Iron-embedded S-scheme heterostructure nanocomposite K2Ti4O9/rGO for pollution control: Photocatalytic activity, stability, reaction intermediate, hazard profiling, and mechanism

The worsening environmental pollution caused by the misuse and careless management of pharmaceuticals has prompted many efforts to break down toxic antibiotics into harmless compounds. These substances, defined as representative emerging contaminants, can be harmful and cause allergic reactions when combined with coliform bacteria in soil or water environments. Layered titanate has attracted considerable attention for its potential to solve various environmental problems because of its unique material properties. This study examined newly fabricated layered titanate (K₂Ti₄O₉) nanobelts for the degradation of antibiotic tetracycline, one of the most widely used antibiotics, and high-strength coliform bacteria isolated from real wastewater. The K₂Ti₄O₉-reduced graphene oxide/Fe (KTO/rGO/α-Fe₂O₃) with a step scheme (S-Scheme) nanostructure was integrated by the simultaneous reduction of GO and α-Fe₂O₃. The toxicological relationships of nanomaterials were evaluated using the ecological structure–activity relations (ECOSAR) model, and the environmental impact of the photocatalytic degradation process was examined through a toxicity evaluation of the reaction intermediates. Under blue LED light, the nanocomposite removed 93 % of the tetracycline in 120 min. In addition, it was effective in real wastewater disinfection by inactivating 99 % of total coliforms within the same time frame, indicating the superior properties of the KTO/rGO/α-Fe₂O₃ S-Scheme nanocomposite. The heterostructure was confirmed by X-ray diffraction, ultraviolet diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and photoluminescence measurements. Gas chromatography-mass spectrometry confirmed the complete mineralization of tetracycline and the possible degradation pathway. These results highlight the potential for effectively controlling refractory pollutants in wastewater through the remarkable stability and cyclic performance of the new visible-light-driven photocatalyst.