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.

中文翻译：

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UV / H2O2降解邻苯二甲酸二甲酯：实验方法与量子化学计算的结合

通过UV / H2O2工艺研究了典型邻苯二甲酸酯（例如邻苯二甲酸二甲酯（DMP））在水中的光化学降解。DMP的降解速率受几个反应因素的影响，包括初始DMP浓度，H2O2浓度，UV光强度以及共存的阳离子和阴离子。DMP降解速率随初始DMP浓度的增加而降低。碳酸根离子显着降低了70.2％的反应速率，而在三价铁离子存在下，降解速率提高了十倍。使用密度泛函理论（DFT）研究了初始反应机理和可能的降解产物，包括B3LYP和M062X杂合官能团。在DMP环的C4位加OH自由基（OH•），在能量上有利于DMP与OH•的初始反应。4-羟基邻苯二甲酸二甲酯（DMP-4OH）是最初的降解中间体之一。还基于GC / MS分析和量子化学计算提出了一种可能的反应机理。DMP-4OH的形成已通过量子化学计算得到了解释，这表明了该方法在降解机理分析中的优势和有希望的作用。