Sulfamerazine degradation employing a novel Z-scheme TiO 2 /KNbO 3 / g-C 3 N 4 photocatalyst under artificial sunlight: Insights on degradation mechanism and toxicity

The development of a novel TiO 2 /KNbO 3 /g-C 3 N 4 photocatalyst for the degradation of sulfamerazine under artificial sunlight was investigated in this study, aiming to obtain a highly effective material through the formation of Z -scheme heterojunctions between the proposed semiconductors. The characterizations confirmed the formation of the intended heterojunctions in the ternary composite photocatalyst, as the presence of TiO 2 , KNbO 3 , and g-C 3 N 4 was successfully verified. Furthermore, the coupling between the semiconductors in the form of the ternary photocatalyst led to structural, morphological, and optical modifications of the TiO 2 base matrix, such as a higher specific surface area and larger visible light absorption. The optimized ternary material (TiO 2 - 5% KNbO 3 -0.25% g-C 3 N 4 ) exhibited the highest reaction degradation capacity for the sulfamerazine (SFMZ) in both solar (86.5% degradation) and visible light (60% degradation) tests, confirming a significant enhancement over the pure TiO 2 , which achieved 48% degradation under solar light and 10% degradation under visible light. This result was mainly attributed to the formation of Z -scheme heterojunctions between the semiconductors, which enhanced the charge -transport efficiency during photonic excitation. Lastly, the degradation pathway proposed using mass spectroscopy analysis indicated the formation of mainly less toxic intermediates, as estimated through quantitative structure -activity relationship (QSAR) predictions.