title: Removal of selenium from water with nanoscale zero-valent iron: mechanisms of intraparticle reduction of Se(IV).
abstract: 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.
authors.affiliation: State Key Laboratory of Pollution Control and Resource Reuse, PR China; College of Environmental Science and Engineering, Tongji University, Shanghai 200092, PR China.
authors.forename: Lan
authors.initials: L
authors.lastname: Ling
authors.affiliation: State Key Laboratory of Pollution Control and Resource Reuse, PR China; School of the Environment, Nanjing University, Nanjing, Jiangsu 210023, PR China.
authors.forename: Bingcai
authors.initials: B
authors.lastname: Pan
authors.affiliation: State Key Laboratory of Pollution Control and Resource Reuse, PR China; College of Environmental Science and Engineering, Tongji University, Shanghai 200092, PR China. Electronic address: zhangwx@tongji.edu.cn.
authors.forename: Wei-xian
authors.initials: WX
authors.lastname: Zhang
mesh_terms: D007501:Iron / Q000737:chemistry*; D017348:Microscopy, Electron, Scanning Transmission; D053758:Nanoparticles; D012643:Selenium / Q000737:chemistry / Q000302:isolation & purification*; D013052:Spectrometry, X-Ray Emission; D014874:Water Pollutants, Chemical / Q000737:chemistry / Q000302:isolation & purification*; D018508:Water Purification / Q000379:methods*
chemical_list: D014874:Water Pollutants, Chemical; D007501:Iron; D012643:Selenium
keywords: Selenium; Spherical aberration corrected scanning transmission electron microscopy (Cs-STEM); Wastewater; X-ray energy dispersive spectroscopy (XEDS); Zero-valent iron