Surface complexation of Pb(II) at oxide-water interfaces .2. XAFS and bond-valence determination of mononuclear Pb(II) sorption products and surface functional groups on iron oxides
Surface complexation of Pb(II) at oxide-water interfaces .2. XAFS and bond-valence determination of mononuclear Pb(II) sorption products and surface functional groups on iron oxides
复制标题
DOI：
10.1016/s0016-7037(97)00125-7
复制
发表时间：
1997-07-01
影响因子：
5
通讯作者：
Parks, GA
中科院分区：
文献类型：
--
作者：
Bargar, JR;Brown, GE;Parks, GA
使用 XAFS 光谱法，在室温下研究针铁矿和赤铁矿粉末上 Pb(II) 的吸附与 pH (6-8)、吸附密度 (2-10 mu moles/m(2)) 和 0.1 M NaNO3 电解质中的 [Pb](eq) (0.2 mu M - 1.2 mM) 的函数关系。研究发现，在所有条件下，Pb(II) 离子都会被水解并以单核二齿配合物的形式吸附到针铁矿和赤铁矿上的 FeO6 八面体的边缘。 Pb(II) 的水解似乎是与 Pb(II) 表面络合相关的质子释放的主要来源。使用键价模型将氧化铁表面官能团和 Pb(II) 吸附配合物的相对稳定性与其结构和组成联系起来。这种组合方法表明 Pb(II) 吸附主要发生在未质子化的 [Fe-Fe(Fe)(sic)O-1/2] 位点和 [Fe-OH2+1/2] 位点。提出了几种吸附反应。与氧化铝上 Pb(II) 吸附的 EXAFS 结果相比表明，表面 AlO6 或 FeO6 八面体的边长部分决定了可用表面位点的反应性和密度。这项研究的结果为构建 Fe（氢）氧化物上 Pb(II) 表面络合反应的化学真实描述奠定了基础。版权所有 (C) 1997 爱思唯尔科学有限公司
Pb(II) sorption on goethite and hematite powders was studied at room temperature as a function of pH (6-8), sorption density (2-10 mu moles/m(2)), and [Pb](eq) (0.2 mu M - 1.2 mM) in 0.1 M NaNO3 electrolyte using XAFS spectroscopy. Pb(II) ions were found to be hydrolyzed and adsorbed as mononuclear bidentate complexes to edges of FeO6 octahedra on both goethite and hematite under all conditions. Hydrolysis of Pb(II) appears to be a primary source of proton release associated with surface complexation of Pb(II). A bond-valence model was used to relate the relative stabilities of iron-oxide surface functional groups and Pb(II) adsorption complexes to their structures and compositions. This combined approach suggests that Pb(II) adsorption occurs primarily at unprotonated [Fe-Fe(Fe)(sic)O-1/2] sites and at [Fe-OH2+1/2] sites. Several adsorption reactions are proposed. Comparison to EXAFS results from Pb(II) adsorption on aluminum oxides suggests that the edge lengths of surface AlO6 or FeO6 octahedra partially determine the reactivities and densities of available surface sites. The results of this study provide a basis for constructing chemically realistic descriptions of Pb(II) surface complexation reactions on Fe (hydr)oxides. Copyright (C) 1997 Elsevier Science Ltd.