Fouling and Mitigation Behavior of Foulants on Ion Exchange Membranes with Surface Property in Reverse Electrodialysis

In this study, two different types of ion exchange membranes are used to investigate the tendency of membrane fouling with respect to surface roughness and hydrophilicity. Commercially available membranes reinforced by electrospun nanofiber have rough and hydrophilic surfaces, and lab-made pore-filling membranes exhibit a smooth and hydrophobic surface. Three different organic surfactants (i.e., cationic, anionic and non-ionic surfactants) are chosen as foulants with similar molecular weights. It is confirmed that membrane fouling by electrical attraction mainly occurs, in which anionic and cationic foulants influence anion and cation exchange membranes, respectively. Thus, less fouling is obtained on both membranes for the non-charged foulant. The membranes with a rough surface show a higher fouling tendency than those with a smooth surface in the short-term continuous fouling tests. However, during the cyclic operations of fouling and mitigation of the commercially available membranes, the irregularities of a rough membrane surface cause a rapid increase in electrical resistance from the beginning of fouling due to excessive adsorption on the surface, but the fouling is easily mitigated due to the hydrophilic surface. On the other hand, the membranes with a smooth surface show alleviated fouling from the beginning of fouling, but the irreversible fouling occurs as foulants accumulate on the hydrophobic surface which causes membrane fouling to be favorable.

Automated summary

This study investigates the impact of surface roughness and hydrophilicity on membrane fouling using two types of ion exchange membranes. The commercially available membranes have rough and hydrophilic surfaces, while the lab-made membranes have smooth and hydrophobic surfaces. The fouling tests confirm that electrical attraction is the main cause of membrane fouling, with anionic and cationic foulants affecting anion and cation exchange membranes, respectively. The results show that a rough surface has a higher fouling tendency in short-term tests, but the fouling can be easily mitigated due to the hydrophilic surface. Conversely, a smooth surface initially reduces fouling, but leads to irreversible fouling due to the accumulation of foulants on the hydrophobic surface.