Department of Civil and Environmental Engineering, University of Delaware, Newark, Delaware 19716, United States.
Department of Chemical Engineering, Manhattan College, Riverdale, New York 10471, United States.
Environ Sci Technol. 2021 Oct 5;55(19):12973-12983. doi: 10.1021/acs.est.1c03333. Epub 2021 Sep 17.
3-Nitro-1,2,4-triazol-5-one (NTO) is a major and the most water-soluble constituent in the insensitive munition formulations IMX-101 and IMX-104. While NTO is known to undergo redox reactions in soils, its reaction with soil humic acid has not been evaluated. We studied NTO reduction by anthraquinone-2,6-disulfonate (AQDS) and Leonardite humic acid (LHA) reduced with dithionite. Both LHA and AQDS reduced NTO to 3-amino-1,2,4-triazol-5-one (ATO), stoichiometrically at alkaline pH and partially (50-60%) at pH ≤ 6.5. Due to NTO and hydroquinone speciation, the pseudo-first-order rate constants () varied by 3 orders of magnitude from pH 1.5 to 12.5 but remained constant from pH 4 to 10. This distinct pH dependency of suggests that NTO reactivity decreases upon deprotonation and offsets the increasing AQDS reactivity with pH. The reduction of NTO by LHA deviated continuously from first-order behavior for >600 h. The extent of reduction increased with pH and LHA electron content, likely due to greater reactivity of and/or accessibility to hydroquinone groups. Only a fraction of the electrons stored in LHA was utilized for NTO reduction. Electron balance analysis and LHA redox potential profile suggest that the physical conformation of LHA kinetically limited NTO access to hydroquinone groups. This study demonstrates the importance of carbonaceous materials in controlling the environmental fate of NTO.
3-硝基-1,2,4-三唑-5-酮（NTO）是钝感弹药制剂 IMX-101 和 IMX-104 中主要且水溶性最强的成分。尽管已知 NTO 在土壤中会发生氧化还原反应，但尚未评估其与土壤腐殖酸的反应。我们研究了蒽醌-2,6-二磺酸钠（AQDS）和连二亚硫酸盐还原的莱奥纳德ite 腐殖酸（LHA）还原 NTO 的反应。LHA 和 AQDS 在碱性 pH 条件下将 NTO 定量还原为 3-氨基-1,2,4-三唑-5-酮（ATO），在 pH≤6.5 时部分还原（50-60%）。由于 NTO 和对苯二酚的形态，在 pH 1.5 至 12.5 范围内，假一级速率常数（kobs）变化了 3 个数量级，但在 pH 4 至 10 范围内保持不变。NTO 反应性随去质子化而降低，这与 AQDS 随 pH 增加而增加的反应性相抵消，这一明显的 pH 依赖性表明。LHA 还原 NTO 的反应在 >600 h 内连续偏离一级行为。还原程度随 pH 和 LHA 电子含量增加而增加，可能是由于对苯二酚基团的反应性增加和/或可及性增加。LHA 中储存的电子只有一部分用于还原 NTO。电子平衡分析和 LHA 氧化还原电位曲线表明，LHA 的物理构象在动力学上限制了 NTO 对氢醌基团的接近。这项研究表明了碳质材料在控制 NTO 环境归宿方面的重要性。
