Photocatalytic Degradation of Perfluorooctanoic Acid in Water by Free and Immobilised ZnO, g-C3N4 and Their Composite under UV and Visible Light Irradiation

Perfluorooctanoic acid (PFOA) is among perfluoroalkyl and polyfluoroalkyl substances (PFAS) that is widely detected in the environment. ZnO and graphitic carbon nitride are among the most economical semiconductors which have not been widely used for PFOA decomposition. Therefore, ZnO could be an alternative to In₂O₃, as a benchmark photocatalyst for PFOA degradation, under ultraviolet (UV) irradiation. More interestingly, suspended ZnO nanoparticles showed promising for PFOA degradation under visible light irradiation (unlike In₂O₃ nanoparticles). The probable production of sulphate radicals by the addition of peroxymonosulfate (PMS) up to ~0.53 g/L significantly improved PFOA decomposition to ~70% within 2 h (~53 mg/L PFOA concentration, ~0.53 g/L ZnO nanoparticles, 254 nm UV). More importantly, the same amount of PMS improved PFOA degradation under visible light illumination (source of light: 300W xenon lamp), while ZnO with its wide band gap energy is not usually considered a visible light activated semiconductor. Electrophoretic deposition was effectively used for the immobilisation of ZnO nanoparticles on FTO plate. Notably, the addition of PMS (~0.27 g/L) improved the apparent rate constant of PFOA decomposition under both UV and visible light irradiation, clarifying the crucial role of sulphate radicals in PFOA decomposition. The optimal ZnO coating was also used as the photoanode for the degradation of PFOA using photoelectrocatalysis (at V = 0) where the apparent rate constant of 0.331 h⁻¹ was obtained under UV irradiation and ~53 mg/L PFOA concentration. Citric acid was effectively used to modify g-C₃N₄ with increasing the photo-absorption ability and lowering the recombination rate of charge carriers. Hence, ZnO@citric acid-modified carbon nitride nanocomposites were successfully produced by ball milling and effectively used for PFOA decomposition. Although citric acid-modified was not effective for PFOA degradation, ZnO@citric acid-modified carbon nitride (5 wt%) nanocomposite showed superior efficiency than initial ZnO nanoparticles under UV irradiation (0.406 h⁻¹ against 0.103 h⁻¹) in 2 h (~53 mg/L PFOA concentration, ~0.53 g/L catalysts). The optimal nanocomposite also showed extremely higher proficiency than pure ball-milled ZnO nanoparticles (control) under visible light irradiation.

Author dc:creator

• Navidpour, Amir Hossein

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• info:eu-repo/semantics/openAccess
• The author owns the copyright in this thesis including all reproduction and reuse rights for the work. The work may not be altered without the permission of the copyright owner. Attribution is essential when quoting or paraphrasing from this thesis.
• © 2023 Amir Hossein Navidpour
• au.edu.uts.lib/cph

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en_US

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http://hdl.handle.net/10453/177716

OAI identifier oai:identifier

oai:opus.lib.uts.edu.au:10453/177716