Migration behavior of organic foulants toward anion exchange membrane under the electric field.

Anion exchange membrane (AEM) fouling has sparked extensive research, especially on the interaction of foulants with the AEM. However, there is still a lack of clear explanation about how foulants migrate from feedwater to the AEM surface. This study systematically investigated the migration of foulants and influencing factors in electrodialysis (ED). The behavior of negatively charged foulants in ED was found to occur in three stages according to the variety of the rate of diluate conductivity change: blocking by boundary layer, approaching, and arriving at the AEM surface. The results revealed that the membrane was rarely fouled in the first stage, whereas the fouling level significantly increased in the second and stabilized in the third. A limiting conductivity was identified, marking the point where the fouling level began to rise, indicating the transition from the first to subsequent stages. The current value was found to be highly responsible for limiting conductivity (contribution >95 %). Based on that, an operation strategy with low energy consumption and high desalination efficiency was proposed by adjusting the current according to feed water conductivity. This study brings insights into completing the whole fouling behavior and developing anti-fouling strategies for AEM by mitigating foulants' migration, which increases ED desalination performance facing fouling.