Chang Shuang-jun, Liu Yu-cun
College of Chemical Engineering and Environment, North University of China, Taiyuan 030051, China.
J Environ Sci (China). 2007;19(12):1430-5. doi: 10.1016/s1001-0742(07)60233-2.
The 2,4,6-trinitrotoluene (TNT) is a potential carcinogens and TNT contaminated wastewater, which could not be effectively disposed with conventional treatments. The supercritical water oxidation (SCWO) to treat TNT contaminated wastewater was studied in this article. The TNT concentration in wastewater was measured by high-performance liquid chromatograph (HPLC) and the degraded intermediates were analyzed using GC-MS. The results showed that SCWO could degrade TNT efficiently in the presence of oxygen. The reaction temperature, pressure, residence time and oxygen excess were the main contributing factors in the process. The decomposition of TNT was accelerated as the temperature or residence time increased. At 550 degrees C, 24 MPa, 120 s and oxygen excess 300%, TNT removal rate could exceed 99.9%. Partial oxidation occured in SCWO without oxygen. It was concluded that supercritical water was a good solvent and had excellent oxidation capability in the existence of oxygen. The main intermediates of TNT during SCWO included toluene, 1,3,5-trinitrobenzene, nitrophenol, naphthalene, fluorenone, dibutyl phthalate, alkanes and several dimers based on the intermediate analysis. Some side reactions, such as coupled reaction, hydrolysis reaction and isomerization reaction may take place simultaneously when TNT was oxidized by SCWO.
2,4,6-三硝基甲苯（TNT）是一种潜在致癌物，且TNT污染废水无法通过传统处理方法有效处置。本文研究了用超临界水氧化法（SCWO）处理TNT污染废水。采用高效液相色谱仪（HPLC）测定废水中TNT浓度，并用气相色谱-质谱联用仪（GC-MS）分析降解中间产物。结果表明，在有氧气存在的情况下，超临界水氧化法能有效降解TNT。反应温度、压力、停留时间和氧气过量是该过程的主要影响因素。随着温度或停留时间的增加，TNT的分解加快。在550℃、24MPa、120s和氧气过量300%的条件下，TNT去除率可超过99.9%。在无氧的超临界水氧化过程中会发生部分氧化。得出的结论是，超临界水是一种良好的溶剂，在有氧气存在时具有优异的氧化能力。根据中间产物分析，超临界水氧化过程中TNT的主要中间产物包括甲苯、1,3,5-三硝基苯、硝基苯酚、萘、芴酮、邻苯二甲酸二丁酯、烷烃以及几种二聚体。当TNT通过超临界水氧化法氧化时，可能会同时发生一些副反应，如偶联反应、水解反应和异构化反应。
