Visible-light driven tetracycline hydrochloride degradation by nano-lanthanum hydroxide modified carbon nitride: performance, mechanism, and application in real wastewater treatment†

In this study, La(OH)₃/g-C₃N₄ photocatalyst was designed for degradation of tetracycline hydrochloride (TCH) under visible light. The impact of different operational factors (dosage, initial TCH concentration, photocatalytic time, temperature, and competing anions and organic matter) on the removal of TCH was analyzed. La(OH)₃/g-C₃N₄ exhibits a narrowed bandgap (2.90 eV) and enhanced visible-light absorption, leading to efficient TCH degradation (90.1%) and excellent reuse potential. The degradation intermediates were analyzed by liquid chromatography-mass spectrometry (LC-MS) to deduce the plausible degradation pathways. Quantitative structure activity relationship (QSAR) assessment indicated that the toxicity of the degradation products was greatly reduced. Furthermore, La(OH)₃/g-C₃N₄ can simultaneously remove TCH, COD and PO₄^3? from real wastewater by 56.31%, 69.63% and 89.9% respectively, demonstrating its robust potential in water and wastewater engineering and science.