3D flower-like layered double hydroxides empower anti-wetting PVDF membrane for robust membrane distillation

Membrane wetting remains one of the major challenges in membrane distillation (MD), limiting its further application. Herein, this study reported a novel layered double hydroxides (LDHs) composite membrane fabricated combining the hydrothermal synthesis and coating methods. This approach facilitated the in-situ nucleation and growth of the micro-nano hierarchical MgAl-LDHs nanoflowers on dopamine-treated PVDF substrate. Then, the further fluorination was conducted by the 1H, 1H, 2H, 2H-perfluorodecyltriethoxysilane (PFDS). By comprehensive characterization, including surface structure, wettability and MD performance, the superhydrophobic MLDH@PVDF composite membrane exhibited water contact angle of 160.1 ± 0.37° and slide angle of 4.67°. These results were achieved through the integration of the micro-nano LDHs architecture with the PFDS coating, thereby ensuring a stable Cassie-Baxter state. The modified membrane was applied for membrane distillation desalination, achieving the average MD flux of 32.79 kg m −2  h −1 and 23.55 kg m −2  h −1 when treating 0.6 M and 3 M NaCl solution, respectively. Especially, the feed saline can be concentrated to 4.01 M, demonstrating its excellent tolerance to a wide salinity range. Moreover, when the feed saline containing 200 ppm humic acid or n-Hexane, the prepared composite membrane kept relatively stable flux without wetting happening. These findings demonstrated that this hierarchical flower-like LDH structure endows the PVDF membrane with robust anti-wetting properties, enabling stable MD performance even in challenging environments of saline water containing humic acid.