Structural incorporation and thermodynamic properties of Mo6+ iniron oxides and their role in Mo immobilization in soils

Mo6铁氧化物的结构掺入和热力学性质及其在土壤中Mo固定化中的作用

• 批准号: 370263568
• 负责人: Professor Dr. Juraj Majzlan, Ph.D., since 1/2019
• 金额: --
• 依托单位: Lehrstuhl für Bodenkunde
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2017
• 资助国家: 德国
• 起止时间: 2016-12-31 至 2020-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/370263568?language=en
• 关键词: Structural; incorporation; thermodynamic; properties; Mo6+

In this project we propose to investigate the importance of iron oxides on the mobility and bioavailability of Mo6+ in soils. Molybdenum represents a critical prerequisite for the biosynthesis of several metalloenzymes and is therefore essential for all known life (Mendel & Bittner, 2006; McGrath et al., 2010, Duval et al., 2015). Its mobility and bioavailability in soils is low and directly coupled with the presence of iron oxides (Lang & Kaupenjohann, 1999). In order to evaluate the importance of iron oxides for Mo immobilization, previous studies focused predominantly on adsorption mechanisms (e.g. Goldberg et al., 1996; Brinza et al., 2008), whereas the possibility of structural incorporation by a heterovalent substitution of Fe3+ by Mo6+ was almost completely ignored (Richmond et al., 2004; Carroll & Richmond, 2008; Zemberyová et al., 2010).Iron oxides possess several structural mechanisms which can permit a heterovalent substitution (e.g. Balko & Clarkson, 2001; Khan et al., 2008; Bolanz et al., 2013; Ciobanu et al., 2013). For Mo6+, the most abundant Mo specie in oxic systems (Barron et al., 2009), however, almost no convincing data for structural incorporation into iron oxides exist. This tremendous gap in the knowledge is transferable to the thermodynamic properties of Mo-bearing iron oxides. Minerals, which structurally incorporate foreign ions like Mo6+, can exhibit fundamentally different thermodynamic properties and therefore stabilities (Heaney, 2000). Molybdenum could therefore alter its own bioavailability.Therefore, this project has four milestones including (i) synthesis and characterization of Mo6+-bearing iron oxides, (ii) identification of the mechanisms which allow iron oxides to structurally incorporate Mo6+, (iii) to provide calorimetric data (enthalpies of mixing, enthalpies of formation) of Mo-substituted iron oxides and to evaluate the effects of structurally incorporated Mo6+ on the thermodynamic stabilities of iron oxides, (iv) a transfer of the acquired incorporation mechanisms from synthetic Mo6+-bearing iron oxides, formed under laboratory conditions and their thermodynamic properties, to natural iron oxide in various soil types. In order to achieve these goals, a combination of bulk, micro- and nano-resolution techniques will be employed comprising powder X-ray diffraction, inductively- mass spectrometry, mass spectrometer-coupled gas emission system, transmission electron microscope and X-ray absorption spectroscopy techniques.It is expected that this study will significantly improve our understanding about the structural incorporation mechanisms of Mo6+ in iron oxides by heterovalent substitution reactions and establish a foundation for future research on Mo mobility and bioavailability in soils.

在这个项目中，我们建议研究铁氧化物对土壤中 Mo6+ 的移动性和生物利用度的重要性。钼是多种金属酶生物合成的关键先决条件，因此对于所有已知生命都至关重要（Mendel & Bittner，2006；McGrath 等人，2010；Duval 等人，2015）。它在土壤中的移动性和生物利用度较低，并且与氧化铁的存在直接相关（Lang & Kaupenjohann，1999）。为了评估铁氧化物对Mo固定化的重要性，以前的研究主要集中在吸附机制上（例如Goldberg等人，1996年；Brinza等人，2008年），而通过Mo6+异价取代Fe3+进行结构掺入的可能性几乎完全被忽略（Richmond等人，2004年；Carroll＆Richmond，2008年；Zemberyová等人） al., 2010)。铁氧化物具有多种允许异价取代的结构机制（例如 Balko & Clarkson, 2001; Khan 等人, 2008; Bolanz 等人, 2013; Ciobanu 等人, 2013）。然而，对于含氧系统中最丰富的 Mo 物种 Mo6+（Barron 等，2009），几乎没有令人信服的结构掺入铁氧化物的数据。这种知识上的巨大差距可以转移到含钼铁氧化物的热力学性质上。矿物质在结构上含有 Mo6+ 等外来离子，可以表现出根本不同的热力学性质，因此也表现出稳定性（Heaney，2000）。因此，钼可以改变其自身的生物利用度。因此，该项目有四个里程碑，包括（i）含 Mo6+ 的铁氧化物的合成和表征，（ii）确定铁氧化物在结构上结合 Mo6+ 的机制，（iii）提供钼取代的铁氧化物的量热数据（混合热函、形成热函）并评估效果 结构掺入的 Mo6+ 对铁氧化物热力学稳定性的影响，（iv）将获得的掺入机制从实验室条件下形成的合成含 Mo6+ 铁氧化物及其热力学性质转移到各种土壤类型中的天然氧化铁。为了实现这些目标，将采用体相、微米和纳米分辨率技术的组合，包括粉末X射线衍射、电感质谱、质谱仪耦合气体发射系统、透射电子显微镜和X射线吸收光谱技术。预计这项研究将显着提高我们对铁氧化物中Mo6+结构掺入机制的理解。 异价取代反应，为未来土壤中钼的流动性和生物利用度研究奠定基础。