Advanced solar photocatalysis in continuous mode: H2O2-enhanced removal of organic contaminants in simulated and real wastewater

The feasibility of a solar-powered continuous-flow photocatalytic system for the degradation of organic pollutants in aqueous streams was investigated. Fe-doped TiO 2 immobilized on polystyrene was tested as a reusable photocatalyst under both batch and continuous operation, using rhodamine B (RB) as a model pollutant. However, the scalability and long-term outdoor performance of Fe-TiO 2 photocatalysis remain poorly understood. The system was first optimized in batch experiments under artificial light. Optimization considered H 2 O 2 dosage and addition mode, optical path length, and liquid-to-solid ratio. The system was subsequently validated outdoors over eight months, demonstrating stable performance under varying solar irradiance. The addition of H 2 O 2 significantly enhanced photocatalytic activity. It increased the maximum degradation rate constant from 0.293 h −1 to 1.313 h −1 . It also reduced the half-saturation irradiance from 210 to 130 W/m 2 . These effects result from combined heterogeneous photocatalysis and surface-bound photo-Fenton reactions. Continuous-flow tests confirmed the scalability and predictability of the system: up to 99.8 % RB removal and substantial TOC reduction (from 21.5 to 14.3 mg/L) were achieved in real pharmaceutical wastewater at a residence time of 39 min (4.65 mL/h) under natural solar light (irradiance 700–900 w/m 2 ) with H 2 O 2 addition (0.068 mmol/h). This represents the first demonstration of solar-driven continuous operation using immobilized Fe-TiO 2 on polystyrene. The study highlights that the use of a supported photocatalyst, rather than a simple bio-based adsorbent, allows for complete degradation of pollutants via oxidative pathways, rather than mere adsorption. This approach makes the system suitable for low-energy, solar-driven, decentralized water treatment. • Fe-TiO 2 tested in continuous-flow under real sunlight ( I < 900 W/m 2 , HTR = 13–39 min). • H 2 O 2 enhanced degradation rate up to 5 times (1.5 mL/L, n = 3). • Catalyst showed high stability in repeated cycles ( n > 5). • Real WWT confirmed TOC removal (from 22 to 14 mg/L; HRT = 39 min). • Solar collector improved performance under low sunlight ( I < 210 W/m 2 ).