Enhanced performance of PVDF membranes with multi-walled carbon nanotubes for membrane distillation desalination

The global freshwater scarcity crisis necessitates the development of efficient desalination technologies. Membrane distillation (MD) is a promising thermal process capable of utilizing low-grade heat and treating high-salinity brines. However, its performance is often limited by the properties of the hydrophobic membrane. This study addresses this challenge by fabricating and optimizing poly (vinylidene fluoride) (PVDF) membranes incorporated with multi-walled carbon nanotubes (MWCNTs) for enhanced MD performance. A series of flat-sheet membranes with MWCNTs loadings from 0 to 1.0 wt % were systematically characterized and evaluated in direct contact membrane distillation (DCMD). The results demonstrated that MWCNTs significantly altered the membrane's microstructure, enhancing porosity, optimizing pore size distribution, and improving hydrophobicity and mechanical strength. The membrane with 0.5 wt % MWCNTs (C-3) exhibited an optimal balance of properties, achieving a high DCMD flux of 15.15 ± 0.15 kg/m 2 ·h and a salt rejection 99.99% using a 3.5 wt % NaCl feed at 60 °C. This flux was 61% higher than that of a commercial PVDF membrane. The enhanced performance is attributed to the MWCNTs acting as nano-reinforcements and structural modifiers. This work provides valuable insights for designing high-performance composite membranes for sustainable desalination. • Optimal 0.5 wt% MWCNTs-PVDF yields 61% higher flux than a commercial PVDF membrane. • Effective-dispersed MWCNTs enable a highly porous and optimized membrane structure. • A clear volcano-type performance trend is established versus MWCNTs loading. • The composite exhibits superior wetting resistance and robust mechanical strength.