| 李巍,李荣,卢阳,石振清,吴文成.水铁矿厌氧转化过程中Cd的纳米尺度固存机制[J].农业环境科学学报,2026,45(2):340-351. |
| 水铁矿厌氧转化过程中Cd的纳米尺度固存机制 |
| Nanoscale sequestration mechanism of Cd during anaerobic transformation of ferrihydrite |
| 投稿时间：2025-02-25 修订日期：2025-04-23 |
| DOI：10.11654/jaes.2025-0180 |
| 中文关键词: Cd 水铁矿共沉淀 铁氧化物转化 球差校正扫描透射电子显微镜 微观固存机制 |
| 英文关键词: Cd ferrihydrite coprecipitates Fe oxides transformation Cs-STEM microscopic sequestration mechanism |
| 基金项目:国家自然科学基金项目（42107264，42377008）；广州市科技计划项目（2025A04J4492） |
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| 中文摘要: |
| 为深入探究Cd在铁氧化物厌氧转化过程中的固存释放行为以及与铁氧化物的微观交互机理，本研究选取环境中广泛分布的铁氧化物——水铁矿为研究对象，设置二价铁[Fe（Ⅱ）]介导下的水铁矿-Cd（Ⅱ）共沉淀转化体系，通过化学批量提取实验探究了铁氧化物转化不同时间点上重金属Cd的固存-释放特性，通过X射线衍射（XRD）、X射线光电子能谱（XPS）和球差校正扫描透射电子显微镜（Cs-STEM）系统揭示 Cd对铁氧化物转化过程的影响以及 Cd在铁氧化物纳米颗粒上的微观固存机制。结果表明：针铁矿（80.9%）和磁铁矿（19.1%）是Fe（Ⅱ）介导的水铁矿-Cd（Ⅱ）共沉淀转化体系的最终产物，纤铁矿为中间产物。化学提取实验表明34.1%的Cd（Ⅱ）以不可提取的形态最终被铁氧化物固存。Cs-STEM对矿物元素含量的分析结果显示，8 h时Cd（Ⅱ）在针铁矿上的含量（1.9%）显著高于其在磁铁矿（0.8%）和纤铁矿（0.3%）上的含量。对单一针铁矿颗粒亚纳米尺度的精细成像和晶面间距的分析表明，Cd（Ⅱ）在针铁矿特征晶面上呈现明显亮点，针铁矿晶面间距变化最大的为G（111）晶面，相较于不含Cd的纯水铁矿处理，其间距增加0.043 8 Å。XPS结果显示，转化过程中金属—氧键比例由45.0%（8 h）显著下降至4.8%（168 h），表面结合态Cd比例下降。综合化学提取实验、Cs-STEM和XPS结果得出，Cd（Ⅱ）可以通过铁氧化物的厌氧转化以同晶取代的方式固存在针铁矿晶体结构中，从而降低其迁移特性。 |
| 英文摘要: |
| This study aims to elucidate the immobilization and release behavior of Cd during the anaerobic transformation of iron oxides, as well as its microscopic interaction mechanisms with iron oxides. Ferrihydrite, a widely distributed iron oxide in the environment, was selected, and Fe（Ⅱ）induced ferrihydrite- Cd（Ⅱ）coprecipitates transformation were conducted. Batch extraction experiments were used to explore the sequestration and release characteristics of Cd at various aging times of iron oxides. Advanced characterization techniques, including X-ray diffraction（XRD）, X-ray photoelectron spectroscopy（XPS）, and spherical aberration-corrected scanning transmission electron microscopy（Cs-STEM）were conducted to elucidate the influence of Cd on the transformation process of iron oxides and the sequestration mechanisms of Cd on iron oxide nanoparticles. Results revealed that goethite（80.9%）and magnetite（19.1%）were the final products of the Fe（Ⅱ）-induced ferrihydrite-Cd（Ⅱ）coprecipitation transformation system, with lepidocrocite serving as an intermediate phase. Batch extraction experiments indicated that 34.1% of Cd（Ⅱ）was ultimately immobilized by iron oxides in a non-extractable form. Elemental analysis of minerals using Cs-STEM demonstrated that the Cd（Ⅱ）content on goethite（1.9%）was significantly higher than that on magnetite（0.8%）and lepidocrocite（0.3%）at 8 h. Sub-nanoscale high-resolution imaging and interplanar spacing analysis of individual goethite particles revealed distinct bright spots corresponding to Cd（Ⅱ）on the characteristic crystal planes of goethite. The most significant change in interplanar spacing was observed for the G（111）plane, which exhibited an increase of 0.043 8 Å compared to Cdfree pure goethite. XPS results demonstrated a notable decrease in the metal-oxygen bond ratio from 45.0%（8 h）to 4.8%（168 h）during the transformation process, accompanied by a reduction in surface-bound Cd. Integrating chemical extraction experiments, Cs-STEM, and XPS results, this study confirms that Cd（Ⅱ）can be immobilized within the goethite crystal structure through isomorphous substitution during the anaerobic transformation of iron oxides, thereby reducing its mobility. |
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