Chair of Urban Water Systems Engineering, Technical University of Munich, Am Coulombwall 3, 85748 Garching, Germany.
Environ Sci Technol. 2023 Nov 28;57(47):18825-18833. doi: 10.1021/acs.est.2c06709. Epub 2023 Apr 26.
Aliphatic amines are abundant micropollutants in wastewater treatment plant effluents. In order to mitigate such micropollutants, ozonation is one of the most commonly employed advanced treatment processes. Current research regarding ozone efficiency is heavily focusing on reaction mechanisms of different contaminant groups, including structures with amine moieties as reactive sites. This study analyzes pH-dependent reaction kinetics and pathways of gabapentin (GBP), an aliphatic primary amine with an additional carboxylic acid group. The transformation pathway was elucidated applying a novel approach using isotopically labeled ozone (O) and quantum chemistry calculations. While the direct reaction of GBP with ozone is highly pH-dependent and slow at pH 7 (13.7 M s), the rate constant of the deprotonated species (1.76 × 10 M s) is comparable to those of other amine compounds. Pathway analysis based on LC-MS/MS measurements revealed that ozonation of GBP leads to the formation of a carboxylic acid group and simultaneous nitrate formation, which was also observed in the case of the aliphatic amino acid glycine. Nitrate was formed with a yield of approximately 100%. Experiments with O-labeled ozone demonstrated that the intermediate aldehyde does most likely not include any oxygen originating from ozone. Furthermore, quantum chemistry calculations did not provide an explanation for the C-N scission during GBP ozonation without ozone involvement, although this reaction was slightly more favorable than for respective glycine and ethylamine reactions. Overall, this study contributes to a deeper understanding of reaction mechanisms of aliphatic primary amines during wastewater ozonation.
脂肪胺是废水处理厂废水中丰富的微量污染物。为了减轻这些微量污染物的影响，臭氧氧化是最常用的高级处理工艺之一。目前，关于臭氧效率的研究主要集中在不同污染物群体的反应机制上，包括具有胺基作为反应位点的结构。本研究分析了加巴喷丁（GBP）的 pH 依赖性反应动力学和途径，GBP 是一种带有额外羧酸基团的脂肪族伯胺。应用同位素标记的臭氧（O）和量子化学计算的新方法阐明了转化途径。虽然 GBP 与臭氧的直接反应高度依赖 pH，在 pH 7 时反应缓慢（13.7 M s），但去质子化物种的速率常数（1.76×10 M s）与其他胺类化合物相当。基于 LC-MS/MS 测量的途径分析表明，GBP 的臭氧化导致羧酸基团的形成和同时形成硝酸盐，在脂肪族氨基酸甘氨酸的情况下也观察到了这种情况。硝酸盐的产率约为 100%。用 O 标记的臭氧进行的实验表明，中间醛很可能不包含任何来自臭氧的氧。此外，尽管与相应的甘氨酸和乙胺反应相比，GBP 臭氧化过程中没有臭氧参与时的 C-N 键断裂反应稍微更有利，但量子化学计算并没有对此提供解释。总的来说，这项研究有助于更深入地了解脂肪族伯胺在废水臭氧氧化过程中的反应机制。
