Tailoring photocatalysts and elucidating mechanisms of photocatalytic degradation of perfluorocarboxylic acids (PFCAs) in water: a comparative overview

Abstract

A perfluorooctanoic acid (PFOA), as the most important representative of perfluorocarboxylic acids (PFCAs), is environmentally persistent and bioaccumulative. Among treatment techniques for PFOA decomposition, photocatalytic degradation of PFOA has received considerable attention. A series of candidate photocatalytic materials, including TiO2‐, carbonaceous‐, Ga2O3‐, In2O3‐based, etc., have been successfully proposed to eliminate PFOA. Overall, there are two types of mechanisms for photocatalytic degradation of PFCAs, including conventional mechanism and charge transfer mechanism. For a conventional mechanism, the mechanism of PFOA photodegradation over bulk TiO2 via two pathways: photo‐redox and β‐scission. For the charge transfer mechanism, the PFOA degradation pathway in water‐soluble H3PW12O40 is mainly via charge‐transfer excited complex ([PW12O40]3−*). Finally, attention on critical challenges and prospects for photodegradation of PFOA are also intensified. © 2020 Society of Chemical Industry

Indium Oxides and Related Indium‐based Photocatalysts for Water Treatment: Materials Studied, Photocatalytic Performance, and Special Highlights

“…The superior performance of In 2 O 3 relative to TiO 2 continues to attract attention and be reaffirmed by researchers interested in the photocatalytic removal of perfluorochemicals from contaminated water (as evidenced by recent publications on this topic). [133][134][135][136][137] Research activities continue on understanding the underlying mechanisms of the degradation processes using In 2 O 3 photocatalysts [133,134] with an aim to optimize photocatalyst design. Recent examples are high surface area In 2 O 3 nanosheets [138] and In-doped Ga 2 O 3 with enhanced targeted PFOA adsorption properties.…”

Challenges Facing Sustainable Visible Light Induced Degradation of Poly- and Perfluoroalkyls (PFA) in Water: A Critical Review

“…A number of review articles have recently focused on the photocatalytic degradation of PFA using UV light sources at λ = 254, 365, and 315–400 nm. ,,,,− However, the proportion of UV radiation available in this wavelength range in the terrestrial solar spectrum is insufficient to expect these catalysts to lead to reasonable photocatalytic conversion efficiencies under sunlight.…”

“…The studies on the degradation of PFA compounds in laboratories have so far been restricted to standard aqueous solutions of pure compounds in deionized and distilled waters only. Photocatalytic studies using acidic solutions of pure PFA in the concentration range 1–200 mg/L are unrealistic for real-world applications. ,,,,,− The average concentrations of PFA in wastewater effluents and surface/groundwater are reported in the range of 1 ng/L–28 μg/L and <0.1 ng/L–2.3 μg/L, respectively. , The pH of these waters also varied from neutral to lightly alkaline . Furthermore, as discussed in section , the photocatalytic degradation process is promoted by either h VB + , e CB – , • OH, O 2 •– , or by combinations of these, and these reactive species have no preferential selectivity toward PFA compared to the other oxidizable organic and inorganic species present in real polluted waters and effluents.…”

Solar-light-driven LaFexNi1−xO3 perovskite oxides for photocatalytic Fenton-like reaction to degrade organic pollutants

“…Meanwhile, the remaining divalent iron complexes in the system can return to the circulation of hydrogen peroxide reaction and continuously form new hydroxide radicals [20]. Therefore, based on our knowledge of photocatalysis [21,22], the benefits of Fenton reaction and photocatalysis are combined to develop a conceptual catalytic design to expand the photocatalytic pathway of Fenton oxidation, called photocatalytic Fenton-like reaction or heterogeneous photo-Fenton-like reaction [23].…”