Synergetic degradation of PFOS by HALT conditions enhanced by Fe-based amorphous alloys

Pengtao Cai; Tong Chen; Mingxiu Zhan; Xiaojun Ma; Masaki Takaoka; Chen Sun; Xiaodong Li

doi:10.1016/j.jhazmat.2024.137015

Synergetic degradation of PFOS by HALT conditions enhanced by Fe-based amorphous alloys

J Hazard Mater. 2024 Dec 25:486:137015. doi: 10.1016/j.jhazmat.2024.137015. Online ahead of print.

Authors

Pengtao Cai¹, Tong Chen², Mingxiu Zhan³, Xiaojun Ma⁴, Masaki Takaoka⁵, Chen Sun⁶, Xiaodong Li¹

Affiliations

¹ State Key Laboratory of Clean Energy Utilization, Zhejiang University, Hangzhou 310027, China.
² State Key Laboratory of Clean Energy Utilization, Zhejiang University, Hangzhou 310027, China; Jiaxing Research Institute, Zhejiang University, Jiaxing, Zhejiang Province 314051, China. Electronic address: chentong@zju.edu.
³ College of Energy Environment and Safety Engineering, China Jiliang University, Hangzhou, Zhejiang Province 310018, China. Electronic address: zhanmingxiu@cjlu.edu.cn.
⁴ Zhejiang Environmental Protection Group Co.,ltd, Hangzhou 310027, China.
⁵ Department of Environmental Engineering, Graduate School of Engineering, Kyoto University, Kyoto 6158510, Japan.
⁶ Quzhou Research Institute, Zhejiang University, Quzhou, Zhejiang Province 324003, China.

PMID: 39729797
DOI: 10.1016/j.jhazmat.2024.137015

Abstract

Global concern over per- and polyfluoroalkyl substances (PFASs), especially perfluorooctane sulfonate (PFOS), disposal prompts the search for effective degradation methods. Subcritical water hydrothermal treatment shows promise but suffers from unclear degradation pathways, hindering engineering application design due to unknown intermediate products. This study introduces Fe-based amorphous alloy to enhance the subcritical water hydrothermal degradation of PFOS, achieving a degradation rate of approximately 85 % under optimized conditions of 325 °C and 1 M sodium bicarbonate (NaHCO₃), compared to 56 % without the alloy. Analysis of liquid and gas-phase products, along with identification of potential intermediate products, led to proposing a reaction pathway for Fe-based amorphous alloy-enhanced subcritical water hydrothermal PFOS degradation. Additionally, the distribution of fluorine in PFOS was determined by fluorine-19 nuclear magnetic resonance (¹⁹F NMR), and the energy changes of key degradation steps were calculated based on DFT, which provided concrete evidence for the degradation process and verified the mechanism of subcritical hydrothermal degradation of PFOS enhanced by Fe-based amorphous alloys. Most importantly, the Fe-based amorphous alloy demonstrated effectiveness upon repeated use after water washing. These results endorse its potential as a PFOS degradation catalyst.

Keywords: DFT calculation; Degradation mechanism; Perfluorooctane sulfonate (PFOS); Reducing atmosphere; Subcritical hydrothermal.