Avoiding Regrettable Replacements: Can the Introduction of Novel Functional Groups Move PFAS from Recalcitrant to...

Area of Science:

• Environmental Chemistry
• Atmospheric Chemistry
• Fluorinated Compounds

Background:

• Per- and polyfluoroalkyl substances (PFASs) are widely used in consumer products due to their stability, leading to environmental persistence.
• Developing PFAS with enhanced degradability is crucial for mitigating environmental contamination.
• Heteroatom linkages in fluorosurfactant structures offer potential pathways for degradation.

Purpose of the Study:

• To investigate the atmospheric fate of novel fluorosurfactant building blocks.
• To determine the gas-phase OH oxidation rate constants and identify degradation products.
• To assess the potential for mineralization and benign degradation pathways.

Main Methods:

• Synthesis of novel fluorosurfactant building blocks with ether, thioether, and polyfluorinated carbon linkages.
• Atmospheric chamber experiments to monitor OH oxidation rate constants and products at room temperature.
• Analysis using online high-resolution chemical ionization mass spectrometry (CIMS) and offline UPLC-MS/MS.

Main Results:

• Thioether congeners, FESOH and MeFESOH, exhibited the highest OH oxidation rate constants (k_FESOH = 2.82 × 10⁻¹² cm³ molecules⁻¹ s⁻¹, k_MeFESOH = 2.17 × 10⁻¹² cm³ molecules⁻¹ s⁻¹).
• First-, second-, and third-generation oxidation products were identified over time.
• Terminal degradation products included ultrashort perfluoropropionic acid (PFPrA) and short polyfluoroether acids for FESOH and ProFdiEOH; MeFESOH showed evidence of full mineralization.

Conclusions:

• Novel fluorosurfactant structures with heteroatom linkages demonstrate varying atmospheric degradation rates.
• The thioether linkage appears to enhance reactivity towards OH radicals.
• MeFESOH's potential for full mineralization suggests a promising, more benign chemical architecture for future PFAS development.