Mechanism of oleate interaction on salt-type minerals. V : Adsorption and precipitation reactions in relation to the solid/liquid ratio in the synthetic fluorite-sodium oleate system
Mechanism of oleate interaction on salt-type minerals. V : Adsorption and precipitation reactions in relation to the solid/liquid ratio in the synthetic fluorite-sodium oleate system
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DOI：
10.1016/0021-9797(91)90365-f
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发表时间：
1991-09
影响因子：
9.9
通讯作者：
K. Rao;J. Cases;K. Forssberg
中科院分区：
文献类型：
--
作者：
K. Rao;J. Cases;K. Forssberg
通过吸附、电动和漫反射红外光谱测量，结合热力学化学平衡计算，研究了油酸盐与萤石的相互作用机理。吸附等温线的斜率在油酸盐密度10μm−2以上有一个无限的增加。这个吸附密度对应于油酸盐通过二维缩合形成的双层结构，其分子覆盖面积为33A˚2(液晶态)。理论化学平衡与实验数据的比较表明，等温线斜率的无限增大是由于油酸钙的析出。该三维相的溶度积在pKrange 14.4-14.5之间，与文献中所引用的大部分值一致。红外光谱研究表明，油酸通过反钠离子和钙离子单配位形成单层填充物。萤石的ζ电位与油酸盐吸附到双层形成，以及在高油酸盐浓度下在表面形成油酸钙(在基质上三维生长)有关。油酸盐在萤石表面的二维缩合和第二层碳链(尾尾键)的缔合，在油酸钙在主体溶液中沉淀之前，被认为是吸附机理。
The mechanism of oleate interaction with fluorite is investigated through adsorption, electrokinetic, and diffuse reflectance FT-IR measurements coupled with theoretical thermodynamic chemical equilibrium calculations. The adsorption isotherms exhibit an infinite increase in the slope beyond an oleate density of 10 μmole m−2. This adsorption density corresponds to a bilayer formation of oleate by two-dimensional condensation with a reported molecular coverage area of 33A˚2(liquid-crystal state). Comparison of the theoretical chemical equilibria with the experimental data shows that the infinite increase in the slope of the isotherms is due to the precipitation of calcium oleate. The solubility product of this three-dimensional phase is found to be in thepKrange 14.4–14.5, and agrees with most of the values quoted in the literature. From IR studies, monocoordination of oleate through counter sodium and calcium ions is suggested for the monolayer filling. ζ potentials of fluorite are correlated to the adsorption of oleate up to bilayer formation, and formation on surface of calcium oleate (three-dimensional growth on substrate) at high oleate concentrations. Two-dimensional condensation of oleate on the fluorite surface followed by the association of hydrocarbon chains (tail—tail bond) for the second layer, prior to the precipitation of calcium oleate in the bulk solution, is proposed as the adsorption mechanism.