Enhanced, hydrophobic, fluorine-containing, thermally rearranged (TR) nanofiber membranes for desalination via membrane distillation

Though membrane distillation (MD) has been considered as a promising desalination process, it is still required to develop a desirable membrane which has high water flux and long-term stability for practical use in the MD process. In our previous work, thermally rearranged nanofiber membranes (TR-NFMs), which exhibited high water flux (80kgm−2h−1) and salt rejection (> 99.99%) as well as outstanding long-term stability (more than 180h), were first introduced as a promising candidate for MD applications. However, nascent TR-NFM is susceptible to fluctuations in operating conditions due to insufficient liquid entry pressure with water (LEPw). In continuation of our enhanced hydrophobic TR-NFM study, we develop fluorine-containing thermally-rearranged nanofiber membranes (F-TR-NFMs) for MD applications for the first time. F-TR-NFMs showed enhanced hydrophobic properties such as high water contact angle (143°), high LEPw (1.3bar), and high effective evaporation area (EEA) due to the introduction of fluorine atoms in the backbone of the TR membrane. As the result, the developed F-TR-NFMs exhibited outstanding MD performance (114.8kgm−2h−1 of water flux and > 99.99% of salt rejection at feed and permeate temperatures of 80°C and 20°C, respectively) and excellent energy efficiency (52.1% at feed and permeate temperatures of 50°C and 20°C, respectively). The long-term stability of F-TR-NFM is also investigated over more than 250h of operation time.