Photocatalytic Degradation and Defluorination of Per- and poly-fluoroalkyl substances (PFAS) using TiO₂ Nanoparticles under UV-visible Light

Per- and poly-fluoroalkyl substances (PFAS) 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 PFAS in aqueous water using TiO₂ nanoparticles under UV-visible. 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 pH 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 the particle size distribution 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 PFAS were performed at various initial solution pH 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 with a rate constant decreasing as the pH solution increases; hence the degradation increases at lower solution pH. Without UV-visible light, the photocatalysis achieved less degradation and defluorination efficiency. The photocatalysis showed that the pH solution and UV irradiation greatly influence the degradation and defluorination. Therefore, TiO₂ nanoparticles were effective for the degradation and defluorination of PFAS under UV-visible light which has the influence for treatment of PFAS in wastewater.