Theoretical Study on the Degradation Mechanism of Sulfonamide Catalyzed by Titanium Dioxide

Abstract Sulfonamide and its derivatives have made great contributions to medicine and can be used to synthesize sulfonamides‐based antibacterial drugs. However, improper treatment of the sulfonamides may bring severe environmental pollutions. In this paper, the density functional theory (DFT) calculation method was used to study the adsorption properties and degradation mechanism of sulfonamide on different surfaces of titanium dioxide (TiO 2 ), i. e. TiO 2 (101) and TiO 2 (001). First, by calculating the adsorption energy, we obtained the most stable adsorption configurations of sulfonamide on different TiO 2 surfaces. In both cases, the sulfonamides lie parallel on the surfaces of TiO 2 and the amino group attached directly to the benzene ring forms hydrogen bonds with the oxygens on the surfaces of the TiO 2 while the sulfonyl groups interact with the titanium of the surfaces. After that, six possible degradation pathways were investigated in detail based on the stable configurations. According to the calculation results, we conclude that the optimal degradation path of sulfonamide on TiO 2 surface is the path initialized by attacking carbon atom attached to the sulfonyl group in sulfonamide with hydroxyl radical, for which the reaction barrier on TiO 2 (001) surface is 13.8 kcal/mol, and that of TiO 2 (101) surface is 13.1 kcal/mol. Therefore, the degradation effects of the two surfaces are similar. Our present work indicates that the effect of TiO 2 in degrading sulfonamide is remarkable, which provides a theoretical basis for the subsequent development of the degradation method of sulfonamides‐based antibiotics.