Fig. 1(b) depicts the reaction schemes for the synthesis of a TiO2–GO photocatalytic membrane. First, TiO2 nanoparticles were attached to the PSf base membrane by the Ti–O bond formed between Ti4 þ and sulfonic groups and/or by the hydrogen bond between the hydroxyl groups of TiO2 and sulfonic groups [46]. Next, GO was deposited on the TiO2 layer via Ti–O and/or