Continuous flow photocatalytic reactor for degradation of selected pollutants: Modeling, kinetics, mineralization rate, and toxicity assessment

This study focused on developing and evaluating a continuous flow photoreactor with an immobilized photocatalyst. The titanium dioxide powder was deposited on glass beads and packed into sequentially connected columns surrounded by LED lamps. The volume of the reactor without beads is 2.4 L, and with beads, 0.8 L. The photocatalytic efficiency of the reactor was evaluated by observing the degradation of Plasmocorinth B pollutant and selected pharmaceuticals (ibuprofen, sulfamethoxazole and diclofenac) at different flow rates under illumination of varying number of lights in deionized water and ISO medium. CFD simulations were performed to analyze the velocity and radiation field. The relationship between mass transfer and reaction kinetics was quantitatively evaluated by calculating the Peclet number, Damköhler number, and mass transfer coefficients. Total organic carbon (TOC) was also measured in the resulting solutions to determine the rate of mineralization. The toxicity tests were performed by exposing the solutions to the planktonic crustacean Daphnia magna for 48 h. The results showed that the number of lights directly and the flow rate inversely affected the degradation of the parent compound. At lower flow rates, total degradation of 87-97 % of the contaminants was observed in one flow and halving the light intensity resulted in a 10-15 % decrease in overall degradation. The toxicity tests showed that toxic transformation products were formed and were present until the complete degradation of the parent compound, after which they were also degraded. This study shows that the continuous flow photoreactor presents a potential solution for large-scale wastewater treatment.