Electron transfer reactions at iron mineral surfaces in the presence of organic sorbates

有机山梨酸盐存在下铁矿物表面的电子转移反应

• 批准号: 124886542
• 负责人: Professor Dr. Stefan Haderlein
• 金额: --
• 依托单位: Zentrum für Angewandte Geowissenschaften (ZAG)
• 依托单位国家: 德国
• 项目类别: Research Units
• 财政年份: 2009
• 资助国家: 德国
• 起止时间: 2008-12-31 至 2012-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/124886542?language=en
• 关键词: Electron; transfer; reactions; iron; mineral

Redox reactions at iron mineral surfaces play an important role in determining the overall biogeochemical milieu in anoxic groundwater systems. Previous studies have shown that oxidation of sorbed ferrous iron at mineral phases may cause remodelling of the mineralwater interphase and thus may affect electron transfer processes in anoxic aquifers. In the first funding period, we studied in detail how and at which conditions oxidation of ferrous iron at mineral surfaces affects electron transfer processes. Using carbon tetrachloride (CCl4) as model oxidant, we could further demonstrate, that the proposed reactive tracer approach, which is based on changes of the stable isotopic composition of model oxidants, could be successfully applied to characterize the surface reactivity and dynamics of surface bound Fe(II) species at iron(III)hydroxides. Up to date, process based studies on surface mediated transformation of redox active solutes in iron mineral systems have been conducted primarily in model systems devoid of natural organic matter. In natural systems, however, mineral surfaces are inevitably in contact with OM. Sorbed DOM is likely to affect heterogeneous electron transfer processes due to its interactions with iron both in aqueous solution and at the mineral surface. On one hand, DOM sorption at iron hydroxides may interfere with the formation of reactive Fe(II) surface sites. On the other hand, DOM contain redox active quinone moieties and may act as a mediator enhancing the electron-transfer across the mineral surface. In this follow-up project we propose to investigate the effects of various organic sorbates such as redox-inert organic acids as well as redox-active quinones, humic substances and DOM on electron transfer reactions at iron mineral surfaces. Furthermore, we will investigate the effects of sulfide as additional redox active natural component on DOM-iron interfacial redox processes.

铁矿物表面的氧化还原反应在确定缺氧地下水系统的整体地球化学环境中起着重要作用。以往的研究表明，在矿物相的吸附亚铁的氧化可能会导致重塑的mineralwater界面，从而可能会影响缺氧含水层中的电子传递过程。在第一个资助期，我们详细研究了如何以及在何种条件下，矿物表面的亚铁氧化影响电子转移过程。使用四氯化碳（CCl 4）作为模型氧化剂，我们可以进一步证明，所提出的反应性示踪剂的方法，这是基于模型氧化剂的稳定同位素组成的变化，可以成功地应用于表征的表面反应性和动力学的表面结合的Fe（II）物种在铁（III）氢氧化物。到目前为止，基于过程的研究铁矿系统中的氧化还原活性溶质的表面介导的转化主要是在没有天然有机物的模型系统中进行的。然而，在自然系统中，矿物表面不可避免地与OM接触。吸附DOM可能会影响非均相电子转移过程，由于其与铁在水溶液中和矿物表面的相互作用。一方面，DOM吸附在铁的氢氧化物可能会干扰形成反应性Fe（II）的表面网站。另一方面，DOM含有氧化还原活性醌部分，并可作为介体增强电子在矿物表面的转移。在这个后续项目中，我们建议调查各种有机山梨酸盐，如氧化还原惰性的有机酸以及氧化还原活性醌，腐殖物质和DOM对铁矿物表面的电子转移反应的影响。此外，我们将研究硫化物作为额外的氧化还原活性天然组分对DOM-铁界面氧化还原过程的影响。