Fouling mechanisms associated with membrane-based polysaccharide enrichment were determined using a dense ultrafiltration (UF) membrane. Dextran with different molecular weights (MWs) was used as a surrogate for polysaccharides. The influence of dextran MW on fouling mechanisms was quantified using the Hermia model. Flux data obtained with different dextran MWs and filtration cycles were plotted to quantify the more appropriate fouling mechanisms among complete pore blocking, standard pore blocking, intermediate pore blocking, and cake filtration. For 100,000 Da dextran, all four mechanisms contributed to the initial fouling. As the filtration progressed, the dominant fouling mechanism appeared to be cake filtration with a regression coefficient (R2) of approximately 0.9519. For 10,000 Da, the R2 value for cake filtration was about 0.8767 in the initial filtration. Then, the R2 value gradually decreased as the filtration progressed. For 6000 Da, the R2 values of the four mechanisms were very low in the initial filtration. However, as the filtration progressed, the R2 value for cake filtration reached 0.9057. These results clearly show that the fouling mechanism of dense UF membranes during polysaccharide enrichment can be quantified. In addition, it was confirmed that the dominant fouling mechanism can change with the size of the polysaccharide and the duration of filtration.
Keywords: Hermia model; dense UF membrane; fouling mechanisms; membrane fouling; polysaccharide enrichment.