Synergistic interaction of Z-scheme 2D/3D g-CN/BiOI heterojunction and porous PVDF membrane for greatly improving the photodegradation efficiency of tetracycline.

Designing photocatalytic membranes with excellent photocatalytic and self-cleaning ability based on the synergistic effect between the crystal structure of membrane matrix and photocatalyst is highly desirable. Herein, Z-scheme 2D/3D g-CN/BiOI heterojunction blended in beta-phase polyvinylidene fluoride membrane (β-phase PVDF) was prepared via solvent crystallization and phase inversion technique. As expected, the designed g-CN/BiOI/β-phase PVDF photocatalytic membranes (CN/BI/β-phase PVDF PMs) achieved exceptional photocatalytic degradation efficiency for tetracycline (94.6%) as compared to the CN/BI heterojunction power (84.0%) and two other control membrane matrixes (CN/BI/PAN and CN/BI/CA PMs) within 120 min. Meanwhile, the dynamic cyclic degradation system of CN/BI/β-phase PVDF PMs was also investigated that reached to be 94.8% in 80 min. Besides, the CN/BI/β-phase PVDF PMs not only had outstanding self-cleaning activity and remarkable permeability (up to 30,688 L·m·h) but also had high stability and reusability even after five runs. Importantly, the hydroxyl radical detection and ESR analysis identified that the β-phase PVDF membrane could promote photoinduced carrier separation efficiency of 2D/3D g-CN/BiOI heterojunction. This work may open up a novel strategy for designing and constructing high-efficient photocatalytic membranes for water treatment.