Abstract:

Peracetic acid (PAA) is widely used in water treatment due to the well oxidation property and limited formation of harmful by-products. In this study, PAA was successfully activated by pyrolytic CNT, which could degrade 97% sulfamethoxazole (SMX) in 5min. The degradation efficiency of SMX would be influenced by pH with the optimal efficiency under neutral condition. The effect of pyrolysis temperature on the degradation of SMX was investigated, which was determined in 800℃. Electron paramagnetic resonance (EPR) and quenching experiments combined with electrochemical experiments were applied to understand the degradation mechanism. ¹O₂ rather than ·OH played the major role in SMX degradation with organic radicals playing minor roles. The electron transfer process (ETP) was also involved in the degradation process. The satisfactory degradation efficiency of SMX was obtained by pyrolytic CNT/PAA after five cycles reusability, while re-pyrolyzed of used CNT was needed to recover the defects on CNT surface. The occupied reactive sites would be refreshed during re-pyrolysis process and then participate in the reaction. In conclusion, this study focused on the performance and mechanism of SMX degradation by pyrolytic CNT activated PAA, which could provide some theoretic knowledge for pyrolytic CNT/PAA applied in water purification.

Key words: oxidation, peracetic acid, carbon nanotube, degradation, catalyst activation, non-radical pathway, electron transfer process

摘要：

基于过氧乙酸（PAA）的高级氧化工艺（AOP）因其高氧化性、有毒副产物少等特点广泛应用于水处理过程。本研究采用热改性碳纳米管（CNT）活化PAA降解磺胺甲唑（SMX），5min内SMX去除率达97%。pH对该体系的处理效果有影响，中性条件下处理效果最佳。通过比较在不同加热温度下制得的CNT对目标污染物的降解效果，确定了最佳改性条件为800℃。采取电子顺磁共振（EPR）、淬灭实验、电化学实验等手段探究了该体系中污染物的降解机理。在热改性CNT/PAA体系中对SMX降解起主要作用的是单线态氧（¹O₂）而非羟基自由基（·OH），有机自由基起次要作用，电子转移过程（ETP）也为SMX的降解做出贡献。循环实验表明，通过对使用后的CNT再次热改性可以恢复材料表面的缺陷程度，被占据的活性位点再次空出从而参与反应，因此热改性CNT/PAA体系循环使用5次依旧对SMX保持较高的处理效率。本研究聚焦于热改性CNT活化PAA的作用机理及活化位点，为将基于碳材料活化过氧乙酸的高级氧化工艺应用于实际水环境修复提供了更多理论依据。

关键词: 氧化, 过氧乙酸, 碳纳米管, 降解, 催化剂活化, 非自由基途径, 电子转移过程