Freezing-assisted preparation of self-cleaning, high-flux photocatalytic nanocomposite membranes for enhanced degradation of antibiotic activity

The weak light absorption capacity and the embedding of active sites are the main factors that affect the photodegradation performance of blending photocatalytic membrane. Herein, a Z-scheme TiO2/rGO/ZnCdS/PVDF photocatalytic composite membrane (T-rGO-ZCSM) with excellent mechanical properties and good self-cleaning performance was successfully prepared by the freezing phase inversion method. As the solvent turns to crystal under freezing temperature, the micron-scale ordered penetrating porous structure formed after phase inversion, which can efficiently improve the water flux (19000–25000 L m−2 h−1 bar−1) and light penetration. Meanwhile, Z-scheme TiO2/rGO/ZnCdS heterojunctions will be migrated to the surface of the large pore canal due to their hydrophilicity during the phase inversion process. This structure can promote light absorption and increase effectively contact between active sites and pollutants. The T-rGO-ZCSM also exhibits outstanding photocatalytic activity for removing the various antibiotics under visible light, such as tetracycline (TC), levofloxacin (LEV), and ciprofloxacin (CIP). After four cycles (1.0 h for each cycle) of experiments, T-rGO-ZCSM has good stability and reusability. Moreover, the TC degradation efficiency of T-rGO-ZCSM reached the highest of 87.46% under continuous 6.0 h solar irradiation. The superoxide radical (·O2−) and photogenerated h+ were the main active species for organics’ degradation. In summary, the ordered penetrating type macroporous T-rGO-ZCSM has promising potentials for wider applications in wastewater treatment. A hierarchical-ordered penetrating-type porous T-rGO-ZCSM membrane was prepared by freezing phase inversion method. The membrane surface with large pore diameters can provide a more convenient transport pathway, and pollutants can be transferred to the active sites to increase effective contact. It can also enhance the visible light absorption to excite more photogenerated carriers and improve photocatalytic activity. Finally, the photocatalytic degradation efficiency of freezing T-rGO-ZCSM could be increased by 1.71 times compared to that of the conventional blending nf-T-rGO-ZCSM under visible light.