The improvement of nanofiltration membrane performance with lignin Cu complex as interlayer

Nanofiltration (NF) membranes are instrumental in separating small molecular organics and salts, finding widespread application in industrials such as food, pharmaceuticals, and dye printing for product purification and wastewater treatment. However, the performance of these membranes is often restricted by the inherent “trade-off” effect between selectivity and permeability. In this study, a copper- demethylated lignin (Cu-DL) interlayer between the substrate and the selective layer was fabricated, aimed at augmenting the NF membrane's efficiency. This enhancement primarily results from Cu2+ coordination adsorption with piperazine (PIP), serving to regulate the diffusion and optimize the structure of the selective layer. Concurrently, the interlayer prevents the infiltration of the selective layer to reduce the mass transfer resistance. Compared to conventional NF membranes, the NF membrane based on the Cu-DL interlayer, exhibited a marked increase in permeability from 6.2 L m-2h-1bar−1 to 12.9 L m-2h-1bar−1, while essentially maintaining its retention capabilities for Na2SO4 solutions. Additionally, this membrane exhibits the excellent separation of salts and dyes under various concentrations. This work can provide a solution for the fabrication of high-performance NF membranes and new ideas for the utilization of biomass.