Antibacterial nanofiltration membranes fabricated through co-deposition of dopamine and lysozyme

Dopamine-assisted co-deposition is a promising approach for preparing nanofiltration (NF) membranes due to its simplicity, controllability, and versatility. However, limited research has been conducted on the functionalization and membrane formation mechanism of polydopamine (PDA) co-deposition membranes. In this study, lysozyme (Lys) was selected as one model protein and co-deposited with dopamine to prepare antibacterial NF membranes. The effects of the mass ratio of PDA/Lys and deposition time on the selective layer structure and membrane performance, and membrane-forming mechanism were systematically investigated. Results prove that addition of lysozyme into a dopamine solution promotes the rapid formation of a dense selective layer, and the maximum density of the PDA/Lys co-deposition layer reaches 1.53 g·cm −3 with the optimal 1:0.50 mass ratio of dopamine and lysozyme, and the resulting membranes have the effective pore size of 1.5 nm in diameter. The optimal PDA/Lys membranes can achieve high methyl blue (MB) rejection (98.2 %) and low salt rejection (13.1 % for NaCl) while maintaining high water permeance (42.4 L·m −2 ·h −1 ·bar −1 ) and demonstrating excellent long-term operational stability. Moreover, the NF membranes made from co-deposition of PDA and Lys exhibited outstanding antibacterial properties with 92 % bacterial-killing efficiency. Our work provides a simple method for utilizing functional proteins to prepare antibacterial NF membranes, and offers new insights into the membrane-forming mechanism of dopamine-assisted co-deposition membranes.