Chemical and structural characterization of As immobilization by nanoparticles of mackinawite (FeSm)
Chemical and structural characterization of As immobilization by nanoparticles of mackinawite (FeSm)
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DOI：
10.1016/j.chemgeo.2009.08.003
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发表时间：
2009-10
期刊：
影响因子：
3.9
通讯作者：
D. Renock;Tanya J. Gallegos;S. Utsunomiya;K. Hayes;R. Ewing;U. Becker
中科院分区：
文献类型：
--
作者：
D. Renock;Tanya J. Gallegos;S. Utsunomiya;K. Hayes;R. Ewing;U. Becker
亚砷酸盐As（III）在缺氧环境中的流动性和有效性主要受硫化铁吸附和/或固体相砷沉淀的控制。采用高角环形暗场（HAADF）扫描透射电子显微镜（STEM）、STEM元素图谱、高分辨率TEM和x射线光电子能谱（XPS）研究了As（III）与ph5和ph9悬浮液中合成mackinawite （FeSm）的相互作用。在pH值为5时，硫化砷相在fesm颗粒中析出，形成非晶硫化砷水合相。XPS结果表明，As在硫化砷析出物表层的氧化态为“雄黄样”，其3d峰面积的> ~ 75%是由氧化态在0 ~ 2+之间的As形成的。在pH值为9时，不存在离散的硫化砷沉淀，但在STEM-EDX模式下的元素映射显示，砷均匀分布在FeSm上，这表明砷的吸收是由As（III）氧离子的吸附和/或高度分散的硫化砷沉淀在FeSm上引起的。XPS还显示，与pH为9时的样品相比，无As（III）平衡的fesm具有更多的氧化表面组成，这可以从较高的O浓度（比pH为9时高3倍）和组成总Fe（2p3/2）峰的较大比例的Fe（III）物种中看出。这些发现有助于更好地理解硫化铁底物吸附As（III）的氧化还原过程和相变。
The mobility and availability of arsenite, As(III), in anoxic environments is largely controlled by adsorption onto iron sulfides and/or precipitation of arsenic in solid phases. The interaction of As(III) with synthetic mackinawite (FeSm) in pH 5 and 9 suspensions was investigated using high-angle annular dark field (HAADF) scanning transmission electron microscopy (STEM), STEM elemental mapping, high resolution TEM, and X-ray photoelectron spectroscopy (XPS). At pH 5, arsenic sulfide phases precipitate among the FeSmparticles as discrete particles that are an amorphous hydrous phase of arsenic sulfide. The oxidation state of As in the surface layers of the arsenic sulfide precipitates is ‘realgar-like’ based on XPS results showing that >75% of the As 3d peak area is due to As with oxidation states between 0 and 2+. Discrete, arsenic sulfide precipitates are absent at pH 9, but elemental mapping in STEM-EDX mode shows that arsenic is uniformly distributed on the FeSm, suggesting that uptake is caused by the sorption of As(III) oxyanions and/or the precipitation of highly dispersed arsenic sulfides on FeSm. XPS also revealed that the FeSmthat equilibrated without As(III) has a more oxidized surface composition than the sample at pH 9, as indicated by the higher concentration of O (∼three times greater than that at pH 9) and the larger fraction of Fe(III) species making up the total Fe (2p3/2) peak. These findings provide a better understanding of redox processes and phase transitions upon As(III) adsorption on iron sulfide substrates.