Sorption of arsenate on MgAl and MgFe layered double hydroxides derived from calcined dolomite
Sorption of arsenate on MgAl and MgFe layered double hydroxides derived from calcined dolomite
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DOI：
10.1016/j.jece.2015.05.016
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发表时间：
2015-09
影响因子：
7.7
通讯作者：
M. Yoshida;Paulmanickam Koilraj;X. Qiu;T. Hirajima;K. Sasaki
中科院分区：
文献类型：
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作者：
M. Yoshida;Paulmanickam Koilraj;X. Qiu;T. Hirajima;K. Sasaki
层状双氢氧化物(LDHs)具有很强的阴离子交换能力，具有去除不同阴离子的能力。利用天然地球资源合成LDHs是环境保护领域的研究热点。以煅烧白云石(CaO·MgO)为镁源和沉淀剂，通过优化微波水热老化工艺，成功地合成了单相的Mg2.3Al-、Mg2.9Al-和Mg4Fe-LDHs。砷在这些水滑石上的吸附数据符合非线性Langmuir吸附等温式。在所研究的材料中，Mg2.3Al-LDH不仅表现出良好的砷盐吸附能力，而且对砷酸盐具有良好的复盖性。这表明，除了电荷密度之外，还有一些额外的因素影响吸附密度。通过X射线衍射、X射线光电子能谱、傅立叶变换红外光谱、扩展X射线吸收精细结构分析等对吸附后的固体残留物进行表征，探讨了砷的吸附机理。砷在镁铝LDHs上的吸附是通过离子交换和表面吸附实现的，这取决于金属层的电荷密度。然而，随着内表面络合物的形成，砷在镁铁LDH上的吸附是通过离子交换进行的，这导致了扰动层的堆积。
Layered double hydroxides (LDHs) have the property to remove different anions due to their high anion exchange ability. Synthesis of LDHs using natural earth resources is highly desired in environmental concern. Single phases of Mg2.3Al-, Mg2.9Al- and Mg4Fe-LDHs were successfully synthesized from calcined dolomite (CaO·MgO) as Mg source as well as precipitant through optimization of microwave-assisted hydrothermal aging. Sorption data of arsenate over these LDHs were well fitted to non-linear Langmuir adsorption isotherm. Among the materials studied Mg2.3Al-LDH showed not only superior arsenate sorption capacity but also superior coverage of arsenate. This suggests there are some additional factors other than charge density to influence the sorption density. Mechanism of arsenate sorption was probed by different characterization techniques of solid residues after sorption such as X-ray diffraction, X-ray photoelectron spectroscopy, Fourier transformed infrared, extended X-ray absorption fine structure analysis. Sorption of arsenate over MgAl-LDHs mediated through ion-exchange as well as surface adsorption, depending on charge density of metallic layers. However, sorption of arsenate over MgFe-LDH occurred through ion-exchange along with the formation of inner surface complexes, which leads disturbed layer stacking.