Preparation of ZnO/PDA-PEI/PVDF antibacterial hydrophilic membranes for highly efficient oil/water emulsion separation

Abstract

The in-situ growth of ZnO is often used to modify membrane surface for enhanced hydrophilic and antibacterial properties due to significant modification effect, simple process and low cost. Nonetheless, some polymer membranes (such as PVDF membrane) lack active sites for ZnO growth on their surfaces, resulting in a small number of particles and unstable binding. This study utilized PDA/PEI to modify PVDF membranes for adequate active sites to capture Zn²⁺ ions via the chelation action. Thereafter, nano ZnO can be synthesized easily via the alkalization reaction and thermal breakdown of Zn²⁺. Upon improving the modification conditions, ZnO particles were evenly distributed on the PVDF membrane's surface, leading to a reduction in membrane pore size from 0.38 nm to 0.29 nm. The water contact angle of the ZnO/PDA-PEI modified membrane dropped from 130° to 19°, indicating a significant enhancement in hydrophilicity. The modified membrane demonstrated enhanced anti-fouling performance in the oil/water separation experiment, achieving a steady permeance of 298 L·m⁻²·h⁻¹·bar⁻¹, which was sixfold that of the original membrane. In the antibacterial experiment, the modified membrane exhibited significant antibacterial efficacy against both E. coli and S. aureus.