Superhydrophobic nanostructured wood membrane for thermal distillation desalination

Abstract

Membrane distillation (MD) has been widely explored to alleviate the global shortage of fresh water resources for the past few years. However, MD utilizes petroleum-derived polymer membranes at present, which exhibit low biodegradability, leading to obvious environmental concerns regarding their utilization and disposal. Its porosity and thermal conductivity also seriously affect the separation efficiency of water and solutes, thereby impeding the widespread adoption of MD. Here, we demonstrated a sustainable superhydrophobic nanostructured wood membrane incorporating 1H, 1H, 2H, 2H-perfluorodecyltriethoxysilane and SiO₂ nanoparticles to create a stable superhydrophobic coating on the wood membrane surface, achieving a water contact angle exceeding 160°. The superhydrophobic nanostructured wood membrane possessed anisotropic microstructures and hierarchical porous structures characterized by exceptionally high porosity (87 %) and low thermal conductance (0.053 W m⁻¹ K⁻¹ at 60 °C), which could facilitate efficient water vapor transportation. In direct contact MD tests, the superhydrophobic nanostructured wood membrane demonstrated excellent water flux (18.2 ± 0.8 kg m⁻² h⁻¹ at 60 °C) and outstanding thermal efficiency (71 %). The high thermal efficiency, low cost, and sustainability of superhydrophobic nanowood MD membranes confer remarkable research value in the field of off-grid desalination at the water‒energy nexus.