The dark generation of reactive oxygen species (ROS), particularly hydroxyl radicals (·OH), is crucial in the oxidative transformation of various pollutants. However, the mechanisms behind this process are predominantly linked to direct O₂ activation by reduced substances such as Fe(II) and natural organic matter. In this study, we introduce a previously overlooked dual-ligand mechanism that significantly amplifies ·OH generation on iron oxyhydroxides, facilitated by cysteine and pyrophosphate. Our findings reveal that these ligands collaboratively boost ·OH generation by 99.5–125.7% compared to Fe(II) alone. This enhancement occurs through a two-step electron transfer (ET) process, where cysteine transfers electrons to O₂ through iron oxyhydroxides. The complexation of pyrophosphate with iron oxyhydroxides further reduces the thermodynamic barriers, notably promoting this ET process and significantly improving the electron utilization efficiency for O₂ activation by the electron donor cysteine. Such a process has shown its great potential for effectively driving the oxidative transformation of various pollutants, including As(III), dichlorophenol, and carbamazepine. These findings offer valuable insights for nature-based pollutant mitigation in soil and subsurface environments.

中文翻译：

---

双配体驱动的暗活性氧在羟基氢氧化铁上生成：对环境修复的影响


活性氧 （ROS） 的暗生成，特别是羟基自由基 （·OH） 在各种污染物的氧化转化中至关重要。然而，这个过程背后的机制主要与 Fe（II） 和天然有机物等还原物质的直接 O₂ 活化有关。在这项研究中，我们介绍了一种以前被忽视的双配体机制，该机制显着放大了 ·羟基氢氧化铁上 OH 的生成，由半胱氨酸和焦磷酸盐促进。我们的研究结果表明，这些配体协同促进 ·与单独的 Fe（II） 相比，OH 生成量提高了 99.5-125.7%。这种增强是通过两步电子转移 （ET） 过程发生的，其中半胱氨酸通过羟基氧化物将电子转移到 O₂。焦磷酸盐与羟基氢氧化铁的络合进一步降低了热力学势垒，显着促进了这种 ET 过程，并显着提高了电子供体半胱氨酸活化 O₂ 的电子利用效率。这样的过程已显示出其有效驱动各种污染物氧化转化的巨大潜力，包括 As（III）、二氯苯酚和卡马西平。这些发现为土壤和地下环境中基于自然的污染物缓解提供了有价值的见解。