# Analysis of per- and polyfluoroalkyl substances (PFAS) removal with activated carbon using 19F nuclear magnetic resonance spectroscopy

## TL;DR

Researchers used 19F NMR to test how well different activated carbons remove harmful PFAS chemicals from water, finding one type to be the most effective.

## Contribution

This study introduces 19F NMR as a low-cost, efficient method for quantifying PFAS removal by activated carbons, bypassing traditional expensive techniques.

## Key findings

- CAC-4 was the most effective activated carbon for PFAS removal due to high surface area and mesoporosity.
- 19F NMR proved to be a viable and cost-effective alternative for PFAS detection and quantification.
- The method required minimal sample clean-up and used inexpensive internal standards.

## Abstract

Per- and polyfluoroalkyl substances (PFAS) are a toxic and environmentally persistent class of chemicals that are associated with a myriad of adverse health effects in humans. Activated carbon is an effective material for the removal of PFAS at water treatment plants, but there is a necessity to find new, superior coal-derived and biomass-derived forms, due to the increasing accumulation of PFAS in treatable water sources and the need to shift to biomass-derived adsorbent usage to offset the carbon emissions released during their production. Additionally, current methods of PFAS detection and quantification utilise expensive and laborious analytical techniques, such as liquid-chromatography with tandem mass spectrometry. In this study, four commercial activated carbons (CAC-1, CAC-2, CAC-3 and CAC-4) had their chemical/textural properties characterised and had their PFAS removal performances investigated using four different PFAS types (PFBS, PFHxA, PFOA AND PFOS), with detection and quantification conducted with 19F nuclear magnetic resonance (19F-NMR). The adsorption results revealed the overall ranking of adsorbents by performance as CAC-4 > CAC-3 > CAC-2 > CAC-1, with CAC-4 being the highest ranking adsorbent for removing all four PFAS, due to a high surface area coupled with superior mesoporosity as well as containing a higher concentration of surface oxygen-containing functional groups, which fortify adsorption with favourable hydrophobic interactions and electrostatic interactions, respectively. Moreover, the effective use of 19F-NMR for the detection and quantification of total PFAS content after activated carbon treatment was demonstrated, with the use of inexpensive internal standards and a near-complete lack of sample clean-up. As such, quantitative 19F-NMR can be a viable, low-cost alternative to current PFAS analytical techniques for the screening of new adsorbent media.

19F NMR is used to screen and rank activated carbons for PFAS removal, allowing direct quantification of PFOS, PFOA, PFHxA and PFBS to identify the most effective adsorbent.