Demonstration of Photocatalytic Degradation of Per-and Polyfluoroalkyl Substances (PFAS) in Landfill Leachate Using 3D Printed TiO_2 Composite Tiles

摘要

Per- and polyfluoroalkyl substances (PFAS) are a complex group of recalcitrant substances that are present globally in many landfill wastewater leachates and have potential ecological and human health risks. Conventional treatment technologies have shown limited efficacy for many PFAS due to the stable C-F bonds. Therefore, there is growing interest in applying advanced oxidation processes (e.g., photocatalysis) to decrease the aqueous concentrations of PFAS in contaminated wastewater and mitigate risks. The goal of this study was to evaluate the photocatalytic performance of treating PFAS in landfill leachate using a novel photocatalyst composite. Treatment structures were fabricated using polylactic acid (PLA) and compounded with TiO_2 (15 wt), and 3D printed into tiles. The appeal to 3D printing the photocatalytic composites for environmental applications is for limitless geometric customization for the application, including optimizing surface area and prototyping for research improvements prior to scale-up. A pilot-scale treatment system was designed to promote photocatalysis using 3D composite structures and UV irradiance intensity of 1.0 mW cm~(-2) (λ = 280-400 nm) following 24- and 36-h hydraulic retention times. Photocatalytic degradation was achieved for seven of the 11 PFAS evaluated in this study: PFOS, PFOA, PFHPA, PFHxS, PFNA, PFDA, and PFOSAm. Greater than 80 removal of PFOS, PFNA, PFDA, and PFOSAm was observed after 24 h of photocatalysis. These results indicate photocatalysis using TiO_2 polymer composites can achieve beneficial levels of PFAS degradation. This study provides a proof-of-principle approach to inform the application of additive manufacturing of photocatalytic composites for use in the treatment of PFAS-contaminated wastewater.