Chan Ya Ting, Kuan Wen Hui, Chen Tsan Yao, Wang Ming Kuang
Department of Agricultural Chemistry, National Taiwan University, Taipei, 10617, Taiwan.
Water Res. 2009 Sep;43(17):4412-20. doi: 10.1016/j.watres.2009.06.056. Epub 2009 Jul 4.
Removal of selenium oxyanions by the binary oxide systems, Al- or Fe-oxides mixed with X-ray noncrystalline SiO(2), was previously not well understood. This study evaluates the adsorption capacity and kinetics of selenium oxyanions by different metal hydroxides onto SiO(2), and uses X-ray absorption spectroscopy (XAS) to assess the interaction between selenium oxyanions and the sorbents at pH 5.0. The binary oxide systems of Al(III)- or Fe(III)-oxides mixed with SiO(2) were prepared, and were characterized for their surface area, point of zero charge (PZC), pH envelopes, X-ray diffraction analysis (XRD), and then macro-scale adsorption isotherm and kinetics of selenite and selenate, micro-scale adsorption XAS. The adsorption capacity of selenite and selenate on Al(III)/SiO(2) is greater than on Fe(III)/SiO(2). Adsorption isothermal and kinetic data of selenium can be well fitted to the Langmuir isotherm and pseudo-second-order kinetic models. Based on simple geometrical constraints, selenite on both the binary oxide systems forms bidentate inner-sphere surface complexes, and selenate on Fe(III)/SiO(2) forms stronger complexes than on Al(III)/SiO(2).
此前，对于二元氧化物体系（铝氧化物或铁氧化物与X射线非晶态SiO₂混合）去除硒含氧阴离子的情况了解并不充分。本研究评估了不同金属氢氧化物对SiO₂上硒含氧阴离子的吸附容量和动力学，并利用X射线吸收光谱（XAS）在pH 5.0条件下评估硒含氧阴离子与吸附剂之间的相互作用。制备了铝（III）氧化物或铁（III）氧化物与SiO₂混合的二元氧化物体系，并对其表面积、零电荷点（PZC）、pH范围、X射线衍射分析（XRD）进行了表征，然后进行了亚硒酸盐和硒酸盐的宏观吸附等温线及动力学、微观吸附XAS研究。亚硒酸盐和硒酸盐在Al（III）/SiO₂上的吸附容量大于在Fe（III）/SiO₂上的吸附容量。硒的吸附等温线和动力学数据能够很好地拟合朗缪尔等温线和准二级动力学模型。基于简单的几何约束条件，二元氧化物体系上的亚硒酸盐均形成双齿内球表面配合物，且硒酸盐在Fe（III）/SiO₂上形成的配合物比在Al（III）/SiO₂上更强。
