Photocatalytic Degradation and Defluorination of Per- and Poly-Fluoroalkyl Substances (PFASs) Using Biosynthesized TiO₂ Nanoparticles under UV–Visible Light

Abstract

Per- and poly-fluoroalkyl substances (PFASs) are recalcitrant chemicals with stable carbon–fluorine (C–F) bonds. These complex substances are difficult to degrade; therefore, they persist in the environment, causing potential health effects on humans. This study focused on the photocatalytic degradation and defluorination of perfluorooctane sulfonate (PFOS) in aqueous water using TiO2 nanoparticles under UV–visible light. The biosynthesized TiO2 catalysts at pH 8, 10, and 12 were characterized using XRD, HRTEM, and HRSEM. The XRD patterns of the respective TiO2 nanoparticles at different synthesized pHs exhibited similar anatase phases, and it was observed that the crystallite sizes decreased with increasing pH. The HRSEM and HRTEM confirmed the spherical shapes of the produced nanoparticles with particle size distributions of 12.17 nm, 10.65 nm, and 8.81 nm for the synthesized TiO2 nanoparticles at pH 8, 10, and 12, respectively. The photodegradation and defluorination of PFOS were performed at various initial solution pH values of 2, 4, 6, 8, 10, and 12 under UV irradiation for 150 min. The study showed 95.62 and 56.13% degradation and defluorination efficiency at pH 2. The degradation and defluorination efficiencies significantly decreased as the pH of the solution increased; hence, the degradation increases at lower solution pHs. Without UV–visible light, the photocatalysis achieved a lower degradation and defluorination efficiency. The photocatalysis showed that the pH of the solution and UV irradiation greatly influence the degradation and defluorination. Therefore, TiO2 nanoparticles were effective for the degradation and defluorination of PFOS under UV–visible light, which could also have an influence on the treatment of other PFASs in wastewater.

Keywords

• PFAS
• TiO₂ nanoparticles
• degradation
• defluorination
• wastewater