The modulation of peroxymonosulfate (PMS) activation pathway to achieve effective degradation of pollutants is significant, but still challenging. Herein, a series of hydroxyl- and size-controlled MnFe2O4 catalysts were synthesized through an alkaline microenvironment regulation strategy. The variable-sized MnFe2O4 (submicron, nanoscale and microscale) exhibited size-dependent catalytic behavior, while the changes in surface hydroxyl content altered the activation pathway from dissolved radicals to surface-bound radicals. The quenching experiments, electron spin resonance spectroscopy, electrochemical studies, in-situ Raman spectra and density functional theory calculations were conducted to reveal the evolution of reactive oxygen species. Due to strong binding energy, PMS was stabilized by the rich surface hydroxyl to form surface complexed MnFe2O4-HOOSO3− and simultaneously activated by the active bimetallic components, resulting in oriented-production of surface-bonded radicals. Benefiting from smaller particle size and rich hydroxyl groups, the optimal nano-MnFe2O4-OH/PMS system could massively generate surface-bound SO4•−, which achieved a highly efficient removal efficiency (88.6 %) for ofloxacin (10 mg/L) degradation under wide pH ranges from 3.0 to 9.0. The evaluation of ecotoxicity, reusability, pH applicability, universality and anti-interference property confirmed the practical application prospect of nano-MnFe2O4-OH/PMS system.

中文翻译：

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通过 MnFe 2 O 4 将过氧一硫酸盐激活途径从自由基转换为表面结合自由基以增强氧氟沙星的降解：尺寸效应和表面羟基的关键作用


调节过氧一硫酸盐 （PMS） 激活途径以实现污染物的有效降解是重要的，但仍然具有挑战性。在此，通过碱性微环境调节策略合成了一系列羟基和尺寸控制的 MnFe2O4 催化剂。可变大小的 MnFe 2 O 4 （亚微米、纳米级和微米级） 表现出尺寸依赖性催化行为，而表面羟基含量的变化改变了从溶解自由基到表面结合自由基的激活途径。通过猝灭实验、电子自旋共振波谱、电化学研究、原位拉曼光谱和密度泛函理论计算，揭示了活性氧的演变规律。由于结合能强，PMS 被丰富的表面羟基稳定，形成表面络合的 MnFe2O4-HOOSO3−，同时被活性双金属组分激活，导致表面键合自由基的定向产生。得益于更小的粒径和丰富的羟基，最佳的纳米 MnFe2O4-OH/PMS 系统可以大量产生表面结合的 SO4•−，在 3.0 至 9.0 的宽 pH 范围内实现了对氧氟沙星 （10 mg/L） 降解的高效去除效率 （88.6%）。对纳米 MnFe2O4-OH/PMS 体系的生态毒性、可重复使用性、pH 适用性、普遍性和抗干扰性能的评价证实了纳米 MnFe2O4-OH/PMS 体系的实际应用前景。