Fe（II）与羟基氧化铁缔合的溶液和固体表面氧化还原电位的测定,ACS Earth and Space Chemistry

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Fe（II）与羟基氧化铁缔合的溶液和固体表面氧化还原电位的测定
ACS Earth and Space Chemistry ( IF 2.9 ) Pub Date : 2019-03-13 00:00:00 , DOI: 10.1021/acsearthspacechem.9b00001
Xiaomin Li _{1,

2} , Liang Liu _{2,

3} , Yundang Wu ₄ , Tongxu Liu _{2,

4}

Affiliation

考虑到Fe（II）与铁矿物质的氧化还原特性在控制元素和污染物的生物地球化学过程中的重要性，已对其进行了广泛的研究，但Fe（II）的氧化还原电势（E _h）的实验测量与理论计算之间存在牢固的联系II）相关的铁矿物质仍然缺乏。在这项研究中，实验和计算的Fe（II）物种在水铁矿（Fhy）溶液中的E _h值进行了研究。È _ħ的Fe（II）的体积的系统和水铁矿的[Fe（II）-Fhy]和Ë _ħ分别通过开路电势（OCP）和循环伏安法（CV）测量来检查与水铁矿[Fhy-associed Fe（II）]相关的Fe（II）的含量，这两种方法也都是基于改进的Nernst方程计算的。从OCP测量获得的块状Fe（II）–Fhy的实验E _h值和为溶液相Fe（II）计算的E _h值都随着Fe（II）浓度的增加而显着降低，表明块状的氧化还原电位Fe（II）与羟基氧化铁（Fe（II）–IOs）的缔合是通过溶液相Fe（II）来确定的。该ë _{^ h}通过OCP测量获得的Fe（II）-Fhy的大量Fe（II）-IOs值与Fe（II）-Gth的值相近，并且该发现归因于Fe（II）催化的三水铁矿转化为三价铁。针铁矿。通过CV测试获得的表面吸附的Fe（II）的E _h值和Fe（II）-Fhy的计算值接近Fe（II）-Gth的E _h值，这表明表面吸附的Fe（II）的氧化还原电位）由吸附的Fe（II）和刚形成的Fe（III）的氧化还原对确定，但没有结构Fe（III）的确定。因此，新形成的Fe（III）比结构Fe（III）更具反应性。蒽醌-2,6-二磺酸盐（AQDS）还原实验表明，虽然Fe（II）-Fhy和Fe（II）-Gth，Fe ²⁺在没有任何铁氧化物的溶液中，仅降低了9.1％的AQDS。通过电化学测量和理论计算的综合，这项研究表明，吸附的Fe（II）和新鲜形成的Fe（III）的氧化还原对支配了与Fe（II）相关的铁矿物质中的表面反应性，从而提供了新的见解。 Fe（II）-铁矿物质系统的氧化还原特性。

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Determination of the Redox Potentials of Solution and Solid Surface of Fe(II) Associated with Iron Oxyhydroxides

While the redox properties of Fe(II) associated with iron minerals have been widely investigated given their significance in controlling the biogeochemical processes of elements and contaminants, a robust link between the experimental measurements and theoretical calculations of redox potentials (E_h) of Fe(II)-associated iron minerals is still lacking. In this study, the experimental and calculated E_h values of Fe(II) species in solution with ferrihydrite (Fhy) were investigated. E_h of the bulk system of Fe(II) and ferrihydrite [Fe(II)–Fhy] and E_h of Fe(II) associated with ferrihydrite [Fhy-associated Fe(II)] were examined by open circuit potential (OCP) and cyclic voltammetry (CV) measurements, respectively, both of which were also calculated on the basis of the modified Nernst equation. Both the experimental E_h values of bulk Fe(II)–Fhy obtained from the OCP measurements and the E_h values calculated for solution-phase Fe(II) decreased substantially with increasing Fe(II) concentrations, indicating that the redox potentials of bulk Fe(II)-associated with iron oxyhydroxides (Fe(II)–IOs) were determined by solution-phase Fe(II). The E_h values of bulk Fe(II)–IOs obtained from the OCP measurements for Fe(II)–Fhy were close to those of Fe(II)–Gth, and this finding was attributed to the Fe(II)-catalyzed transformation of ferrihydrite to goethite. The E_h values of surface-sorbed Fe(II) obtained from CV tests and the calculation for Fe(II)–Fhy were close to those of Fe(II)–Gth, implying that the redox potentials of surface-sorbed Fe(II) were determined by the redox couple of sorbed Fe(II) and freshly formed Fe(III) but not structural Fe(III); therefore, newly formed Fe(III) was more reactive than structural Fe(III). The anthraquinone-2,6-disulfonate (AQDS) reduction experiments revealed that, while 77.1–82.9% of AQDS could be reduced in the suspensions of Fe(II)–Fhy and Fe(II)–Gth, Fe²⁺ in solution without any iron oxides only reduced 9.1% of AQDS. By integration of electrochemical measurements and theoretical calculation, this study demonstrated that the redox couple of sorbed Fe(II) and freshly formed Fe(III) dominated the surface reactivity in the Fe(II)-associated iron minerals, which provides new insight into the redox properties of the Fe(II)–iron mineral system.

更新日期：2019-03-13

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