Arsenate adsorption on an Fe-Ce bimetal oxide adsorbent: role of surface properties.
Arsenate adsorption on an Fe-Ce bimetal oxide adsorbent: role of surface properties.
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DOI：
10.1021/es050775d
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发表时间：
2005-08
影响因子：
11.4
通讯作者：
Yu Zhang;Min Yang;Xiaowen Dou;Hong He;Dong-sheng Wang
中科院分区：
文献类型：
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作者：
Yu Zhang;Min Yang;Xiaowen Dou;Hong He;Dong-sheng Wang
采用X射线粉末衍射（XRD）、透射电子显微镜（TEM）、傅里叶变换红外光谱（FTIR）和X射线光电子能谱（XPS）等方法研究了Fe-Ce复合吸附剂对As（V）的吸附性能。在吸附试验中，氧化铈吸附剂对As（V）的吸附容量明显高于用相同方法制备的铈和铁氧化物（CeO 2和Fe 3 O 4）以及最近报道的其他一些砷酸盐吸附剂。吸附剂的XRD测试表明，随着Ce 4+用量的增加，Fe 3 O 4相逐渐消失，直至达到Ce 4+：Fe 3+：Fe 2 += 0.08：0.2：0.1（Fe-CeO 8是指在此比例下制备的吸附剂），随着Ce 4+用量的进一步增加，CeO 2相开始出现。结合TEM观察结果，推测Fe-Ce固溶体是随着磁铁矿相的消失而形成的。通过FTIR证实了在氧化物吸附剂上存在特征表面羟基（MOH，金属表面羟基，1126 cm（-1）），其在固溶体状态下显示最高谱带强度。XPS窄扫描O（1 s）谱的定量计算也表明，CeO_2和Fe_3O_4的羟基含量分别为12.6%和19.6%，而Fe_3O_8的羟基含量为30.8%。不同As（V）浓度下Fe-CeO 8对As（V）的吸附实验结果表明，随着1126 cm（-1）处M-OH带积分面积的减小，836 cm（-1）处As-O带积分面积和As（V）吸附量几乎呈线性增加，证明Fe-CeO 8对As（V）的吸附主要是通过定量配体交换机制实现的。As（V）吸附后，Fe在Fe-CeOB上的原子比随着As原子比从0增加到16%而从20.1%下降到7.7%，表明As（V）的吸附可能是通过砷酸根取代Fe（Fe-OH）的M-OH基团实现的。FTIR的As-O带（836 cm（-1））处的v3带的良好分裂和XPS结果计算的Fe-CeO_8的羟基比（1.7）表明，Fe-CeO_8表面可能以双质子化的单齿配合物（SOAsO（OH）_2）为主。
An Fe-Ce bimetal adsorbent was investigated with X-ray powder diffraction (XRD), transmission electron micrograph (TEM), Fourier transform infrared spectra (FTIR), and X-ray photoelectron spectroscopy (XPS) methods for a better understanding of the effect of surface properties on arsenate (As(V)) adsorption. In the adsorption test, the bimetal oxide adsorbent showed a significantly higher As(V) adsorption capacity than the referenced Ce and Fe oxides (CeO2 and Fe3O4) prepared by the same procedure and some other arsenate adsorbents reported recently. XRD measurement of the adsorbent demonstrated that the phase of magnetite (Fe3O4) disappears gradually with the increasing dosage of Ce4+ ions until reaching a molar ratio of Ce4+ to Fe3+ and Fe2+ of 0.08:0.2:0.1 (Fe-CeO8 refers to the adsorbent prepared at this ratio), and the phase of CeO2 begins to appear following a further increase of the Ce dose. Combined with the results of TEM observation, it was assumed that a solid solution of Fe-Ce is formed following the disappearance of the magnetite phase. Occurrence of a characteristic surface hydroxyl group (MOH, metal surface hydroxyl, 1126 cm(-1)), which showed the highest band intensity in the solid solution state, was confirmed on the bimetal oxide adsorbent by FTIR. Quantificational calculation from the XPS narrow scan results of O(1s) spectra also indicated that the formation of the bimetal Fe-CeO8 was composed of more hydroxyl (30.8%) than was the formation of CeO2 and Fe3O4 (12.6% and 19.6%). The results of adsorption tests on Fe-CeO8 at differentAs(V) concentrations indicated that both the integral area of the As-O band at 836 cm(-1) and the As(V) adsorption capacity increased almost linearly with the decrease of the integral area of M-OH bands at 1126 cm(-1), proving that the adsorption of As(V) by Fe-CeO8 is mainly realized through the mechanism of quantitative ligand exchange. The atomic ratio of Fe on Fe-CeOB decreased from 20.1% to 7.7% with the increase of the As atom ratio from 0 to 16% after As(V) adsorption, suggesting that As(V) adsorption might be realized through the replacement of the M-OH group of Fe (Fe-OH) with arsenate. The well splitting of three v3 bands at As-O band (836 cm(-1)) of FTIR and the hydroxyl ratio (1.7) of Fe-CeO8 calculated from the XPS results suggested that the diprotonated monodentate complex (SOAsO(OH)2) is possibly dominant on the surface of Fe-CeO8.