Removal of aromatic contaminants (ACs) in waters by sulfate radical anion (SO₄⁻) based advanced oxidation technology has been extensively studied. Three main mechanisms have frequently been used to account for the first step of radical oxidation of ACs: radical adduct formation, hydrogen atom abstraction, and single electron transfer (SET), among which the SET pathway is the least understood. In this study, we investigated the first step of SET reactions for 76 ACs with SO₄⁻. The result shows that the Gibbs free energy ($\mathrm{\Delta }{G}_{\text{SET}}^{\circ }$) of the reaction increases with a decrease of the electron donating character of the substituents on the ACs. The trend was then quantitatively corroborated by a Hammett type plot, indicating that the electrostatic interaction is the driving force for the SET pathway. Further, we compared the calculated second-order rate constants (k_SET) for the ACs via the SET pathway with their experimental k values, and proposed two fundamental SET reaction mechanisms based on the identified intermediates. The thermodynamic and kinetic results obtained advance the mechanistic understanding of the SET pathway of radical and non-radical bimolecular reactions, and shed light on the applicability of SO₄⁻ in ACs removal during water treatment processes.

在水域芳香族污染物（ACS）由硫酸根阴离子的去除（SO ₄ ^- ）基于高级氧化技术已被广泛研究。经常使用三种主要机制来解释AC自由基氧化的第一步：自由基加合物形成，氢原子抽象和单电子转移（SET），其中对SET途径的了解最少。在这项研究中，我们调查组反应的第一步骤中为76分的AC与SO ₄ ^- 。结果表明，吉布斯自由能（$\mathrm{\Delta }{G}_{\text{放}}^{\circ }$随着AC上取代基的电子给体特性的降低，反应的反应速率增加。然后通过Hammett型图在定量上证实了该趋势，表明静电相互作用是SET途径的驱动力。此外，我们将通过SET途径计算的AC的二阶速率常数（k _SET）与它们的实验k值进行了比较，并基于鉴定出的中间体提出了两种基本的SET反应机理。热力学和动力学的结果获得的预先自由基和非自由基双分子反应的SET途径的机制理解，并且在SO的适用性棚光₄ ^- 在水处理过程中去除ACs。