Rapid Tris(1,3-dichloropropyl) Phosphate Degradation and Detoxification via TiO2 Nanoparticles under UV Light: Kinetics and Mechanism, Environmental Implications, and Insights into DFT

The widespread use of tris(1,3-dichloropropyl) phosphate (TDCPP), a phosphorus flame retardant, has raised significant environmental concerns because of its persistence and toxicity. This study examines the photodegradation of TDCPP (0.25 mg/L) using titanium dioxide (TiO₂) nanoparticles (P25 NPs) (50 mg/L) under UV irradiation, focusing on the effects of electrolytes, such as NaCl and NaBr, pH, and temperature. TiO₂ NPs degraded TDCPP within 60 min, achieving nearly complete mineralization and release of chloride ions (Cl−). The degradation rate decreased with higher initial TDCPP concentrations but increased with higher TiO₂ dosages. Acidic conditions enhanced photodegradation, while the presence of electrolytes caused nanoparticle aggregation, increasing the particle size and reducing the photocatalytic efficiency. Chloride (Cl−) and bromide ions (Br−) acted as radical scavengers, inhibiting the formation of reactive hydroxyl radicals (HO•). Notably, 89% of the total organic carbon (TOC) was eliminated from TDCPP after 60 min of UV illumination, indicating mineralization into carbon dioxide and water. The degradation intermediates were analyzed using ultrahigh-performance liquid chromatography (UHPLC), and two byproducts were identified after 10 min of treatment. Acute and chronic toxicity analyses revealed that TDCPP’s intermediates were nontoxic. Density functional theory (DFT) calculations provide insights into electronic structures and degradation pathways. This research contributes to strategies for mitigating the environmental impact of hazardous flame retardants such as TDCPP.