Crystalline carbon nitride derived self-assembly composite membranes with enhanced self-cleaning performance toward dye/salt separation

Membrane technology can realize the sustainable management of textile wastewater through dye/salt separation, but its practical implementation has long been hampered by membrane fouling. This work was to develop a novel carbon nitride based two-dimensional (2D) self-assembled membrane for efficient dye/salt separation with excellent photocatalytic self-cleaning performance toward azo dyes (e.g., methyl blue), anthraquinone dyes (e.g., reactive blue 19) and natural organic matters (e.g., humic acid). Specifically, conventional graphite carbon nitride (g-C₃N₄), poly triazine imide (PTI) and the composites of iron oxide doped PTI (PTI-Fe₂O₃) were comparatively investigated for manipulating the lamellar self-catalytic membrane through facile vacuum filtration. The considerable separation factors of sodium chloride to methyl blue (S_salt/dye) of 76.97, 80.72, and 74.33 were obtained by g-C₃N₄, PTI, and PTI-Fe₂O₃, respectively. The generation of radicals and non-radicals were triggered by light irradiation and was accelerated by PTI compared to g-C₃N₄, resulting in the better flux recovery rate (FRR) of 95.7 % for PTI membrane than that of g-C₃N₄ membrane (74.4 %). Besides, the introduction of iron oxide enables the enhanced self-cleaning performance by coupling photocatalytic and Fenton-like process, leading to the highest FRR value of 99.4 %. Meanwhile, the fabricated membranes demonstrate remarkable stability (FRR ≥ 80 %) during prolonged operation (64 h) to both simulated and real textile wastewater, indicating that it can a promising alternative membrane material for textile wastewater management.