Electrospun Nanofibrous Polyphenylene Oxide Membranes for High-Salinity Water Desalination by Direct Contact Membrane Distillation

Desalination by the membrane distillation (MD) process has been proposed to significantly increase the water recovery ratio, especially treating with highly saline waters, for example, seawater and shale gas wastewater. However, the state-of-the-art membranes experience severe wetting phenomenon, which generally leads to a performance decline, resulting in inferior quality of the produced clean water. Herein we report, for the first time, an nanofibrous thin film based on nonfluorinated poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) prepared by an electrospinning method for MD application. The inherently low thermal conductivity of PPO could well preserve the driving force across the membrane during operation, while the corresponding nanofibers with a rather smooth surface can prevent the adhesion of inorganic salts, resulting in much enhanced anti-scaling behavior. Briefly, the PPO membrane could provide a high water recovery ratio of 80 and 60% for seawater and shale gas wastewater desalination, respectively, with only 12.5 and 33% decline in water flux, respectively, whereas 20.8 and 88.8% decline in water flux, respectively, was observed for a commercial polyvinylidene difluoride membrane. Overall, we developed a promising polymer candidate for fabricating novel membrane materials for MD application and highlight its great potential for treating highly salty water samples.