Photocatalytic decomposition behavior and reaction pathway of sulfamethazine antibiotic using TiO2

The photocatalytic degradation of sulfanethazine (SMT), one of the sulfonamide antibiotics, in aqueous solution by TiO2 was investigated. The time courses of SMT concentration, the amount of non-purgeable organic carbon, and the concentrations of ions such as SO42−, NH4+, and NO3− formed during the photocatalytic reaction were measured and the structures of seven intermediates formed with the disappearance of SMT were also estimated by LC/MS/MS analyses. In addition to that of SMT, the decomposition behaviors of model compounds sulfanilic acid (SA) and 4-amino-2, 6-dimethylpyrimidine (ADMP) were investigated using the TiO2/UV system. The observed photocatalytic degradation behaviors of SMT, SA, and ADMP gave new insight into the degradation pathway of SMT. Especially, the formation of p-aminophenol during SMT decomposition, which until now has not been reported in previous studies concerning the photocatalytic decomposition of SMT and other sulfonamide antibiotics. These results indicate the existence of a novel photocatalytic degradation pathway for sulfonamides. The direct substitution of the sulfonamide group with a hydroxyl group is suggested.