# A Deep Insight into Perfluorooctanoic Acid Photodegradation Using Metal Ion-Exchanged Zeolites

## TL;DR

Researchers explored using metal ion-exchanged zeolites to effectively break down PFOA, a hard-to-treat pollutant, through photodegradation.

## Contribution

Fe-exchanged BEA zeolites are shown to efficiently photodegrade PFOA via internal surface reactions.

## Key findings

- Fe-exchanged BEA zeolites effectively photodegrade PFOA through isolated iron species.
- Photodegradation occurs on the internal surface of Fe-BEA zeolites.
- Optimal Fe-BEA zeolite achieved a high sorption coefficient and short PFOA half-life under UV-A.

## Abstract

Treating perfluorooctanoic
acid (PFOA) in an aqueous environment
is problematic due to its low concentration and its high resistance
to biological and chemical degradation. To tackle this challenge,
combinations of pre-enrichment and photodegradation processes are
promising solutions. In this work, we investigated metal ion-exchanged
zeolites as adsorbents and photocatalysts for PFOA treatment. Among
various transition metal ion-exchanged BEA zeolites, Fe-exchanged
BEA (Fe-BEA) zeolites showed significant activity for the photodegradation
of PFOA. The isolated iron species in Fe-BEA zeolite are responsible
for PFOA photodegradation, whereas other iron species present from
excess iron loading in the zeolite will lower its photocatalytic activity.
Furthermore, it was proved via size exclusion tests using branched
PFOA isomers that the photodegradation of PFOA took place on the internal
surface rather than the external surface of Fe-BEA zeolite. Photodegradation
of PFOA was also tested to be effective with Fe-exchanged BEA-type
zeolites having various SiO2/Al2O3 ratios, but ineffective with FAU-type zeolites. The optimal Fe-BEA
zeolite showed a sorption coefficient Kd of 6.0 × 105 L kg–1 at an aqueous
phase PFOA concentration of 0.7 μg L–1 and
a PFOA half-life of 1.8 h under UV-A irradiation. The presented study
offers a deeper understanding of the use of metal ion-exchanged zeolites
for photodegradation of PFOA.