Enhanced removal of perfluorooctanoic acid with sequential photocatalysis and fungal treatment

Abstract

In this paper, we report the degradation of perfluorooctanoic acid (PFOA), which is a persistent contaminant in the environment that can severely impact human health, by exposing it to a photocatalyst, bismuth oxyiodide (BiOI), containing both Bi4O5I2 and Bi5O7I phases and a fungal biocatalyst (Cunninghamella elegans). Individually, the photocatalyst (after 3 h) and biocatalyst (after 48 h) degraded 35–40% of 100 ppm PFOA with 20–30% defluorination. There was a marked improvement in the degree of degradation (90%) and defluorination (60%) when PFOA was first photocatalytically treated, then exposed to the fungus. GC- and LC–MS analysis identified the products formed by the different treatments. Photocatalytic degradation of PFOA yielded short-chain perfluorocarboxylic acids, whereas fungal degradation yielded mainly 5:3 fluorotelomer carboxylic acid, which is a known inhibitor of cytochrome P450-catalysed degradation of PFAS in C. elegans. The combined treatment likely resulted in greater degradation because photocatalysis reduced the PFOA concentration without generating the inhibitory 5:3 fluorotelomer carboxylic acid, enabling the fungus to remove most of the remaining substrate. In addition, new fluorometabolites were identified that shed light on the initial catabolic steps involved in PFOA biodegradation.

Recent advances in fungal xenobiotic metabolism: enzymes and applications

“…A combination of approaches is one potential mechanism to ameliorate the effects of inhibition. For example, by combining sequential photocatalysis and fungal treatment (Khan et al 2023 ) were able to improve the degradation of perfluorooctanoic acid (PFOA). It was suggested that the photocatalysis step reduced the initial concentration of the PFOA without producing the inhibitory 5:3 FTCA, allowing the fungus to remain active for longer, thus leading to an overall improved degradation of the substrate.…”

Exploring Solar Energy Solutions for Per‐ and Polyfluoroalkyl Substances Degradation: Advancements and Future Directions in Photocatalytic Processes

“…[ 69 ] This allows spectral absorption in the VIS region and narrows the energy gap of the materials to values below 2 eV while maintaining efficient charge separation [69b] . Indeed, numerous BiOX materials, including BiOCl, [ 70 ] BiOI, [ 71 ] BIOF, [48e] and p–n BiOI–Bi 5 O 7 heterojunctions, have been described for the degradation of PFOA under VIS light irradiation. [ 72 ]…”