Adsorption characteristics and degradation mechanism of metronidazole on the surface of photocatalyst TiO2: A theoretical study

• Published in: Applied surface science Vol. 478; pp. 896 - 905
• Main Authors: Wang, Danyang, Luo, Hui, Liu, Liuxie, Wei, Wei, Li, Laicai
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.06.2019
• Subjects: Degradation; Density functional; Metronidazole; TiO2 photocatalyst; Degradation; TiO2 photocatalyst; Density functional; Metronidazole
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2019.02.052

In this paper, the adsorption and degradation mechanism of metronidazole on TiO2 (101) and (001) surfaces was elucidated at DFT level. The adsorption stability of metronidazole on the surface of anatase was studied under the condition of vacuum and neutral aqueous solvent respectively, and the most stable adsorption configuration was optimized theoretically. It was found that metronidazole could be adsorbed on the surface of TiO2 under both conditions. The hydrogen bond generated by the adsorption process can enhance the stability of the adsorption structure. The surface adsorption made the CN bond length of metronidazole longer, which could facilitate the reaction of open-loop degradation. The mechanism of ring-opening degradation of metronidazole on two surfaces of TiO2 was also studied. It was found that the activation energy of the degradation reaction of metronidazole on the crystal plane of TiO2 was decreased under the condition of water solvent, which indicated that the solvent condition could promote the degradation of metronidazole. The utilization efficiency of different crystal planes of TiO2 in the visible light and predicted the photocatalysis were achieved. The study found that TiO2 (101) crystal plane catalytic degradation of metronidazole has high visible light utilization rate, explaining the experimental results. Schematic diagram of catalytic ring-opening reaction of metronidazole on TiO2 surface: when the reactant is attacked by OH radical on the surface of the catalyst, the N(1)C(2) bond breaks and the hydroxyl H atom on C(2) is transferred to N(3). [Display omitted] •The most stable adsorption configuration of metronidazole on the surface of TiO2 was optimized.•The degradation of metronidazole on the TiO2(101) surface is easy to occur.•The ring-opening reaction contains two steps: N-C bond breaking and proton transfer on the imidazole ring.