Mineralising toxic ‘Forever Chemicals’ by high energy ball milling Kapish Gobindlal 1,2 , Zoran Zujovic 2 , Cameron C. Weber 1,2,3 , Jonathan Sperry 1,2 1 Centre for Green Chemical Science, University of Auckland, New Zealand, 2 School of Chemical Sciences, University of Auckland, New Zealand, 3 The MacDiarmid Institute for Advanced Materials and Nanotechnology, New Zealand Per- and polyfluoroalkyl substances (PFASs) have emerged as recalcitrant environmental pollutants over the last two decades. 1 The copious use of these commercially important substances across many industrial segments for approximately 70 years has resulted in one of the most critical pollution issues of this century. 2 The environmental sector urgently requires innovative technological solutions to destroy PFASs in contaminated media and obsolete products, as current methods are ineffective, prohibitively expensive, or unsustainable. 3 Recently, mechanochemical destruction (MCD), or high energy ball milling, has demonstrated significant potential to treat PFASs, achieving high destruction efficiencies (DEs) for a wide range of these highly fluorinated organic compounds. 4 In this work, a comprehensive analytical approach was undertaken to determine the fundamental underlying mechanisms of MCD reactions for PFASs spiked onto quartz sand as a grinding auxiliary. The overall process was characterised by conventional techniques, such as liquid chromatography-tandem mass spectroscopy, Fourier transform infrared, and surface area analysis. More novel techniques were also employed, including liquid chromatography-high resolution mass spectroscopy, solid-state nuclear magnetic resonance, and electron paramagnetic resonance. Quantitative analysis of PFASs in milled samples revealed high DEs of 99.95% to 100% for five topical PFASs subjected to mild MCD conditions for up to 720 mins. Extensive product analysis showed that PFASs initially degraded, leading to the formation of shorter chain PFASs. Subsequently, these PFASs were iteratively and simultaneously destroyed upon extended mechanochemical treatment. Direct characterisation of the matrix indicated that carbon-fluorine (C-F) bonds were mineralised and that the fate of fluorine at the end of the MCD process was coupled with silicon on the surfaces of freshly fractured quartz particles, forming silicon-fluorine (Si-F) residues. Collectively, these results directly inform scale-up activities, which are currently underway via a technology partner for the remediation of highly contaminated soil and the treatment of banned PFAS-containing products. References 1. J. P. Giesy and K. Kannan, Environ. Sci. Technol., 2001, 35 , 1339–1342. 2. J. Glüge, M. Scheringer, I. T. Cousins, J. C. Dewitt, G. Goldenman, D. Herzke, R. Lohmann, C. A. Ng, X. Trier and Z. Wang, Environ. Sci. Process. Impacts, 2020, 22 , 2345–2373. 3. C. Berg, B. Crone, B. Gullett, M. Higuchi, M. J. Krause, P. M. Lemieux, T. Martin, E. P. Shields, E. Struble, E. Thoma and A. Whitehill, J. Air Waste Manage. Assoc., 2021, 72 , 540–55. 4. G. Cagnetta, J. Robertson, J. Huang, K. Zhang and G. Yu, J. Hazard. Mater., 2016, 313 , 85–102.
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