Peroxymonosulfate activation by magnetic NiFe₂O₄/g-C₃N₄ for tetracycline hydrochloride degradation under visible light

The widespread use of antibiotics is causing serious environmental issues, so there is an urgent need for the development of new treatments to effectively remove these substances from wastewaters. Here, a new approach is proposed using the NiFe2O4/g-C3N4 heterostructure, prepared by a simple and inexpensive sol-gel method, to activate peroxymonosulfate (PMS) under visible light (VL), for application in the degradation of a simulated wastewater containing tetracycline hydrochloride (TCH) as a model molecule. The NiFe2O4/g-C3N4/PMS/VL system was successful in removing TCH over a wide pH range and in the presence of different anions commonly found in wastewaters. The superior degradation performance observed for the composite, compared to the pure oxides, was attributed to the synergism between heterojunction photocatalysis and PMS activation, generating the highly oxidizing O-1(2), O-2(-), and HO species, which were responsible for effective degradation of TCH. Besides the fast kinetics, it also should be highlighted that the magnetic properties of the heterostructure facilitated separation of the photocatalyst for the purpose of reuse.