Degradation of trimethoprim in the simulated solar light/periodate system: Process and mechanism analysis

Trimethoprim (TMP), a kind of emerging pollutant, has attracted considerable attention. To achieve an effective degradation of the TMP, a simulated solar light/periodate (SSL/PI) system was set up by using the Xe lamp as the SSL source. The critical parameters affecting the degradation, including the PI content, the TMP concentration as well as the initial pH, were analyzed. The obtained results show that the TMP removal could reach 92 % after 50 min of treatment under the condition of 4 mM PI addition while lower TMP concentrations showed higher degradation percentages. The efficient TMP degradation in the SSL/PI system was achieved in a wide range of the solution pH. The quenching test proved that IO3 center dot, IO4 center dot, O-1(2), (OH)-O-center dot, and O-center dot(2)- were critical reactive species for the TMP degradation in the SSL/PI system and the electron spin resonance analysis proved the generation of O-1(2) and (OH)-O-center dot. Three possible pathways of the TMP degradation were proposed according to the LC-MS detection and Pathway II might be the specific one according to the density functional theory (DFT) calculation. Toxicity evaluation showed that the toxicity of the initial TMP solution reduced after the treatment, which confirmed the effectiveness of the PI activation by the SSL.