High-valent metal-oxo species (HMOS) have been extensively recognized in advanced oxidation processes (AOPs) owing to their high selectivity and high chemical utilization efficiency. However, the interactions between HMOS and halide ions in sewage wastewater are complicated, leading to ongoing debates on the intrinsic reactive species and impacts on remediation. Herein, we prepared three typical HMOS, including Fe(IV), Mn(V)-nitrilotriacetic acid complex (Mn(V)NTA) and Co(IV) through peroxymonosulfate (PMS) activation and comparatively studied their interactions with Cl to reveal different reactive chlorine species (RCS) and the effects of HMOS types on RCS generation pathways. Our results show that the presence of Cl alters the cleavage behavior of the peroxide OO bond in PMS and prohibits the generation of Fe(IV), spontaneously promoting SO production and its subsequent transformation to secondary radicals like Cl and Cl. The generation and oxidation capacity of Mn(V)NTA was scarcely influenced by Cl, while Cl would substantially consume Co(IV) and promote HOCl generation through an oxygen-transfer reaction, evidenced by density functional theory (DFT) and deuterium oxide solvent exchange experiment. The two-electron-transfer standard redox potentials of Fe(IV), Mn(V)NTA and Co(IV) were calculated as 2.43, 2.55 and 2.85 V, respectively. Due to the different reactive species and pathways in the presence of Cl, the amounts of chlorinated by-products followed the order of Co(II)/PMS > Fe(II)/PMS > Mn(II)NTA/PMS. Thus, this work renovates the knowledge of halide chemistry in HMOS-based systems and sheds light on the impact on the treatment of salinity-containing wastewater.

中文翻译：

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共存氯化物对高价金属氧物种的转化和调控：反应途径及其对氯化副产物产生的影响


高价金属氧物种（HMOS）由于其高选择性和高化学利用率而在高级氧化工艺（AOP）中得到广泛认可。然而，HMOS 和污水中卤化物离子之间的相互作用很复杂，导致关于内在活性物质和对修复影响的持续争论。在此，我们通过过一硫酸盐（PMS）活化制备了三种典型的HMOS，包括Fe（IV）、Mn（V）-次氮基三乙酸络合物（Mn（V）NTA）和Co（IV），并比较研究了它们与Cl的相互作用，以揭示不同的HMOS。活性氯物种 (RCS) 以及 HMOS 类型对 RCS 生成途径的影响。我们的结果表明，Cl 的存在改变了 PMS 中过氧化物 OO 键的裂解行为，并抑制 Fe(IV) 的生成，从而自发促进 SO 的产生及其随后转化为 Cl 和 Cl 等二次自由基。 Mn(V)NTA的生成和氧化能力几乎不受Cl的影响，而Cl会大量消耗Co(IV)并通过氧转移反应促进HOCl的生成，密度泛函理论(DFT)和氧化氘溶剂交换证明了这一点实验。计算出Fe(IV)、Mn(V)NTA和Co(IV)的双电子转移标准氧化还原电位分别为2.43、2.55和2.85 V。由于Cl存在下的反应物种和途径不同，氯化副产物的量遵循Co(II)/PMS > Fe(II)/PMS > Mn(II)NTA/PMS的顺序。因此，这项工作刷新了基于 HMOS 的系统中卤化物化学的知识，并揭示了其对含盐废水处理的影响。