Plasma etching assisted fabrication of PDA/PEI modified PVDF membranes for oil/water emulsion separation

The PDA/PEI modification technology is commonly employed to improve the resistance to membrane fouling of polymeric membranes used in the treatment of oily wastewater. Nevertheless, the surface characteristics of membrane materials frequently restrict the implementation of the modification technique in terms of both the amount and speed of deposition. The hydrophobic membranes, such as PVDF and PTFE, have a surface with very low surface free energy and only inert functional groups. This surface is not suitable for the deposition of PDA/PEI. This study utilized plasma etching treatment to break the C–H and C–F bonds on the surface of the PVDF membrane, resulting in the introduction of oxygen-containing functional groups. During the deposition process, the PDA/PEI exhibited a tendency to chemically connect to material surfaces that included oxygen-containing functional groups, such as –OH, by processes such as hydrogen bonding. During the modification procedure, the etched membrane experienced an increase in the mass of PDA/PEI deposition and the strength of interfacial bonding. As a result, the modified membrane acquired improved hydrophilicity and anti-fouling performance. In summary, this study offers useful insights for improving the surface properties of hydrophobic polymeric membranes to prevent membrane fouling.