Construction of Water Channels by Mg–Al Layered Double Hydroxide ( LDH ) and Etched ZIF ‐L (Co) for Tight Ultrafiltration ( TUF ) Membrane to Separate Dye/Salt in High‐Salinity Textile Wastewater

ABSTRACT The existing TUF membranes often face challenges such as declining permeation flux and insufficient separation selectivity. This study proposes to improve the above problems by the synergistic effect of Mg–Al layered double hydroxide (LDH) and tannic acid (TA) etched metal–organic frameworks (MOFs): (1) TUF membranes with adjustable interlayer distances and multi‐level mass transfer channels were constructed by doping LDH two‐dimensional (2D) nanosheets; (2) TAZIF‐L (Co) etched by TA was introduced. TA inhibited the swelling of LDH nanosheets through coordination and enhanced the interface binding between ZIF‐L (Co) and the substrate, thereby suppressing its shedding. The results showed that TA can etch ZIF‐L (Co), and the membrane prepared after etching has better selectivity and stability of dye/salt separation. Taking MTAZIF‐0.02 as an example, the pure water flux was 88.23 L m −2 h −1 , which was 1.91 times that of MLDH. The removal rate of congo red (CR) solution was 92.56%. The NaCl rejection in methyl blue (MB)/NaCl solution was 10.88% and in CR/NaCl solution was 10.57%. This study provides an experimental basis for the construction of highly selective ultrafiltration membrane for the treatment of high concentration dye/salt wastewater.