Development of a continuous flow photoreactor for photocatalytic pollutant degradation

The global rise in organic and fluorinated pollutant contamination demands scalable and efficient remediation technologies. In this study, a continuous flow photoreactor is designed and developed for the specific application of photocatalytic pollutant degradation. Photocatalyst powders (TiO 2 (P25), Ta 2 O 5 , La-doped NaTaO 3 , ZnS) were prepared as films for use in the flow photoreactors with reasonable longevity (< 8 days continuous use without significant decrease in activity). A single-pass flow system was demonstrated with in-line analyses to allow for ion and colorimetric detection in real-time. A circulating flow system was also used to achieve greater pollutant conversion/mineralization with increased flow rates. Successful conversion of a methyl orange model dye (60% (365 nm, 105 mW/cm 2 , 0.1 mL/min)), 4-fluorobenzoic acid (4-FBA, 100% (275 nm, 40 mW/cm 2 , 0.1 – 0.8 mL/min)) and perfluorooctanesulfonic acid (PFOS, 86% (365 nm, 206 mW/cm 2 , 0.006 mL/min)) was achieved. The fluoride production from 4-FBA and PFOS degradation under optimized conditions was also monitored and 90% mineralization was reported for 4-FBA (275 nm, 40 mW/cm 2 , 0.1 – 0. 2 mL/min) along with 19% for PFOS (275 nm, 40 mW/cm 2 , 0.2 mL/min). This work highlights the potential of continuous flow photocatalysis for scalable pollutant remediation and provides a robust platform for future optimization and deployment.