Robust halloysite nanotubes modified PVDF membranes with improved wetting resistance for hypersaline wastewater treatment via membrane distillation

Membrane distillation (MD) is a viable technology and potential candidate for desalination of hypersaline wastewater. Nevertheless, MD membranes with high flux and superior antiwetting ability face a significant challenge for realizing high-efficient desalination. Herein, polyvinylidene fluoride (PVDF) hydrophobic porous membranes are fabricated by non-solvent induced phase separation. The structure of PVDF membranes, such as pore type, size, porosity, and surface hydrophobicity, can be well tuned over a wide range via adjusting phase separation conditions. To enhance the robustness of PVDF membrane, hydrophobized halloysite nanotubes (HNTs) are blended for membrane fabrication. The enhanced mechanical strength of membrane increases wetting resistance via inhibiting pore deformation and LEP reduction during salt crystals growth. In the treatment of hypersaline wastewater (70 g∙L −1 ) containing 3 g∙L −1 CaCl 2 and 3 g∙L −1 Na 2 SO 4 via VMD, the HNTs/PVDF membrane with 50 wt% HNTs shows a high flux of 54 L∙m −2 ∙h −1 , over 99.99 % NaCl rejection, and outstanding stability for 100 h. Our work not only offers a novel strategy to enhance wetting resistance of MD membranes for hypersaline wastewater treatment, but also demonstrates that the mechanical strength of membranes also significantly influences antiwetting ability of MD membranes.