Superhydrophilic and antibacterial PVDF membrane modified by TA-PEI@DMSN nanocomposite for efficient oil-water separation

In the realm of wastewater treatment, the removal of grease and the control of microbial reproduction are crucial links. However, the design of a sustainable membrane with high oil filtration efficiency, high water permeability, excellent separation capacity and strong antibacterial function is still a problem that continues to challenge the researchers. In this work, Tannic acid (TA) and polyethylenediamine (PEI) were used as hydrophilic modifiers to combine with dendritic mesoporous silica (DMSN) to prepare a new type of nanocomposite particles (TA-PEI@DMSN). Using glutaraldehyde (GA) as a coupling agent, TA-PEI@DMSN nanoparticles were coated on the surface of polyvinylidene fluoride (PVDF) membrane, and a modified membrane (TA-PEI@DMSN/PVDF) was developed, which was both super-hydrophilic and super-oleophobic underwater conditions. The TA-PEI@DMSN/PVDF membrane can effectively intercept oily substances such as cyclohexane, n-heptane, petroleum ether and n-hexane, achieving an oil rejection rate up to 99.1% for heptane. The modified membrane exhibits superhydrophilicity (CA≈0°) and underwater oil resistance, excellent anti-fouling performance and robust stability. Otherwise, we noticed that the positive charge characteristic of the TA-PEI surface imparts the TA-PEI@DMSN/PVDF membrane with more 99.97% antibacterial activities against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). The molecular simulation results show that the wettability and hydrophilicity are significantly improved compared with the unmodified PVDF membrane, which is consistent with the experiment data. The modified membrane performs well and shows great potential for oil-water separation.