How polyvinyl alcohol-based interlayers affect the performance of polyamide nanofiltration membranes prepared by polyethyleneimine

Polyethyleneimine (PEI) based positive charge nanofiltration (NF) membranes have unique advantages in the removal of heavy metals. The regulation mechanism of the interlayer when PEI was used as monomer was still not clear. In this study, a PVA-based interlayer was constructed on the origin PES sublayer to tailor the interfacial polymerization in PEI systems. It was proved that the PVA interlayer can further elevate the PWP and rejections of heavy metals. Moreover, the absorption effect of interlayers could contribute to better removal of heavy metals. More negative charges of interlayer could result in a more enough and uniform absorption of PEI monomer as well as a slower diffusion rate of PEI monomer during the interfacial polymerization reaction, thus forming a loose top surface but dense sub-separating layer. This study provides new insight into the effect of interlayer on the performance of PEI-based nanofiltration membrane.