Study On Local Membrane Fouling Of Hollow Fiber Membrane By Zeta Potential Combined Flux Detection

How to analyze deeply membrane filtration behavior is the core problem to effective control of hollow fiber membrane fouling, but also the key to guarantee efficient and stable operation of membrane system. It adopted Zeta potential in-situ nondestructive testing technology and local flux method for the deep understanding of local membrane fouling characteristics.Firstly, it optimized the preparations of the yeast standard solution and to study yeast suspension characteristics by different preparations on membrane filtration behavior. The results showed that:the properties of the solution were relatively stable after centrifuging/drying treatment, which was suitable as membrane filtration solution to meet different experimental requirements, and to further analyze the mechanism of cake formation.Secondly, the Zeta potential change regularity in the process of membrane filtration was researched to explore the interactions between Zeta potential and local membrane filtration behavior. The results showed that:Zeta potential could reflect the forms of local membrane fouling. The variations in Zeta potential during membrane filtration performed differently in pore blocking, cake formation and cake compression processes. When Zeta potential decreased rapidly, pore blocking occurred. As Zeta potential dropped gradually and linearly, it came to cake filtration. Subsequently, when Zeta potential became almost stable, it was experiencing cake compression. Besides, the effect of fiber length on local fouling behavior was also studied. With the increase of fiber length, the time taken by three segments to enter the cake layer compression stage was extended and the difference values of Zeta potential in three segments tended to increase. It provided more detailed information for the deep understanding of local membrane fouling mechanism.Lastly, local fouling redistribution phenomenon found in membrane filtration experiments was studied. During membrane filter process found that, the local flux was the maximum near the pump outlet, followed by the middle, the dead-end minimum in the initial stage. Local flux distribution was uneven along membrane fiber due to the uneven distribution of suction pressure. During dead-end hollow membrane filtration process, the suction pressure was the maximum near the pump outlet, thus the local flux was the maximum. But the foulants deposition was also occurred first, so the outlet had the most serious fouling and the fastest flux decline rate. Whereas the slight changes at the dead-end, which lead to uneven flux distribution in initial stage. As membrane filtration proceeds, the rapid increase of pressure drop inside the membrane fiber, the increased ratio of the cake resistance at the outlet of the fiber than that the dead-end, where the mass of deposited cake is lower. So the flux through the membrane in the middle or dead-end parts of the fiber are the largest. Then continued to filter, it was cake layer gradually compressed that formed a dense cake layer stage. The local flux at outlet was the largest again due that the differences in the degree of compaction. A certain degree of local fouling redistribution phenomenon was appeared.