Comprehensive study into psychostimulant photocatalytic removal using immobilized TiO2: Performance, transformation products, and environmental safety

The increasing occurrence of psychostimulants in aquatic environments poses a significant challenge for water treatment, as conventional processes fail to ensure their complete removal. TiO 2 photocatalysis represents a promising candidate for their advanced removal. However, its applicability and overall environmental impacts after the implementation remain undefined. This study evaluates the photocatalytic degradation of methamphetamine (METH) and 3,4-methylenedioxymethamphetamine (MDMA) using immobilized TiO 2 layers prepared by two scalable techniques: airbrush spraying and electrophoretic deposition. Photocatalytic performance was assessed under varying UV intensities, catalyst loadings, analyte concentrations, and water matrices. When degrading 100 ng mL -1 of stimulants in grey water using a 4-milligram airbrush layer, >80% conversion was achieved within 5 h, with MDMA showing consistently faster degradation ( k MDMA ≤ 1.69 × 10 ⁻2 min -1 ) than METH ( k METH ≤ 5.37 × 10 -3 min -1 ). UHPLC-MS/MS analysis revealed seven METH and nine MDMA transformation products, including human metabolites and pharmaceutical derivatives such as pholedrine, ephedrine, and methylone. Maximum concentrations of METH intermediates appeared after 180–240 min, while MDMA products peaked earlier (30–90 min), consistent with their higher inherent reactivity. Ecotoxicity was assessed using the MARA assay. After 5 h of photocatalysis, MDMA toxicity was completely suppressed across all eleven tested microbial strains, while the toxicity profile of METH remained stable, with strain-specific responses shifting. These findings highlight the potential of immobilized TiO 2 photocatalysis as a scalable and environmentally safe technology for mitigating micropollutant contamination in wastewater, aligning with new law requirements. Combining photocatalytic performance, transformation product profiling, and ecotoxicity assessment provides a comprehensive framework for evaluating photocatalysis suitability in practical water treatment applications. TiO 2 layers attained efficient and robust degradation of stimulants TiO 2 immobilization techniques are suitable for the scale-up and application Complex grey water slightly promoted degradation rates compared to pure water Identified transformation products included human metabolites and pharmaceuticals Ecotoxicity testing confirmed environmental safety of photocatalytic treatment