The molecular weight-fouling matrix: A novel dissection of polysaccharide interactions in ultrafiltration processes

Polysaccharides, recognized as critical organic pollutants, exhibit fouling tendencies intricately tied to molecular weight (MW). While extensive discussions have focused on the MW of polysaccharides, a comprehensive understanding of its direct impact on membrane fouling remains elusive. In this study, dextran with different MWs acted as model pollutants, revealing the intricate relationship between polysaccharide MW and fouling behavior. Data on specific flux and filtration resistance indicated an initial decline and subsequent increase in fouling with increased MW. Noteworthily, polysaccharides with an intermediate MW of 40 kDa exhibited the least fouling. Advanced analytical methods indicated the source of the reduced fouling to pronounced intermolecular repulsions and crucial molecular configuration shifts. While the lower MW variants resisted membrane adhesion, their higher MW counterparts fostered dense filter cake layer development, causing serious membrane fouling. By describing the nuanced roles of MW on ultrafiltration membrane fouling, this investigation not only deepens insights into the nexus between organic foulant MW and fouling, but also illuminates pathways for innovative strategies in mitigating polysaccharide-induced fouling in ultrafiltration water treatment processes.