Measurement of Concentration Distributions of Protein Layer Deposited on Membrane in Inclined Ultrafiltration of Protein Solutions

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A dramatic flux decline during ultrafiltration is the thorniest problem in the use of ultrafiltration systems. Such flux decline is mainly attributed to the accumulation of the protein molecules on the membrane surface. Therefore, an understanding of the properties of the protein layer accumulated on the membrane surface can serve as a basis for clarifying the real mechanism of ultrafiltration. In this study, a method has been developed for measuring the concentration variations of the accumulated protein layer tends to have a much more compact structure at the membrane in comparison to a relatively loose condition at the surface. This is the same tendency as the filter cake formed in filtration of particulate suspensions. It was also shown that the thickness of the protein layer increases as the filtration proceeds. This method is of significance for clarifying the real mechanism of ultrafiltration, become few reliable experimental data on the concentration distributions of the protein layer have been reported so far.The compressible cake filtration model has been widely used to describe filtration behaves of particulate suspensions. Recently, the model has been used to explain the mechanism of ultrafiltration. In this study, the experimental results of the concentration variations within the protein layer were compared with the calculations on the basis of the compressible cake filtration model. The measured concentration variations accorded well with the calculated results, which revealed that the dynamic deposition behaviors of the protein layer in ultrafiltration can be accurately described by the compressible cake filtration model.