Robust polyethylenimine bridged layered double hydroxide composite membrane for efficient dye/salt separation

Layered double hydroxide (LDH) membranes, featuring uniform interlayer nanochannels, hold substantial potential for molecular sieving in aqueous solutions. In this study, polyethyleneimine (PEI) rich in amino groups is used as bridging unit to develop a robust PEI-bridged-LDH composite membrane with enhanced molecular sieving performance. The introduction of PEI bridges adjacent nanosheets, strengthens the interlayer bonding strength, creating a continuous LDH nanosheet membrane with high selectivity. Owing to the well-designed lamellar structure ans excellent hydrophilicity, the PEI-bridged-LDH composite membrane achieves high water permeance (864.5 L m −2 h −1 bar −1 ) and superior dye/salt separation performance, with outstanding dye rejections (e.g., Congo Red: 99.1%, Methyl Blue: 99.3%, Victoria Blue B: 99.7%) and low salt rejections (e.g., Na 2 SO 4 : 5.7% and NaCl: 2.2%). Moreover, the PEI-bridged-LDH composite membranes show high mechanical strength due to the hydrogen bond interactions between PEI and LDH nanosheets, thereby exhibiting robustness against mechanical damage and under high trans-membrane pressure of 5 bar. Besides, the composite membrane also demonstrates outstanding anti-fouling properties and long-term operation durability for dye/salt mixtures, suggesting its great potential in treating practical textile wastewater. This work opens a new avenue for developing robust LDH membranes for continuous and stable dye/salt separation.