Infrared spectroscopic and X-ray diffraction characterization of the nature of adsorbed arsenate on ferrihydrite
Infrared spectroscopic and X-ray diffraction characterization of the nature of adsorbed arsenate on ferrihydrite
复制标题
水铁矿上吸附砷酸盐性质的红外光谱和 X 射线衍射表征
DOI：
10.1016/j.gca.2006.12.021
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发表时间：
2007-04-01
影响因子：
5
通讯作者：
Demopoulos, George P.
中科院分区：
文献类型：
--
作者：
Jia, Yongfeng;Xu, Liying;Demopoulos, George P.
傅里叶变换红外（FTIR）光谱用于表征砷酸盐-水铁矿吸附固体在pH 3-8合成。根据650-950 cm（-1）处的As-O伸缩振动带和3000-3500 cm（-1）处的O-H伸缩振动带确定了吸附态砷酸盐的形态。As-O和O-H伸缩振动带的位置随pH值的变化而变化，表明水铁矿表面砷酸盐物种的性质强烈依赖于pH值。吸附密度和合成介质（硫酸盐与硝酸盐）没有明显的影响。在酸性条件下（pH = 3，4），水铁矿表面形成砷酸铁沉淀，构成了水铁矿表面砷酸盐的主要形态。在升高的温度（75 ° C）、pH 3下合成的吸附固体的X射线衍射（XRD）分析清楚地显示了结晶砷酸铁（即臭葱石）的形成。在中性和碱性介质中（pH 7，8），砷酸盐以双齿表面络合物形式（质子化的FeO 2As（O）（OH）（-）和非质子化的FeO 2As（O）（2）（2-）形式）吸附。在弱酸性介质（pH 5、6）中，砷酸铁和表面络合物可能同时存在于水铁矿表面。进一步确定，在合成过程中，水铁矿中掺入的硫酸盐被砷酸盐取代，并且随着pH值的增加更容易交换。（c）2007 Elsevier Ltd.保留所有权利。
Fourier transformed infrared (FTIR) spectroscopy was used to characterize arsenate-ferrihydrite sorption solids synthesized at pH 3-8. The speciation of sorbed arsenate was determined based on the As-O stretching vibration bands located at 650-950 cm(-1) and O-H stretching vibration bands at 3000-3500 cm(-1). The positions of the As-O and O-H stretching vibration bands changed with pH indicating that the nature of surface arsenate species on ferrihydrite was strongly pH dependent. Sorption density and synthesis media (sulfate vs. nitrate) had no appreciable effect. At acidic pH (3, 4), ferric arsenate surface precipitate formed on ferrihydrite and constituted the predominant surface arsenate species. X-ray diffraction (XRD) analyses of he sorption solids synthesized at elevated temperature (75 degrees C), pH 3 clearly showed the development of crystalline ferric arsenate (i.e. scorodite). In neutral and alkaline media (pH 7, 8), arsenate sorbed as a bidentate surface complex (in both protonated FeO2As(O)(OH)(-) and unprotonated FeO2As(O)(2)(2-) forms). For the sorption systems in slightly acidic media (pH 5, 6), both ferric arsenate and surface complex were probably present on ferrihydrite. It was further determined that the incorporated sulfate in ferrihydrite during synthesis was substituted by arsenate and was more easily exchangeable with increasing pH. (c) 2007 Elsevier Ltd. All rights reserved.