Application of TiO2-Coated Materials for Photocatalytic Treatment of Caffeine-Contaminated Water

Caffeine, widely present in everyday beverages such as coffee, tea, and soft drinks, is increasingly being detected in aquatic environments. Its chemical stability and widespread human consumption have contributed to its classification as an emerging contaminant. Due to its resistance to biological degradation [1], conventional wastewater treatment plants often fail to fully eliminate caffeine, allowing it to persist in surface water and wastewater effluents. Although typically present in low concentrations, prolonged exposure to caffeine may cause sub-lethal effects in aquatic organisms, including developmental, behavioral, and physiological disturbances [2]. This raises growing concern regarding its long-term ecological impacts, especially in water bodies that receive continuous discharge from municipal wastewater. In this study, the photocatalytic degradation of caffeine was investigated using titanium dioxide (TiO₂)-coated materials synthesized via the sol-gel method and applied onto various substrates, including glass beads, alumina balls, and ceramic spheres. The degradation performance was evaluated under UV-C irradiation, considering variables such as the type of supporting material, initial caffeine concentration, solution pH, and photocatalyst reusability. Among the tested photocatalysts, TiO₂-coated ceramic balls exhibited the highest removal efficiency, achieving nearly 100 percent degradation and reducing caffeine concentrations to levels well below ecotoxicological thresholds. The degradation followed pseudo-first-order kinetics, with optimal performance observed at near-neutral pH, indicating that highly acidic or alkaline conditions suppressed photocatalytic activity. Furthermore, the photocatalysts retained high efficiency over five reuse cycles, demonstrating excellent reusability and stability. These findings highlight the potential of TiO₂-coated ceramic materials as a sustainable and effective solution for eliminating emerging contaminants like caffeine from aquatic environments.