Carbon and hydrogen isotope fractionation of phthalates during photocatalysis reactions in aqueous solution containing Fe(III) complexes or iron minerals.

The hydrogen and carbon isotope fractionation factor (ε2H, ε13C) of dimethyl-, diethyl‑ and dibutyl phthalic acid ester during photosensitized degradation by artificial sunlight with Fe(III) ions and iron minerals (hematite, goethite and magnetite) in aqueous solution were examined by compound-specific isotope analysis (CSIA) in order to analyze the degradation mechanism. Hematite does not catalyze photosensitized degradation of phthalates. The correlation of 2H and 13C isotope fractionation (Λ = Δδ2H/Δδ13C) of phthalates with increasing chain length (dimethyl-; diethyl‑; and dibutyl-) were compared with values of the ∙OH radical model reaction with the aromatic ring as well as acidic and alkaline hydrolysis. The Λ values of die photosensitized reaction of diethyl phthalate with goethite (-5.1 ± 1.8) and magnetite (-18.9 ± 3.9) show a large difference compared to Fe(III) solutions (4.7 ± 0.9 to 4.8 ± 1.0) suggesting specific reaction mechanisms. The fractionation factors determined here have potential to characterize the degradation of phthalates catalyzed by photo-induced reaction of Fe(III), goethite and magnetite in natural system and in remediation approaches.