Hydroxylamine activated by discharge plasma for synergetic degradation of tetracycline in water: Insight into performance and mechanism

This paper aims to investigate hydroxylamine activated by discharge plasma for tetracycline degradation in water. Results indicated that hydroxylamine can be activated by discharge plasma successfully, and promoted tetracycline degradation. The degradation efficiency of tetracycline by discharge plasma could improve from 70.7% to 90.0% with 0.25 mmol/L hydroxylamine. The energy efficiency (G50) could enhance from 2.28 g/kWh to 3.18 g/kWh, respectively. Synergetic effect could be generated between discharge plasma and hydroxylamine. Ozone and electrons produced by plasma can interact with hydroxylamine to produce more •OH. Capture agent experiment and ESR technique verified that •OH, O2•-, 1O2 and electrons all participated in tetracycline degradation in plasma/hydroxylamine system. The degradation process was investigated thoroughly based on three dimensional fluorescence, LC-MS and DFT analysis, and two main pathways were proposed. Enhancing applied voltage was beneficial to the degradation of tetracycline. Higher degradation efficiency of tetracycline was obtained at lower initial concentration. Compared with acidic condition, alkaline condition was conducive to the decomposition of tetracycline. The addition of hydroxylamine in plasma system promoted the mineralization of tetracycline. Overall, the plasma/hydroxylamine method can be considered as a preferable potential option for the reduction of tetracycline in water.