Sulfamethazine (SMZ) antibacterial compounds are frequently detected in the aquatic environment, and photodegradation is expected to play an important role for sulfamethazine fate in surface water. In order to evaluate the effect of dissolved ions in water on the photo transformation of sulfamethazine, the influence of soluble ions such as P〇43", NO3", NH4+, S〇42" and some heavy metal ions as Zn2+, Cu2+ and Pb2+on the UV- photolysis of sulfamethazine were investigated in this work. Results described that the UV-photo degradation of sulfamethazine followed the pseudo- first-order kinetics. The photodegradation rate of sulfamethazine irradiated with UV light was significantly higher (70.4%) than that irradiated with sunlight (6.32%). PO43" and SO42" reduced the UV-photodegradation rate of sulfamethazine, and the degradation rate decreased monotonously with PO43" and SO42" concentration increased. While, the UV-photolysis rate constant increased at first and then decreased with the increasing concentration of NO3". Whereas NH4+ ion did not demonstrate any obvious effects owing to the light stability of NH4+. Also, the UV-photodegradation of sulfamethazine was significantly suppressed with the addition of Zn2+, Cu2+and Pb2+, especially for the Cu2+. While the UV-photo degradation of sulfamethazine could be increased in the presence of nanoparticle Ti〇2. The above results demonstrated that UV-photo-degradation process of sulfamethazine was affected differently by dissolved ions and nanoparticles in water, which were important for aiding in the transform and fate prediction of sulfamethazine in surface water. Besides, the photolysis main processes of sulfamethazine were speculated by HPLC/ ESI-MS analysis coupled with the frontier molecular orbital theory.
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