| Popis: |
Photochemical degradation of typical phthalate esters, as, e.g. dimethyl phthalate (DMP), in water by the UV/H2O2 process was investigated. The degradation rate of DMP was affected by several reaction factors, including initial DMP concentration, H2O2 concentration, UV light intensity, and coexisting cations and anions. The DMP degradation rate decreased with increasing initial DMP concentration. Carbonate ions significantly reduced the reaction rate by 70.2%, while the degradation rate was improved ten-fold in the presence of ferric ions. The initial reaction mechanism and possible degradation products were investigated using density functional theory (DFT), including B3LYP and M062X hybrid functional. The addition of OH radicals (OH•) to the C4 position of the DMP ring is energetically favored for the initial reaction of DMP with OH•. Dimethyl 4-hydroxyphthalate (DMP-4OH) is one of the initial degradation intermediates. A possible reaction mechanism was also proposed based on GC/MS analysis and quantum chemical calculations. The formation of DMP-4OH has been explained by quantum chemical calculations, which indicates the advantage and promising role of this method in the degradation mechanism analysis. |
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