Preparation and characterization of polyamide thin-film composite (TFC) membranes on plasma-modified polyvinylidene fluoride (PVDF)

The use of polyvinylidene fluoride (PVDF) membrane as a support substrate layer for making a polyamide thin-film composite (TFC) has been hindered by the hydrophobic nature of PVDF. In this study, low temperature plasmas were used to treat a commercial PVDF membrane in order to improve its hydrophilicity and make it suitable for fabrication of a polyamide-polyvinylidene fluoride thin-film composite (PA-PVDF) membrane. The plasma treatment used oxygen, methane, or their 1:1 mixture gas to produce glow discharge for treatment and surface modification of the PVDF membrane. The membrane surfaces were characterized using water contact angle measurements, X-ray photoelectron spectroscopy (XPS), and field emission scanning electron microscopy (FE SEM). Pure water permeability and salt rejection tests were performed to evaluate the performance of the resulting PA-PVDF. Our experimental results indicated that plasma treatment of PVDF membrane could significantly reduce its water contact angle and thus produce a hydrophilic surface that could be then used as the support substrate layer for the fabrication of TFC membrane through interfacial polymerization. Our experimental results also demonstrated that PA-PVDF membrane supports not only demonstrated higher pure water permeability, but also higher salt rejections than those of TFC membrane with polysulfone as the support. (C) 2009 Elsevier B.V. All rights reserved.