National-Regional Joint Engineering Research Center for Soil Pollution Control and Remediation in South China, Guangdong Key Laboratory of Integrated Agro-environmental Pollution Control and Management, Institute of Eco-environmental and Soil Sciences, Guangdong Academy of Sciences, Guangzhou 510650, P. R. China.
The Key Lab of Pollution Control and Ecosystem Restoration in Industry Clusters, Ministry of Education, School of Environment and Energy, South China University of Technology, Guangzhou, Guangdong 510006, P. R. China.
Langmuir. 2021 May 25;37(20):6139-6150. doi: 10.1021/acs.langmuir.1c00124. Epub 2021 May 11.
Although the dual role of natural organic matter (NOM) as an electron shuttle and an electron donor for dissimilatory iron (Fe) reduction has been extensively investigated, the underlying interfacial interactions between various exposed facets and NOM are poorly understood. In this study, fulvic acid (FA), as typical NOM, was used and its effect on the dissimilatory reduction of hematite {001} and {100} by CN-32 was investigated. FA accelerates the bioreduction rates of hematite {001} and {100}, where the rate of hematite {100} is lower than that of hematite {001}. Secondary Fe minerals were not observed, but the HR-TEM images reveal significant defects. The ATR-FTIR results demonstrate that facet-dependent binding mainly occurs via surface complexation between the surface iron atoms and carboxyl groups of NOM. The spectroscopic and mass spectrometry analyses suggest that organic compounds with large molecular weight, highly aromatic and unsaturated structures, and lower H/C ratios are easily adsorbed on Fe oxides or decomposed by bacteria in FA-hematite {001} treatment after iron reduction. Due to the metabolic processes of cells, a significant number of compounds with higher H/C and medium O/C ratios appear. The Tafel curves show that hematite {100} possessed higher resistance (4.1-2.6 Ω) than hematite {001} (3.5-2.2 Ω) at FA concentrations ranging from 0 to 500 mg L, indicating that hematite {100} is less conductive during the electron transfer from reduced FA or cells to Fe oxides than hematite {001}. Overall, the discrepancy in the iron bioreduction of two exposed facets is attributed to both the different electrochemical activities of the Fe oxides and the different impacts on the properties and composition of OM. Our findings shed light on the molecular mechanisms of mutual interactions between FA and Fe oxides with various facets.
虽然天然有机物 (NOM) 作为电子穿梭体和异化铁 (Fe) 还原的电子供体的双重作用已经得到了广泛的研究，但对于各种暴露面和 NOM 之间的界面相互作用知之甚少。在这项研究中，使用了富里酸 (FA) 作为典型的 NOM，并研究了它对 CN-32 异化还原赤铁矿 {001} 和 {100} 的影响。FA 加速了赤铁矿 {001} 和 {100} 的生物还原速率，其中赤铁矿 {100} 的速率低于赤铁矿 {001}。没有观察到次生铁矿物，但高分辨率透射电子显微镜 (HR-TEM) 图像显示出明显的缺陷。ATR-FTIR 结果表明，面依赖性结合主要通过 NOM 表面铁原子和羧基之间的表面络合发生。光谱和质谱分析表明，有机化合物具有较大的分子量、高度芳构化和不饱和结构以及较低的 H/C 比，容易在 FA-赤铁矿 {001} 处理后被氧化铁或细菌吸附或分解，因为铁还原后细胞的代谢过程中，出现了大量 H/C 较高和 O/C 中等的化合物。Tafel 曲线表明，在 FA 浓度从 0 到 500mg/L 的范围内，赤铁矿 {100} 的电阻 (4.1-2.6 Ω) 高于赤铁矿 {001} (3.5-2.2 Ω)，这表明在还原的 FA 或细胞向氧化铁传递电子时，赤铁矿 {100} 的导电性比赤铁矿 {001} 差。总的来说，两个暴露面的铁生物还原的差异归因于氧化铁的电化学活性不同以及对 OM 性质和组成的不同影响。我们的研究结果揭示了 FA 与具有不同面的氧化铁之间相互作用的分子机制。
