Roles of aqueous Fe(III) in oxidation of partially reduced nontronite under sub-acidic conditions
Roles of aqueous Fe(III) in oxidation of partially reduced nontronite under sub-acidic conditions
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亚酸性条件下 Fe(III) 水溶液在部分还原绿脱石氧化中的作用
DOI：
10.1016/j.clay.2020.105689
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发表时间：
2020-09-15
影响因子：
5.6
通讯作者：
Gao, Xubo
中科院分区：
文献类型：
--
作者：
Guo, Jing;Zhang, Xiaobo;Gao, Xubo
富铁粘土矿物界面Fe(II)-Fe（III）电子转移是砷、锑、Tc、CCl4和硝基芳香族化合物等多种环境污染物氧化还原转化的关键过程。目前粘土矿物中电子从水Fe（II）转移到结构Fe（III）的发现提出了一个问题，即电子是否从结构Fe（II）转移到水Fe（III）。为了验证这一假设，将预处理过的nontronite NAu-1用二硫代盐部分还原，然后将其与FeCl3混合在醋酸/醋酸缓冲液（pH 4.0）中。结构铁（II）迅速氧化为铁（III），而水态铁（III）相应还原为铁（II）。低温（13K）穆斯堡尔光谱结合FTIR，基于Fe（II）重态几乎完全消失和Fe(III)-OH吸收带的重新出现，为结构Fe（II）氧化提供了证据。水溶液Fe（III）在pH值升高的醋酸缓冲液中沉淀可能会抑制界面Fe(II)-Fe（III）电子转移，因为固相Fe（III）在不到24小时的时间尺度上对结构Fe（II）具有氧化还原活性。考虑到XRD和化学萃取结果都排除了电子通过NAu-1基面转移的可能性，我们假设边缘可能是Fe(II) str1 -Fe(III)aq电子转移的原因。总体结果对于评估地下环境中的铁循环以及污染物的命运和运输具有重要意义。
The interfacial Fe(II)-Fe(III) electron transfer in iron-rich clay minerals is a critical process for redox transfor-mation of many environmental contaminants including As, Sb, Tc, CCl4 and nitroaromatic compounds. Present findings of electron transfer from aqueous Fe(II) to structural Fe(III) in clay minerals raise question whether electron transfer occurs reversely from structural Fe(II) to aqueous Fe(III). To test this hypothesis, pretreated nontrontite NAu-1 was partially reduced by dithionite, and this was then mixed with FeCl3 in an acetic acid/ acetate buffer (pH 4.0). Structural Fe(II) was rapidly oxidized to Fe(III) whilst aqueous Fe(III) was corre-spondingly reduced to Fe(II). Low-temperature (13K) Mossbauer, accompanied with FTIR, spectroscopy pro-vided evidence for the oxidation of structural Fe(II) based on the almost complete disappearance of the Fe(II) doublet, and the re-appearance of Fe(III)Fe(III)-OH absorption bands. The precipitation of aqueous Fe(III) in acetate buffer with elevated pH value might inhibit interfacial Fe(II)-Fe(III) electron transfer, as solid phase Fe (III) was redox-inactive to structural Fe(II) over a time scale of less than 24 h. Given that both the XRD and chemical extraction results rule out the possibility of electron transfer through basal planes of NAu-1, we hy-pothesize that the edges may be responsible for the Fe(II)str-Fe(III)aq electron transfer. The overall results are important for assessing iron cycling in subsurface environments, as well as the fate and transport of con-taminants.