An Investigation of Thermal Air Degradation and Pyrolysis of Per- and Polyfluoroalkyl Substances and Aqueous Film-Forming Foams in Soil,ACS ES&T Engineering

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An Investigation of Thermal Air Degradation and Pyrolysis of Per- and Polyfluoroalkyl Substances and Aqueous Film-Forming Foams in Soil
ACS ES&T Engineering ( IF 7.4 ) Pub Date : 2022-01-11 , DOI: 10.1021/acsestengg.1c00335
Ali Alinezhad ₁ , Pavankumar Challa Sasi ₁ , Ping Zhang ₂ , Bin Yao _{1,

3} , Alena Kubátová ₃ , Svetlana A. Golovko ₄ , Mikhail Y. Golovko ₄ , Feng Xiao ₁

Affiliation

In this study, we found that thermal decomposition of per- and polyfluoroalkyl substances (PFAS) in soil was rapid at moderate temperatures of 400–500 °C, regardless of whether the soil was contaminated by a single PFAS compound or a PFAS mixture in aqueous film-forming foams. Substantial degradation (>99%) of PFAS in soil, including perfluorooctanoic acid (PFOA), perfluorooctane sulfonate (PFOS), short-chain homologues, cationic and zwitterionic precursors, and PFOA and PFOS alternatives, occurred in 30 min at 500 °C in both a sealed reactor in air and a horizontal reactor under a continuous flow of N₂. The effect of the initial PFAS level in soil (0.001–10 μmol/g) and soil texture was insignificant, provided a sufficiently high temperature was applied. Furthermore, this study showed, for the first time, that kaolinite dramatically decreased the apparent yield of F from PFAS heated at >300 °C, likely due to the chemisorption of F radicals on kaolinite. This phenomenon was not observed when kaolinite and an inorganic fluoride salt (NaF) were thermally treated. Lastly, various nonpolar thermal degradation products of PFOA and PFOS were reported for the first time. The profile of fluorinated volatiles, particularly perfluoroalkenes, was similar between these two chemicals. The results support a radical-mediated degradation pathway of PFAS.

中文翻译：

土壤中全氟和多氟烷基物质和水成膜泡沫的热空气降解和热解研究

在这项研究中，我们发现土壤中全氟烷基物质和多氟烷基物质 (PFAS) 的热分解在 400-500 °C 的中等温度下快速分解，无论土壤是被单一 PFAS 化合物污染还是被水溶液中的 PFAS 混合物污染。成膜泡沫。土壤中 PFAS 的大量降解 (>99%)，包括全氟辛酸 (PFOA)、全氟辛烷磺酸 (PFOS)、短链同系物、阳离子和两性离子前体以及 PFOA 和 PFOS 替代物，在 500 °C 下 30 分钟内发生空气中的密封反应器和 N ₂连续流动下的卧式反应器. 如果施加足够高的温度，土壤中初始 PFAS 水平（0.001-10 μmol/g）和土壤质地的影响是微不足道的。此外，这项研究首次表明，高岭石显着降低了加热至 > 300 °C 的 PFAS 中 F 的表观收率，这可能是由于 F 自由基在高岭石上的化学吸附。当对高岭石和无机氟化物盐（NaF）进行热处理时，没有观察到这种现象。最后，首次报道了PFOA和PFOS的各种非极性热降解产物。这两种化学品的氟化挥发物，特别是全氟烯烃的分布情况相似。结果支持自由基介导的PFAS降解途径。

更新日期：2022-02-11

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