“Two Birds One Stone” Strategy: PTFE Nanorods for Assembling Nanomaterials and Constructing Hydrophobic Porous Membranes for High-Performance Membrane Distillation

The promising development of porous hydrophobic membranes hybridized with nanomaterials is of great value for desalinating in membrane distillation (MD). The surface morphology of nanomaterials is frequently covered by polymer binders during the assembly process, resulting in reduced mass transfer efficiency. Herein, we constructed a hybridized membrane featuring lotus leaf mimetic hierarchies by vacuum filtration of a commercial polytetrafluoroethylene (PTFE) nanorod emulsion containing wrinkled reduced graphene oxide (rGO) microspheres on a microfiltration substrate. The PTFE nanorods playing the role of “two birds one stone” not only allowed the microspheres to be tightly attached to the substrate without the use of a polymer binder, but they generated a wrinkled rGO microsphere–PTFE nanorod layer with a loose and porous structure as well. Such membrane exhibits strong hydrophobicity (a water contact value of ∼142.6°) and excellent salt rejection of 99.75% with a high water flux of 35.73 kg·m–2·h–1 for separating a 3.5 wt % NaCl solution (70 °C) in a vacuum MD (VMD). It also retains a stable performance after a 700 h continuous operation. An in-depth analysis of the mass transfer process was further performed by theoretical calculation, providing inspiration for constructing high-performance membranes for desalination.