Using five measurement tactics protocoled,the effects of membrane morphology,membrane fouling and concentration polarization on streaming potential were studied.Experimental results show that the compaction of microfiltration membrane can result in some morphological changes,hence in streaming potential variation.But this kind of change of ultrafiltration membrane is not obvious.Among the five measurement tactics used,reducing pressure step by step after compaction at higher pressure is the best.The research work also verified that charged ultrafiltration membrane could partially reject the salt in solution and the presence of concentration polarization and fouling influenced streaming potential.
Surface charge characteristics of a membrane can be determined by the streaming potential. In order to obtain more accurate streaming potential value during the measurement, four measurement operation modes were investigated in this study, and among the four modes, the steady mode with pressure stepped downward was considered the best one. Experimental results showed that the effects of compaction on the streaming potential measurement for a microfiltration membrane was more obvious than that for a ultrafiltration membrane. Both feed pH and presoaking could affect the measurement of streaming potential.
With the flux decline coefficient (m f), flux recovery coefficient (m r), streaming potential (SP) decline coefficient (k f) and SP recovery coefficient(k r), the fouling extent of membrane and its rinsing efficiency were quantitatively characterized. This combined SP and flux method is useful in studying at the interactions between protein and membrane. It was pointed out that the SP variation and flux decline resulted from both the interior BSA adsorption and the exterior BSA fouling (adsorption and deposition). For the SP variation, the interior BSA adsorption was a more important factor. Flux decline was mainly caused by the exterior BSA fouling.
X-ray Photoelctron spectroscopy (XPS) is used to study BSA adsorption on polysulfone (PS) membrane in static and dynamic conditions. The atomic compositions from XPS measurement show that the adsorption ratio, which is defined as the number of made of BSA over that of PS in the test scope, increases with the adsorption time, and dynamic adsorption is more severe than static adsorption at the same adsorption time. The fitting spectra indicate that there are chemical interactions with electron transfer between BSA and PS membrane. Further analysis shows that O 2 dissolved in BSA solution also participates in chemical interaction. These results can explain why the fouling of PS membrane by BSA solution is serious.
Surface charge characteristics of a membrane can be determined by the streaming potential. In order to obtain more accurate streaming potential value during the measurement, four measurement operation modes were investigated in this study, and among the four modes, the steady mode with pressure stepped downward was con- sidered the best one. Experimental results showed that the effects of compaction on the streaming potential meas- urement for a microfiltration membrane was more obvious than that for a ultrafiltration membrane. Both feed pH and presoaking could affect the measurement of streaming potential.
