Effect of polydopamine coating and direct electric current application on anti-biofouling properties of anion exchange membranes in electrodialysis

Abstract

The fouling of anion exchange membranes (AEMs) during an electrodialysis (ED) is a serious problem. Membrane fouling is often classified into organic fouling, inorganic fouling (scaling) and biofouling. In our previous studies, we reduced organic fouling by modifying the membrane surface with dopamine solution, which formed a negatively charged, hydrophilic polydopamine (PDA) layer on the membrane surface. PDA coating also increased monovalent anion permselectivity. Improvement in monovalent anion selectivity is expected to decrease scale formation and consequently improves anti-inorganic fouling properties. In this work, we investigated the effect of PDA coating on biofouling of AEM. The anti-adhesive properties were evaluated with a static adhesion test using Pseudomonas putida (P. putida). It was found that the anti-adhesive properties were effectively improved by surface modification with 0.1kg/m3 dopamine solution. Moreover, we evaluated biofouling during ED operation, for the first time, by measuring the time elapsed before biofouling occurred using a P. putida suspension as the feed solution. The surface was then observed by scanning electron microscope (SEM) after biofouling experiment. The results showed that a direct electric current application suppressed bacterial attachment on the AEM surface in addition to the effect of membrane surface modification with PDA.