Enhancement of the photocatalytic degradation performance for tetracycline of magnetic Fe3O4/ZnO/g-C3N4 composites by strengthening the bonding effect

Tetracycline poses a serious threat to the ecosystems even if the concentration is very low due to its structural stability. In this work, a series of magnetic separable Fe₃O₄/ZnO/g-C₃N₄ composite with excellent degrading tetracycline performance were prepared. And, repeated calcination method was used to strengthen the bonding effect of single component improving the formation of heterojunction. Electrochemical analysis confirmed that the ZnO/g-C₃N₄ and Fe₃O₄/ZnO/g-C₃N₄ heterojunctions were generated, effectively accelerating the electron separation and transfer in photocatalytic process. The characterization results also showed that ZnO and Fe₃O₄ nanoparticles are evenly distributed on the surface of g-C₃N₄. With the increase of the loading mass concentration of ZnO/g-C₃N₄, the degradation rate of tetracycline on Fe₃O₄/ZnO/g-C₃N₄ composite increased and then decreased. The degradation rate of tetracycline on optimal Fe₃O₄/ZnO/g-C₃N₄ composite reached to 94.50% while the TC mineralization rate reached to 61.61% under visible light irradiation for 120 min, exhibiting excellent photocatalytic performance. Due to the effect of Fe₃O₄, Fe₃O₄/ZnO/g-C₃N₄ materials exhibited good magnetic property, which is beneficial to separation and recovery of photocatalysts. The reusability experiment showed that the degradation rate of tetracycline was 80.66% after five cycles, displaying good reusability.