Department of Environmental Science and Engineering, Nanjing Agricultural University, Nanjing 210095, China.
Department of Civil and Environmental Engineering, University of Washington, Seattle, Washington 98195, United States.
Environ Sci Technol. 2022 Jun 21;56(12):7935-7944. doi: 10.1021/acs.est.2c00702. Epub 2022 May 12.
Recent studies found that both nitrite (NO) and ammonium (NH) lead to nitrophenolic byproducts in SO oxidation processes, during which NO generated through the oxidation of the inorganic nitrogen by SO is the key nitrating agent. This study demonstrates that the formation of phenoxy radicals to which NO can be incorporated immediately is another governing factor. Two types of sites having distinct reactivities in natural organic matter (NOM) molecules can be transformed to phenoxy radicals upon SO oxidation. Fast sites associated with phenolic functionalities are primarily targeted in the reaction sequence involving NO, because both are preferentially oxidized. Following the depletion of NO, NH becomes the main precursor of NO that interacts with slow sites associated with the carboxylic functionalities. Experimental data show that the formation of total organic nitrogen in 24 h reached 6.28 μM during SO oxidation of NOM (4.96 mg/L organic carbon) in the presence of both NO (0.1 mM) and NH (1.0 mM), while the sum of those formed in the presence of each alone was only 3.52 μM. Results of this study provide further insights into the mechanisms of nitrated byproduct formation when SO is applied for environmental remediation.
最近的研究发现，在 SO 氧化过程中，亚硝酸盐（NO）和氨（NH）都会导致硝基酚类副产物生成，其中通过 SO 氧化无机氮生成的 NO 是关键的硝化剂。本研究表明，立即可以与 NO 结合形成苯氧自由基的形成是另一个控制因素。两种具有不同反应性的天然有机物（NOM）分子中的位点在 SO 氧化反应中可以转化为苯氧自由基。与酚官能团相关的快速位点是涉及 NO 的反应序列中的主要目标，因为它们都优先被氧化。NO 耗尽后，NH 成为与羧酸官能团相关的慢速位点相互作用的主要前体 NO。实验数据表明，在存在 NO（0.1 mM）和 NH（1.0 mM）的情况下，NOM（4.96 mg/L 有机碳）的 SO 氧化在 24 小时内形成的总有机氮达到 6.28 μM，而在每种物质单独存在的情况下形成的总氮只有 3.52 μM。本研究的结果进一步深入了解了 SO 用于环境修复时形成硝化副产物的机制。
