First, we tested the pure water flux of the virgin PSf and TiO2– GO membranes in a cross-flow membrane filtration system with a windowed membrane cell (Fig. 2(b)). The window allows a tested membrane to be exposed to different light irradiations during a filtration experiment. The initial fluxes of the PSf and TiO2–GO
membranes were 120 and 45 L/m2/h (LMH), respectively. As
shown in Fig. 9(a), the flux of the virgin PSf membrane in darkness, sunlight, and UV did not change significantly. The slow yet steady flux decline was a result of membrane compaction under hydraulic pressure. For the TiO2–GO membrane (Fig. 9(b)), compared with a slow flux decline (similar to that for the virgin PSf membrane) as observed in the dark experiment, the flux behaviors under sun- light and UV irradiations were dramatically different: a relatively