Tannic acid-mediated interfacial layer-by-layer self-assembly of nanofiltration membranes for high-efficient dye separation

Layer-by-layer (LBL) self-assembly is believed as a simple and versatile strategy to fabricate wastewater purification membranes, whose separation efficiency is highly dependent on the stability of the self-assembly membranes. In this work, a composite nanofiltration membrane was prepared using carboxyl-functionalized poly (arylene ether nitrile) (CPEN) as the substrate, on which the cross-linked nanostructures derived from tannic acid (TA), metal ions, and bovine serum albumin (BSA) were immobilized via the layer-by-layer self-assembly. Particularly, several interfacial interactions, including hydrogen bonding, metal ions coordination, and hydrophobic interaction, were explored to manipulate the surface structures, wettability, and pore morphology of composite membranes. Consequently, the optimized membrane exhibited a low pressure (0.09 MPa) driven dye permeability of 52.04 L m−2 h−1 bar−1, as well as a high rejection rate for Congo Red (CR ∼ 99.9%) and Methylene Blue (MLB ∼ 99.8%), respectively. Thanks to the stable separation performance, structural stability, and dye removal, the protocol reveals in the current work would open new ways for the fabrication of water purification membranes.