Effect of tea polyphenols on the structure and properties of polyacrylonitrile ultrafiltration membrane

The polyacrylonitrile (PAN) ultrafiltration membranes containing different Tea polyphenols (TP) contents were prepared based on the blending-solution phase conversion technology. The antioxidant mechanism of PAN was proposed along with an analysis of the kinetic behavior of phase separation. The effects of TP content on the microstructure, antioxidant properties, filtration properties, and mechanical properties of PAN ultrafiltration membranes were systematically analyzed using X-ray diffractometer (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and thermogravimetry (TG) tests. Interestingly, with the addition of TP, the phase transition behavior of the membrane-forming system changed from solid-liquid phase separation to transient liquid-liquid phase separation, local pore pits appeared on the membrane surface, the cross section developed from a sponge structure to a finger-like structure, and the epithelial layer became thinner. Furthermore, using the grey correlation method, it was determined that the hybrid ultrafiltration membrane with a TP dosing of 2.0 wt% had the best comprehensive performance, with a maximum pure water flux of 202.0 L/(h·m2), flux recovery of 97.3%, and significant oxidation resistance of 21.34%. However, high levels can exceed the maximum saturation of PAN membranes that can be loaded, resulting in reduced mechanical properties. This work combines the antioxidant physiological activity of TP with the double synergistic effect of pore-forming to reveal its mechanism in inhibiting the photo-oxidation process and provides a promising solution for the preparation of long-life PAN membranes. [Display omitted]