Theoretical study on degradation mechanism of ornidazole on anatase TiO2(101) and (001) surfaces

Ornidazole (ONZ) is an emerging pollutant posing a huge threat to the environment and humans. In this paper, the degradation mechanism of ONZ on anatase TiO2(101) and (001) surfaces in vacuum and neutral aqueous solution was elucidated at the DFT level. We found that ONZ was activated and oxidized after being adsorbed on the surface of TiO2; the C–N bond became longer, making the ring-opening degradation more likely to occur. This study found that the degradation of ONZ is more probable on the surface of TiO2(001) than on TiO2(101). When the surroundings of the reaction was changed from a vacuum to aqueous solution, the activation energy of ONZ degradation reaction on TiO2 surfaces was decreased, which indicated that the solvent condition was more favorable for ONZ degradation.