The modification of PVDF hollow fiber membrane via atom transfer radical polymerization (ATRP)
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[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT AUTHOR'S REQUEST.] This work was focused on the fabrication, modification and characterization of polyvinylidene difluoride (PVDF) hollow fiber membranes (HFMs) produced by a phase inversion technique. A PVDF HFM with a high water flux was developed by adjusting fabrication condition, such as the dope solution rate and bore fluid rate. The pristine HFM was modified successfully by grafting 2-carboxyethylacrylate (CAA) from membrane surface via an activator generated by electron transfer (AGET) ATRP and the antifouling characteristics of membrane was evaluated with bovine serum albumin (BSA) solution as a feed at different pH conditions. The grafted membrane with certain amount of CAA with better antifouling property at alkaline pH values of feed solution was produced as expected. Results from this study indicated that, while AGET ATRP could provide the additional benefit of preventing oxygen interference, atmospheric oxygen still interrupted the polymerization process. A simple nitrogen protection was required to eliminate the effect of oxygen during the modification process. This work demonstrated the effects of surface-initiated polymerization on membrane surface morphology. The pore size distribution was narrowed and the membrane roughness decreased for modified HFM. The filtration tests with pristine and modified HFMs showed that the pure water flux could be increased by grafting certain amount of CAA on the membrane surface and the phosphate buffered saline (PBS) solution was better than DI water when used as a cleaning solution. The performances of PVDF, PVDF CAA5, PVDF CAA7.5 HFMs were investigated using feed solutions with different pH values: 6.5, 7.5, 9, 10 demonstrating that the grafted membrane with certain amount of CAA was less fouled and could be readily cleaned by PBS solution when compared with pristine membranes at alkaline pH values of feed solution.
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