Influence of Silica Coatings on Magnetite-Catalyzed Selenium Reduction,Environmental Science & Technology

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Influence of Silica Coatings on Magnetite-Catalyzed Selenium Reduction
Environmental Science & Technology ( IF 10.8 ) Pub Date : 2021-02-19 , DOI: 10.1021/acs.est.0c08146
Sara Goberna-Ferrón ₁ , Maria P. Asta ₂ , Bahareh Zareeipolgardani ₁ , Sarah Bureau ₁ , Nathaniel Findling ₁ , Laura Simonelli ₃ , Jean-Marc Greneche ₄ , Laurent Charlet ₁ , Alejandro Fernández-Martínez ₁

Affiliation

The reactivity of iron(II/III) oxide surfaces may be influenced by their interaction with silica, which is ubiquitous in aquatic systems. Understanding the structure–reactivity relationships of Si-coated mineral surfaces is necessary to describe the complex surface behavior of nanoscale iron oxides. Here, we use Si-adsorption isotherms and Fourier transform infrared spectroscopy to analyze the sorption and polymerization of silica on slightly oxidized magnetite nanoparticles (15% maghemite and 85% magnetite, i.e., ∼2 maghemite surface layers), showing that Si adsorption follows a Langmuir isotherm up to 2 mM dissolved Si, where surface polymerization occurs. Furthermore, the effects of silica surface coatings on the redox-catalytic ability of magnetite are analyzed using selenium as a molecular probe. The results show that for partially oxidized nanoparticles and even under different Si surface coverages, electron transfer is still occurring. The results indicate anion exchange between silicate and the sorbed Se^IV and Se^VI. X-ray absorption near-edge structure analyses of the reacted Se indicate the formation of a mixed selenite/Se⁰ surface phase. We conclude that neither partial oxidation nor silica surface coatings block the sorption and redox-catalytic properties of magnetite nanoparticles, a result with important implications to assess the reactivity of mixed-valence phases in environmental settings.

中文翻译：

二氧化硅涂层对磁铁矿催化硒还原的影响

氧化铁（II / III）表面的反应性可能受其与二氧化硅的相互作用的影响，而二氧化硅在水生系统中无处不在。为了描述纳米级氧化铁的复杂表面行为，了解硅涂层矿物表面的结构-反应关系是必要的。在这里，我们使用硅吸附等温线和傅立叶变换红外光谱分析二氧化硅在轻度氧化的磁铁矿纳米颗粒（15％磁赤铁矿和85％磁铁矿，即约2个磁赤铁矿表面层）上的吸附和聚合，表明Si吸附遵循Langmuir等温线直至溶解的Si达到2 mM，在该处发生表面聚合。此外，使用硒作为分子探针分析了二氧化硅表面涂层对磁铁矿氧化还原催化能力的影响。结果表明，对于部分氧化的纳米颗粒，甚至在不同的Si表面覆盖率下，仍会发生电子转移。结果表明硅酸盐和吸附的硒之间的阴离子交换^IV和Se ^VI。反应的Se的X射线吸收近边缘结构分析表明形成了亚硒酸盐/ Se ⁰混合表面相。我们得出的结论是，部分氧化和二氧化硅表面涂层都不会阻碍磁铁矿纳米颗粒的吸附和氧化还原催化性能，这一结果对评估环境环境中混合价相的反应性具有重要意义。

更新日期：2021-03-02

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