Insight into fouling behavior of poly(vinylidene fluoride) (PVDF) hollow fiber membranes caused by dextran with different pore size distributions

Membrane fouling is the key problem that occurs in membrane process for water treatment.However,how membrane microstrocture influences the fouling behavior is still not clear.In this study,fouling behavior caused by dextran was deeply and systematically investigated by employing four poly(vinylidene fluoride) (PVDF) membranes with different pore sizes,ranging from 24 to 94 nm.The extent of fouling by dextran was accurately characterized by pore reduction,flux decline,and the change of critical flux.The result shows that membrane with the smallest pore size of 24 nm experienced the smallest fouling rate and the lowest fouling extent.As the membrane pore size increased,the critical flux ranges were 105-114,63-73,38-44 and 34-43 L· m-2· h-1,respectively.The critical flux and fouling resistances indicated that the fouling propensity in creases with the increase of membrane pore size.Two pilot membrane modules with mean pore size of 25 nm and 60 nm were applied in membrane filtration of surface water treatment.The results showed that serious irreversible membrane fouling occurred on the membrane with pore size of 60 nm at the permeate flux of 40.5 L· m-2· h-1.On the other hand,membrane with pore size of 25 nm exhibited much better anti-fouling performance when permeate flux was set to 40,5,48 and 60 L· m-2· h-1.