Degradation Of Aqueous Oxytetracycline By High Voltage Pulsed Discharge Plasma

Tetracyclines, utilized in medication and livestock breeding in large quantity, is one of the most widely used antibiotics. Antibiotics can arouse risks to environment and human health when released into the environment. High voltage pulsed discharge plasma is a new advanced oxidation technology. In this thesis, Oxytetracycline(OTC) was selected as the target contaminants, and removal of OTC by needle-plate high voltage pulsed discharge plasma was conducted in this paper. The removal effect, the main factors, the removal mechanism, degradation products and pathways of OTC by high voltage pulsed discharge plasma were studied.The effect of output power, airflow rate, discharge distance, initial concentration, initial pH value, initial conductivity and Fe2+, HA, H2O2concentration on the degradation efficiency of OTC was examined. The results are that the degradation efficiency of OTC increased when output power, airflow rate and discharge distance increased, initial concentration, initial conductivity reduced. But when airflow rate, discharge distance increased to a certain value the removal efficiency of OTC declined. Both strong acidic solution conditions and strong alkaline solution conditions were favorable to the removal of OTC. The degradation efficiency of OTC increased with the adding of Fe2+, H2O2and HA. But when HA concentration increased to a certain value, the removal efficiency of OTC declined.In the degradation process, the pH of OTC solution gradually reduced, but the conductivity increased. The removal efficiency of OTC declined when the hydroxyl radical scavenge was added into the reaction system, because the amount of hydroxyl radical that reacted with OTC would reduced. TOC of the OTC solution decreased with increasing discharge time, and the TOC removal rates reached to57%after discharging for10min, which showed that the macromolecules were degraded to small molecules, and parts of the intermediate products were mineralized into carbon dioxide and water.LC-MS was used to analyze the OTC degradation products. There were all four intermediate products and their m/z were447,445,433and415respectively. On the basis of these results probable degradation pathways were speculated.