Hydroxyl radical dominated degradation of aquatic sulfamethoxazole by Fe0/bisulfite/O2: Kinetics, mechanisms, and pathways,Water Research

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Hydroxyl radical dominated degradation of aquatic sulfamethoxazole by Fe0/bisulfite/O2: Kinetics, mechanisms, and pathways
Water Research ( IF 11.4 ) Pub Date : 2017-12-22 , DOI: 10.1016/j.watres.2017.12.046
Juanshan Du , Wanqian Guo , Huazhe Wang , Renli Yin , Heshan Zheng , Xiaochi Feng , Di Che , Nanqi Ren

In this study, batch experiments were carried out to investigate the key factors on sulfamethoxazole (SMX) removal kinetics in a new AOPs based on the combination of zero valent iron (Fe⁰) and bisulfite (S(IV)). With the increase of Fe⁰ from 0.25 mM to 5 mM, the removal rate of SMX was linearly increased in the Fe⁰/S(IV)/O₂ system by accelerating the activation of S(IV) and Fe⁰ corrosion to accelerate. In the first 10 min of reaction, the increasing concentration of S(IV) inhibited SMX removal after since the high S(IV) concentration quenched reactive oxidative species (ROS). Then SMX removal rate was accelerated with the increase of S(IV) concentration after S(IV) were consumed up. The optimal ratio of S(IV) concentrations to Fe⁰ concentration for SMX removal in the Fe⁰/S(IV)/O₂ system was 1:1. With SMX concentrations increasing from 1 to 50 μM, SMX removal rate was inhibited for the limitation of ROS yields. Although the presence of

SO₄⁻ and

OH was confirmed by electron paramagnetic resonance (EPR) spectrum,

OH was identified as the dominant ROS in the Fe⁰/S(IV)/O₂ system by chemical quenching experiments. Besides, strong inhibitive effects of 1,10-phenanthroline on SMX degradation kinetics by Fe⁰/S(IV)/O₂ proved that the generation of ROS was rely on the release of Fe(II) and Fe(III). The generation of

SO₄⁻ was ascribed to the activation of S(IV) by Fe(II)/Fe(III) recycling and the activation of HSO₅⁻ by Fe(II). And

OH was simultaneously transformed from

SO₄⁻ and generated by Fe⁰/O₂. Density functional theory (DFT) calculation was conducted to reveal special reactive sites on SMX for radicals attacking and predicted intermediates. Finally, four possible SMX degradation pathways were accordingly proposed in the Fe⁰/S(IV)/O₂ system based on experimental methods and DFT calculation.

中文翻译：

Fe ⁰ /亚硫酸氢盐/ O ₂降解水基磺胺甲基异恶唑的羟基自由基：动力学，机理和途径

在这项研究中，进行了批处理实验，以研究基于零价铁（Fe ⁰）和亚硫酸氢盐（S（IV））组合的新型AOP中磺胺甲恶唑（SMX）去除动力学的关键因素。随着Fe ⁰从0.25 mM增加到5 mM，通过加速S（IV）和Fe ⁰的活化，在Fe ⁰ / S（IV）/ O ₂系统中SMX的去除率线性增加。腐蚀加速。在反应的前10分钟，由于高S（IV）浓度淬灭了反应性氧化物质（ROS），S（IV）浓度的增加抑制了SMX的去除。然后，随着S（IV）的消耗，SMX的去除速率随着S（IV）浓度的增加而加快。在Fe ⁰ / S（IV）/ O ₂系统中去除SMX的S（IV）浓度与Fe ⁰浓度的最佳比例为1：1。随着SMX浓度从1增加到50μM，SMX去除率受到抑制，从而限制了ROS产量。虽然存在