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 (80 kg m(-2) h(-1)) and salt rejection (> 99.99%) as well as outstanding long-term stability (more than 180 h), 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 degrees), high LEPw (1.3 bar), 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 (114.8 kg m(-2) h(-1) of water flux and > 99.99% of salt rejection at feed and permeate temperatures of 80 degrees C and 20 degrees C, respectively) and excellent energy efficiency (52.1% at feed and permeate temperatures of 50 degrees C and 20 degrees C, respectively). The long-term stability of F-TR-NFM is also investigated over more than 250 h of operation time.