School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China.
Department of Chemical and Petroleum Engineering, University of Wyoming, Laramie, WY 82071, USA; School of Civil and Environmental Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA.
Chemosphere. 2018 Aug;205:426-432. doi: 10.1016/j.chemosphere.2018.04.029. Epub 2018 Apr 5.
Supercritical water oxidation (SCWO) of 2-, 3- and 4-nitroaniline (NA) was investigated under residence time of 1-6 min, pressure of 18-26 MPa, temperature of 350-500 °C, with initial concentration of 1 mM and 300% excess oxygen. Among these operating conditions, temperature and residence time played a more significant role in decomposing TOC and TN than pressure. Moreover, the products of N-containing species were mainly N, ammonia and nitrate. When temperature, pressure and retention time enhanced, the yields of NO and org-N were reduced, the amount of N was increasing, the proportion of NH, however, presented a general trend from rise to decline in general. The experiment of aniline/nitrobenzene indicated that TN removal behavior between amino and nitro groups would prefer to happen in the molecule rather than between the molecules, therefore, the smaller interval between the amino and nitro group was the more easily to interreact. This might explain the reason why TN removal efficiency was in an order that 2-NA > 3-NA > 4-NA. The NH/NO experiment result demonstrated that ammonia and nitrate did convert into N during SCWO, however, the formation of N was little without auxiliary fuel. Density functional theory (DFT) method was used to calculate the molecular structures of 2-, 3- and 4-NA to further explore reaction mechanism, which verified that amino group was more easily to be attacked than nitro group. Based on these results, the conceivable reaction pathways of 2-, 3- and 4-NA were proposed, which contained three parts, namely denitrification, ring-open and mineralization.
超临界水氧化（SCWO）法降解 2-、3-和 4-硝基苯胺（NA），反应停留时间为 1-6min，压力为 18-26MPa，温度为 350-500°C，初始浓度为 1mM 和 300%过量氧气。在这些操作条件下，温度和停留时间对TOC 和 TN 的分解比压力更为重要。此外，含氮物质的产物主要为 N、氨和硝酸盐。随着温度、压力和保留时间的提高，NO 和有机氮的产率降低，氮的量增加，而 NH 的比例则普遍呈先上升后下降的趋势。苯胺/硝基苯的实验表明，氨基和硝基之间的 TN 去除行为更倾向于在分子内发生，而不是在分子间发生，因此，氨基和硝基之间的间隔越小，越容易相互反应。这或许可以解释 TN 去除效率的顺序为 2-NA > 3-NA > 4-NA 的原因。NH/NO 的实验结果表明，氨和硝酸盐在 SCWO 过程中确实会转化为 N，但没有辅助燃料时，N 的生成量很少。密度泛函理论（DFT）方法用于计算 2-、3-和 4-NA 的分子结构，以进一步探讨反应机制，这验证了氨基比硝基更容易被攻击。基于这些结果，提出了 2-、3-和 4-NA 的可能反应途径，包含三个部分，即脱氮、开环和矿化。
