Strategies to improve degradation kinetics of light-driven AOPs for micropollutant removal: catalyst, radiation, and oxidant synergies

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• TiO 2 /rGO used for the first time in FluHelik photoreactor. • Low-cost TiO 2 /rGO (hydrothermal) + 6 W UV-A fully degraded MPs mixture in 60 min. • TiO 2 /rGO (5 wt%) outperformed commercial TiO 2 P25 in photocatalytic performance. • Chlorine, H 2 O 2 and PS as oxidants greatly accelerated VLX and DCF degradation rates. • UV-C/H 2 O 2 and UV-C/PS removed > 80 % MPs listed in Directive (EU) 2024/3019. The persistence of micropollutants (MPs) in wastewater effluents poses a major environmental challenge, demanding advanced quaternary treatment technologies. Here, we investigate strategies to enhance the simultaneous removal of mixtures of MPs in light-driven advanced oxidation processes (AOPs) through photocatalyst design, radiation source selection, and oxidant addition, aligned with the requirements of Directive (EU) 2024/3019. A TiO 2 /rGO composite containing 5 wt% GO is synthesised and evaluated for the first time in the FluHelik photoreactor configuration. First, UV-A, UV-C and visible light are tested to degrade venlafaxine (VLX) and diclofenac (DCF) as model MPs (750 µg L -1 each). 150 mg L -1 is the optimal TiO 2 /rGO dose and UV-C radiation is the most effective irradiation source. Then, the addition of oxidants − hydrogen peroxide (H 2 O 2 ), hypochlorite (HOCl/OCl - ) or persulphate (PS, S 2 O 8 2- ) (0.6 mM each). − further accelerate the reaction rates (9- and 3-fold for VLX and DCF, respectively, regardless the oxidant). Photocatalyst reusability is confirmed over four consecutive cycles. High-performance liquid chromatography is employed to monitor degradation kinetics. The strategies are then evaluated for the quaternary treatment of urban wastewater targeting six MPs (200 µg L -1 each) (atenolol, carbamazepine, diclofenac, diuron, sulfamethoxazole, and venlafaxine). UV-C/H 2 O 2 and UV-C/PS are the best alternatives to treat urban wastewater, achieving > 80 % removal across all MPs. These results highlight the potential of photochemical technologies − applied in the FluHelik photoreactor −, as an effective and scalable solution for advanced wastewater treatment. They also underscore the relevance of integrating complementary technologies to ensure compliance with environmental regulations.

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