Microfiltration membranes prepared from acryl amide grafted poly(vinylidene fluoride) powder and their pH sensitive behaviour

Acryl amide (AAm) was grafted onto poly(vinylidene fluoride) (PVDF) powder by a pre-irradiation induced graft polymerization technique. The chemical structure of AAm grafted PVDF powder (denoted as PVDF-g-PAM powder) was characterized by FT-IR spectroscopy and X-ray photoelectron spectroscopy (XPS) analysis. Then, the microfiltration (MF) membranes were cast from PVDF-g-PAM powder with different degrees of grafting (DG) using a phase inversion method. The contact angle of those modified MF membranes decreased with increased DG, indicating the enhanced hydrophilicity of modified MF membranes due to the existence of PAM side chains. The morphology of MF membranes was studied by scanning electron microscopy (SEM), pore size and distribution was determined by mercury porosimetry analysis, and water filtration properties was tested at different pH values. The results showed that MF membranes made from PVDF-g-PAM powder have better water flux performance than that of the pristine one due to the enhanced hydrophilicity. Moreover, modified MF membranes showed certain pH sensitivity behaviour with high DG, where the flux changes with the pH value of fed aqueous solution and it is reproducible during the 12 times cyclic test.