GO/TiO2-decorated electrospun polyvinylidene fluoride membrane prepared based on metal-polyphenol coordination network for oil–water separation and desalination

Over the years, graphene oxide (GO) with unique permeability and selectivity has been extensively researched for hydrophilic enhancement modification, especially as the separation layer of oil–water separation composite membranes. However, the poor stability caused by hydration of GO, and the low water flux caused by the lamellar compaction limit its application. In this study, a surface modification strategy based on metal polyphenol coordination was proposed to address these problems by co-deposition of tannic acid-graphene oxide (TA-GO) and TiO2 on electrospun polyvinylidene fluoride (PVDF) membrane. TiO2 was inserted into GO layers to expand the interlayer spacing and prevent membrane compaction. Moreover, the interlayer force was enhanced by TA and Fe3+ through covalent bonds, cation-π, and coordination bond. The results demonstrated that the underwater oil contact angle of resultant composite membrane reached 152.5°. In addition, it has a high flux (243.11 L/h·m2·bar) and oil (> 98%)/salt (> 47%) rejection, which can be maintained even after ultrasonic treatment for 30 min. This work proposed a practical and environmental approach to construct a steady GO-modified hydrophilic membrane.Graphical abstract