability, IEC, and WU decrease after fouling of the membrane, which in turn affects the RED cell performance. SDBS, an aromatic substance, shows a higher adsorption capacity as compared to the other two foulants, and therefore causes severe degradation. Among the two aliphatic substances, namely, HA and SA, HA exhibited higher adsorption capacity than SA because it has fewer carboxylic groups. To summarize, the degradation behavior of the anion exchange membrane was clearly different based on the characteristics of each organic foulant.