Fouling dynamics of anion polyacrylamide on anion exchange membrane in electrodialysis

摘要

Anion polyacrylamide (APAM) fouling towards anion exchange membrane (AEM) during electrodialysis (ED) of industrial effluent draws recent attention. The fouling dynamics was herein investigated via different approaches in monitoring the variation of the solution and membrane properties. The results showed that conductivity and pH variation is less sensitive than electrochemical signals via transmembrane electric potential (TMEP) and electrochemical impedance spectroscopy (EIS) focusing on micro-scale variation occurred on/near the membrane interface. Initially, the deposition of APAM caused few current transfer limitations as supported by the plateau region for the TMEP profile. Further building-up of APAM fouling gradually hindered the current transfer, resulting into an increased TMEP due to the formation of gel layer on AEM and/or blockage of free volume. Later, the water splitting indicated by an obvious pH variation in dilute and concentrate occurred, which may further accelerate the fouling via modifying the particle size of APAM. EIS successfully distinguished the electrochemical property of membrane bulk and boundary layer, implying the internal fouling is largely responsible for the increased membrane resistance. Future work is suggested to further clarify the external and internal fouling on ion exchange membrane (IEM) and investigate effective fouling mitigation methods in ED.