脉冲气相放电降解水中TNT的影响因素与机理

Influencing Factors and the Degradation Mechanism of Aqueous 2,4,6-Trinitrotoluene by Pulsed Gas Phase Discharge

研究了在高压脉冲气相放电处理TNT废水过程中,脉冲峰值电压、脉冲频率、pH值等因素对降解效率的影响,并探讨了降解机理。结果表明,TNT降解效率随着脉冲峰值电压和脉冲频率的增加而提高;初始pH值对TNT降解有一定的影响,pH值为6.8的条件下效果最好。在脉冲峰值电压为9.8kV、脉冲频率为125Hz的实验条件下,初始浓度为30mg/L的TNT溶液处理60min后,降解率达到66.1%。通过添加叔丁醇的实验证实TNT降解以.OH作用为主。IC和GC/MS降解产物分析表明,受.OH攻击,TNT生成2,4,6-三硝基苯甲酸,后者被氧化成1,3,5-三硝基苯,经过开环最终生成甲酸、NO-2和NO3-等。

Degradation of 2,4,6 trinitrotoluene （TNT） in waste water is investigated by a pulsed high voltage gas phase discharge above the water surface. The effect of different experimental conditions, including peak pulsed voltage, pulsed frequency and the initial value of pH, on the TNT degradation rate and the degradation mechanism are studied. The obtained results show that the removal efficiency of TNT increases with the increase of peak pulsed voltage and pulsed frequency. The initial value of pH also has some influence on the TNT degradation rate. The removal efficiency of TNT under the condition of pH=6.8 is best. In the case of 9.8kV peak pulsed voltage, 120 Hz pulsed frequency, the degradation rate of 30mg/L TNT solution with pH value of 6.8 reached 66.1 % after 60min treatment. TNT conversion and the production of major oxidation products in the solution have been determined, using ion chromatography with conductivity detector and gas chromatography with MS detector. It is found that hydroxyl radical plays an important role on TNT degradation. The degradation of 2,4,6-trinitrotoluene is attacked by hydroxyl radical to form 2,4,6-trinitrotobenzoic acid. The later is oxidized to 1,3,5-trinitrobenzene. Therefore, the ring is opened to simple organic acids such as formate acid, NO2^- and NO3^-, etc.