Sun Runze, Bhat Akash P, Arnold William A, Xiao Feng
Department of Civil and Environmental Engineering, University of Missouri, Columbia, Missouri 65211, United States.
Department of Civil, Environmental, and Geo-Engineering, University of Minnesota, Minneapolis, Minnesota 55455, United States.
Environ Sci Technol. 2025 Jan 28;59(3):1756-1768. doi: 10.1021/acs.est.4c05059. Epub 2025 Jan 10.
Recent regulations on perfluorinated compounds in drinking water underscore the need for a deeper understanding of the formation of perfluorinated compounds from polyfluoroalkyl substances during chlorine disinfection. Among the compounds investigated in this study, N-(3-(dimethylaminopropan-1-yl)perfluoro-1-hexanesulfonamide (N-AP-FHxSA) underwent rapid transformation during chlorination. Within an hour, it produced quantitative yields of various poly- and per-fluorinated products, including perfluorohexanoic acid (PFHxA). Sixteen reactions involving chlorine with N-AP-FHxSA and its quaternary ammonium analog were investigated; seven were confirmed, while the remainder were either disproved or found to be insignificant. The quaternary ammonium moiety did not determine a polyfluoroalkyl substance's reactivity toward chlorine. For example, while 6:2 fluorotelomer sulfonamide betaine transformed rapidly to PFHxA, other quaternary-ammonium-containing polyfluoroalkyl substances, such as 5:1:2 and 5:3 fluorotelomer betaines, showed significant resistance to chlorination. Further investigation identified potential sites for electrophilic attacks near the amine region by examining the highest occupied molecular orbitals of the polyfluoroalkyl substances. Visualization techniques helped pinpoint electron-deficient and electron-rich sites as potential targets for nucleophilic and electrophilic attacks, respectively. Increasing the solution pH from 6 to 10 did not diminish the apparent degradation of the studied polyfluoroalkyl substances, likely due to the greater reactivity of the deprotonated forms compared to the conjugate acids. Finally, we also examined the hydrolysis of polyfluoroalkyl substances at pH 6 to 11 in the absence of chlorine.
近期关于饮用水中全氟化合物的规定凸显了深入了解含氟烷基物质在氯消毒过程中形成全氟化合物的必要性。在本研究中所调查的化合物中，N-(3-(二甲基氨基丙基)全氟-1-己烷磺酰胺（N-AP-FHxSA）在氯化过程中经历了快速转化。在一小时内，它定量生成了各种多氟和全氟产物，包括全氟己酸（PFHxA）。研究了涉及氯与N-AP-FHxSA及其季铵类似物的16个反应；其中7个得到证实，其余的要么被否定，要么被发现不显著。季铵部分并不能决定含氟烷基物质对氯的反应活性。例如，虽然6:2氟调聚物磺酰胺甜菜碱迅速转化为PFHxA，但其他含季铵的含氟烷基物质，如5:1:2和5:3氟调聚物甜菜碱，对氯化表现出显著抗性。通过检查含氟烷基物质的最高占据分子轨道，进一步研究确定了胺区域附近亲电攻击的潜在位点。可视化技术有助于分别确定缺电子和富电子位点作为亲核和亲电攻击的潜在目标。将溶液pH从6提高到10并没有减少所研究的含氟烷基物质的表观降解，这可能是由于去质子化形式比共轭酸具有更高的反应活性。最后，我们还研究了在无氯条件下，含氟烷基物质在pH 6至11时的水解情况。
