| Summary: | 碩士 === 中原大學 === 化學工程研究所 === 90 === The combination of shearing action and electric field in crossflow filtration has been recognized as an effective means of reducing both concentration polarization and membrane deposition. However, the process has not yet received wide acceptance. One of the reasons for that is the excessive operation cost due to a high energy requirement. In order to minimize the power consumption, attention has been directed to the use of pulsed electric field. There have been brief reports that the use of pulsed electric field can lead to substantial improvements in filtration rates of microfiltration, but so far, the effect of an pulsed field on the performance of ultrafiltration has been studied in few cases.
In order to investigate the characteristics of pulsed electro-ultrafiltration for separating protein solution, experiments with BSA solution by a flat-channel filter were conducted to show the effect of electric field strength and pulsed frequency on the filtration rate, protein retentivity and power consumption under various MWCO PES membranes.
When the filter was imposed with constant electric field strengths, its filtration rate increased almost linearly with the strength, but the slopes of the linear plotting have some deviations from that of BSA mobility determined using electrophoretic measurement. For the cases with 10 and 300 kDa membranes, the electric field strength only gave a little effect on the transmission, but there was an obvious decrease of transmission with the electric field strength when a 100 kDa membrane was used.
The phenomenon that an instantaneous change of filtration rate was associated with the imposed on or off of the pulsed electric field indicated clearly that the electroosmosis plays the major role in enhancing the filtration rate. Due to the amount of filtrate received from pulsed operations was only slightly small as compared with that using constant electric field strength, the former has an obviously high electric energy efficiency based on per unit mass of filtrate. The another advantage of this method is that the thermal effect which is a drawback for heat sensitive materials can be avoid. In addition, it was also found that the gradual attenuation of filtration rate in the duration with constant electric field strength was almost not observed in the pulsed processes except with the large MWCO such as 300 kDa membrane.
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