Hamed Karkhanechi

1.7 PVDF Hollow Fibers Membranes

With the fast growth of population during last century, serious global issues raised that global warming and potable water shortage are the major ones that challenge humankind life. During last decades, membrane technology has developed very quickly and attracted much attention as a great potential for solving humankind problems. Poly(vinylidene fluoride) (PVDF) hollow fiber is one of the technologies that are already well industrialized. In this chapter, preparation, modification, and application of PVDF hollow-fiber membrane are summarized. In preparation part, we especially focus on the thermally induced phase separation and nonsolvent-induced phase separation. These two methods widely have been applied for membrane preparation in industrial scale. For both methods, phase diagram, kinetic effects, and preparation parameters are discussed in detail. In some cases, the results of flat-sheet membranes which expected that could be potentially applied for hollow-fiber membrane preparation in the future are also included. Since virgin PVDF membrane comes with some drawbacks, modification for PVDF membranes (making it more hydrophilic and hydrophobic) is studied. Finally, the important application of PVDF membrane is summarized.

Adsorption of Bovine Serum Albumin on Poly(vinylidene fluoride) Surfaces in the Presence of Ions: A Molecular Dynamics Simulation

Adsorption of bovine serum albumin (BSA) on poly(vinylidene fluoride) (PVDF) surfaces in an aqueous environment was investigated in the presence and absence of excess ions using molecular dynamics simulations. The adsorption process involved diffusion of protein to the surface and dehydration of surface-protein interactions, followed by adsorption and denaturation. Although adsorption of BSA on PVDF surface was observed in the absence of excess ions, denaturation of BSA was not observed during the simulation (1 μs). Basic and acidic amino acids of BSA were found to be directly interacting with PVDF surface. Simulation in a 0.1 M NaCl solution showed delayed adsorption of BSA on PVDF surfaces in the presence of excess ions, with BSA not observed in close proximity to PVDF surface within 700 ns. Adsorption of Cl- on PVDF surface increased its negative charge, which repelled negatively charged BSA, thereby delaying the adsorption process. These results will be helpful for understanding membrane fouling phenomena in polymeric membranes, and fundamental advancements in these areas will lead to a new generation of membrane materials with improved antifouling properties and reduced energy demands.