Poly- and per-fluoroalkyl substances (PFASs) have raised a great public health concern because these compounds are persistent, bioaccumulative and toxic. Previous studies reported biodegradation of 6:2 FTOH by several FTOH-degrading bacteria to various shorter-chain PFASs. Metal oxides and photocatalysts were proven to degrade a wide group of contaminants including some PFASs. Some transition metals, like zinc oxide (ZnO), have some interesting semiconducting, adsorbing and optical properties in addition to their ability to photocatalyticly degrade contaminants. However, the ability of ZnO to degrade PFASs has not been investigated. We hypothesized that an approach that combines biological and chemical treatment will be an effective way to degrade PFASs. This study focused on photodegradation of PFASs using ZnO under neutral pH and room temperature. Two types of ZnO used in this study: the commercial microscale ZnO and the tetrapod nanoscale ZnO. Results showed that photo-defluorination efficiency for a 5:3 polyfluorinated acid was about 14.9% and 13.8% using commercial and tetrapod ZnO, respectively. ZnO could not successfully degrade any of the three perfluoroalkyl acids (PFAAs) used in this study, i.e. PFOA, Perfluorohexanoic acid (PFHxA) and Perfluorobutyric acid (PFBA). Adding persulfate with the tetrapod ZnO improved the defluorination efficiency for PFOA, but it reduced the efficiency for defluorinating the 5:3 acid and the 6:2 FTOH. Having high doses of persulfate (27 mM) without ZnO can lead to a significant improvement in defluorination of PFOA, PFHxA and PFBA, with PFBA defluorination as high as about 40%. Defluorination of the 5:3 acid by ZnO was eliminated when the experiments took place in a growth medium. The competition of these ions with PFASs for adsorption sites onto the ZnO was proposed as the main reason for the inhibition of defluorination that was observed. However, defluorination of the 5:3 acid was not much affected by the presence of PFOA in the solution, which indicates that PFOA does not adsorb strongly enough on ZnO to inhibit adsorption of the 5:3 acid. Finally, solutions of the 5:3 acid that had undergone photodegradation with tetrapod ZnO were further examined for their treatability by biological processes as a second degradation step. Biodegradation trials using <i>P. flurescens </i>DSM 8341 did not show a significant improvement in the defluorination. This is the first report studying the photodegradation of PFASs using ZnO.

Degradation of Poly- and Per-Fluoroalkyl Substances (PFAS<sub>S</sub>) using photocatalyst zinc oxide

253rd National Meeting (2017)

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Degradation of Poly- and Per-Fluoroalkyl Substances (PFASS) using photocatalyst zinc oxide

Degradation of Poly- and Per-Fluoroalkyl Substances (PFAS_S) using photocatalyst zinc oxide