One-step in situ growth of heterojunction carbon dots-TiO2/ZIF-8 on the surface of meltblown fibers: Towards recyclable photocatalysts for degradation of organic dyes

Conventional photocatalysts utilized in the photodegradation of organic dyes are prone to cause agglomeration of nanocatalysts, which affects the photocatalytic efficiency and is difficult to recycle. In this paper, photocatalysts were rapidly loaded onto polypropylene (PP) meltblown nonwoven material fibers possessing a large specific surface area using water as a solvent and a one-step in situ growth method under ultrasonic conditions. That is, by ultrasonically and rapidly growing zeolite imidazolium skeleton material (ZIF-8) in situ on the surface of dopamine-modified PP meltblown fibers and directly doping carbon dots (CDs) modified TiO₂ during the in situ growth of ZIF-8, a CDs-TiO₂/ZIF-8/PP composite photocatalytic material was formed. The microstructure, chemical structure, and photocatalytic performance of CDs-TiO₂/ZIF-8/PP composite photocatalytic material were characterized. The findings indicated that the CDs-TiO₂/ZIF-8 heterojunction nanocatalysts were effectively loaded onto the exterior of PP meltblown fibers. The CDs-TiO₂/ZIF-8/PP composite photocatalytic materials exhibited highly efficient and synergistic photocatalytic degradation of the anionic dye Congo red (CR). Upon exposure to visible light, the degradation of CR could reach 99.1 % within 100 min and 99.6 % within 120 min. The first-order kinetic constant for photocatalytic degradation was measured to be 0.0419 min⁻¹. Furthermore, the photodegradation of CR by the CDs-TiO₂/ZIF-8/PP composite photocatalytic material maintained about 85 % after 5 cycles. Finally, the mechanism of in situ deposition and photocatalytic activity of the nanocomposites on the fiber surface was proposed. The composite photocatalytic material can be recycled, and the preparation process is green, simple, and efficient, which has potential application prospects for industrial wastewater treatment.