Hydrophilic modification of PVDF porous membrane via a simple dip-coating method in plant tannin solution

To improve the hydrophilicity of polyvinylidene fluoride (PVDF) porous membranes, herein, we report for the first time a low-cost and environmental plant tannin coating, which is strongly constructed on the surface of the PVDF membrane via a simple dip-coating method. An oxidation induced aggregation mechanism was detected in the tannin solution through the use of ultraviolet spectrophotometry (UV-Vis). The morphology and chemical composition of the tannin coated PVDF membrane were characterized via field-emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS) and attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR). After coating with the tannin coating, hydrophilicity and filtration performance are both greatly enhanced, and the modified membranes also have a good emulsion separation performance and excellent antifouling property (after emulsion separation, the flux recovery ratio even reaches 100%). Moreover, these membranes possess outstanding durability that is disclosed by a long-term rinsing experiment. These results indicate that the plant tannin coating has great potential application for the hydrophilic modification of hydrophobic membranes.