In-situ topotactic transition of LaVO4/Bi12O17Br2 NCs by unveiling O defects and p-n heterojunction formation for photodegradation of metronidazole: Reactions, pathway and its by-product toxicity evaluation

It is difficult to develop an effective photocatalytic system, but it is essential to conquering every challenge in all the aspects that contribute to the system. The opting of materials along with its tendency to active under visible light, and the arrangements of their band edges, which limit the charge carriers from recombination. This study presents the successful fabrication of a LaVO ₄/Bi ₁₂O ₁₇Br ₂ nanocomposite (NC) using an ultrasonication-assisted hydrothermal approach, aimed to proficiently eliminate metronidazole (MET) antibiotics from wastewater. Herein, the defect engineering and formation of a p-n heterojunction in the LaVO ₄/Bi ₁₂O ₁₇Br ₂ NCs significantly enhanced the reactive sites which are crucial for the photooxidation process. Experiments on photocatalysis were conducted and examining various operational parameters such as drug concentration, nanomaterial concentration, pH, and ion presence. Among these, the optimal photocatalytic efficiency was observed with a combination of 75 mg/L LaVO ₄/Bi ₁₂O ₁₇Br ₂ NCs and 20 mg/L MET at pH 4. The results indicated a remarkable 98.3% degradation under visible light irradiation for 90 min. In addition, the photodegradation process exhibited pseudo-first-order kinetics, ^.OH and h ⁺ identified as the primary reactive species take part in the reaction. Even after six consecutive cycle tests, LaVO ₄/Bi ₁₂O ₁₇Br ₂ NCs shown to have outstanding photostability and reusability. Furthermore, a potential photodegradation pathway was outlined based on the intermediates identified through GC-MS analysis. These degraded intermediates underwent evaluation for both chronic and acute toxicity using the ECOSAR program. The findings contribute to advancing our comprehension of the development of innovative photocatalytic systems tailored for the efficient elimination of harmful pharmaceutically active pollutants.