Preparation of magnetic ZnO/ZnFe2O4/CCA for highly efficient removal of methylene blue by synergistic adsorption-photocatalysis under visible light irradiation

The development of highly efficient, visible-light-responsive and easily recoverable photocatalysts is a major challenge for the advancement of photocatalytic technology. For this purpose, we developed magnetic recyclable composite photocatalysts of ZnO/ZnFe₂O₄/cellulose carbon aerogels (ZnO/ZnFe₂O₄/CCA) for the degradation of methylene blue (MB) under visible light irradiation. In the prepared ZnO/ZnFe₂O₄/CCA-400, composite particles of ZnO/ZnFe₂O₄ were loaded on the matrix of cellulose carbon aerogel with a honeycomb structure. The as-prepared ZnO/ZnFe₂O₄/CCA photocatalysts exhibited enhanced degradation efficiency of MB under synergistic adsorption/photocatalytic. Notably, the ZnO/ZnFe₂O₄/CCA-400 photocatalyst exhibited the optimal removal efficiency of 98.1% after 2.5 hours of visible light irradiation. The enhancement of photocatalytic activity can be primarily ascribed to the formation of a Z-scheme heterojunction between ZnO and ZnFe₂O₄ using cellulose carbon aerogels (CCA) as the conductive channel. Moreover, the photocatalyst can be easily recovered using a magnet; and even after five cycles, the removal efficiency of MB still remained 85.5%. Additionally, the active species in the photocatalytic process were investigated by free radical trapping experiments, and a Z-scheme photocatalytic mechanism was proposed to explain the highly efficient degradation of MB. This study offers a facile approach to design carbon-bridged heterojunction photocatalysts for the degradation of organic pollutants in wastewater.