The degradation of diethyl phthalate (DEP) during ozonation: oxidation by-products study

The degradation of diethyl phthalate (DEP) in an aqueous solution during ozonation was investigated by identifying the oxidation intermediates using GC–MS. The experiments were carried out in semi-batch mode with a 1.5 mg l⁻¹-min ozone dose. The proposed degradation pathways were divided into hydrolysis of the aliphatic chain (pathway (A)) and hydroxylation resulting from ∙OH attack in the aromatic ring (pathway (B)). With increasing ozone dose, the aromatic ring of DEP was opened and acidic compounds, such as malonic acid, succinic acid and glutaric acid were formed. In addition, the ozonation of DEP for 18 min induced hydrogen peroxide (H₂O₂) generation at levels six times higher than pure water. Of the intermediates indentified, phthalic acid (PA) and phthalic anhydride (PAH) enhanced the degradation of DEP by promoting ozone decomposition.