*2.3. Fluorination of the Surface of the TiO2–PVDF Membrane*

First toluene was purged with nitrogen for one hour to remove its oxygen content as much as possible. Then, to reduce its temperature, toluene was refrigerated for 2 h. FTCS powder was then added to toluene within a controlled temperature in the range of 0 to −5 ◦C. Then while the solution was stirred it was treated with an ice bath. The FTCS solution was coated on the membrane surface of the TiO2–PVDF nanocomposite by the self-assembly method. In this method, after preparing the FTCS solution, the samples coated with titanium nanoparticles were placed in the solution so that the FTCS molecules were bonded with the TiO2–PVDF membrane by the self-assembly method (Figure 3). Hereafter, the membrane is called the 'FTCS–TiO2–PVDF' membrane.

**Figure 3.** The preparation process of the FTCS–TiO2–PVDF membrane: (**a**) purifying toluene using nitrogen; (**b**) reducing the temperature of toluene in a refrigerator; (**c**) mixing toluene with FTCS; (**d**) stirring the mix at a low temperature (−5 ◦C–0 ◦C); (**e**) using ultrasonication and ice bath to dissolve the mix completely; (**f**) the self-assembly process of the FTCS solution on the TiO2–PVDF membrane; (**g**) the FTCS–TiO2–PVDF membrane.
