Effects of low-molecular-weight organic acids/thiols on hydroxyl radical production from natural siderite oxidation
Effects of low-molecular-weight organic acids/thiols on hydroxyl radical production from natural siderite oxidation
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低分子量有机酸/硫醇对天然菱铁矿氧化产生羟基自由基的影响
DOI：
10.1016/j.chemgeo.2021.120537
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发表时间：
2021-12
期刊：
影响因子：
3.9
通讯作者：
Mustapha Nasiru Abba
中科院分区：
文献类型：
--
作者：
Yu Hao;Zhang Peng;Liu Jiayu;Zheng Yunsong;Mustapha Nasiru Abba
菱铁矿的氧化作用会产生能够转化污染物的羟基自由基(·OH)。然而，广泛存在于土壤和水中的低分子有机酸(LMWOAs)/硫醇(LMWOTs)对菱铁矿氧化生成·OH的影响还知之甚少。研究结果表明，在pH=6~8时，LMWOAS/LMWOTS的存在显著促进了氧化菱铁矿氧化生成·OH。例如，在pH=7的条件下，对于1微克/L的菱铁矿，24小时内的累积·OH浓度仅为1.3兆μM，而当分别加入1毫米乙二胺四乙酸酯和半胱氨酸时，·OH的累积浓度分别增加到19.7和7.2兆μM。·OH生成增强的机理与LMWOAs/LMWOts的络合能力和氧化还原活性有关。在没有LMWOAs/LMWOTS的情况下，·OH主要是由吸附的Fe(II)被O2氧化生成的，其次是菱铁矿表面结构Fe(II)的氧化。在LMWOAs存在下，LMWOAs与吸附的Fe(II)和结构Fe(II)反应生成络合Fe(II)。因此，O2对LMWOAs络合Fe(II)的氧化主要是产生·OH。尽管LMWOTS的络合能力弱于LMOWAs，但LMWOTS能还原O2生成·O2-−和过氧化氢，从而促进·OH的产生。基于所提出的机理，建立了动力学模型来量化每条途径对·OH产生的相对贡献。在菱铁矿悬浮液中加入1 mM柠檬酸和半胱氨酸，三氯乙烯的脱除率可分别提高到15%和7%。我们的研究揭示了在氧化还原动力学条件下，LMWOAs/LMWOTS在提高菱铁矿氧化生成·OH方面被忽视的催化作用。
Oxygenation of siderite produces hydroxyl radicals (•OH) that are capable of transforming the pollutants. Yet, the influence of low-molecular-weight organic acids (LMWOAs)/ thiols (LMWOTs) which are widely occurring in soils and waters on •OH production from the oxygenation process of siderite is poorly understood. Results of this study show that the presence of LMWOAs/LMWOTs significantly facilitated •OH production from siderite oxidation by O2at pH 6–8. For instance, at pH 7, the cumulative •OH concentration within 24 h was only 1.3 μM for oxygenation of 1 g/L siderite, while it boosted to 19.7 and 7.2 μM, respectively, with the respective addition of 1 mM ethylenediaminotetraacetate and cysteine. The mechanisms responsible for the enhanced •OH production are associated with the complexation ability and redox activity of LMWOAs/LMWOTs. In the absence of LMWOAs/LMWOTs, •OH is mainly produced from the oxidation of adsorbed Fe(II) by O2, followed by the oxidation of structural Fe(II) on siderite surface. In the presence of LMWOAs, LMWOAs react with adsorbed Fe(II) and structural Fe(II) to produce complexed Fe(II). Therefore, the oxidation of LMWOAs complexed Fe(II) by O2predominantly contributed to •OH production. Although the complexation ability of LMWOTs is weaker than that of LMOWAs, LMWOTs can reduce O2to generate •O2−and H2O2, thus facilitating •OH production. Based on the proposed mechanisms, a kinetic model was developed to quantify the relative contribution of each pathway to •OH production. The addition of 1 mM citrate and cysteine in siderite suspension could increase the removal of trichloroethylene from <5% to 15% and 7%, respectively. Our study reveals the overlooked catalytic effects of LMWOAs/LMWOTs in enhancing •OH production from siderite oxidation by O2under redox-dynamic conditions.
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作者：
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