Kinetic Study of the Influence of Humic Acids on the Oxidation of As(III) by Acid Birnessite
Kinetic Study of the Influence of Humic Acids on the Oxidation of As(III) by Acid Birnessite
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DOI：
10.1021/acsestwater.2c00547
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发表时间：
2023-03
期刊：
影响因子：
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通讯作者：
David Nielsen-Franco;M. Ginder‐Vogel
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文献类型：
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作者：
David Nielsen-Franco;M. Ginder‐Vogel
自然环境中的溶解态砷（As）受金属氧化物表面吸附控制，其形态主要受生物锰氧化物和天然有机质（NOM）的影响。锰（III/IV）氧化物是土壤和沉积物中普遍存在的强氧化剂，而腐殖酸（HA）是NOM溶解组分中的典型物质。在这里，我们研究了HA如何影响合成氧化锰对As（III）的氧化，即，酸性水钠锰矿（MnO 2）。我们发现As与HA和MnO 2的反应动力学受表面复合物形成的控制。观察到的主要影响是在HA存在下总体氧化速率的降低。另外，MnO 2预暴露24 h后，由于MnO 2表面活性位被占据，导致反应速率进一步降低，从而导致表面钝化。我们的研究结果表明，HA的影响的反应机理的As（III）的氧化MnO 2通过吸附到活性表面位点和形成的水相配合物。
Dissolved arsenic (As) in natural environments is controlled by sorption onto metal oxide surfaces; its speciation is principally influenced by biogenic manganese oxides and natural organic matter (NOM). Manganese (III/IV) oxides are strong oxidants that are ubiquitous in soils and sediments, and humic acids (HA) are typical substances found in the dissolved fraction of NOM. However, the mechanism of As(III) oxidation by MnO2in the presence of NOM remains poorly understood. Here, we investigate how HA impact the oxidation of As(III) by a synthetic manganese oxide, i.e., acid birnessite (MnO2). We find that the reaction kinetics of As with HA and MnO2are controlled by the formation of surface complexes. The main observed effect is a decrease of the overall oxidation rate in the presence of HA. In addition, pre-exposure of MnO2to HA for 24 h further decreases the reaction rate, which is attributed to the occupation of MnO2surface active sites, thus causing surface passivation. Our results demonstrate that HA influence the reaction mechanism of As(III) oxidation by MnO2via sorption onto active surface sites and the formation of aqueous complexes.