Many phenolic compounds found as contaminants in natural waters are susceptible to oxidation by manganese oxides. However, there is often variability between oxidation rates reported in pristine matrices and studies using more environmentally relevant conditions. For example, the presence of cations generally results in slower phenolic oxidation rates. However, the underlying mechanism of cation interference is not well understood. In this study, cation co-solutes inhibit the transformation of four target phenols (bisphenol A, estrone, p-cresol, and triclosan) by acid birnessite. Oxidation rates for these compounds by acid birnessite follow the same trend (Na+ > K+ > Mg2+ > Ca2+) when cations are present as co-solutes. We further demonstrate that the same trend applies to these cations when they are absent from solution but pre-exchanged with the mineral. We analyze valence state, surface area, crystallinity, and zeta potential to characterize changes in oxide structure. The findings of this study show that pre-exchanged cations have a large effect on birnessite reactivity even in the absence of cation co-solutes, indicating that the inhibition of phenolic compound oxidation is not due to competition for surface sites, as previously suggested. Instead, the reaction inhibition is attributed to changes in aggregation and the mineral microstructure.

中文翻译：

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确定酸性水钠锰矿对苯酚氧化的阳离子抑制机制

在天然水中作为污染物发现的许多酚类化合物容易被氧化锰氧化。然而，在原始基质中报告的氧化速率与使用更环境相关条件的研究之间通常存在差异。例如，阳离子的存在通常会导致酚类氧化速率变慢。然而，阳离子干扰的潜在机制尚不清楚。在这项研究中，阳离子共溶质抑制了酸性水钠石对四种目标酚（双酚 A、雌酮、对甲酚和三氯生）的转化。当阳离子作为共溶质存在时，酸性水钠锰矿对这些化合物的氧化速率遵循相同的趋势（Na+ > K+ > Mg2+ > Ca2+）。我们进一步证明，当这些阳离子不存在于溶液中但与矿物质预先交换时，同样的趋势也适用于这些阳离子。我们分析价态、表面积、结晶度和 zeta 电位来表征氧化物结构的变化。这项研究的结果表明，即使在没有阳离子共溶质的情况下，预交换的阳离子对水钠锰矿的反应性也有很大影响，这表明酚类化合物氧化的抑制不是由于对表面位点的竞争，如前所述。相反，反应抑制归因于聚集和矿物微观结构的变化。这项研究的结果表明，即使在没有阳离子共溶质的情况下，预交换的阳离子对水钠锰矿的反应性也有很大影响，这表明酚类化合物氧化的抑制不是由于对表面位点的竞争，如前所述。相反，反应抑制归因于聚集和矿物微观结构的变化。这项研究的结果表明，即使在没有阳离子共溶质的情况下，预交换的阳离子对水钠锰矿的反应性也有很大影响，这表明酚类化合物氧化的抑制不是由于对表面位点的竞争，如前所述。相反，反应抑制归因于聚集和矿物微观结构的变化。