PhD Defence - Eleni Savvidou

Abstract

Per- and polyfluoroalkyl substances (PFAS) are a large group of synthetic chemicals with unique physicochemical properties that have led to their widespread use, ranging from everyday consumer products to critical technologies. Their extreme persistence, combined with other hazardous properties, raises significant concerns for human health and the environment. Limited understanding of PFAS uses across different applications, together with gaps in analytical capabilities, hampers progress towards their phase out and replacement with safer alternatives.

In this work, analytical investigations were combined with a search of potential PFAS alternatives. Fluorine-based analytical approaches were applied to assess PFAS use across different product categories (Papers I and II), and pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS) was explored to address analytical gaps related to polymeric PFAS (Paper II). Emissions of fluorinated compounds associated with the lifecycle of lithium-ion batteries (LIBs) were investigated to evaluate their relevance as a contamination source in Europe (Paper III). Finally, alternative chemistries to PFAS were explored for applications in stone sealers (Paper I) and LIBs (Paper IV).

In Paper I, total fluorine (TF) analysis of commercial stone sealers revealed that 81% contained fluorine, with concentrations reaching up to 27 150 µg F/g, most likely originating from polymeric PFAS. Extractable organofluorine (EOF) analysis confirmed the predominantly organic nature of the fluorine, and targeted analysis identified polyfluoroalkyl phosphate esters (PAPs) as the dominant PFAS class. Six products were presumably identified as not containing intentionally added PFAS, instead relying on organosilicon-based chemistries, some of which are currently under regulatory scrutiny.

Paper II investigated the application of Py-GC-MS following initial TF screening of cookware (up to 550 000 µg F/g), textiles (up to 1 600 µg F/g), electronics (up to 2 100 µg F/g) and personal care products (up to 630 000 µg F/g). The method demonstrated the ability to detect polytetrafluoroethylene (PTFE) in unknown samples down to 0.1-0.2 wt% and to differentiate between different side-chain fluorinated polymers commonly used in textile applications.

In Paper III, targeted analysis of electrolyte-related anions used in LIBs, such as bis(trifluoromethanesulfonyl)imide (TFSI-), hexafluorophosphate (PF6-) and tetrafluoroborate (BF4-), revealed their widespread occurrence in water samples, with varying regional profiles. BF4- dominated the contamination profile of the Danube in Hungary, while temporal sampling of the River Erpe in Germany showed elevated TFSI- and PF6- concentrations potentially connected to industrial activities, with marked decreases observed during a temporary plant shutdown. In Sweden, recycling and landfill sites were identified as major contributors to environmental TFSI- and PF6-, with concentrations reaching up to 300 ng/L for TFSI- and 39 000 ng/L for PF6-, primarily in landfill-related samples.

Paper IV examined the availability of PFAS alternatives for critical LIB components, specifically cathodes and electrolytes, through a literature review and interviews with experts from academia and industry. The results indicate that while PFAS-free LIBs appear to be technically feasible, such solutions are not yet widely established and require further evaluation with respect to performance, durability, and economic viability. Nevertheless, the outlook is rather promising, as several companies have already introduced PFAS-free solutions or are actively developing them.

Overall, the combination of fluorine mass balance approaches and Py-GC-MS proved effective for screening consumer products for PFAS and for supporting regulatory enforcement. The results further highlight substitution, guided by robust analytical data and lifecycle considerations, as the most effective long-term strategy to reduce PFAS emissions. However, alternatives require careful evaluation to avoid regrettable substitution, particularly in critical technologies such as LIBs.

Thesis in DiVA

Zoom link for the public defense 13th March at 10.00