Advanced oxidation processes (AOPs) based on hydroxyl radicals (•OH) are the most important technologies for the removal of bio-recalcitrant organic pollutants in industrial wastewater. The pH is one of the crucial environmental parameters that affect the removal efficiency of pollutants in AOPs. In this work, the mechanistic and kinetic insights into the roles of pH on the hydroxylation of five aromatic acids and bases in UV/H₂O₂ process have been investigated using theoretical calculation methods. Results show that the reactivity of •OH towards the twelve ionic/neutral species is positively correlated with electron-donating effect of substituents, which contributes to the positively pH-dependent reactivity of aromatic acids and bases towards •OH. The hydroxylation apparent rate constants (k_app, M⁻¹ s⁻¹) (at 298 K) increase as the pH values increase from about 1 to 10, but they decrease as the pH values increase from about 10 to 14. However, the best pH values for degradation are not around 10 because the [•OH] decreases continuously with the increasing pH values from 3 to 9.5. Combining the factors of k_app and [•OH], the best degradation pH values are around 5.5~7.5 for p-hydroxybenzoic acid, p-aminophenol, aniline and benzoic acid, 3.0~7.5 for phenol and 5.5~7.5 for mixed pollutants of these aromatic acids/bases in UV/H₂O₂ process. Moreover, a significant number of hydroxylation by-products are more toxic or harmful to aquatic organisms and rat (oral) than their parental pollutants. Altogether, this work provides comprehensive understanding of the roles of pH on •OH-initiated degradation behavior of aromatic acids and bases.

基于羟基自由基（•OH）的高级氧化工艺（AOP）是去除工业废水中难降解的有机污染物的最重要技术。pH是影响AOP中污染物去除效率的关键环境参数之一。在这项工作中，机理和动力学洞察了pH值对UV / H ₂ O ₂中五种芳香酸和碱的羟基化的作用。已经使用理论计算方法对过程进行了研究。结果表明，•OH对十二种离子/中性物质的反应性与取代基的供电子作用呈正相关，这有助于芳香酸和碱对•OH的正pH依赖性反应。羟化表观速率常数（k _app，M ^-1 s ^-1）（在298 K下）随着pH值从大约1增大到10而增加，但是随着pH值从大约10增大到14而减小。降解的最佳p​​H值不在10左右，因为[•OH]随着pH值从3增加到9.5连续降低。结合k _app的因素对羟基苯甲酸，对氨基苯酚，苯胺和苯甲酸的最佳降解pH值在5.5〜7.5左右，苯酚的最佳降解pH值在3.0〜7.5左右，而这些芳香酸/碱的混合污染物在5.5〜7.5左右。 UV / H ₂ O ₂工艺。而且，许多羟基化副产物比其母体污染物对水生生物和大鼠（口腔）有更大的毒性或危害。总之，这项工作提供了对pH在•OH引发的芳族酸和碱降解行为中作用的全面理解。