Photocatalytic self-cleaning graphene oxide membrane coupled with carbon nitride and Ti3C2-Mxene for enhanced wastewater purification

In this study, an original photocatalytic self-cleaning composite membrane with the fabrication of graphene oxide (GO), polyacrylic acid (PAA), and g-C3N4 (CN)/amorphous Ti-peroxo complexes (CATC) was prepared on the commercial cellulose acetate membrane (CAM) through the vacuum filtration approach to overcome the common membrane fouling issues. The material properties of composites or membranes were characterized. Here, the permeability and separation performance of membranes were optimized by CATC and PAA dosages. A series of membrane separation tests revealed that the produced membrane had better permeability and dye removal capabilities. A pure water flux (PWF) of the GO/PAA/CATC (GPC) membrane was 30.95 L·m−2·h−1, corresponding to 3.43 times in comparison to that of the pure GO membrane. The removal efficiencies for the GPC membrane towards methylene blue (MB), rhodamine b (RhB), Cu(NO3)2, and congo red (CR) were over 99% due to the hydrogen bond, π-π, electrostatic, and physical sieving effects. Also, the GPC membrane demonstrated a favorable separation performance towards oil/water emulsion (over 98%). In addition, the GPC membrane maintained stable rejections towards MB, CR, RhB, and Cu(NO3)2 at pH 3, 5, 7, 9, and 11 environments. Meanwhile, the self-cleaning GPC membrane was endowed with satisfactory reusability after 6 cycles because of the photocatalytic effect at the roles of h+, O2−, and OH free radicals. Hence, it can be expected that the GPC membrane synthesized in this study poses a favorable utilization capability in wastewater treatment.