State Key Laboratory of Pollution Control and Resource Reuse, PR China; College of Environmental Science and Engineering, Tongji University, Shanghai 200092, PR China.
State Key Laboratory of Pollution Control and Resource Reuse, PR China; School of the Environment, Nanjing University, Nanjing, Jiangsu 210023, PR China.
Water Res. 2015 Mar 15;71:274-81. doi: 10.1016/j.watres.2015.01.002. Epub 2015 Jan 10.
Increasing evidences suggest that nanoscale zero-valent iron (nZVI) is an effective agent for treatment and removal of selenium from water. For example, 1.3 mM selenite was quickly removed from water within 3 min with 5 g/L nZVI. In this work, reaction mechanisms of selenite [Se(IV)] in a single core-shell structured nanoscale zero-valent iron (nZVI) particle were studied with the method of spherical aberration corrected scanning transmission electron microscopy (Cs-STEM) integrated with X-ray energy dispersive spectroscopy (XEDS). This method was utilized to visualize solid phase translocation and transformation of Se(IV) such as diffusion, reduction, deposition and the effect of surface defects in a single nanoparticle. Se(IV) was reduced to Se(-II) and Se(0), which then formed a 0.5 nm layer of selenium at the iron oxide-Fe(0) interface at a depth of 6 nm from the surface. The results provided near atomic-resolution proof on the intraparticle diffusion-reduction of Se(IV) induced by nZVI. The STEM mapping also discovered that defects on the surface layer accelerate the diffusion of selenium and increase the capacity of nZVI for selenium sequestration.
越来越多的证据表明，纳米零价铁（nZVI）是一种有效处理和去除水中硒的试剂。例如，在 5g/L nZVI 的作用下，3min 内即可快速去除 1.3mM 的亚硒酸盐。在这项工作中，利用球差校正扫描透射电子显微镜（Cs-STEM）与 X 射线能量色散光谱（XEDS）相结合的方法，研究了单壳层结构纳米零价铁（nZVI）颗粒中亚硒酸盐[Se(IV)]的反应机制。该方法用于可视化硒（IV）在单个纳米颗粒中的固相迁移和转化，如扩散、还原、沉积以及表面缺陷的影响。硒（IV）被还原为硒（-II）和硒（0），随后在距表面 6nm 深处的氧化铁-Fe(0)界面处形成 0.5nm 厚的硒层。结果提供了近原子分辨率的证据，证明了 nZVI 诱导的硒（IV）的颗粒内扩散还原。STEM 映射还发现，表面层的缺陷加速了硒的扩散，并提高了 nZVI 对硒的固定容量。
