Key Laboratory for City Cluster Environmental Safety and Green Development of the Ministry of Education, School of Ecology, Environment and Resources, Guangdong University of Technology, Guangzhou 510006, China.
Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), Guangzhou 511458, China.
Environ Sci Technol. 2022 Feb 1;56(3):1492-1509. doi: 10.1021/acs.est.1c04530. Epub 2022 Jan 10.
High-valent iron(IV)-oxo complexes are of great significance as reactive intermediates implicated in diverse chemical and biological systems. The aqueous iron(IV)-oxo complex (FeO) is the simplest but one of the most powerful ferryl ion species, which possesses a high-spin state, high reduction potential, and long lifetime. It has been well documented that FeO reacts with organic compounds through various pathways (hydrogen-atom, hydride, oxygen-atom, and electron transfer as well as electrophilic addition) at moderate reaction rates and show selective reactivity toward inorganic ions prevailing in natural water, which single out FeO as a superior candidate for oxidative water treatment. This review provides state-of-the-art knowledge on the chemical properties and oxidation mechanism and kinetics of FeO, with special attention to the similarities and differences to two representative free radicals (hydroxyl radical and sulfate radical). Moreover, the prospective role of FeO in Fe activation-initiated advanced oxidation processes (AOPs) has been intensively investigated over the past 20 years, which has significantly challenged the conventional recognition that free radicals dominated in these AOPs. The latest progress in identifying the contribution of FeO in Fe-based AOPs is thereby reviewed, highlighting controversies on the nature of the reactive oxidants formed in several Fe activated peroxide and oxyacid processes. Finally, future perspectives for advancing the evaluation of FeO reactivity from an engineering viewpoint are proposed.
高价铁(IV)-氧配合物作为涉及多种化学和生物系统的反应中间体具有重要意义。水合铁(IV)-氧配合物 (FeO) 是最简单但也是最强大的双氧离子物种之一，具有高自旋态、高还原电位和长寿命。有充分的文献记载表明，FeO 通过各种途径（氢原子、氢化物、氧原子和电子转移以及亲电加成）与有机化合物在中等反应速率下反应，并对天然水中占主导地位的无机离子表现出选择性反应性，这使 FeO 成为一种优越的候选氧化剂用于水的氧化处理。本综述提供了 FeO 的化学性质和氧化机制和动力学的最新知识，特别关注与两个代表性自由基（羟基自由基和硫酸根自由基）的异同。此外，过去 20 年来，FeO 在 Fe 激活引发的高级氧化过程 (AOP) 中的潜在作用得到了深入研究，这极大地挑战了自由基在这些 AOP 中占主导地位的传统认识。因此，综述了确定 Fe 基 AOP 中 FeO 贡献的最新进展，强调了在几种 Fe 激活过氧化物和含氧酸过程中形成的反应性氧化剂的性质存在争议。最后，提出了从工程角度评估 FeO 反应性的未来展望。
