Perfluorooctane sulfonate (PFOS) is a persistent organic pollutant that is toxic and bio-accumulative. Previously, we used hydrated electrons (e_aq^–) generated by the UV photolysis of nitrilotriacetic acid (NTA) to initiate the photoreductive decomposition of PFOS. However, due to the protonation of NTA and the scavenging effect of H⁺ on e_aq^–, this process relies highly on alkaline conditions. Herein, we report on an enhanced UV photoreductive system based on Fe^ⅡNTA, which results in the decomposition of PFOS at pH 8.0 under anoxic conditions. After 10 h of photolysis, the degradation and defluorination efficiencies of PFOS in the UV/Fe^ⅡNTA system were ~ 60% and 29.5%, respectively, with a pseudo first-order degradation rate constant of k_obs = 0.081 h⁻¹. Laser flash photolysis results combined with time-dependent density functional theory (TDDFT) calculations indicate that PFOS, Fe(H₂O)₆²⁺, and NTA form a penta-coordinated metal–ligand complex that undergoes a UV-induced directional electron transfer from Fe^ⅡNTA to PFOS. PFOS decomposes via a mechanism that proceeds through a concerted photoinduced intramolecular charge transfer instead of direct attack by e_aq^–. Model chelate studies show that the inherent properties of the transition metal ion and the electron-donating capabilities of the complexing ligands determine the efficiency for photoreductive electron transfer. A low apparent activation energy of 4.74 kJ/mol over a broad pH range results in higher electron transfer efficiencies for UV/Fe^ⅡNTA photolysis compared to photolysis initiated by un-complexed NTA.

全氟辛烷磺酸 (PFOS) 是一种持久性有机污染物，具有毒性和生物累积性。以前，我们使用次氮基三乙酸 (NTA) 的紫外线光解产生的水合电子 ( e _aq ^– ) 来启动全氟辛烷磺酸的光还原分解。然而，由于 NTA 的质子化和 H ⁺对e _aq ^–的清除作用，该过程高度依赖于碱性条件。在此，我们报告了一种基于 Fe ^Ⅱ NTA的增强型紫外光还原系统，该系统可在缺氧条件下在 pH 8.0 下分解全氟辛烷磺酸。光解 10 h 后全氟辛烷磺酸在 UV/Fe ^Ⅱ中的降解和脱氟效率NTA 系统分别为～60% 和 29.5%，伪一级降解速率常数 k _obs  = 0.081 h ^-1。激光闪光光解结果与瞬态密度泛函理论 (TDDFT) 计算相结合表明，全氟辛烷磺酸、Fe(H ₂ O) ₆ ²⁺和 NTA 形成了五配位金属配体配合物，该配合物经历了紫外线诱导的定向电子转移从 Fe ^Ⅱ NTA 到 PFOS。全氟辛烷磺酸通过一种机制进行分解，该机制通过协同的光诱导分子内电荷转移而不是由e _aq的直接攻击进行^-. 模型螯合物研究表明，过渡金属离子的固有特性和络合配体的给电子能力决定了光还原电子转移的效率。与未络合的 NTA 引发的光解相比，在较宽的 pH 范围内，4.74 kJ/mol 的低表观活化能导致 UV/Fe ^Ⅱ NTA 光解的电子转移效率更高。