POLYMERIZATION OF SILICATE ANIONS IN SOLUTIONS AT LOW CONCENTRATIONS
POLYMERIZATION OF SILICATE ANIONS IN SOLUTIONS AT LOW CONCENTRATIONS
复制标题
DOI：
10.1038/318649a0
复制
发表时间：
1985-01-01
期刊：
影响因子：
64.8
通讯作者：
SPARKS, DL
中科院分区：
文献类型：
--
作者：
ALVAREZ, R;SPARKS, DL
形成四面体的离子（例如硅酸盐和磷酸盐）的吸附被认为是这些阴离子保留在水合铝氧化物和铁氧化物表面的主要原因。这种保留在自然和人为现象中的重要性一直是许多研究的主题。在进行吸附研究时，往往强调表面的作用和潜在决定离子在其上产生的电荷，而很少考虑或研究吸附物的性质。然而，排除或平衡的解决方案是制定吸附机制或模型的信息的种子来源。存在于平衡溶液中的离子种类实际上总是被认为是理所当然的，也就是说，从以前公布的数据。他们被认为是solutionpH值的一个简单的函数，没有进一步分析的离子形态的变化，发生在吸附过程中。在这里，我们提供了直接的实验证据，使用先进的和敏感的光谱技术，激光拉曼光谱（LRS），在低浓度的水平衡硅酸盐溶液中含有聚合物和/或其他阴离子络合物，而不仅仅是单体物种。这些低浓度是相似的，在大多数以前的吸附实验中使用的铁和铝的倍半氧化物和热带酸性土壤。我们的研究结果清楚地表明，任何机制和模型，提出来描述阴离子吸附倍半氧化物应考虑硅酸盐，可能还有其他一些四面体形成的阴离子，并不存在于溶液中的单体离子物种，因为大多数研究人员假设1 -11。将实验数据拟合到先前报道的模型中的不愉快促使了这项研究2 - 4，6，12。
Adsorption of tetrahedral-forming ions, such as silicates and phosphates, is considered to be the main cause of retention of these anions on the surfaces of hydrated Al- and Fe-oxides. The importance of this retention in natural and man-caused phenomena has been the subject of many investigations. When adsorption studies are conducted, the role of the surface and the charges developed on it by the potentially determining ions tend to be emphasized, while the nature of the sorbate is rarely considered or investigated. Nevertheless, the excluded or equilibrium solution is the seminal source of information in the formulation of adsorption mechanisms or models. The ionic species present in the equilibrium solution are practically always taken for granted, that is, from data previously published. They are thought to be a simple function of solutionpH, without further analysis of ionic speciation changes that occur during the sorption process. Here, we provide direct experimental evidence, using an advanced and sensitive spectroscopic technique, laser Raman spectroscopy (LRS), that aqueous equilibrium silicate solutions at low concentrations contain polymeric and/or other anionic complexes and not just monomeric species. These low concentrations are similar to those used in most previous sorption experiments on Fe- and Al-sesquioxides and on tropical acidic soils. Our findings clearly indicate that any mechanisms and models that are proposed to describe anion sorption on sesquioxides should consider that silicates, and probably some other tetrahedral-forming anions, are not present in solution solely as monomeric ionic species as most investigators have assumed1–11. Irregularities in fitting experimental data to models previously reported prompted this research2–4,6,12.